Quality assurance plan for discharge measurements using broadband acoustic Doppler current profilers

USGS Publications Warehouse

Lipscomb, S.W.

1995-01-01

The recent introduction of the Acoustic Doppler Current Profiler (ADCP) as an instrument for measuring velocities and discharge in the riverine and estuarine environment promises to revolutionize the way these data are collected by the U.S. Geological Survey. The ADCP and associated software, however, compose a complex system and should be used only by qualifies personnel. Standard procedures should be rigorously followed to ensure that the quality of data collected is commensurate with the standards set by the Water Resources Division for all its varied activities in hydrologic investigations.

Variance of discharge estimates sampled using acoustic Doppler current profilers from moving boats

USGS Publications Warehouse

Garcia, Carlos M.; Tarrab, Leticia; Oberg, Kevin; Szupiany, Ricardo; Cantero, Mariano I.

2012-01-01

This paper presents a model for quantifying the random errors (i.e., variance) of acoustic Doppler current profiler (ADCP) discharge measurements from moving boats for different sampling times. The model focuses on the random processes in the sampled flow field and has been developed using statistical methods currently available for uncertainty analysis of velocity time series. Analysis of field data collected using ADCP from moving boats from three natural rivers of varying sizes and flow conditions shows that, even though the estimate of the integral time scale of the actual turbulent flow field is larger than the sampling interval, the integral time scale of the sampled flow field is on the order of the sampling interval. Thus, an equation for computing the variance error in discharge measurements associated with different sampling times, assuming uncorrelated flow fields is appropriate. The approach is used to help define optimal sampling strategies by choosing the exposure time required for ADCPs to accurately measure flow discharge.

Performance, Stability, and Plume Characterization of the HERMeS Thruster with Boron Nitride Silica Composite Discharge Channel

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Gilland, James H.; Haag, Thomas W.; Mackey, Jonathan; Yim, John; Pinero, Luis; Williams, George; Peterson, Peter; Herman, Daniel

2017-01-01

NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5kW Technology Demonstration Unit-3 (TDU-3) has been the subject of extensive technology maturation in preparation for flight system development. Detailed performance, stability, and plume characterization tests of the thruster were performed at NASA GRC's Vacuum Facility 5 (VF-5). The TDU-3 thruster implements a magnetic topology that is identical to TDU-1. The TDU-3 boron nitride silica composite discharge channel material is different than the TDU-1 heritage boron nitride discharge channel material. Performance and stability characterization of the TDU-3 thruster was performed at discharge voltages between 300V and 600V and at discharge currents between 5A and 21.8A. The thruster performance and stability were assessed for varying magnetic field strength, cathode flow fractions between 5% and 9%, varying harness inductance, and for reverse magnet polarity. Performance characterization test results indicate that the TDU-3 thruster performance is in family with the TDU-1 levels. TDU-3's thrust efficiency of 65% and specific impulse of 2,800sec at 600V and 12.5kW exceed performance levels of SOA Hall thrusters. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations (discharge current peak-to-peak and root mean square magnitudes), discharge current waveform power spectral density analysis, and maps of the current-voltage-magnetic field. Stability characterization test results indicate a stability profile similar to TDU-1. Finally, comparison of the TDU-1 and TDU-3 plume profiles found that there were negligible differences in the plasma plume characteristics between the TDU with heritage boron nitride versus the boron nitride silica composite discharge channel.

QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—User’s manual for version 2.8

USGS Publications Warehouse

Mueller, David S.

2016-05-12

The software program, QRev computes the discharge from moving-boat acoustic Doppler current profiler measurements using data collected with any of the Teledyne RD Instrument or SonTek bottom tracking acoustic Doppler current profilers. The computation of discharge is independent of the manufacturer of the acoustic Doppler current profiler because QRev applies consistent algorithms independent of the data source. In addition, QRev automates filtering and quality checking of the collected data and provides feedback to the user of potential quality issues with the measurement. Various statistics and characteristics of the measurement, in addition to a simple uncertainty assessment are provided to the user to assist them in properly rating the measurement. QRev saves an extensible markup language file that can be imported into databases or electronic field notes software. The user interacts with QRev through a tablet-friendly graphical user interface. This report is the manual for version 2.8 of QRev.

extrap: Software to assist the selection of extrapolation methods for moving-boat ADCP streamflow measurements

NASA Astrophysics Data System (ADS)

Mueller, David S.

2013-04-01

Selection of the appropriate extrapolation methods for computing the discharge in the unmeasured top and bottom parts of a moving-boat acoustic Doppler current profiler (ADCP) streamflow measurement is critical to the total discharge computation. The software tool, extrap, combines normalized velocity profiles from the entire cross section and multiple transects to determine a mean profile for the measurement. The use of an exponent derived from normalized data from the entire cross section is shown to be valid for application of the power velocity distribution law in the computation of the unmeasured discharge in a cross section. Selected statistics are combined with empirically derived criteria to automatically select the appropriate extrapolation methods. A graphical user interface (GUI) provides the user tools to visually evaluate the automatically selected extrapolation methods and manually change them, as necessary. The sensitivity of the total discharge to available extrapolation methods is presented in the GUI. Use of extrap by field hydrographers has demonstrated that extrap is a more accurate and efficient method of determining the appropriate extrapolation methods compared with tools currently (2012) provided in the ADCP manufacturers' software.

Discharge-measurement system using an acoustic Doppler current profiler with applications to large rivers and estuaries

USGS Publications Warehouse

Simpson, Michael R.; Oltmann, Richard N.

1993-01-01

Discharge measurement of large rivers and estuaries is difficult, time consuming, and sometimes dangerous. Frequently, discharge measurements cannot be made in tide-affected rivers and estuaries using conventional discharge-measurement techniques because of dynamic discharge conditions. The acoustic Doppler discharge-measurement system (ADDMS) was developed by the U.S. Geological Survey using a vessel-mounted acoustic Doppler current profiler coupled with specialized computer software to measure horizontal water velocity at 1-meter vertical intervals in the water column. The system computes discharge from water-and vessel-velocity data supplied by the ADDMS using vector-algebra algorithms included in the discharge-measurement software. With this system, a discharge measurement can be obtained by engaging the computer software and traversing a river or estuary from bank to bank; discharge in parts of the river or estuarine cross sections that cannot be measured because of ADDMS depth limitations are estimated by the system. Comparisons of ADDMS-measured discharges with ultrasonic-velocity-meter-measured discharges, along with error-analysis data, have confirmed that discharges provided by the ADDMS are at least as accurate as those produced using conventional methods. In addition, the advantage of a much shorter measurement time (2 minutes using the ADDMS compared with 1 hour or longer using conventional methods) has enabled use of the ADDMS for several applications where conventional discharge methods could not have been used with the required accuracy because of dynamic discharge conditions.

Comparison of acoustic doppler current profiler and Price AA mechanical current meter measurements made during the 2011 Mississippi River Flood

USGS Publications Warehouse

O'Brien, Patrick; Mueller, David; Pratt, Thad

2012-01-01

The Mississippi River and Tributaries project performed as designed during the historic 2011 Mississippi River flood, with many of the operational decisions based on discharge targets as opposed to stage. Measurement of discharge at the Tarbert Landing, Mississippi range provides critical information used in operational decisions for the floodways located in Louisiana. Historically, discharge measurements have been made using a Price AA current meter and the mid-section method, and a long record exists based on these types of measurements, including historical peak discharges. Discharge measurements made using an acoustic Doppler current profiler from a moving boat have been incorporated into the record since the mid 1990's, and are used along with the Price AA mid-section measurements. During the 2011 flood event, both methods were used and appeared to provide different results at times. The apparent differences between the measurement techniques are due to complex hydrodynamics at this location that created large spatial and temporal fluctuations in the flow. The data and analysis presented herein show the difference between the two methods to be within the expected accuracy of the measurements when the measurements are made concurrently. The observed fluctuations prevent valid comparisons of data collected sequentially or even with different observation durations.

The Relationships Between ELM Suppression, Pedestal Profiles, and Lithium Wall Coatings in NSTX

DOE Office of Scientific and Technical Information (OSTI.GOV)

D.P. Boyle, R. Maingi, P.B. Snyder, J. Manickam, T.H. Osborne, R.E. Bell, B.P. LeBlanc, and the NSTX Team

2012-08-17

Recently in the National Spherical Torus Experiment (NSTX), increasing lithium wall coatings suppressed edge localized modes (ELMs), gradually but not quite monotonically. This work details profile and stability analysis as ELMs disappeared throughout the lithium scan. While the quantity of lithium deposited between discharges did not uniquely determine the presence of ELMs, profile analysis demonstrated that lithium was correlated to wider density and pressure pedestals with peak gradients farther from the separatrix. Moreover, the ELMy and ELM-free discharges were cleanly separated by their density and pedestal widths and peak gradient locations. Ultimately, ELMs were only suppressed when lithium caused themore » density pedestal to widen and shift inward. These changes in the density gradient were directly reflected in the pressure gradient and calculated bootstrap current. This supports the theory that ELMs in NSTX are caused by peeling and/or ballooning modes, as kink/peeling modes are stabilized when the edge current and pressure gradient shift away from the separatrix. Edge stability analysis using ELITE corroborated this picture, as reconstructed equilibria from ELM-free discharges were generally farther from their kink/peeling stability boundaries than ELMy discharges. We conclude that density profile control provided by lithium is the key first step to ELM suppression in NSTX« less

The relationships between edge localized modes suppression, pedestal profiles and lithium wall coatings in NSTX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyle, D. P.; Maingi, R.; Snyder, P. B.

2011-01-01

Recently in the National Spherical Torus Experiment (NSTX), increasing lithium wall coatings suppressed edge localized modes (ELMs), gradually but not quite monotonically. This work details profile and stability analysis as ELMs disappeared throughout the lithium scan. While the quantity of lithium deposited between discharges did not uniquely determine the presence of ELMs, profile analysis demonstrated that lithium was correlated with wider density and pressure pedestals with peak gradients farther from the separatrix. Moreover, the ELMy and ELM-free discharges were cleanly separated by their density and pedestal widths and peak gradient locations. Ultimately, ELMs were only suppressed when lithium caused themore » density pedestal to widen and shift inward. These changes in the density gradient were directly reflected in the pressure gradient and calculated bootstrap current. This supports the theory that ELMs in NSTX are caused by peeling and/or ballooning modes, as kink/peeling modes are stabilized when the edge current and pressure gradient shift away from the separatrix. Edge stability analysis using ELITE corroborated this picture, as reconstructed equilibria from ELM-free discharges were generally farther from their kink/peeling stability boundaries than ELMy discharges. We conclude that density profile control provided by lithium is the key first step to ELM suppression in NSTX.« less

Evaluation of Acoustic Doppler Current Profiler to Measure Discharge at New York Power Authority's Niagara Power Project, Niagara Falls, New York

USGS Publications Warehouse

Zajd, Henry J.

2007-01-01

The need for accurate real-time discharge in the International Niagara River hydro power system requires reliable, accurate and reproducible data. The U.S. Geological Survey has been widely using Acoustic Doppler Current Profilers (ADCP) to accurately measure discharge in riverine channels since the mid-1990s. The use of the ADCP to measure discharge has remained largely untested at hydroelectric-generation facilities such as the New York Power Authority's (NYPA) Niagara Power Project in Niagara Falls, N.Y. This facility has a large, engineered diversion channel with the capacity of high volume discharges in excess of 100,000 cubic feet per second (ft3/s). Facilities such as this could benefit from the use of an ADCP, if the ADCP discharge measurements prove to be more time effective and accurate than those obtained from the flow-calculation techniques that are currently used. Measurements of diversion flow by an ADCP in the 'Pant Leg' diversion channel at the Niagara Power Project were made on November 6, 7, and 8, 2006, and compared favorably (within 1 percent) with those obtained concurrently by a conventional Price-AA current-meter measurement during one of the ADCP measurement sessions. The mean discharge recorded during each 2-hour individual ADCP measurement session compared favorably with (3.5 to 6.8 percent greater than) the discharge values computed by the flow-calculation method presently in use by NYPA. The use of ADCP technology to measure discharge could ultimately permit increased power-generation efficiency at the NYPA Niagara Falls Power Project by providing improved predictions of the amount of water (and thus the power output) available.

Feedback control of the lower hybrid power deposition profile on Tore Supra

NASA Astrophysics Data System (ADS)

Barana, O.; Mazon, D.; Laborde, L.; Turco, F.

2007-07-01

The Tore Supra facility is well suited to study ITER relevant topics such as the real-time control of plasma current and the sustaining of steady-state discharges. This work describes a tool that was recently developed and implemented on Tore Supra to control in real time, by means of the direct knowledge of the suprathermal electron local emission profile, the width of the lower hybrid power deposition profile. This quantity can be considered to some extent equivalent to the width of the plasma current density profile in case of fully non-inductive discharges. This system takes advantage of an accurate hard x-ray diagnostics, of an efficient lower hybrid additional heating and of a reliable real-time communication network. The successful experiments carried out to test the system employed, as actuators, the parallel refractive index n// and the total power PLH. The control of the suprathermal electron local emission profile through n// was also integrated with the feedback control of the total plasma current IP with PLH and of the loop voltage Vloop with the central solenoid flux. These results demonstrate that the system is robust, reliable and able to counterbalance destabilizing events. This tool can be effectively used in the future in fully non-inductive discharges to improve the MHD stability and to maintain internal transport barriers or lower hybrid enhanced performance modes. The real-time control of the lower hybrid power deposition profile could also be used in conjunction with the electron-cyclotron radiofrequency heating for synergy studies.

Consistent and efficient processing of ADCP streamflow measurements

USGS Publications Warehouse

Mueller, David S.; Constantinescu, George; Garcia, Marcelo H.; Hanes, Dan

2016-01-01

The use of Acoustic Doppler Current Profilers (ADCPs) from a moving boat is a commonly used method for measuring streamflow. Currently, the algorithms used to compute the average depth, compute edge discharge, identify invalid data, and estimate velocity and discharge for invalid data vary among manufacturers. These differences could result in different discharges being computed from identical data. Consistent computational algorithm, automated filtering, and quality assessment of ADCP streamflow measurements that are independent of the ADCP manufacturer are being developed in a software program that can process ADCP moving-boat discharge measurements independent of the ADCP used to collect the data.

Edge Stability and Performance of the ELM-Free Quiescent H-Mode and the Quiescent Double Barrier Mode on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, W P; Burrell, K H; Casper, T A

2004-12-03

The quiescent H (QH) mode, an edge localized mode (ELM)-free, high-confinement mode, combines well with an internal transport barrier to form quiescent double barrier (QDB) stationary state, high performance plasmas. The QH-mode edge pedestal pressure is similar to that seen in ELMing phases of the same discharge, with similar global energy confinement. The pedestal density in early ELMing phases of strongly pumped counter injection discharges drops and a transition to QH-mode occurs, leading to lower calculated edge bootstrap current. Plasmas current ramp experiment and ELITE code modeling of edge stability suggest that QH-modes lie near an edge current stability boundary.more » At high triangularity, QH-mode discharges operate at higher pedestal density and pressure, and have achieved ITER level values of {beta}{sub PED} and {nu}*. The QDB achieves performance of {alpha}{sub N}H{sub 89} {approx} 7 in quasi-stationary conditions for a duration of 10 tE, limited by hardware. Recently we demonstrated stationary state QDB discharges with little change in kinetic and q profiles (q{sub 0} > 1) for 2 s, comparable to ELMing ''hybrid scenarios'', yet without the debilitating effects of ELMs. Plasma profile control tools, including electron cyclotron heating and current drive and neutral beam heating, have been demonstrated to control simultaneously the q profile development, the density peaking, impurity accumulation and plasma beta.« less

Transport simulation of EAST long-pulse H-mode discharge with integrated modeling

NASA Astrophysics Data System (ADS)

Wu, M. Q.; Li, G. Q.; Chen, J. L.; Du, H. F.; Gao, X.; Ren, Q. L.; Li, K.; Chan, Vincent; Pan, C. K.; Ding, S. Y.; Jian, X.; Zhu, X.; Lian, H.; Qian, J. P.; Gong, X. Z.; Zang, Q.; Duan, Y. M.; Liu, H. Q.; Lyu, B.

2018-04-01

In the 2017 EAST experimental campaign, a steady-state long-pulse H-mode discharge lasting longer than 100 s has been obtained using only radio frequency heating and current drive, and the confinement quality is slightly better than standard H-mode, H98y2 ~ 1.1, with stationary peaked electron temperature profiles. Integrated modeling of one long-pulse H-mode discharge in the 2016 EAST experimental campaign has been performed with equilibrium code EFIT, and transport codes TGYRO and ONETWO under integrated modeling framework OMFIT. The plasma current is fully-noninductively driven with a combination of ~2.2 MW LHW, ~0.3 MW ECH and ~1.1 MW ICRF. Time evolution of the predicted electron and ion temperature profiles through integrated modeling agree closely with that from measurements. The plasma current (I p ~ 0.45 MA) and electron density are kept constantly. A steady-state is achieved using integrated modeling, and the bootstrap current fraction is ~28%, the RF drive current fraction is ~72%. The predicted current density profile matches the experimental one well. Analysis shows that electron cyclotron heating (ECH) makes large contribution to the plasma confinement when heating in the core region while heating in large radius does smaller improvement, also a more peaked LHW driven current profile is got when heating in the core. Linear analysis shows that the high-k modes instability (electron temperature gradient driven modes) is suppressed in the core region where exists weak electron internal transport barriers. The trapped electron modes dominates in the low-k region, which is mainly responsible for driving the electron energy flux. It is found that the ECH heating effect is very local and not the main cause to sustained the good confinement, the peaked current density profile has the most important effect on plasma confinement improvement. Transport analysis of the long-pulse H-mode experiments on EAST will be helpful to build future experiments.

River Discharge and Bathymetry Estimation from Hydraulic Inversion of Surface Currents and Water Surface Elevation Observations

NASA Astrophysics Data System (ADS)

Simeonov, J.; Holland, K. T.

2015-12-01

We developed an inversion model for river bathymetry and discharge estimation based on measurements of surface currents, water surface elevation and shoreline coordinates. The model uses a simplification of the 2D depth-averaged steady shallow water equations based on a streamline following system of coordinates and assumes spatially uniform bed friction coefficient and eddy viscosity. The spatial resolution of the predicted bathymetry is related to the resolution of the surface currents measurements. The discharge is determined by minimizing the difference between the predicted and the measured streamwise variation of the total head. The inversion model was tested using in situ and remote sensing measurements of the Kootenai River east of Bonners Ferry, ID. The measurements were obtained in August 2010 when the discharge was about 223 m3/s and the maximum river depth was about 6.5 m. Surface currents covering a 10 km reach with 8 m spatial resolution were estimated from airborne infrared video and were converted to depth-averaged currents using acoustic Doppler current profiler (ADCP) measurements along eight cross-stream transects. The streamwise profile of the water surface elevation was measured using real-time kinematic GPS from a drifting platform. The value of the friction coefficient was obtained from forward calibration simulations that minimized the difference between the predicted and measured velocity and water level along the river thalweg. The predicted along/cross-channel water depth variation was compared to the depth measured with a multibeam echo sounder. The rms error between the measured and predicted depth along the thalweg was found to be about 60cm and the estimated discharge was 5% smaller than the discharge measured by the ADCP.

Characterization of Downstream Ion Energy Distributions From a High Current Hollow Cathode in a Ring Cusp Discharge Chamber

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

2003-01-01

The presence of energetic ions produced by a hollow cathodes operating at high emission currents (greater than 10 Angstroms) has been documented in the literature. As part of an ongoing effort to uncover the underlying physics of the formation of these ions, ion efflux from a high current hollow cathode operating in an ion thruster discharge chamber was investigated. Using a spherical sector electrostatic energy analyzer located downstream of the discharge cathode, the ion energy distribution over a 0 to 60 eV energy range was measured. The sensitivity of the ion energy distribution function to zenith angle was also assessed at 3 different positions: 0, 15, and 25 degrees. The measurements suggest that the majority of the ion current at the measuring point falls into the analyzer with an energy approximately equal to the discharge voltage. The ion distribution, however, was found to be quite broad. The high energy tail of the distribution function tended to grow with increasing discharge current. Sensitivity of the profiles to flow rate at fixed discharge current was also investigated. A simple model is presented that provides a potential mechanism for the production of ions with energies above the discharge voltage.

Laboratory facility for testing electric-vehicle batteries Test rig for simulating duty cycles with different discharge modes

NASA Astrophysics Data System (ADS)

Hamilton, J. A.; Rand, D. A. J.

1983-03-01

A test rig has been designed and constructed to examine the performance of batteries under laboratory conditions that simulate the power characteristics of electric vehicles. Each station in the rig subjects a battery to continuous charge/discharge cycles, with an equalising charge every eighth cycle. The battery discharge follows the current-verse-time profile of a given vehicle operating under a driving schedule normal to road service. The test rig allows both smooth- and pulsed-current discharge to be investigated. Data collection is accomplished either with multi-pen recorders or with a computer-based information logger.

Steady state scenario development with elevated minimum safety factor on DIII-D

DOE PAGES

Holcomb, Christopher T.; Ferron, John R.; Luce, Timothy C.; ...

2014-08-15

On DIII-D, a high β scenario with minimum safety factor (q min) near 1.4 has been optimized with new tools and shown to be a favourable candidate for long pulse or steady state operation in future devices. Furthermore, the new capability to redirect up to 5 MW of neutral beam injection (NBI) from on- to off-axis improves the ability to sustain elevated q min with a less peaked pressure profile. The observed changes increase the ideal magnetohydrodynamics (MHD) n = 1 mode β N limit thus providing a path forward for increasing the noninductive current drive fraction by operating atmore » high β N. Quasi-stationary discharges free of tearing modes have been sustained at βN = 3.5 and β T = 3.6% for two current profile diffusion timescales (about 3 s) limited by neutral beam duration. The discharge performance has normalized fusion performance expected to give fusion gain Q ≈ 5 in a device the size of ITER. Analysis of the poloidal flux evolution and current drive balance show that the loop voltage profile is almost relaxed even with 25% of the current driven inductively, and q min remains elevated near 1.4. Our observations increase confidence that the current profile will not evolve to one unstable to a tearing mode. In preliminary tests a divertor heat flux reduction technique based on producing a radiating mantle with neon injection appears compatible with this operating scenario. 0D model extrapolations suggest it may be possible to push this scenario up to 100% noninductive current drive by raising β N. Similar discharges with q min = 1.5–2 were susceptible to tearing modes and off-axis fishbones, and with q min > 2 lower normalized global energy confinement time is observed.« less

Experiments and Simulations of ITER-like Plasmas in Alcator C-Mod

DOE Office of Scientific and Technical Information (OSTI.GOV)

.R. Wilson, C.E. Kessel, S. Wolfe, I.H. Hutchinson, P. Bonoli, C. Fiore, A.E. Hubbard, J. Hughes, Y. Lin, Y. Ma, D. Mikkelsen, M. Reinke, S. Scott, A.C.C. Sips, S. Wukitch and the C-Mod Team

Alcator C-Mod is performing ITER-like experiments to benchmark and verify projections to 15 MA ELMy H-mode Inductive ITER discharges. The main focus has been on the transient ramp phases. The plasma current in C-Mod is 1.3 MA and toroidal field is 5.4 T. Both Ohmic and ion cyclotron (ICRF) heated discharges are examined. Plasma current rampup experiments have demonstrated that (ICRF and LH) heating in the rise phase can save voltseconds (V-s), as was predicted for ITER by simulations, but showed that the ICRF had no effect on the current profile versus Ohmic discharges. Rampdown experiments show an overcurrent inmore » the Ohmic coil (OH) at the H to L transition, which can be mitigated by remaining in H-mode into the rampdown. Experiments have shown that when the EDA H-mode is preserved well into the rampdown phase, the density and temperature pedestal heights decrease during the plasma current rampdown. Simulations of the full C-Mod discharges have been done with the Tokamak Simulation Code (TSC) and the Coppi-Tang energy transport model is used with modified settings to provide the best fit to the experimental electron temperature profile. Other transport models have been examined also. __________________________________________________« less

Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge

NASA Technical Reports Server (NTRS)

Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

2007-01-01

The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakami, S.; Ohno, N.; Shibata, Y.

2013-11-15

According to an early work [Y. Shibata et al., Nucl. Fusion 50, 025015 (2010)] on the behavior of the plasma current decay in the JT-60U disruptive discharges caused by the radiative collapse with a massive neon-gas-puff, the increase of the internal inductance mainly determined the current decay time of plasma current during the initial phase of current quench. To investigate what determines the increase of the internal inductance, we focus attention on the relationship between the electron temperature (or the resistivity) profile and the time evolution of the current density profile and carry out numerical calculations. As a result, wemore » find the reason of the increase of the internal inductance: The current density profile at the start of the current quench is broader than an expected current density profile in the steady state, which is determined by the temperature (or resistivity) profile. The current density profile evolves into peaked one and the internal inductance is increasing.« less

Transport modeling of L- and H-mode discharges with LHCD on EAST

NASA Astrophysics Data System (ADS)

Li, M. H.; Ding, B. J.; Imbeaux, F.; Decker, J.; Zhang, X. J.; Kong, E. H.; Zhang, L.; Wei, W.; Shan, J. F.; Liu, F. K.; Wang, M.; Xu, H. D.; Yang, Y.; Peysson, Y.; Basiuk, V.; Artaud, J.-F.; Yuynh, P.; Wan, B. N.

2013-04-01

High-confinement (H-mode) discharges with lower hybrid current drive (LHCD) as the only heating source are obtained on EAST. In this paper, an empirical transport model of mixed Bohm/gyro-Bohm for electron and ion heat transport was first calibrated against a database of 3 L-mode shots on EAST. The electron and ion temperature profiles are well reproduced in the predictive modeling with the calibrated model coupled to the suite of codes CRONOS. CRONOS calculations with experimental profiles are also performed for electron power balance analysis. In addition, the time evolutions of LHCD are calculated by the C3PO/LUKE code involving current diffusion, and the results are compared with experimental observations.

Modifications to the edge current profile with auxiliary edge current drive and improved confinement in a reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, B.E.; Biewer, T.M.; Chattopadhyay, P.K.

2000-09-01

Auxiliary edge current drive is routinely applied in the Madison Symmetric Torus [R.N. Dexter, D. W. Kerst, T.W. Lovell et.al., Fusion Technol. 19, 131 (1991)] with the goal of modifying the parallel current profile to reduce current- driven magnetic fluctuations and the associated particle and energy transport. Provided by an inductive electric field, the current drive successfully reduces energy transport. First-time measurements of the modified edge current profile reveal that, relative to discharges without auxiliary current drive, the edge current density decreases. This decrease is explicable in terms of newly measured reductions in the dynamo (fluctuation-based) electric field and themore » electrical conductivity. Induced by the current drive, these two changes to the edge plasma play as much of a role in determining the resultant edge current profile as does the current drive itself.« less

General field and office procedures for indirect discharge measurements

USGS Publications Warehouse

Benson, M.A.; Dalrymple, Tate

2001-04-01

The discharge of streams is usually measured by the current-meter method. During flood periods, however, it is frequently impossible or impractical to measure the discharges by this method when they occur. Consequently, many peak discharges must be determined after the passage of the flood by indirect methods, such as slope-area, contracted-opening, flow-over-dam, and flow-through-culvert, rather than by direct current-meter measurement. Indirect methods of determining peak discharge are based on hydraulic equations which relate the discharge to the water-surface profile and the geometry of the channel. A field survey is made after the flood to determine the location and elevation of high-water marks and the characteristics of the channel. Detailed descriptions of the general procedures used in collecting the field data and in computing the discharge are given in this report. Each of the methods requires special procedures described in subsequent chapters.

Acceleration processes in the quasi-steady magnetoplasmadynamic discharge. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Boyle, M. J.

1974-01-01

The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.

Pulsed glow discharge enables direct mass spectrometric measurement of fluorine in crystal materials - Fluorine quantification and depth profiling in fluorine doped potassium titanyl phosphate

NASA Astrophysics Data System (ADS)

Bodnar, Victoria; Ganeev, Alexander; Gubal, Anna; Solovyev, Nikolay; Glumov, Oleg; Yakobson, Viktor; Murin, Igor

2018-07-01

A pulsed direct current glow discharge time-of-flight mass spectrometry (GD TOF MS) method for the quantification of fluorine in insoluble crystal materials with fluorine doped potassium titanyl phosphate (KTP) KTiOPO4:KF as an example has been proposed. The following parameters were optimized: repelling pulse delay, discharge duration, discharge voltage, and pressure in the discharge cell. Effective ionization of fluorine in the space between sampler and skimmer under short repelling pulse delay, related to the high-energy electron impact at the discharge front, has been demonstrated. A combination of instrumental and mathematical correction approaches was used to cope for the interferences of 38Ar2+ and 1H316O + on 19F+. To maintain surface conductivity in the dielectric KTP crystals and insure its effective sputtering in combined hollow cathode cell, silver suspension applied by the dip-coating method was employed. Fluorine quantification was performed using relative sensitivity factors. The analysis of a reference material and scanning electron microscope-energy dispersive X-ray spectroscopy was used for validation. Fluorine limit of detection by pulsed direct current GD TOF MS was 0.01 mass%. Real sample analysis showed that fluorine seems to be inhomogeneously distributed in the crystals. That is why depth profiling of F, K, O, and P was performed to evaluate the crystals' non-stoichiometry. The approaches designed allow for fluorine quantification in insoluble dielectric materials with minimal sample preparation and destructivity as well as performing depth profiling to assess crystal non-stoichiometry.

Comparison of bottom-track to global positioning system referenced discharges measured using an acoustic Doppler current profiler

USGS Publications Warehouse

Wagner, Chad R.; Mueller, David S.

2011-01-01

A negative bias in discharge measurements made with an acoustic Doppler current profiler (ADCP) can be caused by the movement of sediment on or near the streambed. The integration of a global positioning system (GPS) to track the movement of the ADCP can be used to avoid the systematic negative bias associated with a moving streambed. More than 500 discharge transects from 63 discharge measurements with GPS data were collected at sites throughout the US, Canada, and New Zealand with no moving bed to compare GPS and bottom-track-referenced discharges. Although the data indicated some statistical bias depending on site conditions and type of GPS data used, these biases were typically about 0.5% or less. An assessment of differential correction sources was limited by a lack of data collected in a range of different correction sources and different GPS receivers at the same sites. Despite this limitation, the data indicate that the use of Wide Area Augmentation System (WAAS) corrected positional data is acceptable for discharge measurements using GGA as the boat-velocity reference. The discharge data based on GPS-referenced boat velocities from the VTG data string, which does not require differential correction, were comparable to the discharges based on GPS-referenced boat velocities from the differentially-corrected GGA data string. Spatial variability of measure discharges referenced to GGA, VTG and bottom-tracking is higher near the channel banks. The spatial variability of VTG-referenced discharges is correlated with the spatial distribution of maximum Horizontal Dilution of Precision (HDOP) values and the spatial variability of GGA-referenced discharges is correlated with proximity to channel banks.

Field evaluation of shallow-water acoustic doppler current profiler discharge measurements

USGS Publications Warehouse

Rehmel, M.S.

2007-01-01

In 2004, the U.S. Geological Survey (USGS) Office of Surface Water staff and USGS Water Science employees began testing the StreamPro, an acoustic Doppler current profiler (ADCP) for shallow-water discharge measurements. Teledyne RD Instruments introduced the StreamPro in December of 2003. The StreamPro is designed to make a "moving boat" discharge measurement in streams with depths between 0.15 and 2 m. If the StreamPro works reliably in these conditions, it will allow for use of ADCPs in a greater number of streams than previously possible. Evaluation sites were chosen to test the StreamPro over a range of conditions. Simultaneous discharge measurements with mechanical and other acoustic meters, along with stable rating curves at established USGS streamflow-gaging stations, were used for comparisons. The StreamPro measurements ranged in mean velocity from 0.076 to 1.04 m/s and in discharge from 0.083 m 3/s to 43.4 m 3/s. Tests indicate that discharges measured with the StreamPro compare favorably to the discharges measured with the other meters when the mean channel velocity is greater than 0.25 m/s. When the mean channel velocity is less than 0.25 m/s, the StreamPro discharge measurements for individual transects have greater variability than those StreamPro measurements where the mean channel velocity is greater than 0.25 m/s. Despite this greater variation in individual transects, there is no indication that the StreamPro measured discharges (the mean discharge for all transects) are biased, provided that enough transects are used to determine the mean discharge. ?? 2007 ASCE.

Measuring discharge with acoustic Doppler current profilers from a moving boat

USGS Publications Warehouse

Mueller, David S.; Wagner, Chad R.; Rehmel, Michael S.; Oberg, Kevin A.; Rainville, Francois

2013-01-01

The use of acoustic Doppler current profilers (ADCPs) from a moving boat is now a commonly used method for measuring streamflow. The technology and methods for making ADCP-based discharge measurements are different from the technology and methods used to make traditional discharge measurements with mechanical meters. Although the ADCP is a valuable tool for measuring streamflow, it is only accurate when used with appropriate techniques. This report presents guidance on the use of ADCPs for measuring streamflow; this guidance is based on the experience of U.S. Geological Survey employees and published reports, papers, and memorandums of the U.S. Geological Survey. The guidance is presented in a logical progression, from predeployment planning, to field data collection, and finally to post processing of the collected data. Acoustic Doppler technology and the instruments currently (2013) available also are discussed to highlight the advantages and limitations of the technology. More in-depth, technical explanations of how an ADCP measures streamflow and what to do when measuring in moving-bed conditions are presented in the appendixes. ADCP users need to know the proper procedures for measuring discharge from a moving boat and why those procedures are required, so that when the user encounters unusual field conditions, the procedures can be adapted without sacrificing the accuracy of the streamflow-measurement data.

Modifications to the edge current profile with auxiliary edge current drive and improved confinement in a reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, B. E.; Biewer, T. M.; Chattopadhyay, P. K.

2000-09-01

Auxiliary edge current drive is routinely applied in the Madison Symmetric Torus [R. N. Dexter, D. W. Kerst, T. W. Lovell et al., Fusion Technol. 19, 131 (1991)] with the goal of modifying the parallel current profile to reduce current-driven magnetic fluctuations and the associated particle and energy transport. Provided by an inductive electric field, the current drive successfully reduces fluctuations and transport. First-time measurements of the modified edge current profile reveal that, relative to discharges without auxiliary current drive, the edge current density decreases. This decrease is explicable in terms of newly measured reductions in the dynamo (fluctuation-based) electricmore » field and the electrical conductivity. Induced by the current drive, these two changes to the edge plasma play as much of a role in determining the resultant edge current profile as does the current drive itself. (c) 2000 American Institute of Physics.« less

Modeling of the control of the driven current profile in ICRF MCCD on EAST plasma

NASA Astrophysics Data System (ADS)

Yin, L.; Yang, C.; Gong, X. Y.; Lu, X. Q.; Cao, J. J.; Wu, Z. Y.; Chen, Y.; Du, D.

2018-05-01

Control of the current profile is a crucial issue for improved confinement and the inhibition of instability in advanced tokamak operation. Using typical discharge data for the Experimental Advanced Superconducting Tokamak, numerical simulations of driven-current profile control in mode conversion current drive (MCCD) in the ion cyclotron range of frequencies were performed employing a full-wave method and Ehst-Karney efficiency formula. Results indicate that the driven current profile in MCCD can be effectively modified by shifting the mode conversion layer. The peak of the driven current can be located at an aimed position in the normalized minor radius range (-0.60 ≤r/a≤0) by changing the radiofrequency and the minority-ion concentration. The efficiency of the off-axis MCCD can reach 233 kA/MW through optimization, and the mode converted ion cyclotron wave plays an important role in such scenarios. The effects of electron temperature and plasma density on the driven current profile are also investigated.

Wave-driven fluxes through New River Inlet, NC

NASA Astrophysics Data System (ADS)

Wargula, A.; Raubenheimer, B.; Elgar, S.

2012-12-01

The importance of wave forcing to inlet circulation is examined using observations of waves, water levels, and currents collected in and near New River Inlet, NC during April and May, 2012. A boat-mounted system was used to measure current profiles along transects across the inlet mouth during three 14-hr periods, providing information on cross-inlet current structure, as well as discharge. Additionally, an array of 13 colocated pressure gages and profilers were deployed along 2 km of the inlet channel (5 to 10 m water depths) and ebb shoal channel (2 to 3 m water depths) and 19 colocated pressure gages and acoustic Doppler velocimeters were deployed across and offshore of the ebb shoal (1 to 5 m water depths) (Figure 1). The inlet is well mixed and tidal currents ranged from +/- 1.5 m/s, maximum discharge rates at peak ebb and flood were about 700 to 900 m3/s, offshore significant wave heights Hsig were 0.5 to 2.5 m, and wind speeds ranged from 0 to 14 m/s. Time-integrated residual discharge over semi-diurnal tidal cycles with similar ranges was ebb dominant during calm conditions (May 11, net out-of-inlet discharge ~ 55 m3, Hsig ~ 0.5 m, NW winds ~ 3 m/s) and flood dominant during stormier conditions (May 14, net into-inlet discharge ~ 15 m3, Hsig ~ 1.2 m, S winds ~ 6.5 m/s). Low-pass filtered in situ profiler data suggest wave-forcing affects the fluxes into and out of the inlet. The observations will be used to examine the momentum balance governing the temporal and cross-inlet (channel vs. shoal) variation of these fluxes, as well as the effect of waves on ebb and flood flow dominance. Funding provided by the Office of Naval Research and a National Security Science and Engineering Faculty Fellowship.; Figure 1: Google Earth image of New River Inlet, NC. Colors are depth contours (scale on the right, units are m relative to mean sea level) and symbols are locations of colocated current meters and pressure gages.

Conducting wall Hall thrusters in magnetic shielding and standard configurations

NASA Astrophysics Data System (ADS)

Grimaud, Lou; Mazouffre, Stéphane

2017-07-01

Traditional Hall thrusters are fitted with boron nitride dielectric discharge channels that confine the plasma discharge. Wall properties have significant effects on the performances and stability of the thrusters. In magnetically shielded thrusters, interactions between the plasma and the walls are greatly reduced, and the potential drop responsible for ion acceleration is situated outside the channel. This opens the way to the utilization of alternative materials for the discharge channel. In this work, graphite walls are compared to BN-SiO2 walls in the 200 W magnetically shielded ISCT200-MS and the unshielded ISCT200-US Hall thrusters. The magnetically shielded thruster shows no significant change in the discharge current mean value and oscillations, while the unshielded thruster's discharge current increases by 25% and becomes noticeably less stable. The electric field profile is also investigated through laser spectroscopy, and no significant difference is recorded between the ceramic and graphite cases for the shielded thruster. The unshielded thruster, on the other hand, has its acceleration region shifted 15% of the channel length downstream. Lastly, the plume profile is measured with planar probes fitted with guard rings. Once again the material wall has little influence on the plume characteristics in the shielded thruster, while the unshielded one is significantly affected.

Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

NASA Astrophysics Data System (ADS)

Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; Park, G. Y.; Snyder, P. B.; Chang, C. S.

2017-06-01

The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. The neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] is used in carrying out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. Simulations with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. However, the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.

Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

DOE PAGES

Pankin, A. Y.; Rafiq, T.; Kritz, A. H.; ...

2017-06-08

The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulationsmore » with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.« less

Investigation of the plasma shaping effects on the H-mode pedestal structure using coupled kinetic neoclassical/MHD stability simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pankin, A. Y.; Rafiq, T.; Kritz, A. H.

The effects of plasma shaping on the H-mode pedestal structure are investigated. High fidelity kinetic simulations of the neoclassical pedestal dynamics are combined with the magnetohydrodynamic (MHD) stability conditions for triggering edge localized mode (ELM) instabilities that limit the pedestal width and height in H-mode plasmas. We use the neoclassical kinetic XGC0 code [Chang et al., Phys. Plasmas 11, 2649 (2004)] to carry out a scan over plasma elongation and triangularity. As plasma profiles evolve, the MHD stability limits of these profiles are analyzed with the ideal MHD ELITE code [Snyder et al., Phys. Plasmas 9, 2037 (2002)]. In simulationsmore » with the XGC0 code, which includes coupled ion-electron dynamics, yield predictions for both ion and electron pedestal profiles. The differences in the predicted H-mode pedestal width and height for the DIII-D discharges with different elongation and triangularities are discussed. For the discharges with higher elongation, it is found that the gradients of the plasma profiles in the H-mode pedestal reach semi-steady states. In these simulations, the pedestal slowly continues to evolve to higher pedestal pressures and bootstrap currents until the peeling-ballooning stability conditions are satisfied. The discharges with lower elongation do not reach the semi-steady state, and ELM crashes are triggered at earlier times. The plasma elongation is found to have a stronger stabilizing effect than the plasma triangularity. For the discharges with lower elongation and lower triangularity, the ELM frequency is large, and the H-mode pedestal evolves rapidly. It is found that the temperature of neutrals in the scrape-off-layer (SOL) region can affect the dynamics of the H-mode pedestal buildup. But the final pedestal profiles are nearly independent of the neutral temperature. The elongation and triangularity affect the pedestal widths of plasma density and electron temperature profiles differently. This provides a new mechanism of controlling the pedestal bootstrap current and the pedestal stability.« less

Methods for accurate estimation of net discharge in a tidal channel

USGS Publications Warehouse

Simpson, M.R.; Bland, R.

2000-01-01

Accurate estimates of net residual discharge in tidally affected rivers and estuaries are possible because of recently developed ultrasonic discharge measurement techniques. Previous discharge estimates using conventional mechanical current meters and methods based on stage/discharge relations or water slope measurements often yielded errors that were as great as or greater than the computed residual discharge. Ultrasonic measurement methods consist of: 1) the use of ultrasonic instruments for the measurement of a representative 'index' velocity used for in situ estimation of mean water velocity and 2) the use of the acoustic Doppler current discharge measurement system to calibrate the index velocity measurement data. Methods used to calibrate (rate) the index velocity to the channel velocity measured using the Acoustic Doppler Current Profiler are the most critical factors affecting the accuracy of net discharge estimation. The index velocity first must be related to mean channel velocity and then used to calculate instantaneous channel discharge. Finally, discharge is low-pass filtered to remove the effects of the tides. An ultrasonic velocity meter discharge-measurement site in a tidally affected region of the Sacramento-San Joaquin Rivers was used to study the accuracy of the index velocity calibration procedure. Calibration data consisting of ultrasonic velocity meter index velocity and concurrent acoustic Doppler discharge measurement data were collected during three time periods. Two sets of data were collected during a spring tide (monthly maximum tidal current) and one of data collected during a neap tide (monthly minimum tidal current). The relative magnitude of instrumental errors, acoustic Doppler discharge measurement errors, and calibration errors were evaluated. Calibration error was found to be the most significant source of error in estimating net discharge. Using a comprehensive calibration method, net discharge estimates developed from the three sets of calibration data differed by less than an average of 4 cubic meters per second, or less than 0.5% of a typical peak tidal discharge rate of 750 cubic meters per second.

Modeling the Influence of Conductivity Profiles on Red Sprite Formation and Structure

NASA Astrophysics Data System (ADS)

Tonev, P.; Velinov, P.

Strong quasi-electrostatic fields generated in the mesosphere and lower ionosphere after a lightning discharge by a succeeding redistribution of the induced spatial charges, are considered to be responsible for red sprite generation. Factors considered here as important for sprite occurrence and size and shape are the discharge parameters and conductivity profile. Thundercloud charges are assumed to be of hundreds of Coulombs distributed within layers with a horizontal extent of tens (or hundreds) of kilometers as typical for big convective multi-cell systems. Cloud- t o -ground positive strokes, characterized by their charge moment change, are considered, and the large continuing currents are taken into account. The thermal breakdown mechanism is considered as responsible for sprite onset. The conditions under which sprites initially occur (i.e. when atmospheric parameters are not disturbed) and their spatial and temporal characteristics are studied in dependence on the conductivity profiles. A self-consistent analytical modeling is proposed for this purpose. Maxwell equations are applied under quasi-electrostatic conditions, when magnetic field component is neglected and the electric field is assumed to be a potential one. The features of a lightning discharge as well as of conductivity profiles (including the slight anisotropy in lower ionosphere) are taken into account in the model. The conductivity profiles are approximated between 0 and 100 km by stepwise profiles, defined on layered atmosphere with ~100 layers. Horizontal conductivity variations occurring at sprite heights (50-90 km) due to electron heating and ionization are represented in the model by a stepped functions in each layer. Continuity of the electrical current density component normal to each sector boundary is required. Results obtained show that for sprite occurrence in daytime conditions larger lightning charge moment change of the parent discharge is needed and sprites are lower localized than at night. The question is studied under what conditions (concerning the discharge and conductivity parameters) the presence of a `ledge' in the conductivity profile in lower ionosphere can influence the occurrence of a diffuse upper portion of a sprite observed [Barrington-Leigh C.P. and U.S.Inan, Identification of sprites and elves with intensified video and broadband array photometry, J.geophys.Res., 106, A2, 1741-1750, 2001]. Conditions under which features of this diffuse structure can be influenced also by anisotropy in this region, and thus can depend on the local magnetic field orientation, are investigated.

Magnetic flux pumping mechanism prevents sawtoothing in 3D nonlinear MHD simulations of tokamak plasmas

NASA Astrophysics Data System (ADS)

Krebs, Isabel; Jardin, Stephen C.; Guenter, Sibylle; Lackner, Karl; Hoelzl, Matthias; Strumberger, Erika; Ferraro, Nate

2017-10-01

3D nonlinear MHD simulations of tokamak plasmas have been performed in toroidal geometry by means of the high-order finite element code M3D-C1. The simulations are set up such that the safety factor on axis (q0) is driven towards values below unity. As reported in and the resulting asymptotic states either exhibit sawtooth-like reconnection cycling or they are sawtooth-free. In the latter cases, a self-regulating magnetic flux pumping mechanism, mainly provided by a saturated quasi-interchange instability via a dynamo effect, redistributes the central current density so that the central safety factor profile is flat and q0 1 . Sawtoothing is prevented if β is sufficiently high to allow for the necessary amount of flux pumping to counterbalance the tendency of the current density profile to centrally peak. We present the results of 3D nonlinear simulations based on specific types of experimental discharges and analyze their asymptotic behavior. A set of cases is presented where aspects of the current ramp-up phase of Hybrid ASDEX Upgrade discharges are mimicked. Another set of simulations is based on low-qedge discharges in DIII-D.

Visualizing flow fields using acoustic Doppler current profilers and the Velocity Mapping Toolbox

USGS Publications Warehouse

Jackson, P. Ryan

2013-01-01

The purpose of this fact sheet is to provide examples of how the U.S. Geological Survey is using acoustic Doppler current profilers for much more than routine discharge measurements. These instruments are capable of mapping complex three-dimensional flow fields within rivers, lakes, and estuaries. Using the Velocity Mapping Toolbox to process the ADCP data allows detailed visualization of the data, providing valuable information for a range of studies and applications.

Electron Temperature Evolution During Local Helicity Injection on the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Schlossberg, D. J.; Barr, J. L.; Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Rodriguez Sanchez, C.

2016-10-01

Understanding the electron temperature (Te) evolution during local helicity injection (LHI) is critical for scaling up this non-solenoidal startup technique to MA-class devices. The first comprehensive Te measurements during LHI reveal centrally-peaked profiles with Te > 100 eV for plasma current Ip > 120 kA, toroidal field 0.15 T, and electron density ne 1019 m-3. Te rises and is sustained from just after magnetic relaxation through the plasma decoupling from edge-localized injectors. Results are presented for two injector edge locations: outboard midplane and inboard divertor. Outboard midplane injection couples LHI with inductive drive from poloidal field ramps and radial compression during inward plasma growth. Comparisons of Te at different LHI-to-inductive drive ratios show some profile flattening for higher LHI drive fraction. The latter, constant-shape discharges were necessarily lower performance, with Ip 50 kA and reduced Te , max. Inboard divertor injection achieves higher Ip using minimal inductive drive and thus isolates effects of LHI drive on Te. Initial results in this configuration show Te rising rapidly at the injector location as the discharge grows, settling to a roughly flat profile 100 eV. Thus far, both scenarios provide relatively stable discharges with moderate ne and high-Te, suitable for coupling to auxiliary current drive. Detailed studies of confinement dynamics and discharge optimization are planned for the near future. Work supported by US DOE Grant DE-FG02-96ER54375.

Prerequisites for Accurate Monitoring of River Discharge Based on Fixed-Location Velocity Measurements

NASA Astrophysics Data System (ADS)

Kästner, K.; Hoitink, A. J. F.; Torfs, P. J. J. F.; Vermeulen, B.; Ningsih, N. S.; Pramulya, M.

2018-02-01

River discharge has to be monitored reliably for effective water management. As river discharge cannot be measured directly, it is usually inferred from the water level. This practice is unreliable at places where the relation between water level and flow velocity is ambiguous. In such a case, the continuous measurement of the flow velocity can improve the discharge prediction. The emergence of horizontal acoustic Doppler current profilers (HADCPs) has made it possible to continuously measure the flow velocity. However, the profiling range of HADCPs is limited, so that a single instrument can only partially cover a wide cross section. The total discharge still has to be determined with a model. While the limitations of rating curves are well understood, there is not yet a comprehensive theory to assess the accuracy of discharge predicted from velocity measurements. Such a theory is necessary to discriminate which factors influence the measurements, and to improve instrument deployment as well as discharge prediction. This paper presents a generic method to assess the uncertainty of discharge predicted from range-limited velocity profiles. The theory shows that a major source of error is the variation of the ratio between the local and cross-section-averaged velocity. This variation is large near the banks, where HADCPs are usually deployed and can limit the advantage gained from the velocity measurement. We apply our theory at two gauging stations situated in the Kapuas River, Indonesia. We find that at one of the two stations the index velocity does not outperform a simple rating curve.

Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

2015-01-01

ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the same time.

Radial scanning diagnostics of bremsstrahlung and line emission in T-10 plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemets, A. R., E-mail: Nemets-AR@nrcki.ru; Krupin, V. A.; Klyuchnikov, L. A., E-mail: lklyuchnikov@list.ru

2016-12-15

The paper describes the scanning spectroscopic diagnostics designed for measurement of line integrated plasma radiation in two visible spectral ranges. This diagnostic system is aimed at measuring the bremsstrahlung absolute values and profile with high spatial resolution. The bremsstrahlung absolute values are used to determine the value and radial distribution of effective plasma ion charge Z{sub eff}(r) in T-10 discharges. The importance of Z{sub eff} measurement is due to its strong influence on plasma heating, confinement, and stability. The spatial distribution of emission for one of the chosen spectral lines is measured simultaneously with bremsstrahlung. The spatial resolution of measurementsmore » is ~1 cm, and the temporal resolution is up to 10 ms. The spectral equipment and methods for its calibration are described. Examples of line integrated brightness distribution in a “continuum window” of 5236 ± 6 Å and brightness of the lines C{sup 5+} (5291 Å), He{sup 1+} (4686 Å), and D{sub β} (4861 Å) are given. Flattening of the bremsstrahlung brightness profile in the central region of the plasma column in some discharges with sawtooth oscillations in the T-10 is observed. The measured effective ion charge profiles in ohmic discharges with high plasma density and low discharge currents demonstrate accumulation of light impurities at the column axis; as a consequence, quenching of sawtooth oscillations in some discharges is observed. The developed diagnostics provides necessary data for investigation of heat, particle, and current transport in the plasma of the T-10. Successful application of the obtained data on Z{sub eff}(r) for investigation of geodesic acoustic modes of plasma oscillations in the T-10 should be specially noted.« less

Demonstrating the Physics Basis for the ITER 15 MA Inductive Discharge on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Kessel, C. E.; Wolfe, S. M.; Hutchinson, I. H.; Hughes, J. W.; Lin, Y.; Ma, Y.; Mikkelsen, D. R.; Poli, F.; Reinke, M. L.; Wukitch, S. J.

2012-10-01

Rampup discharges in C-Mod, matching ITE's current diffusion times show ICRF heating can save V-s but results in only weak effects on the current profile, despite strong modifications of the central electron temperature. Simulation of these discharges with TSC, and TORIC for ICRF, using multiple transport models, do not reproduce the temperature profile evolution, or the experimental internal self-inductance li, by sufficiently large amounts to be unacceptable for projections to ITER operation. For the flattop phase experiments EDA H-modes approach the ITER parameter targets of q95=3, H98=1, n/nGr=0.85, betaN=1.7, and k=1.8, and sustain them similar to a normalized ITER flattop time. The discharges show a degradation of energy confinement at higher densities, but increasing H98 with increasing net power to the plasma. For these discharges intrinsic impurities (B, Mo) provided radiated power fractions of 25-37%. Experiments show the plasma can remain in H-mode in rampdown with ICRF injection, the density will decrease with Ip while in the H-mode, and the back transition occurs when the net power reaches about half the L-H transition power. C-Mod indicates that faster rampdowns are preferable. Work supported by US Dept of Energy under DE-AC02-CH0911466 and DE-FC02-99ER54512.

Geohydrologic Investigations and Landscape Characteristics of Areas Contributing Water to Springs, the Current River, and Jacks Fork, Ozark National Scenic Riverways, Missouri

USGS Publications Warehouse

Mugel, Douglas N.; Richards, Joseph M.; Schumacher, John G.

2009-01-01

The Ozark National Scenic Riverways (ONSR) is a narrow corridor that stretches for approximately 134 miles along the Current River and Jacks Fork in southern Missouri. Most of the water flowing in the Current River and Jacks Fork is discharged to the rivers from springs within the ONSR, and most of the recharge area of these springs is outside the ONSR. This report describes geohydrologic investigations and landscape characteristics of areas contributing water to springs and the Current River and Jacks Fork in the ONSR. The potentiometric-surface map of the study area for 2000-07 shows that the groundwater divide extends beyond the surface-water divide in some places, notably along Logan Creek and the northeastern part of the study area, indicating interbasin transfer of groundwater between surface-water basins. A low hydraulic gradient occurs in much of the upland area west of the Current River associated with areas of high sinkhole density, which indicates the presence of a network of subsurface karst conduits. The results of a low base-flow seepage run indicate that most of the discharge in the Current River and Jacks Fork was from identified springs, and a smaller amount was from tributaries whose discharge probably originated as spring discharge, or from springs or diffuse groundwater discharge in the streambed. Results of a temperature profile conducted on an 85-mile reach of the Current River indicate that the lowest average temperatures were within or downstream from inflows of springs. A mass-balance on heat calculation of the discharge of Bass Rock Spring, a previously undescribed spring, resulted in an estimated discharge of 34.1 cubic feet per second (ft3/s), making it the sixth largest spring in the Current River Basin. The 13 springs in the study area for which recharge areas have been estimated accounted for 82 percent (867 ft3/s of 1,060 ft3/s) of the discharge of the Current River at Big Spring during the 2006 seepage run. Including discharge from other springs, the cumulative discharge from springs was over 90 percent of the river discharge at most of the spring locations, and was 92 percent at Big Spring and at the lower end of the ONSR. The discharge from the 1.9-mile long Pulltite Springs Complex measured in the 2006 seepage run was 88 ft3/s. Most of this (77 ft3/s) was from the first approximately 0.25 mi of the Pulltite Springs Complex. It has been estimated that the annual mean discharge from the Current River Springs Complex is 125 ft3/s, based on an apparent discharge of 50 ft3/s during a 1966 U.S. Geological Survey seepage run. However, a reinterpretation of the 1966 seepage run data shows that the discharge from the Current River Springs Complex instead was about 12.6 ft3/s, and the annual mean discharge was estimated to be 32 ft3/s, substantially less than 125 ft3/s. The 2006 seepage run showed a gain of only 12 ft3/s from the combined Round Spring and Current River Springs Complex from the mouth of Sinking Creek to 0.7 mi upstream from Root Hollow. The 2006 temperature profile measurements did not indicate any influx of spring discharge throughout the length of the Current River Springs Complex. The spring recharge areas with the largest number of identified sinkholes are Big Spring, Alley Spring, and Welch Spring. The spring recharge areas with the largest number of sinkholes per square mile of recharge area are Alley Spring, Blue Spring (Jacks Fork), Welch Spring, and Round Spring and the Current River Springs Complex. Using the currently known locations of losing streams, the Big Spring recharge area has the largest number of miles of losing stream, and the Bass Rock Spring recharge area has the largest number of miles of losing stream per unit recharge area. The spring recharge areas with the most open land and the least forested land per unit recharge area are Blue Spring (Jacks Fork), Welch Spring, Montauk Springs, and Alley Spring. The spring recharge areas with the least amount

Photogrammetric discharge monitoring of small tropical mountain rivers - A case study at Rivière des Pluies, Réunion island

NASA Astrophysics Data System (ADS)

Stumpf, André; Augereau, Emmanuel; Delacourt, Christophe; Bonnier, Julien

2016-04-01

Reliable discharge measurements are indispensable for an effective management of natural water resources and floods. Limitations of classical current meter profiling and stage-discharge ratings have stimulated the development of more accurate and efficient gauging techniques. While new discharge measurements technologies such as acoustic doppler current profilers and large-scale image particle velocimetry (LSPIV) have been developed and tested in numerous studies, the continuous monitoring of small mountain rivers and discharge dynamics during strong meteorological events remains challenging. More specifically LSPIV studies are often focused on short-term measurements during flood events and there are still very few studies that address its use for long-term monitoring of small mountain rivers. To fill this gap this study targets the development and testing of largely autonomous photogrammetric discharge measurement system with a special focus on the application to small mountain river with high discharge variability and a mobile riverbed in the tropics. It proposes several enhancements among previous LSPIV methods regarding camera calibration, more efficient processing in image geometry, the automatic detection of the water level as well as the statistical calibration and estimation of the discharge from multiple profiles. To account for changes in the bed topography the riverbed is surveyed repeatedly during the dry seasons using multi-view photogrammetry or terrestrial laser scanners. The presented case study comprises the analysis of several thousand videos spanning over two and a half year (2013-2015) to test the robustness and accuracy of different processing steps. An analysis of the obtained results suggests that the quality of the camera calibration reaches a sub-pixel accuracy. The median accuracy of the watermask detections is F1=0.82, whereas the precision is systematically higher than the recall. The resulting underestimation of the water surface area and level leads to a systematic underestimation of the discharge and error rates of up to 25 %. However, the bias can be effectively removed using a least-square cross-calibration which reduces the error to a MAE of 6.39% and a maximum error of 16.18%. Those error rates are significantly lower than the uncertainties among multiple profiles (30%) and illustrate the importance of the spatial averaging from multiple measurements. The study suggests that LSPIV can already be considered as a valuable tool for the monitoring of torrential flows, whereas further research is still needed to fully integrate night-time observation and stereo-photogrammetric capabilities.

Area scaling investigations of charging phenomena. [discharge pulse characteristics of Teflon thermal control tape

NASA Technical Reports Server (NTRS)

Aron, P. R.; Staskus, J. V.

1979-01-01

The charging and discharging behavior of square, planar samples of silvered, fluorinated ethylene-propylene (FEP) Teflon thermal control tape was measured. The equilibrium voltage profiles scaled with the width of the sample. A wide range of discharge pulse characteristics was observed, and the area dependences of the peak current, charge, and pulse widths are described. The observed scaling of the peak currents with area was weaker than that previously reported. The discharge parameters were observed to depend strongly on the grounding impedance and the beam voltage. Preliminary results suggest that measuring only the return-current-pulse characteristics is not adequate to describe the spacecraft discharging behavior of this material. The seams between strips of tape appear to play a fundamental role in determining the discharging behavior. An approximate propagation velocity for the charge cleanoff was extracted from the data. The samples - 232, 1265, and 5058 square centimeters in area - were exposed at ambient temperature to a 1- to 2-nA/sq cm electron beam at energies of 10, 15, and 20 kilovolts in a 19-meter-long by 4.6-meter-diameter simulation facility at the Lewis Research Center.

Experimental Investigation of Pseudospark generated electron beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.; Pal, U. N.

2012-11-01

The pseudospark (PS) discharge is, however, more recently recognized as a different type of discharge which is capable of generating electron beams with the highest combined current density and brightness of any known type of electron source. PS discharge is a specific type of gas discharge, which operates on the left-hand side of the hollow cathode analogy to the Paschen curve with axially symmetric parallel electrodes and central holes on the electrodes. The PS discharge generated electron beam has tremendous applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been carried out experimentally for different applied voltages. The investigation has been done at different axial and radial location inside the drift tube in argon atmosphere. This paper represents experimentally derived axial and radial variation of the beam current inside the plasma filled drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed. It has been further confirmed the successful propagation of electron beam in confined manner without any assistance of external magnetic field.

Extending the validation of multi-mode model for anomalous transport to high beta poloidal tokamak scenario in DIII-D

NASA Astrophysics Data System (ADS)

Pankin, A. Y.; Kritz, A. H.; Rafiq, T.; Garofalo, A. M.; Holod, I.; Weiland, J.

2018-05-01

The Multi-Mode Model (MMM7.1) for anomalous transport is tested in predictive modeling of temperature profiles of a high beta poloidal DIII-D discharge. This new H-mode plasma regime, with high beta poloidal and high bootstrap currents, has been studied in DIII-D tokamak discharges [A. Garofalo et al., Nucl. Fusion 55, 123025 (2015)]. The role of instabilities that can drive the anomalous transport described by MMM7.1 is investigated. The temperature profiles for a high beta poloidal DIII-D discharge are computed using the NCLASS model for the neoclassical transport and the Weiland and Electron Temperature Gradient (ETG) components of the MMM7.1 model for the anomalous transport. The neoclassical transport is found to be the main contributor to the ion thermal transport in the plasma core. The contributions from the ion temperature gradient driven modes are found to be important only outside of the internal transport barrier. The magnitudes of the predicted temperature profiles are found to be in a reasonable agreement with experimental profiles. The simulation results approximately reproduce the internal transport barrier in the ion temperature profile but not in the electron temperature profile due to a weak dependence of the ETG driven transport on the Shafranov shift in the ETG component of MMM7.1. Possible effects that can contribute to stabilization of these modes, for example, effects associated with the large beta poloidal such as the Shafranov shift stabilization in the MMM7.1 model, are discussed. It is demonstrated that the E × B flow shear has a relatively small effect in the formation of the internal transport barrier in the high beta poloidal DIII-D discharge 154406. The Shafranov shift (alpha stabilization) and small or reversed magnetic shear profiles are found to be the primary reasons for quenched anomalous transport in this discharge.

Comparison of fusion alpha performance in JET advanced scenario and H-mode plasmas

NASA Astrophysics Data System (ADS)

Asunta, O.; Kurki-Suonio, T.; Tala, T.; Sipilä, S.; Salomaa, R.; contributors, JET-EFDA

2008-12-01

Currently, plasmas with internal transport barriers (ITBs) appear the most likely candidates for steady-state scenarios for future fusion reactors. In such plasmas, the broad hot and dense region in the plasma core leads to high fusion gain, while the cool edge protects the integrity of the first wall. Economically desirable large bootstrap current fraction and low inductive current drive may, however, lead to degraded fast ion confinement. In this work the confinement and heating profile of fusion alphas were compared between H-mode and ITB plasmas in realistic JET geometry. The work was carried out using the Monte Carlo-based guiding-center-following code ASCOT. For the same plasma current, the ITB discharges were found to produce four to eight times more fusion power than a comparable ELMy H-mode discharge. Unfortunately, also the alpha particle losses were larger (~16%) compared with the H-mode discharge (7%). In the H-mode discharges, alpha power was deposited to the plasma symmetrically around the magnetic axis, whereas in the current-hole discharge, the power was spread out to a larger volume in the plasma center. This was due to wider particle orbits, and the magnetic structure allowing for a broader hot region in the centre.

Sputter crater formation in the case of microsecond pulsed glow discharge in a Grimm-type source. Comparison of direct current and radio frequency modes

NASA Astrophysics Data System (ADS)

Efimova, Varvara; Hoffmann, Volker; Eckert, Jürgen

2012-10-01

Depth profiling with pulsed glow discharge is a promising technique. The application of pulsed voltage for sputtering reduces the sputtering rate and thermal stress and hereby improves the analysis of thin layered and thermally fragile samples. However pulsed glow discharge is not well studied and this limits its practical use. The current work deals with the questions which usually arise when the pulsed mode is applied: Which duty cycle, frequency and pulse length must be chosen to get the optimal sputtering rate and crater shape? Are the well-known sputtering effects of the continuous mode valid also for the pulsed regime? Is there any difference between dc and rf pulsing in terms of sputtering? It is found that the pulse length is a crucial parameter for the crater shape and thermal effects. Sputtering with pulsed dc and rf modes is found to be similar. The observed sputtering effects at various pulsing parameters helped to interpret and optimize the depth resolution of GD OES depth profiles.

Modeling of anomalous electron mobility in Hall thrusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koo, Justin W.; Boyd, Iain D.

Accurate modeling of the anomalous electron mobility is absolutely critical for successful simulation of Hall thrusters. In this work, existing computational models for the anomalous electron mobility are used to simulate the UM/AFRL P5 Hall thruster (a 5 kW laboratory model) in a two-dimensional axisymmetric hybrid particle-in-cell Monte Carlo collision code. Comparison to experimental results indicates that, while these computational models can be tuned to reproduce the correct thrust or discharge current, it is very difficult to match all integrated performance parameters (thrust, power, discharge current, etc.) simultaneously. Furthermore, multiple configurations of these computational models can produce reasonable integrated performancemore » parameters. A semiempirical electron mobility profile is constructed from a combination of internal experimental data and modeling assumptions. This semiempirical electron mobility profile is used in the code and results in more accurate simulation of both the integrated performance parameters and the mean potential profile of the thruster. Results indicate that the anomalous electron mobility, while absolutely necessary in the near-field region, provides a substantially smaller contribution to the total electron mobility in the high Hall current region near the thruster exit plane.« less

Studies on plasma profiles and its effect on dust charging in hydrogen plasma

NASA Astrophysics Data System (ADS)

Kakati, B.; Kausik, S. S.; Saikia, B. K.; Bandyopadhay, M.

2010-02-01

Plasma profiles and its influence on dust charging are studied in hydrogen plasma. The plasma is produced in a high vacuum device by a hot cathode discharge method and is confined by a cusped magnetic field cage. A cylindrical Espion advanced Langmuir probe having 0.15 mm diameter and 10.0 mm length is used to study the plasma parameters for various discharge conditions. Optimum operational discharge parameters in terms of charging of the dust grains are studied. The charge on the surface of the dust particle is calculated from the capacitance model and the current by the dust grains is measured by the combination of a Faraday cup and an electrometer. Unlike our previous experiments in which dust grains were produced in-situ, here a dust dropper is used to drop the dust particles into the plasma.

Experimental Analysis of Pseudospark Sourced Electron Beam

NASA Astrophysics Data System (ADS)

Kumar, Niraj; Pal, U. N.; Verma, D. K.; Prajapati, J.; Kumar, M.; Meena, B. L.; Tyagi, M. S.; Srivastava, V.

2011-12-01

The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

Validation of streamflow measurements made with acoustic doppler current profilers

USGS Publications Warehouse

Oberg, K.; Mueller, D.S.

2007-01-01

The U.S. Geological Survey and other international agencies have collaborated to conduct laboratory and field validations of acoustic Doppler current profiler (ADCP) measurements of streamflow. Laboratory validations made in a large towing basin show that the mean differences between tow cart velocity and ADCP bottom-track and water-track velocities were -0.51 and -1.10%, respectively. Field validations of commercially available ADCPs were conducted by comparing streamflow measurements made with ADCPs to reference streamflow measurements obtained from concurrent mechanical current-meter measurements, stable rating curves, salt-dilution measurements, or acoustic velocity meters. Data from 1,032 transects, comprising 100 discharge measurements, were analyzed from 22 sites in the United States, Canada, Sweden, and The Netherlands. Results of these analyses show that broadband ADCP streamflow measurements are unbiased when compared to the reference discharges regardless of the water mode used for making the measurement. Measurement duration is more important than the number of transects for reducing the uncertainty of the ADCP streamflow measurement. ?? 2007 ASCE.

Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus

NASA Astrophysics Data System (ADS)

Yang, J.; Lee, J. W.; Jung, B. K.; Chung, K. J.; Hwang, Y. S.

2014-11-01

An internal magnetic probe using Hall sensors to measure a current density profile directly with perturbation of less than 10% to the plasma current is successfully operated for the first time in Versatile Experiment Spherical Torus (VEST). An appropriate Hall sensor is chosen to produce sufficient signals for VEST magnetic field while maintaining the small size of 10 mm in outer diameter. Temperature around the Hall sensor in a typical VEST plasma is regulated by blown air of 2 bars. First measurement of 60 kA VEST ohmic discharge shows a reasonable agreement with the total plasma current measured by Rogowski coil in VEST.

Profile modification computations for LHCD experiments on PBX-M using the TSC/LSC model

NASA Astrophysics Data System (ADS)

Kaita, R.; Ignat, D. W.; Jardin, S. C.; Okabayashi, M.; Sun, Y. C.

1996-02-01

The TSC-LSC computational model of the dynamics of lower hybrid current drive has been exercised extensively in comparison with data from a Princeton Beta Experiment-Modification (PBX-M) discharge where the measured q(0) attained values slightly above unity. Several significant, but plausible, assumptions had to be introduced to keep the computation from behaving pathologically over time, producing singular profiles of plasma current density and q. Addition of a heuristic current diffusion estimate, or more exactly, a smoothing of the rf-driven current with a diffusion-like equation, greatly improved the behavior of the computation, and brought theory and measurement into reasonable agreement. The model was then extended to longer pulse lengths and higher powers to investigate performance to be expected in future PBX-M current profile modification experiments.

Mode suppression of a two-dimensional potential relaxation instability in a weakly magnetized discharge plasma

NASA Astrophysics Data System (ADS)

Gyergyek, T.; Čerček, M.; Jelić, N.; Stanojević, M.

1993-05-01

A potential relaxation instability (PRI) is modulated by an external signal using an additional grid to modulate the radial plasma potential profile in a magnetized plasma column in a linear magnetized discharge plasma device. It is observed that the electrode current oscillations follow the van der Pol equation with an external forcing term, and the linear growth rate of the instability is measured.

Lower Hybrid Wave Induced SOL Emissivity Variation at High Density on the Alcator C-Mod Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faust, I.; Terry, J. L.; Reinke, M. L.

Lower Hybrid Current Drive (LHCD) in the Alcator C-Mod tokamak provides current profile control for the generation of Advanced Tokamak (AT) plasmas. Non-thermal electron bremsstrahlung emission decreases dramatically at n-bar{sub e}>1{center_dot}10{sup 20}[m{sup -3}] for diverted discharges, indicating low current drive efficiency. It is suggested that Scrape-Off-Layer (SOL) collisional absorption of LH waves is the cause for the absence of non-thermal electrons at high density. VUV and visible spectroscopy in the SOL provide direct information on collision excitation processes. Deuterium Balmer-, Lyman- and He-I transition emission measurements were used for initial characterization of SOL electron-neutral collisional absorption. Data from Helium andmore » Deuterium LHCD discharges were characterized by an overall increase in the emissivity as well as an outward radial shift in the emissivity profile with increasing plasma density and applied LHCD power. High-temperature, high-field (T{sub e} = 5keV,B{sub t} = 8T) helium discharges at high density display increased non-thermal signatures as well as reduced SOL emissivity. Variations in emissivity due to LHCD were seen in SOL regions not magnetically connected to the LH Launcher, indicating global SOL effects due to LHCD.« less

Is the negative glow plasma of a direct current glow discharge negatively charged?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanov, E. A.; Saifutdinov, A. I.; Demidov, V. I., E-mail: Vladimir.Demidov@mail.wvu.edu

A classic problem in gas discharge physics is discussed: what is the sign of charge density in the negative glow region of a glow discharge? It is shown that traditional interpretations in text-books on gas discharge physics that states a negative charge of the negative glow plasma are based on analogies with a simple one-dimensional model of discharge. Because the real glow discharges with a positive column are always two-dimensional, the transversal (radial) term in divergence with the electric field can provide a non-monotonic axial profile of charge density in the plasma, while maintaining a positive sign. The numerical calculationmore » of glow discharge is presented, showing a positive space charge in the negative glow under conditions, where a one-dimensional model of the discharge would predict a negative space charge.« less

Floods in the Wapsipinicon River Basin, Iowa

USGS Publications Warehouse

Schwob, Harlan H.

1971-01-01

Flood-profile sheets show profiles of actual flood occurrences and computed profiles of the 25- and 50-year floods at most locations. These sheets also contain tabulations of the flood discharges profiled. A low-water profile and tabulated discharge indicate the range in elevation and discharge along the streams.

Advanced ST plasma scenario simulations for NSTX

NASA Astrophysics Data System (ADS)

Kessel, C. E.; Synakowski, E. J.; Bell, M. E.; Gates, D. A.; Harvey, R. W.; Kaye, S. M.; Mau, T. K.; Menard, J.; Phillips, C. K.; Taylor, G.; Wilson, R.; NSTX Research Team

2005-08-01

Integrated scenario simulations are done for NSTX that address four primary objectives for developing advanced spherical torus (ST) configurations: high β and high βN inductive discharges to study all aspects of ST physics in the high β regime; non-inductively sustained discharges for flattop times greater than the skin time to study the various current drive techniques; non-inductively sustained discharges at high β for flattop times much greater than a skin time which provides the integrated advanced ST target for NSTX and non-solenoidal startup and plasma current rampup. The simulations done here use the tokamak simulation code and are based on a discharge 109070. TRANSP analysis of the discharge provided the thermal diffusivities for electrons and ions, the neutral beam deposition profile and other characteristics. CURRAY is used to calculate the high harmonic fast wave (HHFW) heating depositions and current drive. GENRAY/CQL3D is used to establish the heating and CD deposition profiles for electron Bernstein waves (EBW). Analysis of the ideal MHD stability is done with JSOLVER, BALMSC and PEST2. The simulations indicate that the integrated advanced ST plasma is reachable, obtaining stable plasmas with βT ap 40% at βN's of 7.7-9, IP = 1.0 MA and BT = 0.35 T. The plasma is 100% non-inductive and has a flattop of four skin times. The resulting global energy confinement corresponds to a multiplier of H98(y),2 = 1.5. The simulations have demonstrated the importance of HHFW heating and CD, EBW off-axis CD, strong plasma shaping, density control and early heating/H-mode transition for producing and optimizing these plasma configurations.

Study on effect of tool electrodes on surface finish during electrical discharge machining of Nitinol

NASA Astrophysics Data System (ADS)

Sahu, Anshuman Kumar; Chatterjee, Suman; Nayak, Praveen Kumar; Sankar Mahapatra, Siba

2018-03-01

Electrical discharge machining (EDM) is a non-traditional machining process which is widely used in machining of difficult-to-machine materials. EDM process can produce complex and intrinsic shaped component made of difficult-to-machine materials, largely applied in aerospace, biomedical, die and mold making industries. To meet the required applications, the EDMed components need to possess high accuracy and excellent surface finish. In this work, EDM process is performed using Nitinol as work piece material and AlSiMg prepared by selective laser sintering (SLS) as tool electrode along with conventional copper and graphite electrodes. The SLS is a rapid prototyping (RP) method to produce complex metallic parts by additive manufacturing (AM) process. Experiments have been carried out varying different process parameters like open circuit voltage (V), discharge current (Ip), duty cycle (τ), pulse-on-time (Ton) and tool material. The surface roughness parameter like average roughness (Ra), maximum height of the profile (Rt) and average height of the profile (Rz) are measured using surface roughness measuring instrument (Talysurf). To reduce the number of experiments, design of experiment (DOE) approach like Taguchi’s L27 orthogonal array has been chosen. The surface properties of the EDM specimen are optimized by desirability function approach and the best parametric setting is reported for the EDM process. Type of tool happens to be the most significant parameter followed by interaction of tool type and duty cycle, duty cycle, discharge current and voltage. Better surface finish of EDMed specimen can be obtained with low value of voltage (V), discharge current (Ip), duty cycle (τ) and pulse on time (Ton) along with the use of AlSiMg RP electrode.

Veff Scaling of Te and ne Measurements During Local Helicity Injection on the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Rodriguez Sanchez, C.

2017-10-01

Understanding the electron confinement of local helicity injection (LHI) is critical in order to evaluate its scalability as a startup technique to MA-class devices. Electron confinement in the Pegasus Toroidal Experiment is investigated using multi-point Thomson scattering (TS). The Pegasus TS system utilizes a set of high-throughput transmission gratings and intensified CCDs to measure Te and ne profiles. Previous TS measurements indicated peaked Te profiles 120 eV in outboard injector discharges characterized by strong inductive drive and low LHI drive. Injectors designed to have dominant non-inductive drive have recently been installed in the divertor region of Pegasus to understand the relationship between effective drive voltage, Veff, and plasma performance. At low Veff and reduced plasma current, Ip 60 kA, TS measurements reveal a flat Te profile 50 eV, with a peaked ne profile 1 ×1019 m-3, resulting in a slightly peaked pe profile. As current drive is increased, the Te profiles become hollow with a core Te 50 eV and an edge Te 120 -150 eV. These hollow profiles appear after the start of the Ip flattop and are sustained until the discharge terminates. The ne profiles drop in magnitude to < 1 ×1019 m-3 but remain somewhat peaked. Initial results suggest a weak scaling between input power and core Te. Additional studies are planned to identify the mechanisms behind the anomalous profile features. Work supported by US DOE Grant DE-FG02-96ER54375.

In situ X-ray near-edge absorption spectroscopy investigation of the state of charge of all-vanadium redox flow batteries.

PubMed

Jia, Chuankun; Liu, Qi; Sun, Cheng-Jun; Yang, Fan; Ren, Yang; Heald, Steve M; Liu, Yadong; Li, Zhe-Fei; Lu, Wenquan; Xie, Jian

2014-10-22

Synchrotron-based in situ X-ray near-edge absorption spectroscopy (XANES) has been used to study the valence state evolution of the vanadium ion for both the catholyte and anolyte in all-vanadium redox flow batteries (VRB) under realistic cycling conditions. The results indicate that, when using the widely used charge-discharge profile during the first charge process (charging the VRB cell to 1.65 V under a constant current mode), the vanadium ion valence did not reach V(V) in the catholyte and did not reach V(II) in the anolyte. Consequently, the state of charge (SOC) for the VRB cell was only 82%, far below the desired 100% SOC. Thus, such incompletely charged mix electrolytes results in not only wasting the electrolytes but also decreasing the cell performance in the following cycles. On the basis of our study, we proposed a new charge-discharge profile (first charged at a constant current mode up to 1.65 V and then continuously charged at a constant voltage mode until the capacity was close to the theoretical value) for the first charge process that achieved 100% SOC after the initial charge process. Utilizing this new charge-discharge profile, the theoretical charge capacity and the full utilization of electrolytes has been achieved, thus having a significant impact on the cost reduction of the electrolytes in VRB.

Effect of pulsed discharge on the ignition of pulse modulated radio frequency glow discharge at atmospheric pressure

NASA Astrophysics Data System (ADS)

Qiu, Shenjie; Guo, Ying; Han, Qianhan; Bao, Yun; Zhang, Jing; Shi, J. J.

2018-01-01

A pulsed discharge is introduced between two sequential pulse-modulated radio frequency glow discharges in atmospheric helium. The dependence of radio frequency discharge ignition on pulsed discharge intensity is investigated experimentally with the pulse voltage amplitudes of 650, 850, and 1250 V. The discharge characteristics and dynamics are studied in terms of voltage and current waveforms, and spatial-temporal evolution of optical emission. With the elevated pulsed discharge intensity of two orders of magnitude, the ignition of radio frequency discharge is enhanced by reducing the ignition time and achieving the stable operation with a double-hump spatial profile. The ignition time of radio frequency discharge is estimated to be 2.0 μs, 1.5 μs, and 1.0 μs with the pulse voltage amplitudes of 650, 850, and 1250 V, respectively, which is also demonstrated by the spatial-temporal evolution of optical emission at 706 and 777 nm.

Overview of hydro-acoustic current-measurement applications by the U.S. geological survey in Indiana

USGS Publications Warehouse

Morlock, Scott E.; Stewart, James A.

1999-01-01

The U.S. Geological Survey (USGS) maintains a network of 170 streamflow-gaging stations in Indiana to collect data from which continuous records of river discharges are produced. Traditionally, the discharge record from a station is produced by recording river stage and making periodic discharge measurements through a range of stage, then developing a relation between stage and discharge. Techniques that promise to increase data collection accuracy and efficiency include the use of hydro-acoustic instrumentation to measure river velocities. The velocity measurements are used to compute river discharge. In-situ applications of hydro-acoustic instruments by the USGS in Indiana include acoustic velocity meters (AVM's) at six streamflow-gaging stations and newly developed Doppler velocity meters (DVM's) at two stations. AVM's use reciprocal travel times of acoustic signals to measure average water velocities along acoustic paths, whereas DVM's use the Doppler shift of backscattered acoustic signals to compute water velocities. In addition to the in-situ applications, three acoustic Doppler current profilers (ADCP's) are used to make river-discharge measurements from moving boats at streamflow-gaging stations in Indiana. The USGS has designed and is testing an innovative unmanned platform from which to make ADCP discharge measurements.

Flood-inundation maps for the Tippecanoe River at Winamac, Indiana

USGS Publications Warehouse

Menke, Chad D.; Bunch, Aubrey R.

2015-09-25

For this study, flood profiles were computed for the Tippecanoe River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the most current stage-discharge relations at the Tippecanoe River streamgage, in combination with the current (2014) Federal Emergency Management Agency flood-insurance study for Pulaski County. The calibrated hydraulic model was then used to determine nine water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The 1-percent annual exceedance probability (AEP) flood stage (flood with recurrence intervals within 100 years) has not been determined yet for this streamgage location. The rating has not been developed for the 1-percent AEP because the streamgage dates to only 2001. The simulated water-surface profiles were then used with a geographic information system (GIS) digital elevation model (DEM, derived from Light Detection and Ranging [lidar]) in order to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage 03331753, Tippecanoe River at Winamac, Ind., and forecast stream stages from the NWS AHPS, provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Electron temperature response to ECRH on FTU tokamak in transient conditions.

NASA Astrophysics Data System (ADS)

Jacchia, A.; Bruschi, A.; Cirant, S.; Granucci, G.; Sozzi, C.; de Luca, F.; Amadeo, P.; Bracco, G.; Tudisco, O.

2001-10-01

Steady-state electron heat transport analysis of FTU high density plasmas under Electron Cyclotron Heating (ECRH) shows "stiff" electron temperature profiles [1,2,3]. Plasma response to off-axis EC heating, in fact, exibits a lower limit to electron temperature gradient length, Lc , below which electron thermal conductivity switches to higher values. Stiffness, however, is attenuated in the plasma core of saw-tooth free discharges with flat-hollow temperature profile and during current ramp-up [3,4,5], in which cases the temperature gradient length can be brought to very low values by means of on-axis ECH. Steady and current ramp-up discharges probed by steady and modulated ECH are analyzed in terms of stiffnes. Critical gradient length dependence on local features of computed current density profile is discussed. [1] Sozzi, C. et al., Paper EXP5/13, Plasma Phys. Contr. Fus. Res., Proc.18th IAEA Conf., Sorrento, 2000. [2] Jacchia, A. et al. Topical Conference on Radio Frequency Power in Plasmas, Oxnard, USA, (2001). [3] Cirant, S. et al. Topical Conference on Radio Frequency Power in Plasmas, Oxnard, USA, (2001). [4] Sozzi, C. et al., EPS, Madeira 2001. [5] Bracco, G. et al.,Plasma Phys. Contr. Fus. Res., Proc.18th IAEA Conf., Sorrento, 2000.

Studies on laser-assisted Penning ionization by the optogalvanic effect in Ne/Eu hollow cathode discharge.

PubMed

Saini, V K; Kumar, P; Dixit, S K; Nakhe, S V

2015-02-01

Laser-assisted Penning ionization (LAPI) is detected in a Ne/Eu hollow cathode (HC) discharge lamp using the pulsed optogalvanic (OG) method. In the Ne/Eu discharge, doubly ionized europium excited energy levels Eu[4f(7)(P(7/2,5/2)6)] lie within the thermal limit (∼kT) from the laser-excited neon's energy level [2p(5)(P3/202)3p or 2p(8) (in Paschen notation)] lying at 149,848  cm(-1). Therefore, Penning ionization (PI) of europium atoms likely to occur into its highly excited ionic states is investigated. To probe the PI of europium, the temporal profiles of its counterpart neon OG signal are studied as a function of discharge current for the transitions (1s(4)→2p(8)) and (1s(2)→2p(2)), corresponding to 650.65 and 659.89 nm wavelengths, respectively. It is observed that PI of europium alters the overall discharge characteristics significantly and, hence, modifies the temporal profile of the OG signals accordingly. The quasi-resonant ionizing energy transfer collisions between laser-excited Ne 2p(8) atoms and electronically excited europium P(9/2)10 atoms are used to explain the LAPI mechanism. Such LAPI studies carried out in HC discharge could be useful for the discharge of a metal-vapor laser with appropriate Penning mixtures.

Direct measurements of safety factor profiles with motional Stark effect for KSTAR tokamak discharges with internal transport barriers

NASA Astrophysics Data System (ADS)

Ko, J.; Chung, J.

2017-06-01

The safety factor profile evolutions have been measured from the plasma discharges with the external current drive mechanism such as the multi-ion-source neutral beam injection for the Korea Superconducting Tokamak Advanced Research (KSTAR) for the first time. This measurement has been possible by the newly installed motional Stark effect (MSE) diagnostic system that utilizes the polarized Balmer-alpha emission from the energetic neutral deuterium atoms induced by the Stark effect under the Lorentz electric field. The 25-channel KSTAR MSE diagnostic is based on the conventional photoelastic modulator approach with the spatial and temporal resolutions less than 2 cm (for the most of the channels except 2 to 3 channels inside the magnetic axis) and about 10 ms, respectively. The strong Faraday rotation imposed on the optical elements in the diagnostic system is calibrated out from a separate and well-designed polarization measurement procedure using an in-vessel reference polarizer during the toroidal-field ramp-up phase before the plasma experiment starts. The combination of the non-inductive current drive during the ramp-up and shape control enables the formation of the internal transport barrier where the pitch angle profiles indicate flat or slightly hollow profiles in the safety factor.

Self-Organisation and Intermittent Coherent Oscillations in the EXTRAP T2 Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Cecconello, M.; Malmberg, J.-A.; Sallander, E.; Drake, J. R.

Many reversed-field pinch (RFP) experiments exhibit a coherent oscillatory behaviour that is characteristic of discrete dynamo events and is associated with intermittent current profile self-organisation phenomena. However, in the vast majority of the discharges in the resistive shell RFP experiment EXTRAP T2, the dynamo activity does not show global, coherent oscillatory behaviour. The internally resonant tearing modes are phase-aligned and wall-locked resulting in a large localised magnetic perturbation. Equilibrium and plasma parameters have a level of high frequency fluctuations but the average values are quasi-steady. For some discharges, however, the equilibrium parameters exhibit the oscillatory behaviour characteristic of the discrete dynamo events. For these discharges, the trend observed in the tearing mode spectra, associated with the onset of the discrete relaxation event behaviour, is a relative higher amplitude of m = 0 mode activity and relative lower amplitude of the m = 1 mode activity compared with their average values. Global plasma parameters and model profile calculations for sample discharges representing the two types of relaxation dynamics are presented.

A multi-frequency investigation of the influences of groundwater discharge on hydrocarbon emission and transport in the Baltic Sea

NASA Astrophysics Data System (ADS)

Weidner, E. F.; Jakobsson, M.; Nycander, J.; Mayer, L. A.

2017-12-01

In nearshore coastal regions submarine groundwater discharge is a major component of the hydro-geological cycle: transporting nutrients and pollutants to the ocean, producing up-welling currents through buoyancy effects, and acting as an erosional force at discharge sites. In nearshore regions where biogenic gas production is high, groundwater discharge could potentially act as a control on hydrocarbon emission and transport from the seafloor though the water-column. In the southern Stockholm Archipelago of the Baltic Sea, terraces and semi-circular depressions on shallow (<20 meters) seafloor have been linked to the discharge of ground water, traveling along the permeable layers in glacial clay deposits (Söderberg and Flodén 1995; Jakobsson et al., 2016). Sub-bottom profiles over the same region have identified widespread areas of subsurface blanking, commonly attributed to gas, as well as water-column seep features, both in spatial proximity to the groundwater discharge sites. High-resolution multibeam bathymetry and chirp sub-bottom profiles were combined with water-column data sets collected at multiple frequencies (300 kHz, 45-90 kHz, 160-260 kHz) to map the spatial distribution of seeps and investigate their relationship to localized groundwater discharge as determined by seafloor and subsurface morphology. The spatial extent of seep sites appears closely tied to regions of suspected groundwater discharge, suggesting direct or indirect controls on gas emission pathways. Additionally, seep morphology in the broadband data hints at the possibility of groundwater and gas flow mixing.

An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

Evaluation of Acoustic Doppler Current Profiler measurements of river discharge

USGS Publications Warehouse

Morlock, S.E.

1996-01-01

The standard deviations of the ADCP measurements ranged from approximately 1 to 6 percent and were generally higher than the measurement errors predicted by error-propagation analysis of ADCP instrument performance. These error-prediction methods assume that the largest component of ADCP discharge measurement error is instrument related. The larger standard deviations indicate that substantial portions of measurement error may be attributable to sources unrelated to ADCP electronics or signal processing and are functions of the field environment.

Ozone production by corona discharges during a convective event in DISCOVER-AQ Houston

NASA Astrophysics Data System (ADS)

Kotsakis, Alexander; Morris, Gary A.; Lefer, Barry; Jeon, Wonbae; Roy, Anirban; Minschwaner, Ken; Thompson, Anne M.; Choi, Yunsoo

2017-07-01

An ozonesonde launched near electrically active convection in Houston, TX on 5 September 2013 during the NASA DISCOVER-AQ project measured a large enhancement of ozone throughout the troposphere. A separate ozonesonde was launched from Smith Point, TX (∼58 km southeast of the Houston site) at approximately the same time as the launch from Houston and did not measure that enhancement. Furthermore, ozone profiles for the descent of both sondes agreed well with the ascending Smith Point profile, suggesting a highly localized event in both space and time in which an anomalously large enhancement of 70-100 ppbv appeared in the ascending Houston ozonesonde data. Compared to literature values, such an enhancement appears to be the largest observed to date. Potential sources of the localized ozone enhancement such as entrainment of urban or biomass burning emissions, downward transport from the stratosphere, photochemical production from lightning NOx, and direct ozone production from corona discharges were investigated using model simulations. We conclude that the most likely explanation for the large ozone enhancement is direct ozone production by corona discharges. Integrating the enhancement seen in the Houston ozone profile and using the number of electrical discharges detected by the NLDN (or HLMA), we estimate a production of 2.48 × 1028 molecules of ozone per flash which falls within the range of previously recorded values (9.89 × 1026-9.82 × 1028 molecules of ozone per flash). Since there is currently no parameterization for the direct production of ozone from corona discharges we propose the implementation of an equation into a chemical transport model. Ultimately, additional work is needed to further understand the occurrence and impact of corona discharges on tropospheric chemistry on short and long timescales.

Ozone Production by Corona Discharges During a Convective Event in DISCOVER-AQ Houston

NASA Technical Reports Server (NTRS)

Kotsakis, Alexander; Morris, Gary A.; Lefer, Barry; Jeon, Wongbae; Roy, Anirban; Minschwaner, Ken; Thompson, Anne M.; Choi, Yunsoo

2017-01-01

An ozonesonde launched near electrically active convection in Houston, TX on 5 September 2013 during the NASA DISCOVER-AQ project measured a large enhancement of ozone throughout the troposphere. A separate ozonesonde was launched from Smith Point, TX (approx. 58 km southeast of the Houston site) at approximately the same time as the launch from Houston and did not measure that enhancement. Furthermore, ozone profiles for the descent of both sondes agreed well with the ascending Smith Point profile, suggesting a highly localized event in both space and time in which an anomalously large enhancement of 70 - 100 ppbv appeared in the ascending Houston ozonesonde data. Compared to literature values, such an enhancement appears to be the largest observed to date. Potential sources of the localized ozone enhancement such as entrainment of urban or biomass burning emissions, downward transport from the stratosphere, photochemical production from lightning NO(sub x), and direct ozone production from corona discharges were investigated using model simulations. We conclude that the most likely explanation for the large ozone enhancement is direct ozone production by corona discharges. Integrating the enhancement seen in the Houston ozone profile and using the number of electrical discharges detected by the NLDN (or HLMA), we estimate a production of 2.48 x 10(exp. 28) molecules of ozone per flash which falls within the range of previously recorded values (9.89 x 10(exp. 26) - 9.82 x 10)exp. 28) molecules of ozone per flash). Since there is currently no parameterization for the direct production of ozone from corona discharges we propose the implementation of an equation into a chemical transport model. Ultimately, additional work is needed to further understand the occurrence and impact of corona discharges on tropospheric chemistry on short and long timescales.

Preliminary Results Of A 600 Joules Small Plasma Focus Device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S. H.; Yap, S. L.; Wong, C. S.

Preliminary results of a 600 J (3.7 muF, 18 kV) Mather type plasma focus device operated at low pressure will be presented. The discharge is formed between a solid anode with length of 6 cm and six symmetrically and coaxially arranged cathode rods of same lengths. The cathode base is profiled in a knife-edge design and a set of coaxial plasma gun are attached to it in order to initiate the breakdown and enhance the current sheath formation. The experiments have been performed in argon gas under a low pressure condition of several microbars. The discharge current and the voltagemore » across the electrodes during the discharge are measured with high voltage probe and current coil. The current and voltage characteristics are used to determine the possible range of operating pressure that gives good focusing action. At a narrow pressure regime of 9.0+-0.5 mubar, focusing action is observed with good reproducibility. Preliminary result of ion beam energy is presented. More work will be carried out to investigate the radiation output.« less

Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

NASA Astrophysics Data System (ADS)

Gao, Q. D.; Budny, R. V.

2015-03-01

By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (Ti,e) and toroidal velocity (Vϕ) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LH driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.

Integrated modeling of high βN steady state scenario on DIII-D

DOE PAGES

Park, Jin Myung; Ferron, J. R.; Holcomb, Christopher T.; ...

2018-01-10

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with β N > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state ( d/dt = 0) solutions and reproduces most features of DIII-D high β N discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high q min > 2 scenario achieves stable operation at β N as high as 5 by using a very broadmore » current density profile to improve the ideal-wall stabilization of low- n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high β N steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.« less

Integrated modeling of high βN steady state scenario on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jin Myung; Ferron, J. R.; Holcomb, Christopher T.

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with β N > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state ( d/dt = 0) solutions and reproduces most features of DIII-D high β N discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high q min > 2 scenario achieves stable operation at β N as high as 5 by using a very broadmore » current density profile to improve the ideal-wall stabilization of low- n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high β N steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.« less

Integrated modeling of high βN steady state scenario on DIII-D

NASA Astrophysics Data System (ADS)

Park, J. M.; Ferron, J. R.; Holcomb, C. T.; Buttery, R. J.; Solomon, W. M.; Batchelor, D. B.; Elwasif, W.; Green, D. L.; Kim, K.; Meneghini, O.; Murakami, M.; Snyder, P. B.

2018-01-01

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with βN > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state (d/dt = 0) solutions and reproduces most features of DIII-D high βN discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high qmin > 2 scenario achieves stable operation at βN as high as 5 by using a very broad current density profile to improve the ideal-wall stabilization of low-n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high βN steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.

The real time multi point Thomson scattering diagnostic at NSTX-U

NASA Astrophysics Data System (ADS)

Laggner, Florian; Kolemen, Egemen; Diallo, Ahmed; Leblanc, Benoit; Rozenblat, Roman; Tchilinguirian, Greg; NSTX-U Team Team

2017-10-01

This contribution presents the upgrade of the multi point Thomson scattering (MPTS) diagnostic for real time application. As a key diagnostic at NSTX-U, the MPTS diagnostic simultaneously measures the electron density (ne) and electron temperature (Te) profiles of a plasma discharge. Therefore, this powerful diagnostic can directly access the electron pressure of the plasma. Currently, only post-discharge evaluation of the data is available, however, since the plasma pressure is one important drive for instabilities, real time measurements of this quantities would be beneficial for plasma control. In a first step, ten MPTS channels were equipped with real time electronics, which improve the data acquisition rate by five orders of magnitude. The commissioning of the system is ongoing and first benchmarks of the real time evaluation routines against the standard, post-discharge evaluation show promising results: The Te as well as ne profiles of both types of analyses agree within their uncertainties. This work was supported by the US Department of Energy under DE-SC0015878 and DE-SC0015480.

Stage-discharge relationship in tidal channels

NASA Astrophysics Data System (ADS)

Kearney, W. S.; Mariotti, G.; Deegan, L.; Fagherazzi, S.

2016-12-01

Long-term records of the flow of water through tidal channels are essential to constrain the budgets of sediments and biogeochemical compounds in salt marshes. Statistical models which relate discharge to water level allow the estimation of such records from more easily obtained records of water stage in the channel. While there is clearly structure in the stage-discharge relationship, nonlinearity and nonstationarity of the relationship complicates the construction of statistical stage-discharge models with adequate performance for discharge estimation and uncertainty quantification. Here we compare four different types of stage-discharge models, each of which is designed to capture different characteristics of the stage-discharge relationship. We estimate and validate each of these models on a two-month long time series of stage and discharge obtained with an Acoustic Doppler Current Profiler in a salt marsh channel. We find that the best performance is obtained by models which account for the nonlinear and time-varying nature of the stage-discharge relationship. Good performance can also be obtained from a simplified version of these models which approximates the fully nonlinear and time-varying models with a piecewise linear formulation.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

NASA Astrophysics Data System (ADS)

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Howell, E. C.; Knowlton, S. F.; Maurer, D. A.; Traverso, P. J.

2018-01-01

Collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of q = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. This improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.

Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

DOE PAGES

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; ...

2018-01-31

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of qmore » = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.« less

Calculation of the non-inductive current profile in high-performance NSTX plasmas

NASA Astrophysics Data System (ADS)

Gerhardt, S. P.; Fredrickson, E.; Gates, D.; Kaye, S.; Menard, J.; Bell, M. G.; Bell, R. E.; Le Blanc, B. P.; Kugel, H.; Sabbagh, S. A.; Yuh, H.

2011-03-01

The constituents of the current profile have been computed for a wide range of high-performance plasmas in NSTX (Ono et al 2000 Nucl. Fusion 40 557); these include cases designed to maximize the non-inductive fraction, pulse length, toroidal-β or stored energy. In the absence of low-frequency MHD activity, good agreement is found between the reconstructed current profile and that predicted by summing the independently calculated inductive, pressure-driven and neutral beam currents, without the need to invoke any anomalous beam ion diffusion. Exceptions occur, for instance, when there are toroidal Alfvén eigenmode avalanches or coupled m/n = 1/1 + 2/1 kink-tearing modes. In these cases, the addition of a spatially and temporally dependent fast-ion diffusivity can reduce the core beam current drive, restoring agreement between the reconstructed profile and the summed constituents, as well as bringing better agreement between the simulated and measured neutron emission rate. An upper bound on the fast-ion diffusivity of ~0.5-1 m2 s-1 is found in 'MHD-free' discharges, based on the neutron emission, the time rate of change in the neutron signal when a neutral beam is stepped and reconstructed on-axis current density.

Characterization and Performance of a High-Current-Density Ion Implanter with Magnetized Hollow-Cathode Plasma Source

NASA Astrophysics Data System (ADS)

Falkenstein, Zoran; Rej, Donald; Gavrilov, Nikolai

1998-10-01

In a collaboration between the Institute of Electrophysics (IEP) and the Los Alamos National Laboratory (LANL), the IEP has developed an industrial scalable, high-power, large-area ion source for the surface modification of materials. The plasma source of the ion beam source can be described as a pulsed glow discharge with a cold, hollow-cathode in a weak magnetic field. Extraction and focusing of positive ions by an acceleration and ion-optical plate system renders the generation of a homogeneous, large-area ion beam with an averaged total ion current of up to 50 mA at acceleration voltages of up to 50 kV. The principle set-up of the ion beam source as well as some electrical characteristics (gas discharge current and the extracted ion beam current) are presented for a lab-scale prototype. Measurements of the radial ion current density profiles within the ion beam for various discharge parameters, as well as results on surface modification by ion implantation of nitrogen into aluminum and chromium are presented. Finally, a comparison of the applied ion dose with the retained ion doses is given.

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4

Low-flow characteristics and profiles for the Deep River in the Cape Fear River basin, North Carolina

USGS Publications Warehouse

Weaver, J.C.

1997-01-01

Drainage area and low-flow discharge profiles are presented for the Deep River. The drainage-area profile shows downstream increases in basin size. At the mouth, the drainage area for the Deep River is 1,441 square miles. Low-flow discharge profiles for the Deep River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included.

Neutralization of an ion beam from the end-Hall ion source by a plasma electron source based on a discharge in crossed E × H fields

NASA Astrophysics Data System (ADS)

Dostanko, A. P.; Golosov, D. A.

2009-10-01

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm2 at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O2 or N2. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).

Rate Dependent Multi-Mechanism Discharge of Ag 0.50VOP 4·1.8H 2O: Insights from In Situ Energy Dispersive X-ray Diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huie, Matthew M.; Bock, David C.; Zhong, Zhong

Ag 0.50VOPO 4·1.8H 2O (silver vanadium phosphate, SVOP) demonstrates a counterintuitive higher initial loaded voltage under higher discharge current. Energy dispersive X-ray diffraction (EDXRD) from synchrotron radiation was used to create tomographic profiles of cathodes at various depths of discharge for two discharge rates. SVOP displays two reduction mechanisms, reduction of a vanadium center accompanied by lithiation of the structure, or reduction-displacement of a silver cation to form silver metal. In-situ EDXRD provides the opportunity to observe spatially resolved changes to the parent SVOP crystal and formation of Ag 0 during reduction. At a C/170 discharge rate V 5+ reductionmore » is the preferred initial reaction resulting in higher initial loaded voltage. At a discharge rate of C/400 reduction of Ag + with formation of conductive Ag 0 occurs earlier during discharge. Discharge rate also affects the spatial location of reduction products. The faster discharge rate initiates reduction close to the current collector with non-uniform distribution of silver metal resulting in isolated cathode areas. The slower rate develops a more homogenous distribution of reduced SVOP and silver metal. This study illuminates the roles of electronic and ionic conductivity limitations within a cathode at the mesoscale and how they impact the course of reduction processes and loaded voltage.« less

Rate Dependent Multi-Mechanism Discharge of Ag 0.50VOP 4·1.8H 2O: Insights from In Situ Energy Dispersive X-ray Diffraction

DOE PAGES

Huie, Matthew M.; Bock, David C.; Zhong, Zhong; ...

2016-09-01

Ag 0.50VOPO 4·1.8H 2O (silver vanadium phosphate, SVOP) demonstrates a counterintuitive higher initial loaded voltage under higher discharge current. Energy dispersive X-ray diffraction (EDXRD) from synchrotron radiation was used to create tomographic profiles of cathodes at various depths of discharge for two discharge rates. SVOP displays two reduction mechanisms, reduction of a vanadium center accompanied by lithiation of the structure, or reduction-displacement of a silver cation to form silver metal. In-situ EDXRD provides the opportunity to observe spatially resolved changes to the parent SVOP crystal and formation of Ag 0 during reduction. At a C/170 discharge rate V 5+ reductionmore » is the preferred initial reaction resulting in higher initial loaded voltage. At a discharge rate of C/400 reduction of Ag + with formation of conductive Ag 0 occurs earlier during discharge. Discharge rate also affects the spatial location of reduction products. The faster discharge rate initiates reduction close to the current collector with non-uniform distribution of silver metal resulting in isolated cathode areas. The slower rate develops a more homogenous distribution of reduced SVOP and silver metal. This study illuminates the roles of electronic and ionic conductivity limitations within a cathode at the mesoscale and how they impact the course of reduction processes and loaded voltage.« less

Off-axis current drive and real-time control of current profile in JT-60U

NASA Astrophysics Data System (ADS)

Suzuki, T.; Ide, S.; Oikawa, T.; Fujita, T.; Ishikawa, M.; Seki, M.; Matsunaga, G.; Hatae, T.; Naito, O.; Hamamatsu, K.; Sueoka, M.; Hosoyama, H.; Nakazato, M.; JT-60 Team

2008-04-01

Aiming at optimization of current profile in high-β plasmas for higher confinement and stability, a real-time control system of the minimum of the safety factor (qmin) using the off-axis current drive has been developed. The off-axis current drive can raise the safety factor in the centre and help to avoid instability that limits the performance of the plasma. The system controls the injection power of lower-hybrid waves, and hence its off-axis driven current in order to control qmin. The real-time control of qmin is demonstrated in a high-β plasma, where qmin follows the temporally changing reference qmin,ref from 1.3 to 1.7. Applying the control to another high-β discharge (βN = 1.7, βp = 1.5) with m/n = 2/1 neo-classical tearing mode (NTM), qmin was raised above 2 and the NTM was suppressed. The stored energy increased by 16% with the NTM suppressed, since the resonant rational surface was eliminated. For the future use for current profile control, current density profile for off-axis neutral beam current drive (NBCD) is for the first time measured, using the motional Stark effect diagnostic. Spatially localized NBCD profile was clearly observed at the normalized minor radius ρ of about 0.6-0.8. The location was also confirmed by multi-chordal neutron emission profile measurement. The total amount of the measured beam driven current was consistent with the theoretical calculation using the ACCOME code. The CD location in the calculation was inward shifted than the measurement.

Particle-in-cell and global simulations of α to γ transition in atmospheric pressure Penning-dominated capacitive discharges

NASA Astrophysics Data System (ADS)

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.; Chabert, P.; Lazzaroni, C.

2014-06-01

Atmospheric pressure radio-frequency (rf) capacitive micro-discharges are of interest due to emerging applications, especially in the bio-medical field. A previous global model did not consider high-power phenomena such as sheath multiplication, thus limiting its applicability to the lower power range. To overcome this, we use one-dimensional particle-in-cell (PIC) simulations of atmospheric He/0.1% N2 capacitive discharges over a wide range of currents and frequencies to guide the development of a more general global model which is also valid at higher powers. The new model includes sheath multiplication and two classes of electrons: the higher temperature ‘hot’ electrons associated with the sheaths, and the cooler ‘warm’ electrons associated with the bulk. The electric field and the electron power balance are solved analytically to determine the time-varying hot and warm temperatures and the effective rate coefficients. The particle balance equations are integrated numerically to determine the species densities. The model and PIC results are compared, showing reasonable agreement over the range of currents and frequencies studied. They indicate a transition from an α mode at low power characterized by relatively high electron temperature Te with a near uniform profile to a γ mode at high power with a Te profile strongly depressed in the bulk plasma. The transition is accompanied by an increase in density and a decrease in sheath widths. The current and frequency scalings of the model are confirmed by the PIC simulations.

Biosocial profile of New Zealand prosthetic eye wearers.

PubMed

Pine, Keith R; Sloan, Brian; Jacobs, Robert J

2012-10-12

To describe the biosocial profile of New Zealand (NZ) artificial eye wearers and establish a basis for future research and international comparison. This retrospective study surveyed 431 NZ artificial eye wearers to investigate their ethnicity, gender, age, causes of eye loss, age of current prosthesis, ocular prosthetic maintenance regimes and the extent and severity of discharge associated with prosthesis wear. Approximately 3000 people wear artificial eyes in NZ. Accidents were the main cause of eye loss prior to 1990 and medical conditions have been the main cause since. In the 1960s, the ratio of men to women losing an eye from accidents was 5:1, but during the past decade the ratio was 1.4:1. Socket discharge occurred at least twice daily for one-third of the study group. Approximately 1 in 1440 people wear artificial eyes in NZ. Decline of eye loss due to accidents is consistent with decreasing workplace and traffic accidents and may be due to improved medical management, workplace safety standards and safer roads. Mucoid discharge is prevalent in the anophthalmic population of NZ and an evidence based treatment protocol for discharge associated with prosthesis wear is needed. Research into this distressing condition is planned.

Influence of catalyst packing configuration on the discharge characteristics of dielectric barrier discharge reactors: A numerical investigation

NASA Astrophysics Data System (ADS)

Gadkari, Siddharth; Gu, Sai

2018-06-01

A two-dimensional numerical fluid model is developed for studying the influence of packing configurations on dielectric barrier discharge (DBD) characteristics. Discharge current profiles and time averaged electric field strength, electron number density, and electron temperature distributions are compared for the three DBD configurations, plain DBD with no packing, partially packed DBD, and fully packed DBD. The results show that a strong change in discharge behaviour occurs when a DBD is fully packed as compared to partial packing or no packing. While the average electric field strength and electron temperature of a fully packed DBD are higher relative to the other DBD configurations, the average electron density is substantially lower and may impede the DBD reactor performance under certain operating conditions. Possible scenarios of the synergistic effect of the combination of plasma with catalysis are also discussed.

Tethered acoustic doppler current profiler platforms for measuring streamflow

USGS Publications Warehouse

Rehmel, Michael S.; Stewart, James A.; Morlock, Scott E.

2003-01-01

A tethered-platform design with a trimaran hull and 900-megahertz radio modems is now commercially available. Continued field use has resulted in U.S. Geological Survey procedures for making tethered-platform discharge measurements, including methods for tethered-boat deployment, moving-bed tests, and measurement of edge distances.

Optimization of Surface Roughness Parameters of Al-6351 Alloy in EDC Process: A Taguchi Coupled Fuzzy Logic Approach

NASA Astrophysics Data System (ADS)

Kar, Siddhartha; Chakraborty, Sujoy; Dey, Vidyut; Ghosh, Subrata Kumar

2017-10-01

This paper investigates the application of Taguchi method with fuzzy logic for multi objective optimization of roughness parameters in electro discharge coating process of Al-6351 alloy with powder metallurgical compacted SiC/Cu tool. A Taguchi L16 orthogonal array was employed to investigate the roughness parameters by varying tool parameters like composition and compaction load and electro discharge machining parameters like pulse-on time and peak current. Crucial roughness parameters like Centre line average roughness, Average maximum height of the profile and Mean spacing of local peaks of the profile were measured on the coated specimen. The signal to noise ratios were fuzzified to optimize the roughness parameters through a single comprehensive output measure (COM). Best COM obtained with lower values of compaction load, pulse-on time and current and 30:70 (SiC:Cu) composition of tool. Analysis of variance is carried out and a significant COM model is observed with peak current yielding highest contribution followed by pulse-on time, compaction load and composition. The deposited layer is characterised by X-Ray Diffraction analysis which confirmed the presence of tool materials on the work piece surface.

Depolarization current relaxation process of insulating dielectrics after corona poling under different charging conditions

NASA Astrophysics Data System (ADS)

Zhang, J. W.; Zhou, T. C.; Wang, J. X.; Yang, X. F.; Zhu, F.; Tian, L. M.; Liu, R. T.

2017-10-01

As an insulating dielectric, polyimide is favorable for the application of optoelectronics, electrical insulation system in electric power industry, insulating, and packaging materials in space aircraft, due to its excellent thermal, mechanical and electrical insulating stability. The charge storage profile of such insulating dielectric is utmost important to its application, when it is exposed to electron irradiation, high voltage corona discharge or other treatments. These treatments could induce changes in physical and chemical properties of treated samples. To investigate the charge storage mechanism of the insulating dielectrics after high-voltage corona discharge, the relaxation processes responsible for corona charged polyimide films under different poling conditions were analyzed by the Thermally Stimulated Discharge Currents method (TSDC). In the results of thermal relaxation process, the appearance of various peaks in TSDC spectra provided a deep insight into the molecular status in the dielectric material and reflected stored space charge relaxation process in the insulating polymers after corona discharge treatments. Furthermore, the different space charge distribution status under various poling temperature and different discharge voltage level were also investigated, which could partly reflect the influence of the ambiance condition on the functional dielectrics after corona poling.

Exploration of the Townsend regime by discharge light emission in a gas discharge device

NASA Astrophysics Data System (ADS)

Hilal Yucel, Kurt

2014-01-01

The Townsend discharge mechanism has been explored in a planar microelectronic gas discharge device (MGDD) with different applied voltages U and interelectrode distance d under various pressures in air. The anode and the cathode of the MGDD are formed by a transparent SnO2 covered glass and a GaAs semiconductor, respectively. In the experiments, the discharge is found to be unstable just below the breakdown voltage Ub, whereas the discharge passes through a homogeneous stable Townsend mode beyond the breakdown voltage. The measurements are made by an electrical circuit and a CCD camera by recording the currents and light emission (LE) intensities. The intensity profiles, which are converted from the 3D light emission images along the semiconductor diameter, have been analysed for different system parameters. Different instantaneous conductivity σt regimes are found below and beyond the Townsend region. These regimes govern the current and spatio-temporal LE stabilities in the plasma system. It has been proven that the stable LE region increases up to 550 Torr as a function of pressure for small d. If the active area of the semiconductor becomes larger and the interlectrode distance d becomes smaller, the stable LE region stays nearly constant with pressure.

Validation of the thermal transport model used for ITER startup scenario predictions with DIII-D experimental data

DOE PAGES

Casper, T. A.; Meyer, W. H.; Jackson, G. L.; ...

2010-12-08

We are exploring characteristics of ITER startup scenarios in similarity experiments conducted on the DIII-D Tokamak. In these experiments, we have validated scenarios for the ITER current ramp up to full current and developed methods to control the plasma parameters to achieve stability. Predictive simulations of ITER startup using 2D free-boundary equilibrium and 1D transport codes rely on accurate estimates of the electron and ion temperature profiles that determine the electrical conductivity and pressure profiles during the current rise. Here we present results of validation studies that apply the transport model used by the ITER team to DIII-D discharge evolutionmore » and comparisons with data from our similarity experiments.« less

Flooding and sedimentation in Wheeling Creek basin, Belmont County, Ohio

USGS Publications Warehouse

Kolva, J.R.; Koltun, G.F.

1987-01-01

The Wheeling Creek basin, which is located primarily in Belmont County, Ohio, experienced three damaging floods and four less severe floods during the 29-month period from February 1979 through June 1981. Residents of the basin became concerned about factors that could have affected the severity and frequency of out-of-bank floods. In response to those concerns, the U.S. Geological Survey, in cooperation with the Ohio Department of Natural Resources, undertook a study to estimate peak discharges and recurrence intervals for the seven floods of interest, provide information on current and historical mining-related stream-channel fill or scour, and examine storm-period subbasin contributions to the sediment load in Wheeling Creek. Streamflow data for adjacent basins, rainfall data, and, in two cases, flood-profile data were used in conjunction with streamflow data subsequently collected on Wheeling Creek to provide estimates of peak discharge for the seven floods that occurred from February 1979 through June 1981. Estimates of recurrence intervals were assigned to the Peak discharges on the basin of regional regression equations that relate selected basin characteristics to peak discharge with fixed recurrence intervals. These estimates indicate that a statistically unusual number of floods with recurrence intervals of 2 years or more occurred within that time period. Three cross sections located on Wheeling Creek and four located on tributaries were established and surveyed quarterly for approximately 2 years. No evidence of appreciable stream-channel fill or scour was observed at any of the cross sections, although minor profile changes were apparent at some locations. Attempts were made to obtain historical cross-section profile data for comparison with current cross-section profiles; however, no usable data were found. Excavations of stream-bottom materials were made near the three main-stem cross-section locations and near the mouth of Jug Run. The bottom materials were examined for evidence of recently deposited sediments of mining-related origin. The only evidence of appreciable mining-related sediment deposition was found at Jug Run, and, to a lesser extent, at one main-stem site.

Validating the energy transport modeling of the DIII-D and EAST ramp up experiments using TSC

NASA Astrophysics Data System (ADS)

Liu, Li; Guo, Yong; Chan, Vincent; Mao, Shifeng; Wang, Yifeng; Pan, Chengkang; Luo, Zhengping; Zhao, Hailin; Ye, Minyou

2017-06-01

The confidence in ramp up scenario design of the China fusion engineering test reactor (CFETR) can be significantly enhanced using validated transport models to predict the current profile and temperature profile. In the tokamak simulation code (TSC), two semi-empirical energy transport models (the Coppi-Tang (CT) and BGB model) and three theory-based models (the GLF23, MMM95 and CDBM model) are investigated on the CFETR relevant ramp up discharges, including three DIII-D ITER-like ramp up discharges and one EAST ohmic discharge. For the DIII-D discharges, all the transport models yield dynamic {{\\ell}\\text{i}} within +/- 0.15 deviations except for some time points where the experimental fluctuation is very strong. All the models agree with the experimental {β\\text{p}} except that the CT model strongly overestimates {β\\text{p}} in the first half of ramp up phase. When applying the CT, CDBM and GLF23 model to estimate the internal flux, they show maximum deviations of more than 10% because of inaccuracies in the temperature profile predictions, while the BGB model performs best on the internal flux. Although all the models fall short in reproducing the dynamic {{\\ell}\\text{i}} evolution for the EAST tokamak, the result of the BGB model is the closest to the experimental {{\\ell}\\text{i}} . Based on these comparisons, we conclude that the BGB model is the most consistent among these models for simulating CFETR ohmic ramp-up. The CT model with improvement for better simulation of the temperature profiles in the first half of ramp up phase will also be attractive. For the MMM95, GLF23 and CDBM model, better prediction of the edge temperature will improve the confidence for CFETR L-mode simulation. Conclusive validation of any transport model will require extensive future investigation covering a larger variety discharges.

Quantifying acoustic doppler current profiler discharge uncertainty: A Monte Carlo based tool for moving-boat measurements

USGS Publications Warehouse

Mueller, David S.

2017-01-01

This paper presents a method using Monte Carlo simulations for assessing uncertainty of moving-boat acoustic Doppler current profiler (ADCP) discharge measurements using a software tool known as QUant, which was developed for this purpose. Analysis was performed on 10 data sets from four Water Survey of Canada gauging stations in order to evaluate the relative contribution of a range of error sources to the total estimated uncertainty. The factors that differed among data sets included the fraction of unmeasured discharge relative to the total discharge, flow nonuniformity, and operator decisions about instrument programming and measurement cross section. As anticipated, it was found that the estimated uncertainty is dominated by uncertainty of the discharge in the unmeasured areas, highlighting the importance of appropriate selection of the site, the instrument, and the user inputs required to estimate the unmeasured discharge. The main contributor to uncertainty was invalid data, but spatial inhomogeneity in water velocity and bottom-track velocity also contributed, as did variation in the edge velocity, uncertainty in the edge distances, edge coefficients, and the top and bottom extrapolation methods. To a lesser extent, spatial inhomogeneity in the bottom depth also contributed to the total uncertainty, as did uncertainty in the ADCP draft at shallow sites. The estimated uncertainties from QUant can be used to assess the adequacy of standard operating procedures. They also provide quantitative feedback to the ADCP operators about the quality of their measurements, indicating which parameters are contributing most to uncertainty, and perhaps even highlighting ways in which uncertainty can be reduced. Additionally, QUant can be used to account for self-dependent error sources such as heading errors, which are a function of heading. The results demonstrate the importance of a Monte Carlo method tool such as QUant for quantifying random and bias errors when evaluating the uncertainty of moving-boat ADCP measurements.

Investigation of Coastal Hydrogeology Utilizing Geophysical and Geochemical Tools along the Broward County Coast, Florida

USGS Publications Warehouse

Reich, Christopher D.; Swarzenski, Peter W.; Greenwood, W. Jason; Wiese, Dana S.

2008-01-01

Geophysical (CHIRP, boomer, and continuous direct-current resistivity) and geochemical tracer studies (continuous and time-series 222Radon) were conducted along the Broward County coast from Port Everglades to Hillsboro Inlet, Florida. Simultaneous seismic, direct-current resistivity, and radon surveys in the coastal waters provided information to characterize the geologic framework and identify potential groundwater-discharge sites. Time-series radon at the Nova Southeastern University National Coral Reef Institute (NSU/NCRI) seawall indicated a very strong tidally modulated discharge of ground water with 222Rn activities ranging from 4 to 10 disintegrations per minute per liter depending on tidal stage. CHIRP seismic data provided very detailed bottom profiles (i.e., bathymetry); however, acoustic penetration was poor and resulted in no observed subsurface geologic structure. Boomer data, on the other hand, showed features that are indicative of karst, antecedent topography (buried reefs), and sand-filled troughs. Continuous resistivity profiling (CRP) data showed slight variability in the subsurface along the coast. Subtle changes in subsurface resistivity between nearshore (higher values) and offshore (lower values) profiles may indicate either a freshening of subsurface water nearshore or a change in sediment porosity or lithology. Further lithologic and hydrologic controls from sediment or rock cores or well data are needed to constrain the variability in CRP data.

Internal transport barrier triggered by non-linear lower hybrid wave deposition under condition of beam-driven toroidal rotation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Q. D., E-mail: qgao@swip.ac.cn; Budny, R. V.

2015-03-15

By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (T{sub i,e}) and toroidal velocity (V{sub ϕ}) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LHmore » driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition.« less

Lower hybrid current drive in experiments for transport barriers at high βN of JET (Joint European Torus)

NASA Astrophysics Data System (ADS)

Cesario, R. C.; Castaldo, C.; Fonseca, A.; De Angelis, R.; Parail, V.; Smeulders, P.; Beurskens, M.; Brix, M.; Calabrò, G.; De Vries, P.; Mailloux, J.; Pericoli, V.; Ravera, G.; Zagorski, R.

2007-09-01

LHCD has been used in JET experiments aimed at producing internal transport barriers (ITBs) in highly triangular plasmas (δ≈0.4) at high βN (up to 3) for steady-state application. The LHCD is a potentially valuable tool for (i) modifying the target q-profile, which can help avoid deleterious MHD modes and favour the formation of ITBs, and (ii) contributing to the non-inductive current drive required to prolong such plasma regimes. The q-profile evolution has been simulated during the current ramp-up phase for such a discharge (B0 = 2.3 T, IP = 1.5 MA) where 2 MW of LHCD has been coupled. The JETTO code was used taking measured plasma profiles, and the LHCD profile modeled by the LHstar code. The results are in agreement with MSE measurements and indicate the importance of the elevated electron temperature due to LHCD, as well as the driven current. During main heating with 18 MW of NBI and 3 MW of ICRH the bootstrap current density at the edge also becomes large, consistently with the observed reduction of the local turbulence and of the MHD activity. JETTO modelling suggests that the bootstrap current can reduce the magnetic shear (sh) at large radius, potentially affecting the MHD stability and turbulence behaviour in this region. Keywords: lower hybrid current drive (LHCD), bootstrap current, q (safety factor) and shear (sh) profile evolutions.

Stability analysis of ELMs in long-pulse discharges with ELITE code on EAST tokamak

NASA Astrophysics Data System (ADS)

Wang, Y. F.; Xu, G. S.; Wan, B. N.; Li, G. Q.; Yan, N.; Li, Y. L.; Wang, H. Q.; Peng, Y.-K. Martin; Xia, T. Y.; Ding, S. Y.; Chen, R.; Yang, Q. Q.; Liu, H. Q.; Zang, Q.; Zhang, T.; Lyu, B.; Xu, J. C.; Feng, W.; Wang, L.; Chen, Y. J.; Luo, Z. P.; Hu, G. H.; Zhang, W.; Shao, L. M.; Ye, Y.; Lan, H.; Chen, L.; Li, J.; Zhao, N.; Wang, Q.; Snyder, P. B.; Liang, Y.; Qian, J. P.; Gong, X. Z.; EAST team

2018-05-01

One challenge in long-pulse and high performance tokamak operation is to control the edge localized modes (ELMs) to reduce the transient heat load on plasma facing components. Minute-scale discharges in H-mode have been achieved repeatedly on Experimental Advanced Superconducting Tokamak (EAST) since the 2016 campaign and understanding the characteristics of the ELMs in these discharges can be helpful for effective ELM control in long-pulse discharges. The kinetic profile diagnostics recently developed on EAST make it possible to perform the pedestal stability analysis quantitatively. Pedestal stability calculation of a typical long-pulse discharge with ELITE code is presented. The ideal linear stability results show that the ELM is dominated by toroidal mode number n around 10–15 and the most unstable mode structure is mainly localized in the steep pressure gradient region, which is consistent with experimental results. Compared with a typical type-I ELM discharge with larger total plasma current (I p = 600 kA), pedestal in the long-pulse H-mode discharge (I p = 450 kA) is more stable in peeling-ballooning instability and its critical peak pressure gradient is evaluated to be 65% of the former. Two important features of EAST tokamak in the long-pulse discharge are presented by comparison with other tokamaks, including a wider pedestal correlated with the poloidal pedestal beta and a smaller inverse aspect ratio and their effects on the pedestal stability are discussed. The effects of uncertainties in measurements on the linear stability results are also analyzed, including the edge electron density profile position, the separatrix position and the line-averaged effective ion charge {Z}{{e}{{f}}{{f}}} value.

Electric field measurement in microwave discharge ion thruster with electro-optic probe.

PubMed

Ise, Toshiyuki; Tsukizaki, Ryudo; Togo, Hiroyoshi; Koizumi, Hiroyuki; Kuninaka, Hitoshi

2012-12-01

In order to understand the internal phenomena in a microwave discharge ion thruster, it is important to measure the distribution of the microwave electric field inside the discharge chamber, which is directly related to the plasma production. In this study, we proposed a novel method of measuring a microwave electric field with an electro-optic (EO) probe based on the Pockels effect. The probe, including a cooling system, contains no metal and can be accessed in the discharge chamber with less disruption to the microwave distribution. This method enables measurement of the electric field profile under ion beam acceleration. We first verified the measurement with the EO probe by a comparison with a finite-difference time domain numerical simulation of the microwave electric field in atmosphere. Second, we showed that the deviations of the reflected microwave power and the beam current were less than 8% due to inserting the EO probe into the ion thruster under ion beam acceleration. Finally, we successfully demonstrated the measurement of the electric-field profile in the ion thruster under ion beam acceleration. These measurements show that the electric field distribution in the thruster dramatically changes in the ion thruster under ion beam acceleration as the propellant mass flow rate increases. These results indicate that this new method using an EO probe can provide a useful guide for improving the propulsion of microwave discharge ion thrusters.

Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, X., E-mail: xzm0005@auburn.edu; Maurer, D. A.; Knowlton, S. F.

2015-12-15

Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. The inversion radius of standard sawteeth is used tomore » infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.« less

Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

NASA Astrophysics Data System (ADS)

Ma, X.; Maurer, D. A.; Knowlton, S. F.; ArchMiller, M. C.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Hebert, J. D.; Herfindal, J. L.; Pandya, M. D.; Roberds, N. A.; Traverso, P. J.

2015-12-01

Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. The inversion radius of standard sawteeth is used to infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.

Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements

DOE PAGES

Ma, X.; Maurer, D. A.; Knowlton, Stephen F.; ...

2015-12-22

Non-axisymmetric free-boundary equilibrium reconstructions of stellarator plasmas are performed for discharges in which the magnetic configuration is strongly modified by ohmically driven plasma current. These studies were performed on the compact toroidal hybrid device using the V3FIT reconstruction code with a set of 50 magnetic diagnostics external to the plasma. With the assumption of closed magnetic flux surfaces, the reconstructions using external magnetic measurements allow accurate estimates of the net toroidal flux within the last closed flux surface, the edge safety factor, and the plasma shape of these highly non-axisymmetric plasmas. Lastly, the inversion radius of standard saw-teeth is usedmore » to infer the current profile near the magnetic axis; with external magnetic diagnostics alone, the current density profile is imprecisely reconstructed.« less

Dynamics and density estimation of hydroxyl radicals in a pulsed corona discharge

NASA Astrophysics Data System (ADS)

Ono, Ryo; Oda, Tetsuji

2002-09-01

Hydroxyl radicals generated by a pulsed corona discharge are measured by laser-induced fluorescence (LIF) with a tunable KrF excimer laser. The discharge with 35 kV voltage and 100 ns pulse current occurs between needle and plate electrodes in H2O/O2/N2 mixture at atmospheric pressure. The density and decay profile of OH radicals are studied. OH radicals decay with time after the discharge with a time constant of about 30-60 µs. The OH density is estimated to be about 7×1014 cm-3 in H2O(2.4%)/N2 mixture 10 µs after the discharge. The OH density is approximately proportional to the energy dissipated in the discharge. The O2 content influences the OH production. When the O2 content is varied in H2O(2.4%)/O2/N2 mixture, the OH density is maximum at an O2 content of 2%. The spatial distribution of OH density shows that OH radicals are produced in the streamers under positive discharge.

Complete velocity distribution in river cross-sections measured by acoustic instruments

USGS Publications Warehouse

Cheng, R.T.; Gartner, J.W.; ,

2003-01-01

To fully understand the hydraulic properties of natural rivers, velocity distribution in the river cross-section should be studied in detail. The measurement task is not straightforward because there is not an instrument that can measure the velocity distribution covering the entire cross-section. Particularly, the velocities in regions near the free surface and in the bottom boundary layer are difficult to measure, and yet the velocity properties in these regions play the most significant role in characterizing the hydraulic properties. To further characterize river hydraulics, two acoustic instruments, namely, an acoustic Doppler current profiler (ADCP), and a "BoogieDopp" (BD) were used on fixed platforms to measure the detailed velocity profiles across the river. Typically, 20 to 25 stations were used to represent a river cross-section. At each station, water velocity profiles were measured independently and/or concurrently by an ADCP and a BD. The measured velocity properties were compared and used in computation of river discharge. In a tow-tank evaluation of a BD, it has been confirmed that BD is capable of measuring water velocity at about 11 cm below the free-surface. Therefore, the surface velocity distribution across the river was extracted from the BD velocity measurements and used to compute the river discharge. These detailed velocity profiles and the composite velocity distribution were used to assess the validity of the classic theories of velocity distributions, conventional river discharge measurement methods, and for estimates of channel bottom roughness.

Understanding the stability of the low torque ITER Baseline Scenario in DIII-D

NASA Astrophysics Data System (ADS)

Turco, Francesca

2017-10-01

Analysis of the evolving current density (J), pedestal and rotation profiles in a database of 200 ITER Baseline Scenario discharges in the DIII-D tokamak sheds light on the cause of the disruptive instability limiting both high and low torque operation of these plasmas. The m =2/n =1 tearing modes, occurring after several pressure-relaxation times, are related to the shape of the current profile in the outer region of the plasma. The q =2 surface is located just inside the current pedestal, near a minimum in J. This well in J deepens at constant betaN and at lower rotation, causing the equilibrium to evolve towards a classically unstable state. Lack of core-edge differential rotation likely biases the marginal point towards instability during the secular trend in J. New results from the 2017 experimental campaign establish the first reproducible, stable operation at T =0 Nm for this scenario. A new ramp-up recipe with delayed heating keeps the discharges stable without the need for ECCD stabilization. The J profile shape in the new shots is consistent with an expansion of the previous ``shallow well'' stable operational space. Realtime Active MHD Spectroscopy (AMS) has been applied to IBS plasmas for the first time, and the plasma response measurements show that the AMS can help sense the approach to instability during the discharges. The AMS data shows the trend towards instability at low rotation, and MARS-K modelling partially reproduces the experimental trend if collisionality and resistivity are included. The modelling results are sensitive to the edge resistivity, and this can indicate that the AMS is measuring the changes in ideal (kink) stability, to which the tearing stability index delta' is correlated. Together these results constitute a crucial step to acquire physical understanding and sensing capability for the MHD stability in the Q =10 ITER scenario. Work supported by US DOE under DE-FC02-04ER54698 and DE-FG02-04ER54761.

Hollow Cathode and Keeper-region Plasma Measurements Using Ultra-fast Miniature Scanning Probes

NASA Technical Reports Server (NTRS)

Goebel, Dan M.; Jameson, Kristina K.; Watkins, Ron M.; Katz, Ira

2004-01-01

In order to support the development of comprehensive performance and life models for future deep space missions that will utilize ion thrusters, we have undertaken a study of the plasma structure in hollow cathodes using an new pneumatic scanning probe diagnostic. This device is designed to insert a miniature probe directly into the hollow cathode orifice from either the upstream insert region in the interior of the hollow cathode, or from the downstream keeper-plasma region at the exit of the hollow cathode, to provide complete axial profiles of the discharge plasma parameters. Previous attempts to diagnose this region with probes was Limited by the melting of small probes in the intense discharge near the orifice, or caused significant perturbation of the plasma by probes large enough to survive. Our new probe is extremely compact, and when configured as a single Langmuir probe, the ceramic tube insulator is only 0.5mm in diameter and the current collecting conductor has a total area of 0.002 cm2. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage waveform to the probe as it is scanned by the pneumatic actuator into and out of the plasma region, The bellow-sealed pneumatic drive scans the probe 4 cm in the cathode insert region and 10 cm in the anode/keeper plasmas region at average speeds of about 1 mm/msec, and the residence time at the end of the insertion stroke in the densest part of the plasma near the orifice is measured to be only 10 msec. Since the voltage sweep time is fast compared to the motion of the probe, axial profiles of the plasma density, temperature and potential with reasonable spatial resolution are obtained. Measurements of the internal cathode pressures and the axial plasma-parameter profiles for a hollow cathode operating at discharge currents of up to 35 A in xenon will be presented.

Theoretical and experimental investigation into high current hollow cathode arc attachment

NASA Astrophysics Data System (ADS)

Downey, Ryan T.

This research addresses several concerns of the mechanisms controlling performance and lifetime of high-current single-channel-hollow-cathodes, the central electrode and primary life-limiting component in Magnetoplasmadynamic thrusters. Specifically covered are the trends, and the theorized governing mechanisms, seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), cathode exit plume plasma density and energy, along with plasma property distributions of the internal plasma column (the IPC) of a single-channel-hollow-cathode. Both experiment and computational modeling were employed in the analysis of the cathodes. Employing Tantalum and Tungsten cathodes (of 2, 6 and 10 mm inner diameter), experiments were conducted to measure the temperature profile of operating cathodes, the width of the active zone, the discharge voltage, power, plasma arc resistance and efficiency, with mass flow rates of 50 to 300 sccm of Argon, and discharge currents of 15 to 50 Amps. Langmuir probing was used to obtain measurements for the electron temperature, plasma density and plasma potential at the cathode exit plane (down stream tip). A computational model was developed to predict the distribution of plasma inside the cathode, based upon experimentally determined boundary conditions. It was determined that the peak cathode temperature is a function of both interior cathode density and discharge current, though the location of the peak temperature is controlled gas density but not discharge current. The active zone width was found to be an increasing function of the discharge current, but a decreasing function of the mass flow rate. The width of the active zone was found to not be controlled by the magnitude of the peak cathode wall temperature. The discharge power consumed per unit of mass throughput is seen as a decreasing function of the mass flow rate, showing the increasing efficiency of the cathode. Finally, this new understanding of the mechanisms of the plasma attachment phenomena of a single-channel-hollow-cathode were extrapolated to the multi-channel-hollow-cathode environment, to explain performance characteristics of these devices seen in previous research.

Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

NASA Astrophysics Data System (ADS)

Schuster, E.; Wehner, W. P.; Barton, J. E.; Boyer, M. D.; Luce, T. C.; Ferron, J. R.; Holcomb, C. T.; Walker, M. L.; Humphreys, D. A.; Solomon, W. M.; Penaflor, B. G.; Johnson, R. D.

2017-11-01

Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feedforward  +  feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q_min=1.3, q95=4.4 ; Target 2: q_min=1.65, q95=5.0 ; Target 3: q_min=2.1, q95=6.2 ) at prescribed times during the plasma formation phase (Target 1: t=1.5 s; Target 2: t=1.3 s; Target 3: t=1.0 s). At the core of the control scheme is a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feedforward  +  feedback control scheme to consistently achieve the desired target profiles at the predefined times. These results also show how the addition of feedback control significantly improves upon the feedforward-only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.

Non-axisymmetric equilibrium reconstruction and suppression of density limit disruptions in a current-carrying stellarator

NASA Astrophysics Data System (ADS)

Ma, Xinxing; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Knowlton, S. F.; Maurer, D. A.

2017-10-01

Non-axisymmetric equilibrium reconstructions have been routinely performed with the V3FIT code in the Compact Toroidal Hybrid (CTH), a stellarator/tokamak hybrid. In addition to 50 external magnetic measurements, 160 SXR emissivity measurements are incorporated into V3FIT to reconstruct the magnetic flux surface geometry and infer the current distribution within the plasma. Improved reconstructions of current and q profiles provide insight into understanding the physics of density limit disruptions observed in current-carrying discharges in CTH. It is confirmed that the final scenario of the density limit of CTH plasmas is consistent with classic observations in tokamaks: current profile shrinkage leads to growing MHD instabilities (tearing modes) followed by a loss of MHD equilibrium. It is also observed that the density limit at a given current linearly increases with increasing amounts of 3D shaping fields. Consequently, plasmas with densities up to two times the Greenwald limit are attained. Equilibrium reconstructions show that addition of 3D fields effectively moves resonance surfaces towards the edge of the plasma where the current profile gradient is less, providing a stabilizing effect. This work is supported by US Department of Energy Grant No. DE-FG02-00ER54610.

Passive MHD Spectroscopy for Enabling Magnetic Reconstructions on Spherical Tokamak Plasmas at General Fusion Inc

NASA Astrophysics Data System (ADS)

O'Shea, Peter; Laberge, Michel; Mossman, Alex; Reynolds, Meritt

2017-10-01

Magnetic reconstructions on lab based plasma injectors at General Fusion relies heavily on edge magnetic (``Bdot'') probes. On plasma experiments built for field compression (PCS) tests, the number and locations of Bdot probes is limited by mechanical constraints. Additional information about the q profiles near the core in our Spector plasmas is obtained using passive MHD spectroscopy. The coaxial helicity injection (CHI) formation process naturally generates hollow current profiles and reversed shear early in each discharge. Central Ohmic heating naturally peaks the current profiles as our plasmas evolve in time, simultaneously reducing the core safety factor, q(0), and reverse shear. As the central, non-monotonic q-profile crosses rational flux surfaces, we observe transient magnetic reconnection events (MRE's) due to the double tearing mode. Modal analysis allows us to infer the q surfaces involved in each burst. The parametric dependence of the timing of MRE's allows us to estimate the continuous time evolution of the core q profile. Combining core MHD spectroscopy with edge magnetic probe measurements greatly enhances our certainty of the overall q profile.

Integrated modeling of temperature and rotation profiles in JET ITER-like wall discharges

NASA Astrophysics Data System (ADS)

Rafiq, T.; Kritz, A. H.; Kim, Hyun-Tae; Schuster, E.; Weiland, J.

2017-10-01

Simulations of 78 JET ITER-like wall D-D discharges and 2 D-T reference discharges are carried out using the TRANSP predictive integrated modeling code. The time evolved temperature and rotation profiles are computed utilizing the Multi-Mode anomalous transport model. The discharges involve a broad range of conditions including scans over gyroradius, collisionality, and values of q95. The D-T reference discharges are selected in anticipation of the D-T experimental campaign planned at JET in 2019. The simulated temperature and rotation profiles are compared with the corresponding experimental profiles in the radial range from the magnetic axis to the ρ = 0.9 flux surface. The comparison is quantified by calculating the RMS deviations and Offsets. Overall, good agreement is found between the profiles produced in the simulations and the experimental data. It is planned that the simulations obtained using the Multi-Mode model will be compared with the simulations using the TGLF model. Research supported in part by the US, DoE, Office of Sciences.

The effects of electron cyclotron heating and current drive on toroidal Alfvén eigenmodes in tokamak plasmas

NASA Astrophysics Data System (ADS)

Sharapov, S. E.; Garcia-Munoz, M.; Van Zeeland, M. A.; Bobkov, B.; Classen, I. G. J.; Ferreira, J.; Figueiredo, A.; Fitzgerald, M.; Galdon-Quiroga, J.; Gallart, D.; Geiger, B.; Gonzalez-Martin, J.; Johnson, T.; Lauber, P.; Mantsinen, M.; Nabais, F.; Nikolaeva, V.; Rodriguez-Ramos, M.; Sanchis-Sanchez, L.; Schneider, P. A.; Snicker, A.; Vallejos, P.; the AUG Team; the EUROfusion MST1 Team

2018-01-01

Dedicated studies performed for toroidal Alfvén eigenmodes (TAEs) in ASDEX-Upgrade (AUG) discharges with monotonic q-profiles have shown that electron cyclotron resonance heating (ECRH) can make TAEs more unstable. In these AUG discharges, energetic ions driving TAEs were obtained by ion cyclotron resonance heating (ICRH). It was found that off-axis ECRH facilitated TAE instability, with TAEs appearing and disappearing on timescales of a few milliseconds when the ECRH power was switched on and off. On-axis ECRH had a much weaker effect on TAEs, and in AUG discharges performed with co- and counter-current electron cyclotron current drive (ECCD), the effects of ECCD were found to be similar to those of ECRH. Fast ion distributions produced by ICRH were computed with the PION and SELFO codes. A significant increase in T e caused by ECRH applied off-axis is found to increase the fast ion slowing-down time and fast ion pressure causing a significant increase in the TAE drive by ICRH-accelerated ions. TAE stability calculations show that the rise in T e causes also an increase in TAE radiative damping and thermal ion Landau damping, but to a lesser extent than the fast ion drive. As a result of the competition between larger drive and damping effects caused by ECRH, TAEs become more unstable. It is concluded, that although ECRH effects on AE stability in present-day experiments may be quite significant, they are determined by the changes in the plasma profiles and are not particularly ECRH specific.

Experiment and simulation of a LiFePO4 battery pack with a passive thermal management system using composite phase change material and graphite sheets

NASA Astrophysics Data System (ADS)

Lin, Chunjing; Xu, Sichuan; Chang, Guofeng; Liu, Jinling

2015-02-01

A passive thermal management system (TMS) for LiFePO4 battery modules using phase change material (PCM) as the heat dissipation source to control battery temperature rise is developed. Expanded graphite matrix and graphite sheets are applied to compensate low thermal conductivity of PCM and improve temperature uniformity of the batteries. Constant current discharge and mixed charge-discharge duties were applied on battery modules with and without PCM on a battery thermal characteristics test platform. Experimental results show that PCM cooling significantly reduces the battery temperature rise during short-time intense use. It is also found that temperature uniformity across the module deteriorates with the increasing of both discharge time and current rates. The maximum temperature differences at the end of 1C and 2C-rate discharges are both less than 5 °C, indicating a good performance in battery thermal uniformity of the passive TMS. Experiments on warm-keeping performance show that the passive TMS can effectively keep the battery within its optimum operating temperature for a long time during cold weather uses. A three dimensional numerical model of the battery pack with the passive TMS was conducted using ANSYS Fluent. Temperature profiles with respect to discharging time reveal that simulation shows good agreement with experiment at 1C-discharge rate.

Comparative modelling of lower hybrid current drive with two launcher designs in the Tore Supra tokamak

NASA Astrophysics Data System (ADS)

Nilsson, E.; Decker, J.; Peysson, Y.; Artaud, J.-F.; Ekedahl, A.; Hillairet, J.; Aniel, T.; Basiuk, V.; Goniche, M.; Imbeaux, F.; Mazon, D.; Sharma, P.

2013-08-01

Fully non-inductive operation with lower hybrid current drive (LHCD) in the Tore Supra tokamak is achieved using either a fully active multijunction (FAM) launcher or a more recent ITER-relevant passive active multijunction (PAM) launcher, or both launchers simultaneously. While both antennas show comparable experimental efficiencies, the analysis of stability properties in long discharges suggest different current profiles. We present comparative modelling of LHCD with the two different launchers to characterize the effect of the respective antenna spectra on the driven current profile. The interpretative modelling of LHCD is carried out using a chain of codes calculating, respectively, the global discharge evolution (tokamak simulator METIS), the spectrum at the antenna mouth (LH coupling code ALOHA), the LH wave propagation (ray-tracing code C3PO), and the distribution function (3D Fokker-Planck code LUKE). Essential aspects of the fast electron dynamics in time, space and energy are obtained from hard x-ray measurements of fast electron bremsstrahlung emission using a dedicated tomographic system. LHCD simulations are validated by systematic comparisons between these experimental measurements and the reconstructed signal calculated by the code R5X2 from the LUKE electron distribution. An excellent agreement is obtained in the presence of strong Landau damping (found under low density and high-power conditions in Tore Supra) for which the ray-tracing model is valid for modelling the LH wave propagation. Two aspects of the antenna spectra are found to have a significant effect on LHCD. First, the driven current is found to be proportional to the directivity, which depends upon the respective weight of the main positive and main negative lobes and is particularly sensitive to the density in front of the antenna. Second, the position of the main negative lobe in the spectrum is different for the two launchers. As this lobe drives a counter-current, the resulting driven current profile is also different for the FAM and PAM launchers.

Psychopathology profiles of acutely suicidal adolescents: Associations with post-discharge suicide attempts and rehospitalization

PubMed Central

Berona, Johnny; Horwitz, Adam G.; Czyz, Ewa K.; King, Cheryl A.

2017-01-01

Background Suicidal adolescents are heterogeneous, which can pose difficulties in predicting suicidal behavior. The Youth Self-Report (YSR) psychopathology profiles predict the future onset of psychopathology and suicide-related outcomes. The present study examined the prevalence and correlates of YSR psychopathology profiles among suicidal adolescents and prospective associations with post-discharge rates of suicide attempts and psychiatric rehospitalization. Methods Participants were acutely suicidal, psychiatrically hospitalized adolescents (N=433 at baseline; n=355 at follow-up) who were enrolled in a psychosocial intervention trial during hospitalization. Psychopathology profiles were assessed at baseline. Suicide attempts and rehospitalization were assessed for up to 12 months following discharge. Results Latent profile analysis identified four psychopathology profiles: subclinical, primarily internalizing, and moderately and severely dysregulated. At baseline, profiles differed by history of non-suicidal self-injury (NSSI) and multiple suicide attempts (MA) as well as severity of suicide ideation, hopelessness, depressive symptoms, anxiety symptoms, substance abuse, and functional impairment. The dysregulation profiles predicted suicide attempts within 3 months post-discharge. The internalizing profile predicted suicide attempts and rehospitalization at 3 and 12 months. Limitations This study’s participants were enrolled in a randomized trial and were predominantly female, which limit generalizability. Additionally, only a history of NSSI was assessed. Conclusions The dysregulation profile was overrepresented among suicidal youth and associated with impairment in several domains as well as suicide attempts shortly after discharge. Adolescents with a severe internalizing profile also reported adverse outcomes throughout the study period. Psychopathology profiles warrant further examination in terms of their potential predictive validity in relation to suicide-related outcomes. PMID:27894037

Transport and Performance in DIII--D Discharges with Weak or Negative Central Magnetic Shear

NASA Astrophysics Data System (ADS)

Greenfield, C. M.

1996-11-01

The previously reported [B.W. Rice et al., Phys. Plasmas 3, 1983 (1996)] improved performance in DIII-D plasmas with weak or negative central magnetic shear has been additionally enhanced in recent experiments where controlled L-H transitions were used to further broaden the pressure profile and delay detrimental MHD activity [E.A. Lazarus et al., submitted to Phys. Rev. Letters]. These discharges exhibit the highest plasma energy (>=4 MJ) and fusion reactivity (R_DD <= 4.8 × 10^16 s-1, Q_DD <= 0.00146, equivalent Q_DT <= 0.32) yet realized in DIII-D. In such discharges, the core magnetic shear is reversed by tailoring the current profile through application of early, low power, neutral beam injection. These plasmas often undergo a transition to a high performance state, usually following an increase in the applied heating power. At the transition time, we observe the formation of an internal transport barrier near the location of the minimum safety factor, q_min. Formation of this barrier, which can result in central peaking of the temperature and density profiles, is consistent with suppression of turbulence by locally enhanced E×B flow shear. Beam emission spectroscopy and far infrared scattering measurements made in the vicinity of the barrier show that at the time of transition to high performance, fluctuation levels are reduced to below the threshold of detection (tilden/n <= 0.1%). Analysis with the ONETWO and TRANSP transport codes indicates concomitant reductions in the core ion thermal diffusivity to levels at or below Chang-Hinton neoclassical. Smaller reductions are indicated for the electrons. An L-H transition is programmed shortly before the plasma would become MHD unstable in order to broaden the profiles and delay the onset of instabilities. In the resulting state, the region exhibiting ion diffusivities at or below neoclassical is extended to nearly the entire plasma. Analysis to date suggests that the effect of strongly negative vs. weak magnetic shear on transport is negligible, although there is a significant effect on stability. A comparison of transport in strong and weakly sheared discharges will be shown, both in L- (peaked profiles) and H-mode (broadened profiles).

2D model of plasma current sheath propagation in a Mather type plasma focus device

NASA Astrophysics Data System (ADS)

Mohamad, Saiful Najmee; Rashid, Natashah Abdul; Halim, Mohd Mahadi; Ali, Jalil

2018-06-01

Plasma focus device is initially developed by two known researchers back in the 1960s, Mather and Filippov. The interest on the research built due to its capability to produce high energetic neutron from a fusion reaction. The relevance of the research in Plasma Focus device remain after decade is because of its competence to produce multi radiation yield and its known physics during nanosecond of plasma compression remain open for discussed. In the recent years, the direction of the plasma research is in device optimisation, where many possible configurations have been present, discuss and highlighting its performance for differences conditions. The significant difference between the electrode configuration is the profile of the dynamics inductance. In this context, this paper comparatively discusses the 1D dynamics model of the plasma current sheath (PSC) propagation axially and radially with the 2D model. The 2D model algorithm for the PSC propagation is developed using macro (Excel) by incorporating a drag force to solve the momentum exchange of the PCS with neutral gas. The discharge current profile of both model successfully calibrated to agree with each other with 2% difference at 1.83 µs after discharge but with an expense of different assumption.

O-regime dynamics and modeling in Tore Supra

NASA Astrophysics Data System (ADS)

Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Ségui, J.-L.

2009-06-01

The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r ) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r ) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

Discharging dynamics in an electrolytic cell

NASA Astrophysics Data System (ADS)

Feicht, Sarah E.; Frankel, Alexandra E.; Khair, Aditya S.

2016-07-01

We analyze the dynamics of a discharging electrolytic cell comprised of a binary symmetric electrolyte between two planar, parallel blocking electrodes. When a voltage is initially applied, ions in the electrolyte migrate towards the electrodes, forming electrical double layers. After the system reaches steady state and the external current decays to zero, the applied voltage is switched off and the cell discharges, with the ions eventually returning to a uniform spatial concentration. At voltages on the order of the thermal voltage VT=kBT /q ≃25 mV, where kB is Boltzmann's constant, T is temperature, and q is the charge of a proton, experiments on surfactant-doped nonpolar fluids observe that the temporal evolution of the external current during charging and discharging is not symmetric [V. Novotny and M. A. Hopper, J. Electrochem. Soc. 126, 925 (1979), 10.1149/1.2129195; P. Kornilovitch and Y. Jeon, J. Appl. Phys. 109, 064509 (2011), 10.1063/1.3554445]. In fact, at sufficiently large voltages (several VT), the current during discharging is no longer monotonic: it displays a "reverse peak" before decaying in magnitude to zero. We analyze the dynamics of discharging by solving the Poisson-Nernst-Planck equations governing ion transport via asymptotic and numerical techniques in three regimes. First, in the "linear regime" when the applied voltage V is formally much less than VT, the charging and discharging currents are antisymmetric in time; however, the potential and charge density profiles during charging and discharging are asymmetric. The current evolution is on the R C timescale of the cell, λDL /D , where L is the width of the cell, D is the diffusivity of ions, and λD is the Debye length. Second, in the (experimentally relevant) thin-double-layer limit ɛ =λD/L ≪1 , there is a "weakly nonlinear" regime defined by VT≲V ≲VTln(1 /ɛ ) , where the bulk salt concentration is uniform; thus the R C timescale of the evolution of the current magnitude persists. However, nonlinear, voltage-dependent, capacitance of the double layer is responsible for a break in temporal antisymmetry of the charging and discharging currents. Third, the reverse peak in the discharging current develops in a "strongly nonlinear" regime V ≳VTln(1 /ɛ ) , driven by neutral salt adsorption into the double layers and consequent bulk depletion during charging. The strongly nonlinear regime features current evolution over three timescales. The current decays in magnitude on the double layer relaxation timescale, λD2/D ; then grows exponentially in time towards the reverse peak on the diffusion timescale, L2/D , indicating that the reverse peak is the results of fast diffusion of ions from the double layer layer to the bulk. Following the reverse peak, the current decays exponentially to zero on the R C timescale. Notably, the current at the reverse peak and the time of the reverse peak saturate at large voltages V ≫VTln(1 /ɛ ) . We provide semi-analytic expressions for the saturated reverse peak time and current, which can be used to infer charge carrier diffusivity and concentration from experiments.

A Critical Fast Ion Beta in the Madison Symmetric Torus Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Capecchi, William J.

The first fast-ion profile measurements have been made in a reversed-field pinch (RFP) plasma. A large population of fast-ions are deposited in the core of the Madison Symmetric Torus (MST) through use of a 1 MW neutral beam injector (NBI) giving rise to a variety of beam-driven instabilities. One such mode, the energetic-particle mode (EPM) has been shown to reduce fast-ion content in MST, evident through drops in signal levels of the advanced neutral particle analyzer (ANPA). EPMs in MST appear as bursts of magnetic fluctuations at a lab frequency of ˜100 kHz reaching peak amplitude and decaying away within 100 microseconds. A burst ensemble of the neutron data does not reveal a drop in neutron emission across a burst, implying the population of fast-ions transported by a burst constitute a small fraction of the total. The burst may also pitch-angle scatter out of the ANPA phase space or be transported to mid-radius where charge-exchange with the background neutrals or fast-ion orbit stochasticity may reduce fast-ion confinement. Data gathered from the expanded neutron diagnostic suite including a new collimated neutron detector (CiNDe) was used to reconstruct the fast-ion profile in MST and measure critical fast-ion beta quantities. Measurements were made in plasma conditions with varying magnetic field strength in order to investigate the interplay between the energetic particle (EP) drive and Alfven continuum damping. The measured values of the core fast-ion beta (7.5% (1.2%) in 300 (500) kA plasmas) are reduced from classical predictions (TRANSP predicts up to 10% core value) due to EPM activity. The frequency, magnitude, and rate of occurrence of the bursts depends on the tearing mode amplitude, Alfven continuum damping rate, fast-ion profile shape, and resonant orbit dynamics. Marginal stability was reached in both moderate- (300 kA) and high- (500 kA) current discharges, marked by sustained EPM activity and a saturated global neutron signal during NBI. The difference in profile shape is interpreted to be related to the core-most resonant tearing mode amplitude, as a larger core magnetic island moves the location of steepest fast-ion gradient further out in radius, resulting in lower confinement of the fast-ions. The reconstructed profile is more strongly peaked at lower current, consistent with a lower measured core-most tearing mode amplitude. A larger dataset at lower current gives enough temporal resolution to investigate the evolution of the fast-ion profile. The suppression of the core-most tearing mode amplitude during NBI results in a rapid and dynamically evolving fast-ion profile at the beginning of the NBI discharge and results in an initially broader profile early evolving into a more strongly peaked profile later in the NBI discharge.

From current-driven to neoclassically driven tearing modes.

PubMed

Reimerdes, H; Sauter, O; Goodman, T; Pochelon, A

2002-03-11

In the TCV tokamak, the m/n = 2/1 island is observed in low-density discharges with central electron-cyclotron current drive. The evolution of its width has two distinct growth phases, one of which can be linked to a "conventional" tearing mode driven unstable by the current profile and the other to a neoclassical tearing mode driven by a perturbation of the bootstrap current. The TCV results provide the first clear observation of such a destabilization mechanism and reconcile the theory of conventional and neoclassical tearing modes, which differ only in the dominant driving term.

A Preliminary Evaluation of Near-Transducer Velocities Collected with Low-Blank Acoustic Doppler Current Profiler

USGS Publications Warehouse

Gartner, J.W.; Ganju, N.K.; ,

2002-01-01

Many streams and rivers for which the US Geological Survey must provide discharge measurements are too shallow to apply existing acoustic Doppler current profiler techniques for flow measurements of satisfactory quality. Because the same transducer is used for both transmitting and receiving acoustic signals in most Doppler current profilers, some small time delay is required for acoustic "ringing" to be damped out of transducers before meaningful measurements can be made. The result of that time delay is that velocity measurements cannot be made close to the transducer thus limiting the usefulness of these instruments in shallow regions. Manufacturers and users are constantly striving for improvements to acoustic instruments which would permit useful discharge measurements in shallow rivers and streams that are still often measured with techniques and instruments more than a century old. One promising area of advance appeared to be reduction of time delay (blank) required between transmitting and receiving signals during acoustic velocity measurements. Development of a low- or zero-blank transducer by RD Instruments3 held promise that velocity measurements could be made much closer to the transducer and thus in much shallower water. Initial experience indicates that this is not the case; limitation of measurement quality appears to be related to the physical presence of the transducer itself within the flow field. The limitation may be the result of changes to water flow pattern close to the transducer rather than transducer ringing characteristics as a function of blanking distance. Results of field experiments are discussed that support this conclusion and some minimum measurement distances from transducer are suggested based on water current speed and ADCP sample modes.

High performance advanced tokamak regimes in DIII-D for next-step experiments

NASA Astrophysics Data System (ADS)

Greenfield, C. M.; Murakami, M.; Ferron, J. R.; Wade, M. R.; Luce, T. C.; Petty, C. C.; Menard, J. E.; Petrie, T. W.; Allen, S. L.; Burrell, K. H.; Casper, T. A.; DeBoo, J. C.; Doyle, E. J.; Garofalo, A. M.; Gorelov, I. A.; Groebner, R. J.; Hobirk, J.; Hyatt, A. W.; Jayakumar, R. J.; Kessel, C. E.; La Haye, R. J.; Jackson, G. L.; Lohr, J.; Makowski, M. A.; Pinsker, R. I.; Politzer, P. A.; Prater, R.; Strait, E. J.; Taylor, T. S.; West, W. P.; DIII-D Team

2004-05-01

Advanced Tokamak (AT) research in DIII-D [K. H. Burrell for the DIII-D Team, in Proceedings of the 19th Fusion Energy Conference, Lyon, France, 2002 (International Atomic Energy Agency, Vienna, 2002) published on CD-ROM] seeks to provide a scientific basis for steady-state high performance operation in future devices. These regimes require high toroidal beta to maximize fusion output and poloidal beta to maximize the self-driven bootstrap current. Achieving these conditions requires integrated, simultaneous control of the current and pressure profiles, and active magnetohydrodynamic stability control. The building blocks for AT operation are in hand. Resistive wall mode stabilization via plasma rotation and active feedback with nonaxisymmetric coils allows routine operation above the no-wall beta limit. Neoclassical tearing modes are stabilized by active feedback control of localized electron cyclotron current drive (ECCD). Plasma shaping and profile control provide further improvements. Under these conditions, bootstrap supplies most of the current. Steady-state operation requires replacing the remaining Ohmic current, mostly located near the half radius, with noninductive external sources. In DIII-D this current is provided by ECCD, and nearly stationary AT discharges have been sustained with little remaining Ohmic current. Fast wave current drive is being developed to control the central magnetic shear. Density control, with divertor cryopumps, of AT discharges with edge localized moding H-mode edges facilitates high current drive efficiency at reactor relevant collisionalities. A sophisticated plasma control system allows integrated control of these elements. Close coupling between modeling and experiment is key to understanding the separate elements, their complex nonlinear interactions, and their integration into self-consistent high performance scenarios. Progress on this development, and its implications for next-step devices, will be illustrated by results of recent experiment and simulation efforts.

Inert gas thrusters

NASA Technical Reports Server (NTRS)

Kaufman, H. R.

1976-01-01

Inert gases are of interest as possible alternatives to the usual electric thruster propellants of mercury and cesium. The multipole discharge chamber investigated was shown capable of low discharge chamber losses and flat ion beam profiles with a minimum of optimization. Minimum discharge losses were 200 to 250 eV/ion for xenon and 300 to 350 eV/ion for argon, while flatness parameters in the plane of the accelerator grid were 0.85 to 0.95. The design used employs low magnetic field strengths, which permits the use of sheet-metal parts. The corner problem of the discharge chamber was resolved with recessed corner anodes, which approximately equalized both the magnetic field above the anodes and the electron currents to these anodes. Argon hollow cathodes were investigated at currents up to about 5 amperes using internal thermionic emitters. Cathode chamber diameter optimized in the 1.0 to 2.5 cm range, while orifices diameter optimized in the 0.5 to 5 mm range. The use of a bias voltage for the internal emitter extended the operating range and facilitated starting. The masses of 15 and 30 cm flight type thrusters were estimated at about 4.2 and 10.8 kg.

Exploring the Model Design Space for Battery Health Management

NASA Technical Reports Server (NTRS)

Saha, Bhaskar; Quach, Cuong Chi; Goebel, Kai Frank

2011-01-01

Battery Health Management (BHM) is a core enabling technology for the success and widespread adoption of the emerging electric vehicles of today. Although battery chemistries have been studied in detail in literature, an accurate run-time battery life prediction algorithm has eluded us. Current reliability-based techniques are insufficient to manage the use of such batteries when they are an active power source with frequently varying loads in uncertain environments. The amount of usable charge of a battery for a given discharge profile is not only dependent on the starting state-of-charge (SOC), but also other factors like battery health and the discharge or load profile imposed. This paper presents a Particle Filter (PF) based BHM framework with plug-and-play modules for battery models and uncertainty management. The batteries are modeled at three different levels of granularity with associated uncertainty distributions, encoding the basic electrochemical processes of a Lithium-polymer battery. The effects of different choices in the model design space are explored in the context of prediction performance in an electric unmanned aerial vehicle (UAV) application with emulated flight profiles.

Extracting Prior Distributions from a Large Dataset of In-Situ Measurements to Support SWOT-based Estimation of River Discharge

NASA Astrophysics Data System (ADS)

Hagemann, M.; Gleason, C. J.

2017-12-01

The upcoming (2021) Surface Water and Ocean Topography (SWOT) NASA satellite mission aims, in part, to estimate discharge on major rivers worldwide using reach-scale measurements of stream width, slope, and height. Current formalizations of channel and floodplain hydraulics are insufficient to fully constrain this problem mathematically, resulting in an infinitely large solution set for any set of satellite observations. Recent work has reformulated this problem in a Bayesian statistical setting, in which the likelihood distributions derive directly from hydraulic flow-law equations. When coupled with prior distributions on unknown flow-law parameters, this formulation probabilistically constrains the parameter space, and results in a computationally tractable description of discharge. Using a curated dataset of over 200,000 in-situ acoustic Doppler current profiler (ADCP) discharge measurements from over 10,000 USGS gaging stations throughout the United States, we developed empirical prior distributions for flow-law parameters that are not observable by SWOT, but that are required in order to estimate discharge. This analysis quantified prior uncertainties on quantities including cross-sectional area, at-a-station hydraulic geometry width exponent, and discharge variability, that are dependent on SWOT-observable variables including reach-scale statistics of width and height. When compared against discharge estimation approaches that do not use this prior information, the Bayesian approach using ADCP-derived priors demonstrated consistently improved performance across a range of performance metrics. This Bayesian approach formally transfers information from in-situ gaging stations to remote-sensed estimation of discharge, in which the desired quantities are not directly observable. Further investigation using large in-situ datasets is therefore a promising way forward in improving satellite-based estimates of river discharge.

Study of short atmospheric pressure dc glow microdischarge in air

NASA Astrophysics Data System (ADS)

Kudryavtsev, Anatoly; Bogdanov, Eugene; Chirtsov, Alexander; Emelin, Sergey

2011-10-01

The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen and oxygen atoms; ozone molecule; and different nitrogen and oxygen ions with different plasmochemical reactions between them. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region. Gas heating plays an important role in shaping the discharge profiles. The results of experiments and simulations of short (without positive column) atmospheric pressure dc glow discharge in air are presented. We used metal steel electrodes with a gap of 5-100 microns. The experimental voltage-current characteristic's (VAC) have a constant or slightly increasing form at low gap. The most stable microdischarges were burning with a flat cathode and rounded anode, when the length of the discharge is automatically established near the minimum of the Paschen curve by changing their binding on the anode. In this case microdischarge was stable and it had growing VAC. For simulations we used 2D fluid model with kinetic description of electrons. We solved the balance equations for the vibrationally- and the electronically-excited states of a nitrogen and oxygen molecules; nitrogen and oxygen atoms; ozone molecule; and different nitrogen and oxygen ions with different plasmochemical reactions between them. Simulations predicted the main regions of the dc glow discharges including cathode and anode sheath and plasma of negative glow, Faraday dark space and transition region. Gas heating plays an important role in shaping the discharge profiles. This work was supported by the FZP and SPbGU

Differential distribution of voltage-gated channels in myelinated and unmyelinated baroreceptor afferents.

PubMed

Schild, John H; Kunze, Diana L

2012-12-24

Voltage gated ion channels (VGC) make possible the frequency coding of arterial pressure and the neurotransmission of this information along myelinated and unmyelinated fiber pathways. Although many of the same VGC isoforms are expressed in both fiber types, it is the relative expression of each that defines the unique discharge properties of myelinated A-type and unmyelinated C-type baroreceptors. For example, the fast inward Na⁺ current is a major determinant of the action potential threshold and the regenerative transmembrane current needed to sustain repetitive discharge. In A-type baroreceptors the TTX-sensitive Na(v)1.7 VGC contributes to the whole cell Na⁺ current. Na(v)1.7 is expressed at a lower density in C-type neurons and in conjunction with TTX-insensitive Na(v)1.8 and Na(v)1.9 VGC. As a result, action potentials of A-type neurons have firing thresholds that are 15-20 mV more negative and upstroke velocities that are 5-10 times faster than unmyelinated C-type neurons. A more depolarized threshold in conjunction with a broader complement of non-inactivating K(V) VGC subtypes produces C-type action potentials that are 3-4 times longer in duration than A-type neurons and at markedly lower levels of cell excitability. Unmyelinated baroreceptors also express KCa1.1 which provides approximately 25% of the total outward K⁺ current. KCa1.1 plays a critically important role in shaping the action potential profile of C-type neurons and strongly impacts neuronal excitability. A-type neurons do not functionally express the KCa1.1 channel despite having a whole cell Ca(V) current quite similar to that of C-type neurons. As a result, A-type neurons do not have the frequency-dependent braking forces of KCa1.1. Lack of a KCa current and only a limited complement of non-inactivating K(V) VGC in addition to a hyperpolarization activated HCN1 current that is nearly 10 times larger than in C-type neurons leads to elevated levels of discharge in A-type neurons, a hallmark of myelinated baroreceptors. Interestingly, HCN2 and HCN4 expression levels are comparable in both fiber types. Collectively, such apportion of VGC constrains the neural coding of myelinated A-type baroreceptors to low threshold, high frequency, high fidelity discharge but with a limited capacity for neuromodulation of afferent bandwidth. Unmyelinated C-type baroreceptors require greater depolarizing forces for spike initiation and have a low frequency discharge profile that is often poorly correlated with the physiological stimulus. But the complement of VGC in C-type neurons provides far greater capacity for neuromodulation of cell excitability than can be obtained from A-type baroreceptors. Copyright © 2012 Elsevier B.V. All rights reserved.

Identification of ballast water discharge profiles of a port to enable effective ballast water management and environmental studies

NASA Astrophysics Data System (ADS)

David, Matej; Gollasch, Stephan; Penko, Ludvik

2018-03-01

Information about the profile of ballast water discharges in a port is one of the basic elements of the decision making process in ballast water risk assessment and management, and supports the evaluation of dimensions and processes of aquatic species invasions with vessels ballast water. In the lack of ballast water reporting, ballast water discharge assessments need to be conducted. In this study we have assessed and compared ballast water discharge profiles of two ports with different maritime traffic and cargo profiles, the Port of Hamburg (Germany) and the Muuga Harbour, Port of Tallinn (Estonia). This study shows methods and approaches which can be used to assess volumes and donor ports of ballast water discharges for a port at the level of each vessel call. These methods and approaches can be applied to any port to support the implementation of feasible and efficient ballast water management measures and to enable environmental studies including long-term accumulation risks of disinfection by-products from ballast water management systems making use of active substances, as well as for discharges of other chemical compounds.

Analysis of Rotation and Transport Data in C-Mod ITB Plasmas

NASA Astrophysics Data System (ADS)

Fiore, C. L.; Rice, J. E.; Reinke, M. L.; Podpaly, Y.; Bespamyatnov, I. O.; Rowan, W. L.

2009-11-01

Internal transport barriers (ITBs) spontaneously form near the half radius of Alcator C-Mod plasmas when the EDA H-mode is sustained for several energy confinement times in either off-axis ICRF heated discharges or in purely ohmic heated plasmas. These plasmas exhibit strongly peaked density and pressure profiles, static or peaking temperature profiles, peaking impurity density profiles, and thermal transport coefficients that approach neoclassical values in the core. It has long been observed that the intrinsic central plasma rotation that is strongly co-current following the H-mode transition slows and often reverses as the density peaks as the ITB forms. Recent spatial measurements demonstrate that the rotation profile develops a well in the core region that decreases continuously as central density rises while the value outside of the core remains strongly co-current. This results in the formation of a steep potential gradient/strong electric field at the location of the foot of the ITB density profile. The resulting E X B shearing rate is also quite significant at the foot. These analyses and the implications for plasma transport and stability will be presented.

System OptimizatIon of the Glow Discharge Optical Spectroscopy Technique Used for Impurity Profiling of ION Implanted Gallium Arsenide.

DTIC Science & Technology

1980-12-01

AFIT/GEO/EE/80D-1 I -’ SYSTEM OPTIMIZATION OF THE GLOW DISCHARGE OPTICAL SPECTROSCOPY TECHNIQUE USED FOR IMPURITY PROFILING OF ION IMPLANTED GALLIUM ...EE/80D-1 (\\) SYSTEM OPTIMIZATION OF THE GLOW DISCHARGE OPTICAL SPECTROSCOPY TECHNIQUE USED FOR IMPURITY PROFILING OF ION IMPLANTED GALLIUM ARSENIDE...semiconductors, specifically annealed and unan- nealed ion implanted gallium arsenide (GaAs). Methods to improve the sensitivity of the GDOS system have

Spatial Concentrations of Silicon Atoms in RF Discharges of Silane.

DTIC Science & Technology

1985-02-18

regions. These profiles were much more sensitive to plasma chemistry changes than profiles obtained from plasma emission. Experiments with nitrogen...addition demonstrated significant changes in the silicon atom profiles near the sheath boundary. Originator supplied keywords include: rf discharge, silane, plasma chemistry , silicon atom, laser-induced fluorescence.

Simulation of profile evolution from ramp-up to ramp-down and optimization of tokamak plasma termination with the RAPTOR code

NASA Astrophysics Data System (ADS)

Teplukhina, A. A.; Sauter, O.; Felici, F.; Merle, A.; Kim, D.; the TCV Team; the ASDEX Upgrade Team; the EUROfusion MST1 Team

2017-12-01

The present work demonstrates the capabilities of the transport code RAPTOR as a fast and reliable simulator of plasma profiles for the entire plasma discharge, i.e. from ramp-up to ramp-down. This code focuses, at this stage, on the simulation of electron temperature and poloidal flux profiles using prescribed equilibrium and some kinetic profiles. In this work we extend the RAPTOR transport model to include a time-varying plasma equilibrium geometry and verify the changes via comparison with ATSRA code simulations. In addition a new ad hoc transport model based on constant gradients and suitable for simulations of L-H and H-L mode transitions has been incorporated into the RAPTOR code and validated with rapid simulations of the time evolution of the safety factor and the electron temperature over the entire AUG and TCV discharges. An optimization procedure for the plasma termination phase has also been developed during this work. We define the goal of the optimization as ramping down the plasma current as fast as possible while avoiding any disruptions caused by reaching physical or technical limits. Our numerical study of this problem shows that a fast decrease of plasma elongation during current ramp-down can help in reducing plasma internal inductance. An early transition from H- to L-mode allows us to reduce the drop in poloidal beta, which is also important for plasma MHD stability and control. This work shows how these complex nonlinear interactions can be optimized automatically using relevant cost functions and constraints. Preliminary experimental results for TCV are demonstrated.

Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schuster, Eugenio J.; Wehner, William P.; Barton, Joseph E.

Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q min = 1.3,q 95 = 4:4; Target 2: q min = 1.65,q 95 = 5.0; Target 3: q min = 2.1,q 95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme ismore » a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.« less

Enhanced reproducibility of L-mode plasma discharges via physics-model-based q-profile feedback control in DIII-D

DOE PAGES

Schuster, Eugenio J.; Wehner, William P.; Barton, Joseph E.; ...

2017-08-09

Recent experiments on DIII-D demonstrate the potential of physics-model-based q-profile control to improve reproducibility of plasma discharges. A combined feed forward + feedback control scheme is employed to optimize the current ramp-up phase by consistently achieving target q profiles (Target 1: q min = 1.3,q 95 = 4:4; Target 2: q min = 1.65,q 95 = 5.0; Target 3: q min = 2.1,q 95 = 6:2) at prescribed times during the plasma formation phase (Target 1: t = 1.5 s; Target 2: t = 1:3 s; Target 3: t = 1.0 s). At the core of the control scheme ismore » a nonlinear, first-principles-driven, physics-based, control-oriented model of the plasma dynamics valid for low confinement (L-mode) scenarios. To prevent undesired L-H transitions, a constraint on the maximum allowable total auxiliary power is imposed in addition to the maximum powers for the individual heating and current-drive sources. Experimental results are presented to demonstrate the effectiveness of the combined feed forward + feedback control scheme to consistently achieve the desired target profiles at the predefined times. Here, these results also show how the addition of feedback control significantly improves upon the feed forward only control solution by reducing the matching error and also how the feedback controller is able to reduce the matching error as the constraint on the maximum allowable total auxiliary power is relaxed while keeping the plasma in L-mode.« less

Time-averaged current analysis of a thunderstorm using ground-based measurements

NASA Astrophysics Data System (ADS)

Driscoll, Kevin T.; Blakeslee, Richard J.; Koshak, William J.

1994-05-01

The amount of upward current provided to the ionosphere by a thunderstorm that appeared over the Kennedy Space Center (KSC) on July 11, 1978, is reexamined using an analytic equation that describes a bipolar thunderstorm's current contribution to the global circuit in terms of its generator current, lightning currents, the altitudes of its charge centers, and the conductivity profile of the atmosphere. Ground-based measurements, which were obtained from a network of electric field mills positioned at various distances from the thunderstorm, were used to characterize the electrical activity inside the thundercloud. The location of the lightning discharges, the type of lightning, and the amount of charge neutralized during this thunderstorm were computed through a least squares inversion of the measured changes in the electric fields following each lightning discharge. These measurements provided the information necessary to implement the analytic equation, and consequently, a time-averaged estimate of this thunderstorm's current contribution to the global circuit was calculated. From these results the amount of conduction current supplied to the ionosphere by this small thunderstorm was computed to be less than 25% of the time-averaged generator current that flowed between the two vertically displaced charge centers.

Validation of exposure time for discharge measurements made with two bottom-tracking acoustic doppler current profilers

USGS Publications Warehouse

Czuba, J.A.; Oberg, K.

2008-01-01

Previous work by Oberg and Mueller of the U.S. Geological Survey in 2007 concluded that exposure time (total time spent sampling the flow) is a critical factor in reducing measurement uncertainty. In a subsequent paper, Oberg and Mueller validated these conclusions using one set of data to show that the effect of exposure time on the uncertainty of the measured discharge is independent of stream width, depth, and range of boat speeds. Analysis of eight StreamPro acoustic Doppler current profiler (ADCP) measurements indicate that they fall within and show a similar trend to the Rio Grande ADCP data previously reported. Four special validation measurements were made for the purpose of verifying the conclusions of Oberg and Mueller regarding exposure time for Rio Grande and StreamPro ADCPs. Analysis of these measurements confirms that exposure time is a critical factor in reducing measurement uncertainty and is independent of stream width, depth, and range of boat speeds. Furthermore, it appears that the relation between measured discharge uncertainty and exposure time is similar for both Rio Grande and StreamPro ADCPs. These results are applicable to ADCPs that make use of broadband technology using bottom-tracking to obtain the boat velocity. Based on this work, a minimum of two transects should be collected with an exposure time for all transects greater than or equal to 720 seconds in order to achieve an uncertainty of ??5 percent when using bottom-tracking ADCPs. ?? 2008 IEEE.

The effect of safety factor profile on transport in steady-state, high-performance scenarios

DOE PAGES

Holcomb, C. T.; Ferron, J. R.; Luce, T. C.; ...

2012-03-09

In this study, an analysis of the dependence of transport on the safety factor profile in high-performance, steady-state scenario discharges is presented. This is based on experimental scans of q 95 and q min taken with fixed β N, toroidal field, double-null plasma shape, divertor pumping, and electron cyclotron current drive input. The temperature and thermal diffusivity profiles were found to vary considerably with the q-profile, and these variations were significantly different for electrons and ions. With fixed q 95, both temperature profiles increase and broaden as q min is increased and the magnetic shear becomes low or negative inmore » the inner half radius, but these temperature profile changes are stronger for the electrons. Power balance calculations show the peak in the ion thermal diffusivity (χ i) at ρ – 0.6 – 0.8 increases with q 95 or q min.« less

Pearl Harbor Biological Survey

DTIC Science & Technology

1974-08-30

properties, uses, and driving mechanisms affecting the harbor is given. The methods of obtaining current data, salinity profiles, and temperature... salinities were used for each calibration In order to check the salinity computation mechanism of the Instrument. Temperature calibrations were...Water Temperature Contours for Navy Thermal Discharges 3.2-23 3.2-7. General Layout of Pearl Harbor Showing Mean Monthly Salinity (3L) Variation

Improvement of Current Drive Efficiency in Projected FNSF Discharges

NASA Astrophysics Data System (ADS)

Prater, R.; Chan, V.; Garofalo, A.

2012-10-01

The Fusion Nuclear Science Facility - Advanced Tokamak (FNSF-AT) is envisioned as a facility that uses the tokamak approach to address the development of the AT path to fusion and fusion's energy objectives. It uses copper coils for a compact device with high βN and moderate power gain. The major radius is 2.7 m and central toroidal field is 5.44 T. Achieving the required confinement and stability at βN˜3.7 requires a current profile with negative central shear and qmin>1. Off-axis Electron Cyclotron Current Drive (ECCD), in addition to high bootstrap current fraction, can help support this current profile. Using the applied EC frequency and launch location as free parameters, a systematic study has been carried out to optimize the ECCD in the range ρ= 0.5-0.7. Using a top launch, making use of a large toroidal component to the launch direction, adjusting the vertical launch angle so that the rays propagate nearly parallel to the resonance, and adjusting the frequency for optimum total current give a high dimensionless efficiency of 0.44 for a broad ECCD profile peaked at ρ=0.7, and the driven current is 17 kA/MW for n20= 2.1 and Te= 10.3 keV locally.

Discharge estimation from H-ADCP measurements in a tidal river subject to sidewall effects and a mobile bed

NASA Astrophysics Data System (ADS)

Sassi, M. G.; Hoitink, A. J. F.; Vermeulen, B.; Hidayat, null

2011-06-01

Horizontal acoustic Doppler current profilers (H-ADCPs) can be employed to estimate river discharge based on water level measurements and flow velocity array data across a river transect. A new method is presented that accounts for the dip in velocity near the water surface, which is caused by sidewall effects that decrease with the width to depth ratio of a channel. A boundary layer model is introduced to convert single-depth velocity data from the H-ADCP to specific discharge. The parameters of the model include the local roughness length and a dip correction factor, which accounts for the sidewall effects. A regression model is employed to translate specific discharge to total discharge. The method was tested in the River Mahakam, representing a large river of complex bathymetry, where part of the flow is intrinsically three-dimensional and discharge rates exceed 8000 m3 s-1. Results from five moving boat ADCP campaigns covering separate semidiurnal tidal cycles are presented, three of which are used for calibration purposes, whereas the remaining two served for validation of the method. The dip correction factor showed a significant correlation with distance to the wall and bears a strong relation to secondary currents. The sidewall effects appeared to remain relatively constant throughout the tidal cycles under study. Bed roughness length is estimated at periods of maximum velocity, showing more variation at subtidal than at intratidal time scales. Intratidal variations were particularly obvious during bidirectional flow conditions, which occurred only during conditions of low river discharge. The new method was shown to outperform the widely used index velocity method by systematically reducing the relative error in the discharge estimates.

Seawater circulation in sediments driven by interactions between seabed topography and fluid density

USGS Publications Warehouse

Konikow, Leonard F.; Akhavan, M.; Langevin, C.D.; Michael, H.A.; Sawyer, A.H.

2013-01-01

Measurements of submarine groundwater discharge (SGD) in coastal areas often show that the saltwater discharge component is substantially greater than the freshwater discharge. Several mechanisms have been proposed to explain these high saltwater discharge values, including saltwater circulation driven by wave and tidal pumping, wave and tidal setup in intertidal areas, currents over bedforms, and density gradients resulting from mixing along the freshwater-saltwater interface. In this study, a new mechanism for saltwater circulation and discharge is proposed and evaluated. The process results from interaction between bedform topography and buoyancy forces, even without flow or current over the bedform. In this mechanism, an inverted salinity (and density) profile in the presence of both a bedform on the seafloor and an upward flow of fresher groundwater from depth induces a downward flow of saline pore water under the troughs and upward flow under the adjacent crest of the bedform. The magnitude and occurrence of the mechanism were tested using numerical methods. The results indicate that this mechanism could drive seawater circulation under a limited range of conditions and contribute 20%–30% of local SGD when and where the process is operative. Bedform shape, hydraulic conductivity, hydraulic head, and salinity at depth in the porous media, aquifer thickness, effective porosity, and hydrodynamic dispersion are among the factors that control the occurrence and magnitude of the circulation of seawater by this mechanism.

Physical Monitoring of Flow Into and Within Great Salt Lake, Utah

NASA Astrophysics Data System (ADS)

Kenney, T. A.; Naftz, D. L.; Perschon, W. C.

2006-12-01

Great Salt Lake (GSL) is the hydrologic terminus for the eastern part of the Great Basin. As the largest inland waterbody in the Western United States, GSL plays a critical ecologic role for many migratory bird species. In terms of harvest quantity and quality, the brine shrimp (Artemia) fishery of GSL is among the strongest in the world. The characteristic of GSL as a hydrologic sink amplifies anthropogenic activities throughout the basin, most specifically activities that occur along its eastern and southern shores, the urban corridor of the Wasatch Front. In 1959 GSL was divided into north and south parts by a rock-fill railroad causeway. Since then, an extreme density gradient between the north and south part exists as a result of limited conveyance of water from the south part where more than 95 percent of the total freshwater input occurs (Loving, and others, 2000). To date, little is known about the loading and cycling of various chemical constituents associated with human activities including nutrients, selenium, and mercury. Hydroacoustic technology, specifically acoustic Doppler technology, is currently being used to obtain a better physical understanding of GSL. Since 1999, stratified bi-directional discharge has been measured at the causeway breach with an acoustic Doppler current profiler. From these measurements, net flow components to the north and south have been used to assess the movement of water and salt through the causeway. Low hydraulic gradients and variable backwater conditions at the two largest inflows to GSL required the deployment of in-situ acoustic Doppler velocity meters to accurately compute continuous discharge, critical for constituent loading analyses. These discharge records, computed using the index velocity method, show sensitivity to large wind events that can lead to a complete reversal of flow. Velocity profiles acquired during two multi-day water-quality synoptic sampling runs with acoustic Doppler current profilers have identified surface currents related to both freshwater inflow and wind throughout main body GSL. Velocity profiles have also determined the flow direction and magnitude of a persistent anoxic layer at depth in the south part of GSL. Movement of this layer between the two main basins of the south along a topographically high divide has also been documented (5 to 31 centimeters per second). References Cited Loving, B.L., Waddell, K.M., and Miller, C.W., 2000, Water and salt balance of Great Salt Lake, Utah, and simulation of water and salt movement through the causeway, 1987-98, U.S. Geological Survey Water-Resources Investigations Report 00-4221, 31 p.

Verification of 1921 peak discharge at Skagit River near Concrete, Washington, using 2003 peak-discharge data

USGS Publications Warehouse

Mastin, M.C.; Kresch, D.L.

2005-01-01

The 1921 peak discharge at Skagit River near Concrete, Washington (U.S. Geological Survey streamflow-gaging station 12194000), was verified using peak-discharge data from the flood of October 21, 2003, the largest flood since 1921. This peak discharge is critical to determining other high discharges at the gaging station and to reliably estimating the 100-year flood, the primary design flood being used in a current flood study of the Skagit River basin. The four largest annual peak discharges of record (1897, 1909, 1917, and 1921) were used to determine the 100-year flood discharge at Skagit River near Concrete. The peak discharge on December 13, 1921, was determined by James E. Stewart of the U.S. Geological Survey using a slope-area measurement and a contracted-opening measurement. An extended stage-discharge rating curve based on the 1921 peak discharge was used to determine the peak discharges of the three other large floods. Any inaccuracy in the 1921 peak discharge also would affect the accuracies of the three other largest peak discharges. The peak discharge of the 1921 flood was recalculated using the cross sections and high-water marks surveyed after the 1921 flood in conjunction with a new estimate of the channel roughness coefficient (n value) based on an n-verification analysis of the peak discharge of the October 21, 2003, flood. The n value used by Stewart for his slope-area measurement of the 1921 flood was 0.033, and the corresponding calculated peak discharge was 240,000 cubic feet per second (ft3/s). Determination of a single definitive water-surface profile for use in the n-verification analysis was precluded because of considerable variation in elevations of surveyed high-water marks from the flood on October 21, 2003. Therefore, n values were determined for two separate water-surface profiles thought to bracket a plausible range of water-surface slopes defined by high-water marks. The n value determined using the flattest plausible slope was 0.024 and the corresponding recalculated discharge of the 1921 slope-area measurement was 266,000 ft3/s. The n value determined using the steepest plausible slope was 0.032 and the corresponding recalculated discharge of the 1921 slope-area measurement was 215,000 ft3/s. The two recalculated discharges were 10.8 percent greater than (flattest slope) and 10.4 percent less than (steepest slope) the 1921 peak discharge of 240,000 ft3/s. The 1921 peak discharge was not revised because the average of the two recalculated discharges (240,500 ft3/s) is only 0.2 percent greater than the 1921 peak discharge.

Does Classification of Chronic Musculoskeletal Disorder Patients Into Psychosocial Subgroups Predict Differential Treatment Responsiveness and 1-Year Outcomes After a Functional Restoration Program?

PubMed

Asih, Sali; Mayer, Tom G; Williams, Mark; Choi, Yun Hee; Gatchel, Robert J

2015-12-01

The objectives of this study: (1) to assess whether Multidimensional Pain Inventory (MPI) profiles predicted differential responses to a functional restoration program (FRP) in chronic disabling occupational musculoskeletal disorder (CDOMD) patients; (2) to examine whether coping style improves following FRP; and (3) to determine whether discharge MPI profiles predict discharge psychosocial and 1-year socioeconomic outcomes. Consecutive CDOMD patients (N=716) were classified into Adaptive Coper (AC, n=209), Interpersonally Distressed (ID, n=154), Dysfunctional (DYS, n=310), and Anomalous (n=43) using the MPI, and reclassified at discharge. Profiles were compared on psychosocial measures and 1-year socioeconomic outcomes. An intent-to-treat sample analyzed the effect of drop-outs on treatment responsiveness. The MPI classification significantly predicted program completion (P=0.001), although the intent-to-treat analyses found no significant effects of drop-out on treatment responsiveness. There was a significant increase in the number of patients who became AC or Anomalous at FRP discharge and a decrease in those who were ID or DYS. Patients who changed or remained as DYS at FRP discharge reported the highest levels of pain, disability, and depression. No significant interaction effect was found between MPI group and time for pain intensity or disability. All groups improved on psychosocial measures at discharge. DYS patients had decreased work retention and a greater health care utilization at 1 year. An FRP was clinically effective for CDOMD patients regardless of initial MPI profiles. The FRP modified profiles, with patients changing from negative to positive profiles. Discharge DYS were more likely to have poor 1-year outcomes. Those classified as Anomalous had a good prognosis for functional recovery similar to ACs.

Dependence of Edge Profiles and Stability on Neutral Beam Power in NSTX

NASA Astrophysics Data System (ADS)

Travis, P.; Canal, G. P.; Osborne, T. H.; Maingi, R.; Sabbagh, S. A.; NSTX-U Team

2016-10-01

Studying the effect of neutral beam injected (NBI) power on edge plasma profiles and magnetohydrodynamic (MHD) stability is central to the understanding of edge-localized modes (ELMs). Higher heating power should quicken the development of pressure and current-driven peeling-ballooning modes. NSTX ELMy H-mode discharges with NBI power of 4, 5 and 6 MW were analyzed with a python-based set of analysis tools that fit plasma profiles, compute kinetic equilibria, and evaluate the MHD stability with the code ELITE. Electron density and temperature from Thomson scattering measurements, and ion density, temperature, and rotation from Charge Exchange Recombination Spectroscopy were inputs to the kinetic equilibrium fits. The power scan provides an opportunity to compare the stability calculations from the ELITE (ideal) and M3D-C1 (resistive) codes. Preliminary analysis shows that edge pressure profiles for the 5 and 6 MW discharges are comparable, suggesting they both reach a stability boundary. The 4 MW case shows lower edge pressure, which is likely limited by edge transport below the edge stability boundary. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

Guiding of High Laser Intensities in Long Plasma Channels

NASA Astrophysics Data System (ADS)

Levin, M.; Eisenmann, S.; Palchan, T.; Zigler, A.; Sugiyama, K.; Nakajima, K.; Kaganovich, D.; Hubbard, R. F.; Ting, A.; Gordon, D. F.; Sprangle, P.; Fraenkel, M.; Maman, S.; Henis, Z.

Plasma channels have been widely used to guide intense laser pulses over many Rayleigh lengths. Using optimized segmented capillary discharges, we demonstrated guided propagation of ultra short (100 fs) high intensity (1016 W/cm-2, limited by the laser system) pulses over distances up to 12.6 cm and intensities above 1018W/cm2 for 1.5cm boron nitride capillary. Both radial and longitudinal density profiles of plasma channels were studied under various discharge conditions. A new diagnostic technique is presented in which the transport of a guided laser pulse at different delay times from the initiation of the discharge is sampled on a single discharge shot. Using external, 10 nsec Nd YAG laser of several tenths of milijoules to ignite polyethylene capillaries we have demonstrated channels of various length in density range of 1017 - 1019 cm-3 and up to 25% deep. The longitudinal profiles were found to be remarkably uniform in both short and long capillaries. The Boron Nitride capillary has provided a guiding medium that can withstand more than 1000 shots. Using these capillaries we have guided laser intensities above 1018W/cm2. The laser ignition of capillary discharge provided reliable almost jitter free approach. The concerns related to influence of relatively high current density flow through capillary on the injected electrons were studied extensively by us both theoretically and experimentally using a simple injection method. The method is based on the interaction of a high intensity laser pulse with a thin wire placed near capillary entrance. The influence of magnetic fields was found to be insignificant. Using this method we have studied transport of electrons though capillary discharge.

Equilibrium theory of cylindrical discharges with special application to helicons

NASA Astrophysics Data System (ADS)

Curreli, Davide; Chen, Francis F.

2011-11-01

Radiofrequency discharges used in industry often have centrally peaked plasma density profiles n(r) although ionization is localized at the edge, even in the presence of a dc magnetic field. This can be explained with a simple cylindrical model in one dimension as long as the short-circuit effect at the endplates causes a Maxwellian electron distribution. Surprisingly, a universal profile can be obtained, which is self-similar for all discharges with uniform electron temperature Te and neutral density nn. When all collisions and ionizations are radially accounted for, the ion drift velocity toward the wall reaches the Bohm velocity at a radius which can be identified with the sheath edge, thus obviating a pre-sheath calculation. For non-uniform Te and nn, the profiles change slightly but are always peaked on axis. For helicon discharges, iteration with the HELIC code for antenna-wave coupling yields profiles consistent with both energy deposition and diffusion profiles. Calculated density is in absolute-value agreement with experiment.

Calculation of Eddy Currents In the CTH Vacuum Vessel and Coil Frame

DOE Office of Scientific and Technical Information (OSTI.GOV)

A. Zolfaghari, A. Brooks, A. Michaels, J. Hanson, and G. Hartwell

2012-09-25

Knowledge of eddy currents in the vacuum vessel walls and nearby conducting support structures can significantly contribute to the accuracy of Magnetohydrodynamics (MHD) equilibrium reconstruction in toroidal plasmas. Moreover, the magnetic fields produced by the eddy currents could generate error fields that may give rise to islands at rational surfaces or cause field lines to become chaotic. In the Compact Toroidal Hybrid (CTH) device (R0 = 0.75 m, a = 0.29 m, B ≤ 0.7 T), the primary driver of the eddy currents during the plasma discharge is the changing flux of the ohmic heating transformer. Electromagnetic simulations are usedmore » to calculate eddy current paths and profile in the vacuum vessel and in the coil frame pieces with known time dependent currents in the ohmic heating coils. MAXWELL and SPARK codes were used for the Electromagnetic modeling and simulation. MAXWELL code was used for detailed 3D finite-element analysis of the eddy currents in the structures. SPARK code was used to calculate the eddy currents in the structures as modeled with shell/surface elements, with each element representing a current loop. In both cases current filaments representing the eddy currents were prepared for input into VMEC code for MHD equilibrium reconstruction of the plasma discharge. __________________________________________________« less

Combined magnetic and kinetic control of advanced tokamak steady state scenarios based on semi-empirical modelling

DOE PAGES

Moreau, Didier; Artaud, J. F.; Ferron, John R.; ...

2015-05-01

This paper shows that semi-empirical data-driven models based on a twotime- scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, β N, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated data obtained using a rapidly converging plasmamore » transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0-D scaling laws and 1.5-D ordinary differential equations. A number of open loop simulations were performed, in which the heating and current drive (H&CD) sources were randomly modulated around the typical values of a reference AT discharge on DIIID. Using these simulated data, a two-time-scale state space model was obtained for the coupled evolution of the poloidal flux profile and βN parameter, and a controller was synthesized based on the near-optimal ARTAEMIS algorithm [D. Moreau et al., Nucl. Fusion 53 (2013) 063020]. The paper discusses the results of closed-loop nonlinear simulations, using this controller for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and β N are satisfactorily tracked with a time scale of about ten seconds, despite large disturbances applied to the feedforward powers and plasma parameters. The effectiveness of the control algorithm is thus demonstrated for long pulse and steady state high-β N AT discharges. Its robustness with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.« less

Multi-temperature state-dependent equivalent circuit discharge model for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Propp, Karsten; Marinescu, Monica; Auger, Daniel J.; O'Neill, Laura; Fotouhi, Abbas; Somasundaram, Karthik; Offer, Gregory J.; Minton, Geraint; Longo, Stefano; Wild, Mark; Knap, Vaclav

2016-10-01

Lithium-sulfur (Li-S) batteries are described extensively in the literature, but existing computational models aimed at scientific understanding are too complex for use in applications such as battery management. Computationally simple models are vital for exploitation. This paper proposes a non-linear state-of-charge dependent Li-S equivalent circuit network (ECN) model for a Li-S cell under discharge. Li-S batteries are fundamentally different to Li-ion batteries, and require chemistry-specific models. A new Li-S model is obtained using a 'behavioural' interpretation of the ECN model; as Li-S exhibits a 'steep' open-circuit voltage (OCV) profile at high states-of-charge, identification methods are designed to take into account OCV changes during current pulses. The prediction-error minimization technique is used. The model is parameterized from laboratory experiments using a mixed-size current pulse profile at four temperatures from 10 °C to 50 °C, giving linearized ECN parameters for a range of states-of-charge, currents and temperatures. These are used to create a nonlinear polynomial-based battery model suitable for use in a battery management system. When the model is used to predict the behaviour of a validation data set representing an automotive NEDC driving cycle, the terminal voltage predictions are judged accurate with a root mean square error of 32 mV.

Flood of April 2007 and Flood-Frequency Estimates at Streamflow-Gaging Stations in Western Connecticut

USGS Publications Warehouse

Ahearn, Elizabeth A.

2009-01-01

A spring nor'easter affected the East Coast of the United States from April 15 to 18, 2007. In Connecticut, rainfall varied from 3 inches to more than 7 inches. The combined effects of heavy rainfall over a short duration, high winds, and high tides led to widespread flooding, storm damage, power outages, evacuations, and disruptions to traffic and commerce. The storm caused at least 18 fatalities (none in Connecticut). A Presidential Disaster Declaration was issued on May 11, 2007, for two counties in western Connecticut - Fairfield and Litchfield. This report documents hydrologic and meteorologic aspects of the April 2007 flood and includes estimates of the magnitude of the peak discharges and peak stages during the flood at 28 streamflow-gaging stations in western Connecticut. These data were used to perform flood-frequency analyses. Flood-frequency estimates provided in this report are expressed in terms of exceedance probabilities (the probability of a flood reaching or exceeding a particular magnitude in any year). Flood-frequency estimates for the 0.50, 0.20, 0.10, 0.04, 0.02, 0.01, and 0.002 exceedance probabilities (also expressed as 50-, 20-, 10-, 4-, 2-, 1-, and 0.2- percent exceedance probability, respectively) were computed for 24 of the 28 streamflow-gaging stations. Exceedance probabilities can further be expressed in terms of recurrence intervals (2-, 5-, 10-, 25-, 50-, 100-, and 500-year recurrence interval, respectively). Flood-frequency estimates computed in this study were compared to the flood-frequency estimates used to derive the water-surface profiles in previously published Federal Emergency Management Agency (FEMA) Flood Insurance Studies. The estimates in this report update and supersede previously published flood-frequency estimates for streamflowgaging stations in Connecticut by incorporating additional years of annual peak discharges, including the peaks for the April 2007 flood. In the southwest coastal region of Connecticut, the April 2007 peak discharges for streamflow-gaging stations with records extending back to 1955 were the second highest peak discharges on record; the 1955 annual peak discharges are the highest peak discharges in the station records. In the Housatonic and South Central Coast Basins, the April 2007 peak discharges for streamflow-gaging stations with records extending back to 1930 or earlier ranked between the fourth and eighth highest discharges on record, with the 1936, 1938, and 1955 floods as the largest floods in the station records. The peak discharges for the April 2007 flood have exceedance probabilities ranging between 0.10 to 0.02 (a 10- to 2-percent chance of being exceeded in a given year, respectively) with the majority (80 percent) of the stations having exceedance probabilities between 0.10 to 0.04. At three stations - Norwalk River at South Wilton, Pootatuck River at Sandy Hook, and Still River at Robertsville - the April 2007 peak discharges have an exceedance probability of 0.02. Flood-frequency estimates made after the April 2007 flood were compared to flood-frequency estimates used to derive the water-surface profiles (also called flood profiles) in FEMA Flood Insurance Studies developed for communities. In general, the comparison indicated that at the 0.10 exceedance probability (a 10-percent change of being exceeded in a given year), the discharges from the current (2007) flood-frequency analysis are larger than the discharges in the FEMA Flood Insurance Studies, with a median change of about +10 percent. In contrast, at the 0.01 exceedance probability (a 1-percent change of being exceeded in a year), the discharges from the current flood-frequency analysis are smaller than the discharges in the FEMA Flood Insurance Studies, with a median change of about -13 percent. Several stations had more than + 25 percent change in discharges at the 0.10 exceedance probability and are in the following communities: Winchester (Still River at Robertsv

Measurements of fast ion spatial dynamics during magnetic activity in the RFP

NASA Astrophysics Data System (ADS)

Goetz, J. A.; Anderson, J. K.; Bonofiglo, P.; Kim, J.; McConnell, R.; Magee, R. M.

2017-10-01

Fast ions in the RFP are only weakly affected by a stochastic magnetic field and behave nearly classically in concentration too low to excite Alfvenic activity. At high fast ion concentration sourced by H-NBI in 300kA RFP discharges, a substantial drop in core-localized high pitch fast ions is observed during bursts of coupled EPM and IAE (magnetic island-induced Alfven eigenmode) activity (100-200kHz) through neutral particle analysis. Sourcing instead fast deuterium with NBI, the DD fusion products can measure the dynamics of the fast ion density profile. Both a collimated neutron detector and a new 3MeV fusion proton detector loaned by TriAlpha Energy measure the fast ion density profile with 5cm spatial resolution and 100 μs temporal resolution. In D-NBI, the bursting EPM is excited at slightly lower frequency and the IAE activity is nearly absent, likely due to an isotope effect and loss of wave-particle interaction. In these cases, neutral particle analysis shows little change in the core-localized high pitch fast ion content, and the fusion product profile indicates little change in the fast ion density profile, leaving unexplained the mechanism removing EPM drive. We measure a substantial redistribution of the fast ion profile due to strong lower-frequency ( 30kHz) MHD activity that accompanies the current profile relaxation in the RFP. Profile flattening is strongest in low bulk density discharges, which often occur with a total increase in global neutron flux from acceleration of the beam ions. Work supported by US DoE.

Numerical investigation of the effect of driving voltage pulse shapes on the characteristics of low-pressure argon dielectric barrier discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eslami, E., E-mail: eeslami@iust.ac.ir; Barjasteh, A.; Morshedian, N.

2015-06-15

In this work, we numerically compare the effect of a sinusoidal, triangular, and rectangular pulsed voltage profile on the calculated particle production, electric current, and gas voltage in a dielectric barrier discharge. The total argon gas pressure of 400 Pa, the distance between dielectrics of 5 mm, the dielectric thickness of 0.7 mm, and the temperature of T = 300 K were considered as input parameters. The different driving voltage pulse shapes (triangular, rectangular, and sinusoidal) are considered as applied voltage with a frequency of 7 kHz and an amplitude of 700 V peak to peak. It is shown thatmore » applying a rectangular voltage, as compared with a sinusoidal or triangle voltage, increases the current peak, while the peak width is decreased. Higher current density is related to high production of charged particles, which leads to the generation of some highly active species, such as Ar* (4s level), and Ar** (4p level) in the gap.« less

Controllable transition from positive space charge to negative space charge in an inverted cylindrical magnetron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rane, R., E-mail: ramu@ipr.res.in; Ranjan, M.; Mukherjee, S.

2016-01-15

The combined effect of magnetic field (B), gas pressure (P), and the corresponding discharge voltage on the discharge properties of argon in inverted cylindrical magnetron has been investigated. In the experiment, anode is biased with continuous 10 ms sinusoidal half wave. It is observed that at a comparatively higher magnetic field (i.e., >200 gauss) and lower operating pressure (i.e., <1 × 10{sup −3} mbar), the discharge extinguishes and demands a high voltage to reignite. Discharge current increases with increase in magnetic field and starts reducing at sufficiently higher magnetic field for a particular discharge voltage due to restricted electron diffusion towards the anode.more » It is observed that B/P ratio plays an important role in sustaining the discharge and is constant for a discharge voltage. The discharge is transformed to negative space charge regime from positive space charge regime at certain B/P ratio and this ratio varies linearly with the discharge voltage. The space charge reversal is indicated by the radial profile of the floating potential and plasma potential in between two electrodes for different magnetic fields. At a particular higher magnetic field (beyond 100 gauss), the floating potential increases gradually with the radial distance from cathode, whereas it remains almost constant at lower magnetic field.« less

A phenomenological model for orificed hollow cathodes. Ph.D. Thesis, 1 Dec. 1981 - 1 Dec. 1982; [electrostatic thruster

NASA Technical Reports Server (NTRS)

Siegfried, D. E.

1982-01-01

A quartz hollow tube cathode was used to determine the operating conditions within a mercury orificed hollow cathode. Insert temperature profiles, cathode current distributions, plasma properties profile, and internal pressure-mass flow rate results are summarized and used in a phenomenological model which qualitatively describes electron emission and plasma production processes taking place within the cathode. By defining an idealized ion production region within which most of the plasma processes are concentrated, this model is expressed analytically as a simple set of equations which relate cathode dimensions and specifiable operating conditions, such as mass flow rate and discharge current, to such important parameters as emission surface temperature and internal plasma properties. Key aspects of the model are examined.

Velocity bias induced by flow patterns around ADCPs and associated deployment platforms

USGS Publications Warehouse

Mueller, David S.

2015-01-01

Velocity measurements near the Acoustic Doppler Current Profiler (ADCP) are important for mapping surface currents, measuring velocity and discharge in shallow streams, and providing accurate estimates of discharge in the top unmeasured portion of the water column. Improvements to ADCP performance permit measurement of velocities much closer (5 cm) to the transducer than has been possible in the past (25 cm). Velocity profiles collected by the U.S. Geological Survey (USGS) with a 1200 kHz Rio Grande Zedhead ADCP in 2002 showed a negative bias in measured velocities near the transducers. On the basis of these results, the USGS initiated a study combining field, laboratory, and numerical modeling data to assess the effect of flow patterns caused by flow around the ADCP and deployment platforms on velocities measured near the transducers. This ongoing study has shown that the negative bias observed in the field is due to the flow pattern around the ADCP. The flow pattern around an ADCP violates the basic assumption of flow homogeneity required for an accurate three-dimensional velocity solution. Results, to date (2014), have indicated velocity biases within the measurable profile, due to flow disturbance, for the TRDI 1200 kHz Rio Grande Zedhead and the SonTek RiverSurveyor M9 ADCPs. The flow speed past the ADCP, the mount and the deployment platform have also been shown to play an important role in the magnitude and extent of the velocity bias.

A motional Stark effect diagnostic analysis routine for improved resolution of iota in the core of the large helical device.

PubMed

Dobbins, T J; Ida, K; Suzuki, C; Yoshinuma, M; Kobayashi, T; Suzuki, Y; Yoshida, M

2017-09-01

A new Motional Stark Effect (MSE) analysis routine has been developed for improved spatial resolution in the core of the Large Helical Device (LHD). The routine was developed to reduce the dependency of the analysis on the Pfirsch-Schlüter (PS) current in the core. The technique used the change in the polarization angle as a function of flux in order to find the value of diota/dflux at each measurement location. By integrating inwards from the edge, the iota profile can be recovered from this method. This reduces the results' dependency on the PS current because the effect of the PS current on the MSE measurement is almost constant as a function of flux in the core; therefore, the uncertainty in the PS current has a minimal effect on the calculation of the iota profile. In addition, the VMEC database was remapped from flux into r/a space by interpolating in mode space in order to improve the database core resolution. These changes resulted in a much smoother iota profile, conforming more to the physics expectations of standard discharge scenarios in the core of the LHD.

The Physics of Local Helicity Injection Non-Solenoidal Tokamak Startup

NASA Astrophysics Data System (ADS)

Redd, A. J.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Jardin, S.

2013-10-01

Non-solenoidal startup via Local Helicity Injection (LHI) uses compact current injectors to produce toroidal plasma current Ip up to 170 kA in the PEGASUS Toroidal Experiment, driven by 4-8 kA injector current on timescales of 5-20 milliseconds. Increasing the Ip buildup duration enables experimental demonstration of plasma position control on timescales relevant for high-current startup. LHI-driven discharges exhibit bursty MHD activity, apparently line-tied kinking of LHI-driven field lines, with the bursts correlating with rapid equilibrium changes, sharp Ip rises, and sharp drops in the injector impedance. Preliminary NIMROD results suggest that helical LHI-driven current channels remain coherent, with Ip increases due to reconnection between adjacent helical turns forming axisymmetric plasmoids, and corresponding sharp drops in the bias circuit impedance. The DC injector impedance is consistent with a space charge limit at low bias current and a magnetic limit at high bias current. Internal measurements show the current density profile starts strongly hollow and rapidly fills in during Ip buildup. Simulations of LHI discharges using the Tokamak Simulation Code (TSC) will provide insight into the detailed current drive mechanism and guide experiments on PEFASUS and NSTX-U. Work supported by US DOE Grants DE-FG02-96ER54375 and DE-SC0006928.

Status of SPV/CPV Testing

NASA Technical Reports Server (NTRS)

Brown, Harry; Hall, Steve

1999-01-01

This presentation reviews the status test of Single Pressure Vessel (SPV)/Common Pressure Vessel (CPV) being conducted by the Navy. Slides review the design and tests by NASA, and the Airforce of CPV's. There are 5 different CPV models of CPV's which have been tested or are currently being tested for NASA and the Air Force. The batteries, tests, and results are presented. Graphs show the life cycle voltage, the pressure trend, the discharge/charge profile and the pressure profile for the batteries tested. Descriptions of those CPV batteries are given for those batteries which have been received but have not been tested. The development of the SPV is briefly described, followed by design specification for two packs from NASA and the Air Force. The acceptance test criteria are reviewed, followed by a review of the life cycle test conditions. The trend plots of voltage vs. cycle is given for the two packs. The end of charge, and the end of discharge voltages plots are shown. Plots showing the pressure and recharge vs. cycle are shown. Plots also show the voltage profiles. These plots are shown for both batteries using the SPV design submitted by NASA and the Air Force.

Extrapolation of the DIII-D high poloidal beta scenario to ITER steady-state using transport modeling

NASA Astrophysics Data System (ADS)

McClenaghan, J.; Garofalo, A. M.; Meneghini, O.; Smith, S. P.

2016-10-01

Transport modeling of a proposed ITER steady-state scenario based on DIII-D high βP discharges finds that the core confinement may be improved with either sufficient rotation or a negative central shear q-profile. The high poloidal beta scenario is characterized by a large bootstrap current fraction( 80%) which reduces the demands on the external current drive, and a large radius internal transport barrier which is associated with improved normalized confinement. Typical temperature and density profiles from the non-inductive high poloidal beta scenario on DIII-D are scaled according to 0D modeling predictions of the requirements for achieving Q=5 steady state performance in ITER with ``day one'' H&CD capabilities. Then, TGLF turbulence modeling is carried out under systematic variations of the toroidal rotation and the core q-profile. Either strong negative central magnetic shear or rotation are found to successfully provide the turbulence suppression required to maintain the temperature and density profiles. This work supported by the US Department of Energy under DE-FC02-04ER54698.

Use of radars to monitor stream discharge by noncontact methods

USGS Publications Warehouse

Costa, J.E.; Cheng, R.T.; Haeni, F.P.; Melcher, N.; Spicer, K.R.; Hayes, E.; Plant, W.; Hayes, K.; Teague, C.; Barrick, D.

2006-01-01

Conventional measurements of river flows are costly, time‐consuming, and frequently dangerous. This report evaluates the use of a continuous wave microwave radar, a monostatic UHF Doppler radar, a pulsed Doppler microwave radar, and a ground‐penetrating radar to measure river flows continuously over long periods and without touching the water with any instruments. The experiments duplicate the flow records from conventional stream gauging stations on the San Joaquin River in California and the Cowlitz River in Washington. The purpose of the experiments was to directly measure the parameters necessary to compute flow: surface velocity (converted to mean velocity) and cross‐sectional area, thereby avoiding the uncertainty, complexity, and cost of maintaining rating curves. River channel cross sections were measured by ground‐penetrating radar suspended above the river. River surface water velocity was obtained by Bragg scattering of microwave and UHF Doppler radars, and the surface velocity data were converted to mean velocity on the basis of detailed velocity profiles measured by current meters and hydroacoustic instruments. Experiments using these radars to acquire a continuous record of flow were conducted for 4 weeks on the San Joaquin River and for 16 weeks on the Cowlitz River. At the San Joaquin River the radar noncontact measurements produced discharges more than 20% higher than the other independent measurements in the early part of the experiment. After the first 3 days, the noncontact radar discharge measurements were within 5% of the rating values. On the Cowlitz River at Castle Rock, correlation coefficients between the USGS stream gauging station rating curve discharge and discharge computed from three different Doppler radar systems and GPR data over the 16 week experiment were 0.883, 0.969, and 0.992. Noncontact radar results were within a few percent of discharge values obtained by gauging station, current meter, and hydroacoustic methods. Time series of surface velocity obtained by different radars in the Cowlitz River experiment also show small‐amplitude pulsations not found in stage records that reflect tidal energy at the gauging station. Noncontact discharge measurements made during a flood on 30 January 2004 agreed with the rated discharge to within 5%. Measurement at both field sites confirm that lognormal velocity profiles exist for a wide range of flows in these rivers, and mean velocity is approximately 0.85 times measured surface velocity. Noncontact methods of flow measurement appear to (1) be as accurate as conventional methods, (2) obtain data when standard contact methods are dangerous or cannot be obtained, and (3) provide insight into flow dynamics not available from detailed stage records alone.

Design and use of multisine signals for Li-ion battery equivalent circuit modelling. Part 1: Signal design

NASA Astrophysics Data System (ADS)

Widanage, W. D.; Barai, A.; Chouchelamane, G. H.; Uddin, K.; McGordon, A.; Marco, J.; Jennings, P.

2016-08-01

The Pulse Power Current (PPC) profile is often the signal of choice for obtaining the parameters of a Lithium-ion (Li-ion) battery Equivalent Circuit Model (ECM). Subsequently, a drive-cycle current profile is used as a validation signal. Such a profile, in contrast to a PPC, is more dynamic in both the amplitude and frequency bandwidth. Modelling errors can occur when using PPC data for parametrisation since the model is optimised over a narrower bandwidth than the validation profile. A signal more representative of a drive-cycle, while maintaining a degree of generality, is needed to reduce such modelling errors. In Part 1 of this 2-part paper a signal design technique defined as a pulse-multisine is presented. This superimposes a signal known as a multisine to a discharge, rest and charge base signal to achieve a profile more dynamic in amplitude and frequency bandwidth, and thus more similar to a drive-cycle. The signal improves modelling accuracy and reduces the experimentation time, per state-of-charge (SoC) and temperature, to several minutes compared to several hours for an PPC experiment.

Computing under-ice discharge: A proof-of-concept using hydroacoustics and the Probability Concept

NASA Astrophysics Data System (ADS)

Fulton, John W.; Henneberg, Mark F.; Mills, Taylor J.; Kohn, Michael S.; Epstein, Brian; Hittle, Elizabeth A.; Damschen, William C.; Laveau, Christopher D.; Lambrecht, Jason M.; Farmer, William H.

2018-07-01

Under-ice discharge is estimated using open-water reference hydrographs; however, the ratings for ice-affected sites are generally qualified as poor. The U.S. Geological Survey (USGS), in collaboration with the Colorado Water Conservation Board, conducted a proof-of-concept to develop an alternative method for computing under-ice discharge using hydroacoustics and the Probability Concept. The study site was located south of Minturn, Colorado (CO), USA, and was selected because of (1) its proximity to the existing USGS streamgage 09064600 Eagle River near Minturn, CO, and (2) its ease-of-access to verify discharge using a variety of conventional methods. From late September 2014 to early March 2015, hydraulic conditions varied from open water to under ice. These temporal changes led to variations in water depth and velocity. Hydroacoustics (tethered and uplooking acoustic Doppler current profilers and acoustic Doppler velocimeters) were deployed to measure the vertical-velocity profile at a singularly important vertical of the channel-cross section. Because the velocity profile was non-standard and cannot be characterized using a Power Law or Log Law, velocity data were analyzed using the Probability Concept, which is a probabilistic formulation of the velocity distribution. The Probability Concept-derived discharge was compared to conventional methods including stage-discharge and index-velocity ratings and concurrent field measurements; each is complicated by the dynamics of ice formation, pressure influences on stage measurements, and variations in cross-sectional area due to ice formation. No particular discharge method was assigned as truth. Rather one statistical metric (Kolmogorov-Smirnov; KS), agreement plots, and concurrent measurements provided a measure of comparability between various methods. Regardless of the method employed, comparisons between each method revealed encouraging results depending on the flow conditions and the absence or presence of ice cover. For example, during lower discharges dominated by under-ice and transition (intermittent open-water and under-ice) conditions, the KS metric suggests there is not sufficient information to reject the null hypothesis and implies that the Probability Concept and index-velocity rating represent similar distributions. During high-flow, open-water conditions, the comparisons are less definitive; therefore, it is important that the appropriate analytical method and instrumentation be selected. Six conventional discharge measurements were collected concurrently with Probability Concept-derived discharges with percent differences (%) of -9.0%, -21%, -8.6%, 17.8%, 3.6%, and -2.3%. This proof-of-concept demonstrates that riverine discharges can be computed using the Probability Concept for a range of hydraulic extremes (variations in discharge, open-water and under-ice conditions) immediately after the siting phase is complete, which typically requires one day. Computing real-time discharges is particularly important at sites, where (1) new streamgages are planned, (2) river hydraulics are complex, and (3) shifts in the stage-discharge rating are needed to correct the streamflow record. Use of the Probability Concept does not preclude the need to maintain a stage-area relation. Both the Probability Concept and index-velocity rating offer water-resource managers and decision makers alternatives for computing real-time discharge for open-water and under-ice conditions.

Computing under-ice discharge: A proof-of-concept using hydroacoustics and the Probability Concept

USGS Publications Warehouse

Fulton, John W.; Henneberg, Mark F.; Mills, Taylor J.; Kohn, Michael S.; Epstein, Brian; Hittle, Elizabeth A.; Damschen, William C.; Laveau, Christopher D.; Lambrecht, Jason M.; Farmer, William H.

2018-01-01

Under-ice discharge is estimated using open-water reference hydrographs; however, the ratings for ice-affected sites are generally qualified as poor. The U.S. Geological Survey (USGS), in collaboration with the Colorado Water Conservation Board, conducted a proof-of-concept to develop an alternative method for computing under-ice discharge using hydroacoustics and the Probability Concept.The study site was located south of Minturn, Colorado (CO), USA, and was selected because of (1) its proximity to the existing USGS streamgage 09064600 Eagle River near Minturn, CO, and (2) its ease-of-access to verify discharge using a variety of conventional methods. From late September 2014 to early March 2015, hydraulic conditions varied from open water to under ice. These temporal changes led to variations in water depth and velocity. Hydroacoustics (tethered and uplooking acoustic Doppler current profilers and acoustic Doppler velocimeters) were deployed to measure the vertical-velocity profile at a singularly important vertical of the channel-cross section. Because the velocity profile was non-standard and cannot be characterized using a Power Law or Log Law, velocity data were analyzed using the Probability Concept, which is a probabilistic formulation of the velocity distribution. The Probability Concept-derived discharge was compared to conventional methods including stage-discharge and index-velocity ratings and concurrent field measurements; each is complicated by the dynamics of ice formation, pressure influences on stage measurements, and variations in cross-sectional area due to ice formation.No particular discharge method was assigned as truth. Rather one statistical metric (Kolmogorov-Smirnov; KS), agreement plots, and concurrent measurements provided a measure of comparability between various methods. Regardless of the method employed, comparisons between each method revealed encouraging results depending on the flow conditions and the absence or presence of ice cover.For example, during lower discharges dominated by under-ice and transition (intermittent open-water and under-ice) conditions, the KS metric suggests there is not sufficient information to reject the null hypothesis and implies that the Probability Concept and index-velocity rating represent similar distributions. During high-flow, open-water conditions, the comparisons are less definitive; therefore, it is important that the appropriate analytical method and instrumentation be selected. Six conventional discharge measurements were collected concurrently with Probability Concept-derived discharges with percent differences (%) of −9.0%, −21%, −8.6%, 17.8%, 3.6%, and −2.3%.This proof-of-concept demonstrates that riverine discharges can be computed using the Probability Concept for a range of hydraulic extremes (variations in discharge, open-water and under-ice conditions) immediately after the siting phase is complete, which typically requires one day. Computing real-time discharges is particularly important at sites, where (1) new streamgages are planned, (2) river hydraulics are complex, and (3) shifts in the stage-discharge rating are needed to correct the streamflow record. Use of the Probability Concept does not preclude the need to maintain a stage-area relation. Both the Probability Concept and index-velocity rating offer water-resource managers and decision makers alternatives for computing real-time discharge for open-water and under-ice conditions.

Evaluation of the Ott Hydromet Qliner for measuring discharge in laboratory and field conditions

USGS Publications Warehouse

McVay, Jason C.

2015-01-01

The U.S. Geological Survey, in collaboration with the University of Iowa IIHR – Hydroscience and Engineering, evaluated the use of the Ott Hydromet Qliner using laboratory flume tests along with field validation tests. Analysis of the flume testing indicates the velocities measured by the Qliner at a 40-second exposure time results in higher dispersion of velocities from the mean velocity of data collected with a 5-minute exposure time. The percent data spread from the mean of a 100-minute mean of Qliner velocities for a 40-second exposure time averaged 16.6 percent for the entire vertical, and a 5-minute mean produced a 6.2 percent data spread from the 100-minute mean. This 16.6 percent variation in measured velocity would result in a 3.32 percent variation in computed discharge assuming 25 verticals while averaging 4 bins in each vertical. The flume testing also provided results that indicate the blanking distance of 0.20 meters is acceptable when using beams 1 and 2, however beam 3 is negatively biased near the transducer and the 0.20-meter blanking distance is not sufficient. Field testing included comparing the measured discharge by the Qliner to the discharge measured by a Price AA mechanical current meter and a Teledyne RDI Rio Grande 1200 kilohertz acoustic Doppler current profiler. The field tests indicated a difference between the discharges measured with the Qliner and the field reference discharge between -14.0 and 8.0 percent; however the average percent difference for all 22 field comparisons was 0.22, which was not statistically significant.

Hybrid-PIC Modeling of a High-Voltage, High-Specific-Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Smith, Brandon D.; Boyd, Iain D.; Kamhawi, Hani; Huang, Wensheng

2013-01-01

The primary life-limiting mechanism of Hall thrusters is the sputter erosion of the discharge channel walls by high-energy propellant ions. Because of the difficulty involved in characterizing this erosion experimentally, many past efforts have focused on numerical modeling to predict erosion rates and thruster lifespan, but those analyses were limited to Hall thrusters operating in the 200-400V discharge voltage range. Thrusters operating at higher discharge voltages (V(sub d) >= 500 V) present an erosion environment that may differ greatly from that of the lower-voltage thrusters modeled in the past. In this work, HPHall, a well-established hybrid-PIC code, is used to simulate NASA's High-Voltage Hall Accelerator (HiVHAc) at discharge voltages of 300, 400, and 500V as a first step towards modeling the discharge channel erosion. It is found that the model accurately predicts the thruster performance at all operating conditions to within 6%. The model predicts a normalized plasma potential profile that is consistent between all three operating points, with the acceleration zone appearing in the same approximate location. The expected trend of increasing electron temperature with increasing discharge voltage is observed. An analysis of the discharge current oscillations shows that the model predicts oscillations that are much greater in amplitude than those measured experimentally at all operating points, suggesting that the differences in oscillation amplitude are not strongly associated with discharge voltage.

An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

Engineering and Abuse Testing of Panasonic Lithium-Ion Battery and Cells

NASA Technical Reports Server (NTRS)

Jeevarajan, Judith A.; Bragg, Bobby J.

2000-01-01

This viewgraph presentation reviews the performance testing of Lithium Ion batteries and cells under different conditions of charge and discharge. The tests show that the 0.5 C rate of charge and discharge might be the ideal condition for long term cycling. It reviews the issues of overcharge and overdischarge of the cells. The cells and the battery have adequate protection under both conditions to prevent any catastrophic occurrences. Temperatures above 150 C are required to vent the cells or cause a thermal runaway, Since this situation is non-credible in the cabin of the Space Shuffle or ISS this should not pose a problem. The presentation includes graphs and charts showing the charge and discharge capacities of the battery and also the current and voltage profiles. A view of a circuit board which contains the controlling mechanism for the battery is also shown.

Observed Characteristics and Origins of Meltwaters Exported from Jakobshavn and Ilulissat Icefjord, Greenland

NASA Astrophysics Data System (ADS)

Beaird, N.; Straneo, F.; Jenkins, W. J.

2017-12-01

Jakobshavn Isbrae has undergone rapid retreat in recent decades and is now among the largest sources of anomalous ice discharge from Greenland's shrinking ice sheet. The characteristics, distribution, and pathways of meltwater sourced from Jakobshavn can have important impacts on ecosystems and regional, perhaps global, ocean circulation. Here we report on novel geochemical (noble gas) observations that enable a quantitative description of the meltwaters exiting Ilulissat Icefjord into Disko Bay, including the partition into Submarine Meltwater sources and Subglacial Discharge sources. We identify a coastally-trapped plume outside of the fjord mouth consistent with a coastal current flowing north. The plume extends to 100 m depth, and 10 km offshore. Temperature and salinity profiles inside the fjord suggest a deep-reaching buoyancy-forced overturning feeding this outflow. Relatively high Submarine Meltwater concentration (2.5%) imply a substantial contribution of iceberg meltwater to the fjord. Subglacial Discharge concentrations in the plume reach 6%.

Use of the Charge/Discharge (C/D) ratio to augment voltage limit (V sub T) charge control in the ERBS spacecraft

NASA Astrophysics Data System (ADS)

Halpert, G.

1982-07-01

A 50-ampere hour nickel cadmium cell test pack was operated in a power profile simulating the orbit of the Earth Radiation Budget Satellite (ERBS). The objective was to determine the ability of the temperature compensated voltage limit (V sub T) charge control system to maintain energy balance in the half sine wave-type current profile expected of this mission. The four-cell pack (50 E) was tested at the Naval Weapons Support Center (NWSC) at Crane, Indiana. The ERBS evaluation test consisted of two distinct operating sequences, each having a specific purpose. The first phase was a parametric test involving the effect of V sub T level, temperature, and Beta angle on the charge/discharge (C/D) ratio, an indicator of the amount of overcharge. The second phase of testing made use of the C/D ratio limit to augment the V sub T charge limit control. When the C/D limit was reached, the current was switched from the taper mode to a C/67 (0.75 A) trickle charge. The use of an ampere hour integrator limiting the overcharge to a C/67 rate provided a fine tuning of the charge control technique which eliminated the sensitivity problems noted in the initial operating sequence.

Recent applications of acoustic Doppler current profilers

USGS Publications Warehouse

Oberg, K.A.; Mueller, David S.

1994-01-01

A Broadband acoustic Doppler current profiler (BB-ADCP) is a new instrument being used by the U.S. Geological Survey (USGS) to measure stream discharge and velocities, and bathymetry. During the 1993 Mississippi River flood, more than 160 high-flow BB-ADCP measurements were made by the USGS at eight locations between Quincy and Cairo, Ill., from July 19 to August 20, 1993. A maximum discharge of 31,400 m3/s was measured at St. Louis, Mo., on August 2, 1993. A BB-ADCP also has been used to measure leakage through three control structures near Chicago, Ill. These measurements are unusual in that the average velocity for the measured section was as low as 0.03 m/s. BB-ADCP's are also used in support of studies of scour at bridges. During the recent Mississippi River flood, BB-ADCP's were used to measure water velocities and bathymetry upstream from, next to, and downstream from bridge piers at several bridges over the Mississippi River. Bathymetry data were collected by merging location data from Global Positioning System (GPS) receivers, laser tracking systems, and depths measured by the BB-ADCP. These techniques for collecting bathymetry data were used for documenting the channel formation downstream from the Miller City levee break and scour near two bridges on the Mississippi River.

Use of the Charge/Discharge (C/D) ratio to aument voltage limit (V sub T) charge control in the ERBS spacecraft

NASA Technical Reports Server (NTRS)

Halpert, G.

1982-01-01

A 50-ampere hour nickel cadmium cell test pack was operated in a power profile simulating the orbit of the Earth Radiation Budget Satellite (ERBS). The objective was to determine the ability of the temperature compensated voltage limit (V sub T) charge control system to maintain energy balance in the half sine wave-type current profile expected of this mission. The four-cell pack (50 E) was tested at the Naval Weapons Support Center (NWSC) at Crane, Indiana. The ERBS evaluation test consisted of two distinct operating sequences, each having a specific purpose. The first phase was a parametric test involving the effect of V sub T level, temperature, and Beta angle on the charge/discharge (C/D) ratio, an indicator of the amount of overcharge. The second phase of testing made use of the C/D ratio limit to augment the V sub T charge limit control. When the C/D limit was reached, the current was switched from the taper mode to a C/67 (0.75 A) trickle charge. The use of an ampere hour integrator limiting the overcharge to a C/67 rate provided a fine tuning of the charge control technique which eliminated the sensitivity problems noted in the initial operating sequence.

Ferroelectric Plasma Sources for Ion Beam Neutralization

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L. R.; Davidson, R. C.

2014-10-01

A 40 keV Ar+ beam with a dimensionless perveance of 4 ×10-4 is propagated through a Ferroelectric Plasma Source (FEPS) to determine the effects of charge neutralization on the transverse beam profile. Neutralization is established 5 μs after the FEPS is triggered, and lasts between 10 and 35 μs. When the beam is fully neutralized, the profile has a Gaussian shape with a half-angle divergence of 0.87°, which is attributed to ion optics. The effects of the resistance and capacitance in the pulser circuit on the FEPS discharge are studied. The electron current emitted by the FEPS is calculated from measurements of the forward and return currents in the circuit. Electron emission typically begins 0.5 μs after the driving pulse, lasting for tens of μs, which is similar to the duration of ion beam neutralization. The total emitted charge does not depend significantly on the resistance, but depends strongly on the storage capacitance. Lowering the capacitance from 141 nF to 47 nF results in a near-complete shut-off of charge emission, although the amplitude of the applied voltage pulse is as high as when high-density plasma is produced. Overall, the data suggest that ferroelectric effects are significant in the physics of the FEPS discharge.

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Wilson, J. R.; Bell, R. E.; Bernabei, S.; Bitter, M.; Bonoli, P.; Gates, D.; Hosea, J.; LeBlanc, B.; Mau, T. K.; Medley, S.; Menard, J.; Mueller, D.; Ono, M.; Phillips, C. K.; Pinsker, R. I.; Raman, R.; Rosenberg, A.; Ryan, P.; Sabbagh, S.; Stutman, D.; Swain, D.; Takase, Y.; Wilgen, J.

2003-05-01

High harmonic fast wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [M. Ono, S. M. Kaye, S. Neumeyer et al., in Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999 (IEEE, Piscataway, NJ, 1999), p. 53] is such a device. An rf heating system has been installed on the NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.

Profile control simulations and experiments on TCV: a controller test environment and results using a model-based predictive controller

NASA Astrophysics Data System (ADS)

Maljaars, E.; Felici, F.; Blanken, T. C.; Galperti, C.; Sauter, O.; de Baar, M. R.; Carpanese, F.; Goodman, T. P.; Kim, D.; Kim, S. H.; Kong, M.; Mavkov, B.; Merle, A.; Moret, J. M.; Nouailletas, R.; Scheffer, M.; Teplukhina, A. A.; Vu, N. M. T.; The EUROfusion MST1-team; The TCV-team

2017-12-01

The successful performance of a model predictive profile controller is demonstrated in simulations and experiments on the TCV tokamak, employing a profile controller test environment. Stable high-performance tokamak operation in hybrid and advanced plasma scenarios requires control over the safety factor profile (q-profile) and kinetic plasma parameters such as the plasma beta. This demands to establish reliable profile control routines in presently operational tokamaks. We present a model predictive profile controller that controls the q-profile and plasma beta using power requests to two clusters of gyrotrons and the plasma current request. The performance of the controller is analyzed in both simulation and TCV L-mode discharges where successful tracking of the estimated inverse q-profile as well as plasma beta is demonstrated under uncertain plasma conditions and the presence of disturbances. The controller exploits the knowledge of the time-varying actuator limits in the actuator input calculation itself such that fast transitions between targets are achieved without overshoot. A software environment is employed to prepare and test this and three other profile controllers in parallel in simulations and experiments on TCV. This set of tools includes the rapid plasma transport simulator RAPTOR and various algorithms to reconstruct the plasma equilibrium and plasma profiles by merging the available measurements with model-based predictions. In this work the estimated q-profile is merely based on RAPTOR model predictions due to the absence of internal current density measurements in TCV. These results encourage to further exploit model predictive profile control in experiments on TCV and other (future) tokamaks.

The effect of surface-bulk potential difference on the kinetics of intercalation in core-shell active cathode particles

NASA Astrophysics Data System (ADS)

Kazemiabnavi, Saeed; Malik, Rahul; Orvananos, Bernardo; Abdellahi, Aziz; Ceder, Gerbrand; Thornton, Katsuyo

2018-04-01

Surface modification of active cathode particles is commonly observed in battery research as either a surface phase evolving during the cycling process, or intentionally engineered to improve capacity retention, rate capability, and/or thermal stability of the cathode material. Here, a continuum-scale model is developed to simulate the galvanostatic charge/discharge of a cathode particle with core-shell heterostructure. The particle is assumed to be comprised of a core material encapsulated by a thin layer of a second phase that has a different open-circuit voltage. The effect of the potential difference between the surface and bulk phases (Ω) on the kinetics of lithium intercalation and the galvanostatic charge/discharge profiles is studied at different values of Ω, C-rates, and exchange current densities. The difference between the Li chemical potential in the surface and bulk phases of the cathode particle results in a concentration difference between these two phases. This leads to a charge/discharge asymmetry in the galvanostatic voltage profiles, causing a decrease in the accessible capacity of the particle. These effects are more significant at higher magnitudes of surface-bulk potential difference. The proposed model provides detailed insight into the kinetics and voltage behavior of the intercalation/de-intercalation processes in core-shell heterostructure cathode particles.

EC power management in ITER for NTM control: the path from the commissioning phase to demonstration discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poli, Francesca M.; Fredrickson, Eric; Henderson, Mark A.

Time dependent simulations that evolve consistently the magnetic equilibrium and plasma pressure profiles and the width and frequency rotation of magnetic islands under the effect of the Electron Cyclotron feedback system are used to assess whether the control of NTMs on ITER is compatible with other simulataneous functionalities of the EC system, like core heating and current profile tailoring, or sawtooth control. Furthermore, results indicate that the power needs for control can be reduced if the EC power is reserved and if pre-emptive control is used as opposed to an active search for an already developed island.

EC power management in ITER for NTM control: the path from the commissioning phase to demonstration discharges

DOE PAGES

Poli, Francesca M.; Fredrickson, Eric; Henderson, Mark A.; ...

2017-10-23

Time dependent simulations that evolve consistently the magnetic equilibrium and plasma pressure profiles and the width and frequency rotation of magnetic islands under the effect of the Electron Cyclotron feedback system are used to assess whether the control of NTMs on ITER is compatible with other simulataneous functionalities of the EC system, like core heating and current profile tailoring, or sawtooth control. Furthermore, results indicate that the power needs for control can be reduced if the EC power is reserved and if pre-emptive control is used as opposed to an active search for an already developed island.

Evaluations of dielectric property and drug release profile of 5-FU patches based on plasma charged electrets

NASA Astrophysics Data System (ADS)

Wang, YUAN; Hejuan, LIANG; Ping, HUANG; Xiaoqiang, AN; Jian, JIANG; Lili, CUI

2018-05-01

In the present study, the electret 5-fluorouracil patch was developed, the effective surface potential, piezoelectric coefficient d 33, open-circuit thermally stimulated discharge (TSD) current spectra and shear adhesion of the patch were measured. The drug release profile of the patch was determined by using high performance liquid chromatography method. A stable potential difference which was positively dependent on the surface potential of the electret was generated on two sides of the patch. The measurements of d 33 coefficient, TSD current spectra and adhesion performance showed that the electrostatic field of the electret could cause polarization and cohesive strength decreasing of the matrix molecules, change the distribution and interaction of the drug molecules in patch, therefore to increase the release of drug from the transdermal patch.

Quantitative imaging of carbon dimer precursor for nanomaterial synthesis in the carbon arc

DOE PAGES

Vekselman, V.; Khrabry, A.; Kaganovich, I.; ...

2018-02-06

Delineating the dominant processes responsible for nanomaterial synthesis in a plasma environment requires measurements of the precursor species contributing to the growth of nanostructures. Here, we performed comprehensive measurements of spatial and temporal profiles of carbon dimers (C 2) in sub-atmospheric-pressure carbon arc by laser-induced fluorescence. Measured spatial profiles of C 2 coincide with the growth region of carbon nanotubes (Fang et al 2016 Carbon 107 273–80) and vary depending on the arc operation mode, which is determined by the discharge current and the ablation rate of the graphite anode. The C 2 density profile exhibits large spatial and timemore » variations due to motion of the arc core. A comparison of the experimental data with the 2D simulation results of self-consistent arc modeling shows good agreement. The model predicts well the main processes determining spatial profiles of carbon dimers (C 2).« less

Quantitative imaging of carbon dimer precursor for nanomaterial synthesis in the carbon arc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vekselman, V.; Khrabry, A.; Kaganovich, I.

Delineating the dominant processes responsible for nanomaterial synthesis in a plasma environment requires measurements of the precursor species contributing to the growth of nanostructures. Here, we performed comprehensive measurements of spatial and temporal profiles of carbon dimers (C 2) in sub-atmospheric-pressure carbon arc by laser-induced fluorescence. Measured spatial profiles of C 2 coincide with the growth region of carbon nanotubes (Fang et al 2016 Carbon 107 273–80) and vary depending on the arc operation mode, which is determined by the discharge current and the ablation rate of the graphite anode. The C 2 density profile exhibits large spatial and timemore » variations due to motion of the arc core. A comparison of the experimental data with the 2D simulation results of self-consistent arc modeling shows good agreement. The model predicts well the main processes determining spatial profiles of carbon dimers (C 2).« less

Comparative analysis of core heat transport of JET high density H-mode plasmas in carbon wall and ITER-like wall

NASA Astrophysics Data System (ADS)

Kim, Hyun-Tae; Romanelli, M.; Voitsekhovitch, I.; Koskela, T.; Conboy, J.; Giroud, C.; Maddison, G.; Joffrin, E.; contributors, JET

2015-06-01

A consistent deterioration of global confinement in H-mode experiments has been observed in JET [1] following the replacement of all carbon plasma facing components (PFCs) with an all metal (‘ITER-like’) wall (ILW). This has been correlated to the observed degradation of the pedestal confinement, as lower electron temperature (Te) values are routinely measured at the top of the edge barrier region. A comparative investigation of core heat transport in JET-ILW and JET-CW (carbon wall) discharges has been performed, to assess whether core confinement has also been affected by the wall change. The results presented here have been obtained by analysing a set of discharges consisting of high density JET-ILW H-mode plasmas and comparing them against their counterpart discharges in JET-CW having similar global operational parameters. The set contains 10 baseline ({βN}=1.5∼ 2 ) discharge-pairs with 2.7 T toroidal magnetic field, 2.5 MA plasma current, and 14 to 17 MW of neutral beam injection (NBI) heating. Based on a Te profile analysis using high resolution Thomson scattering (HRTS) data, the Te profile peaking (i.e. core Te (ρ = 0.3) / edge Te (ρ = 0.7)) is found to be similar, and weakly dependent on edge Te, for both JET-ILW and JET-CW discharges. When ILW discharges are seeded with N2, core and edge Te both increase to maintain a similar peaking factor. The change in core confinement is addressed with interpretative TRANSP simulations. It is found that JET-ILW H-mode plasmas have higher NBI power deposition to electrons and lower NBI power deposition to ions as compared to the JET-CW counterparts. This is an effect of the lower electron temperature at the top of the pedestal. As a result, the core electron energy confinement time is reduced in JET-ILW discharges, but the core ion energy confinement time is not decreased. Overall, the core energy confinement is found to be the same in the JET-ILW discharges compared to the JET-CW counterparts.

Hydrography and circulation of ice-marginal lakes at Bering Glacier, Alaska, U.S.A.

USGS Publications Warehouse

Josberger, E.G.; Shuchman, R.A.; Meadows, G.A.; Savage, S.; Payne, J.

2006-01-01

An extensive suite of physical oceanographic, remotely sensed, and water quality measurements, collected from 2001 through 2004 in two ice-marginal lakes at Bering Glacier, Alaska-Berg Lake and Vitus Lake-show that each has a unique circulation controlled by their specific physical forcing within the glacial system. Conductivity profiles from Berg Lake, perched 135 m a.s.l., show no salt in the lake, but the temperature profiles indicate an apparently unstable situation, the 4??C density maximum is located at 10 m depth, not at the bottom of the lake (90 m depth). Subglacial discharge from the Steller Glacier into the bottom of the lake must inject a suspended sediment load sufficient to marginally stabilize the water column throughout the lake. In Vitus Lake, terminus positions derived from satellite imagery show that the glacier terminus rapidly retreated from 1995 to the present resulting in a substantial expansion of the volume of Vitus Lake. Conductivity and temperature profiles from the tidally influenced Vitus Lake show a complex four-layer system with diluted (???50%) seawater in the bottom of the lake. This lake has a complex vertical structure that is the result of convection generated by ice melting in salt water, stratification within the lake, and freshwater entering the lake from beneath the glacier and surface runoff. Four consecutive years, from 2001 to 2004, of these observations in Vitus Lake show little change in the deep temperature and salinity conditions, indicating limited deep water renewal. The combination of the lake level measurements with discharge measurements, through a tidal cycle, by an acoustic Doppler Current Profiler (ADCP) deployed in the Seal River, which drains the entire Bering system, showed a strong tidal influence but no seawater entry into Vitus Lake. The ADCP measurements combined with lake level measurements established a relationship between lake level and discharge, which when integrated over a tidal cycle, gives a tidally averaged discharge ranging from 1310 to 1510 m3 s-1. ?? 2006 Regents of the University of Colorado.

Study of the Generation of Intense Pulsed Electron Beams Using Glow Discharges

DTIC Science & Technology

1988-02-01

de Investigaciones Opticas, Rep. Argentina. (2) On leave from PROFET (UNCPBA) Programa de Fisica Experimental Tandil, Rep. Argentina. (3) Edwards... de Investigaciones Opticas, (CIC-BA) Rep. Argentina. Section III-D. Measurements of the plasma density andB. T. Szapiro is on leave from Programa de ...discussed. The radial profiles Szapiro was supported by a fellowship from the Universidad Nacional de show the presence of a high-current-density

MHD and resonant instabilities in JT-60SA during current ramp-up with off-axis N-NB injection

NASA Astrophysics Data System (ADS)

Bierwage, A.; Toma, M.; Shinohara, K.

2017-12-01

The excitation of magnetohydrodynamic (MHD) and resonant instabilities and their effect on the plasma profiles during the current ramp-up phase of a beam-driven JT-60SA tokamak plasma is studied using the MHD-PIC hybrid code MEGA. In the simple scenario considered, the plasma is only driven by one negative-ion-based neutral beam, depositing 500 keV deuterons at 5 MW power off-axis at about mid-radius. The beam injection starts half-way in the ramp-up phase. Within 1 s, the beam-driven plasma current and fast ion pressure produce a configuration that is strongly unstable to rapidly growing MHD and resonant modes. Using MEGA, modes with low toroidal mode numbers in the range n = 1-4 are examined in detail and shown to cause substantial changes in the plasma profiles. The necessity to develop reduced models and incorporate the effects of such instabilities in integrated codes used to simulate the evolution of entire plasma discharges is discussed.

Comparison of resistive MHD simulations and experimental CHI discharges in NSTX

NASA Astrophysics Data System (ADS)

Hooper, E. B.; Sovinec, C. R.; Raman, R.; Fatima, F.

2013-10-01

Resistive MHD simulations using NIMROD simulate CHI discharges for NSTX startup plasmas. Quantitative comparison with experiment ensures that the simulation physics includes a minimal physics set needed to extend the simulations to new experiments, e.g. NSTX-U. Important are time-varying vacuum magnetic field, ohmic heating, thermal transport, impurity radiation, and spatially-varying plasma parameters including density. Equilibria are compared with experimental injector currents, voltages and parameters including toroidal current, photographs of emitted light and measurements of midplane temperature profiles, radiation and surface heating. Initial results demonstrate that adjusting impurity radiation and cross-field transport yields temperatures and injected-current channel widths similar to experiment. These determine the plasma resistance, feeding back to the impedance on the injector power supply. Work performed under the auspices of the U.S. Department of Energy under contracts DE-AC52-07NA27344 at LLNL and DE-AC02-09CH11466 at PPPL, and grants DE-FC02-05ER54813 at PSI Center (U. Wisc.) and DOE-FG02-12ER55115 (at Princeton U.).

A 60 mA DC H- multi cusp ion source developed at TRIUMF

NASA Astrophysics Data System (ADS)

Jayamanna, K.; Ames, F.; Bylinskii, I.; Lovera, M.; Minato, B.

2018-07-01

This paper describes the latest high-current multi cusp type ion source developed at TRIUMF, which is capable of producing a negative hydrogen ion beam (H-) of 60 mA of direct current at 140V and 90A arc. The results achieved to date including emittance measurements and filament lifetime issues are presented. The low current version of this ion source is suitable for medical cyclotrons as well as accelerators and the high current version is intended for producing large neutral hydrogen beams for fusion research. The description of the source magnetic configuration, the electron filter profile and the differential pumping techniques given in the paper will allow the building of an arc discharge H- ion source with similar properties.

Development of Integrated Magnetic and Kinetic Control-oriented Transport Model for q-profile Response Prediction in EAST Discharges

NASA Astrophysics Data System (ADS)

Wang, Hexiang; Schuster, Eugenio; Rafiq, Tariq; Kritz, Arnold; Ding, Siye

2016-10-01

Extensive research has been conducted to find high-performance operating scenarios characterized by high fusion gain, good confinement, plasma stability and possible steady-state operation. A key plasma property that is related to both the stability and performance of these advanced plasma scenarios is the safety factor profile. A key component of the EAST research program is the exploration of non-inductively driven steady-state plasmas with the recently upgraded heating and current drive capabilities that include lower hybrid current drive and neutral beam injection. Anticipating the need for tight regulation of the safety factor profile in these plasma scenarios, a first-principles-driven (FPD)control-oriented model is proposed to describe the safety factor profile evolution in EAST in response to the different actuators. The TRANSP simulation code is employed to tailor the FPD model to the EAST tokamak geometry and to convert it into a form suitable for control design. The FPD control-oriented model's prediction capabilities are demonstrated by comparing predictions with experimental data from EAST. Supported by the US DOE under DE-SC0010537,DE-FG02-92ER54141 and DE-SC0013977.

Non-inductive current drive and transport in high βN plasmas in JET

NASA Astrophysics Data System (ADS)

Voitsekhovitch, I.; Alper, B.; Brix, M.; Budny, R. V.; Buratti, P.; Challis, C. D.; Ferron, J.; Giroud, C.; Joffrin, E.; Laborde, L.; Luce, T. C.; McCune, D.; Menard, J.; Murakami, M.; Park, J. M.; JET-EFDA contributors

2009-05-01

A route to stationary MHD stable operation at high βN has been explored at the Joint European Torus (JET) by optimizing the current ramp-up, heating start time and the waveform of neutral beam injection (NBI) power. In these scenarios the current ramp-up has been accompanied by plasma pre-heat (or the NBI has been started before the current flat-top) and NBI power up to 22 MW has been applied during the current flat-top. In the discharges considered transient total βN ≈ 3.3 and stationary (during high power phase) βN ≈ 3 have been achieved by applying the feedback control of βN with the NBI power in configurations with monotonic or flat core safety factor profile and without an internal transport barrier (ITB). The transport and current drive in this scenario is analysed here by using the TRANSP and ASTRA codes. The interpretative analysis performed with TRANSP shows that 50-70% of current is driven non-inductively; half of this current is due to the bootstrap current which has a broad profile since an ITB was deliberately avoided. The GLF23 transport model predicts the temperature profiles within a ±22% discrepancy with the measurements over the explored parameter space. Predictive simulations with this model show that the E × B rotational shear plays an important role for thermal ion transport in this scenario, producing up to a 40% increase of the ion temperature. By applying transport and current drive models validated in self-consistent simulations of given reference scenarios in a wider parameter space, the requirements for fully non-inductive stationary operation at JET are estimated. It is shown that the strong stiffness of the temperature profiles predicted by the GLF23 model restricts the bootstrap current at larger heating power. In this situation full non-inductive operation without an ITB can be rather expensive strongly relying on the external non-inductive current drive sources.

Density currents in the Chicago River: Characterization, effects on water quality, and potential sources

USGS Publications Warehouse

Jackson, P. Ryan; Garcia, Carlos M.; Oberg, Kevin A.; Johnson, Kevin K.; Garcia, Marcelo H.

2008-01-01

Bidirectional flows in a river system can occur under stratified flow conditions and in addition to creating significant errors in discharge estimates, the upstream propagating currents are capable of transporting contaminants and affecting water quality. Detailed field observations of bidirectional flows were made in the Chicago River in Chicago, Illinois in the winter of 2005-06. Using multiple acoustic Doppler current profilers simultaneously with a water-quality profiler, the formation of upstream propagating density currents within the Chicago River both as an underflow and an overflow was observed on three occasions. Density differences driving the flow primarily arise from salinity differences between intersecting branches of the Chicago River, whereas water temperature is secondary in the creation of these currents. Deicing salts appear to be the primary source of salinity in the North Branch of the Chicago River, entering the waterway through direct runoff and effluent from a wastewater-treatment plant in a large metropolitan area primarily served by combined sewers. Water-quality assessments of the Chicago River may underestimate (or overestimate) the impairment of the river because standard water-quality monitoring practices do not account for density-driven underflows (or overflows). Chloride concentrations near the riverbed can significantly exceed concentrations at the river surface during underflows indicating that full-depth parameter profiles are necessary for accurate water-quality assessments in urban environments where application of deicing salt is common.

Generation of multiple toroidal dust vortices by a non-monotonic density gradient in a direct current glow discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaur, Manjit, E-mail: manjit@ipr.res.in; Bose, Sayak; Chattopadhyay, P. K.

2015-09-15

Observation of two well-separated dust vortices in an unmagnetized parallel plate DC glow discharge plasma is reported in this paper. A non-monotonic radial density profile, achieved by an especially designed cathode structure using a concentric metallic disk and ring of different radii, is observed to produce double dust tori between cathode and anode. PIV analysis of the still images of the double tori shows oppositely rotating dust structures between the central disk and the ring. Langmuir probe measurements of background plasma shows a non-uniform plasma density profile between the disk and the ring. Location and sense of rotation of themore » dust vortices coincides with the location and direction of the radial gradient in the ion drag force caused by the radial density gradient. The experimentally observed dust vorticity matches well with the calculated one using hydrodynamic formulations with shear in ion drag dominating over the dust charge gradient. These results corroborate that a radial gradient in the ion drag force directed towards cathode is the principal cause of dust rotation.« less

Measured density of copper atoms in the ground and metastable states in argon magnetron discharge correlated with the deposition rate

NASA Astrophysics Data System (ADS)

Naghshara, H.; Sobhanian, S.; Khorram, S.; Sadeghi, N.

2011-01-01

In a dc-magnetron discharge with argon feed gas, densities of copper atoms in the ground state Cu(2S1/2) and metastable state Cu*(2D5/2) were measured by the resonance absorption technique, using a commercial hollow cathode lamp as light source. The operating conditions were 0.3-14 µbar argon pressure and 10-200 W magnetron discharge power. The deposition rate of copper in a substrate positioned at 18 cm from the target was also measured with a quartz microbalance. The gas temperature, in the range 300-380 K, was deduced from the emission spectral profile of N2(C 3Πu - B 3Πg) 0-0 band at 337 nm when trace of nitrogen was added to the argon feed gas. The isotope-shifts and hyperfine structures of electronic states of Cu have been taken into account to deduce the emission and absorption line profiles, and hence for the determination of atoms' densities from the measured absorption rates. To prevent error in the evaluation of Cu density, attributed to the line profile distortion by auto-absorption inside the lamp, the lamp current was limited to 5 mA. Density of Cu(2S1/2) atoms and deposition rate both increased with the enhanced magnetron discharge power. But at fixed power, the copper density augmented with argon pressure whereas the deposition rate followed the opposite trend. Whatever the gas pressure, the density of Cu*(2D5/2) metastable atoms remained below the detection limit of 1 × 1010 cm-3 for magnetron discharge powers below 50 W and hence increased much more rapidly than the density of Cu(2S1/2) atoms, over passing this later at some discharge power, whose value decreases with increasing argon pressure. This behaviour is believed to result from the enhancement of plasma density with increasing discharge power and argon pressure, which would increase the excitation rate of copper into metastable states. At fixed pressure, the deposition rate followed the same trend as the total density of copper atoms in the ground and metastable states. Two important conclusions of this work are (i) copper atoms sputtered from the target under ion bombardment are almost all in the ground state Cu(2S1/2) and hence in the plasma volume they can be excited into the metastable states; (ii) all atoms in the long-lived ground and metastable states contribute to the deposition of copper layer on the substrate.

Merging altimeter data with Argo profiles to improve observation of tropical Pacific thermocline circulation and ENSO

NASA Astrophysics Data System (ADS)

Zhang, D.; Lee, T.; Wang, F.; McPhaden, M. J.; Kessler, W. S.

2016-12-01

Meridional thermocline currents play an important role in the recharge and discharge of tropical Pacific warm water during the development and transition of ENSO cycles. Previous analyses have shown large variations of the equatorward meridional thermocline convergence/divergence on ENSO and decadal time scales in the interior ocean. The total convergence/divergence is however unknown due to the lack of long term observation in the western boundary currents. Numerical modelling studies suggested a tendency of compensation between the interior and western boundary currents, but the exact compensation is model dependent. While Argo floats provide reasonable data coverage in the interior ocean, few floats are in the western boundary currents. Recent multi-mission satellite altimeter data and advanced processing techniques have resulted in higher resolution sea surface height anomaly (SSHA) products with better accuracy closer to the coasts. This study utilizes the statistical relationship between Argo dynamic height profiles and altimeter SSHA to calculate geostrophic thermocline currents in both the interior ocean and the western boundary of the tropical Pacific. The derived thermocline currents in the western boundary are validated by a 3.5-year moored Acoustic Doppler Current Profiler (ADCP) measurement in the Mindanao Current and by a series of glider surveys (Davis et al. 2012) in the Solomon Sea. The meridional transport timeseries of the interior and western boundary currents in the thermocline show different lead-lag relationships to the Nino 3.4 index. Results will be discussed in the context of recent 2014-2015 El Nino development and the potential contribution to the Tropical Pacific Observing System (TPOS).

Randomized clinical trial of hydrocodone/acetaminophen versus codeine/acetaminophen in the treatment of acute extremity pain after emergency department discharge.

PubMed

Chang, Andrew K; Bijur, Polly E; Munjal, Kevin G; John Gallagher, E

2014-03-01

The objective was to test the hypothesis that hydrocodone/acetaminophen (Vicodin [5/500]) provides more efficacious analgesia than codeine/acetaminophen (Tylenol #3 [30/300]) in patients discharged from the emergency department (ED). Both are currently Drug Enforcement Administration (DEA) Schedule III narcotics. This was a prospective, randomized, double-blind, clinical trial of patients with acute extremity pain who were discharged home from the ED, comparing a 3-day supply of oral hydrocodone/acetaminophen (5 mg/500 mg) to oral codeine/acetaminophen (30 mg/300 mg). Pain was measured on a valid and reproducible verbal numeric rating scale (NRS) ranging from 0 to 10, and patients were contacted by telephone approximately 24 hours after being discharged. The primary outcome was the between-group difference in improvement in pain at 2 hours following the most recent ingestion of the study drug, relative to the time of phone contact after ED discharge. Secondary outcomes compared side-effect profiles and patient satisfaction. The median time from ED discharge to follow-up was 26 hours (interquartile range [IQR] = 24 to 39 hours). The mean NRS pain score before the most recent dose of pain medication after ED discharge was 7.6 NRS units for both groups. The mean decrease in pain scores 2 hours after pain medications were taken were 3.9 NRS units in the hydrocodone/acetaminophen group versus 3.5 NRS units in the codeine/acetaminophen group, for a difference of 0.4 NRS units (95% confidence interval [CI] = -0.3 to 1.2 NRS units). No differences were found in side effects or patient satisfaction. Both medications decreased NRS pain scores by approximately 50%. However, the oral hydrocodone/acetaminophen failed to provide clinically or statistically superior pain relief compared to oral codeine/acetaminophen when prescribed to patients discharged from the ED with acute extremity pain. Similarly, there were no clinically or statistically important differences in side-effect profiles or patient satisfaction. If the DEA reclassifies hydrocodone as a Schedule II narcotic, as recently recommended by its advisory board, our data suggest that the codeine/acetaminophen may be a clinically reasonable Schedule III substitute for hydrocodone/acetaminophen at ED discharge. These findings should be regarded as tentative and require independent validation in similar and other acute pain models. © 2014 by the Society for Academic Emergency Medicine.

Investigation on porous MnO microsphere anode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Zhong, Kaifu; Zhang, Bin; Luo, Shihai; Wen, Wen; Li, Hong; Huang, Xuejie; Chen, Liquan

MnO microspheres with and without carbon coating are prepared as anode materials for lithium ion batteries. The MnO microsphere material shows a reversible capacity of 800 mAh g -1 and an initial efficiency of 71%. It can deliver 600 mAh g -1 at a rate of 400 mA g -1. Results of Mn K-edge X-ray absorption near-edge structure (XANES) spectra and extended X-ray absorption fine structure (EXAFS) confirm further the conversion reaction mechanism, indicate that pristine MnO is reduced to Mn 0 after discharging to 0 V and part of reduced Mn 0 is not oxidized to Mn 2+ after charging to 3 V. This explains the origin of the initial irreversible capacity loss partially. The quasi open circuit voltage and the relationship between the current density and the overpotential are investigated. Both indicate that there is a significant voltage difference between the charging and discharging profiles even when the current density decreases to zero.

Elves and associated electron density changes due to cloud-to-ground and in-cloud lightning discharges

NASA Astrophysics Data System (ADS)

Marshall, R. A.; Inan, U. S.; Glukhov, V. S.

2010-04-01

A 3-D finite difference time domain model is used to simulate the lightning electromagnetic pulse (EMP) and its interaction with the lower ionosphere. Results agree with the frequently observed, doughnut-shaped optical signature of elves but show that the structure exhibits asymmetry due to the presence of Earth's ambient magnetic field. Furthermore, in-cloud (horizontal) lightning channels produce observable optical emissions without the doughnut shape and, in fact, produce a much stronger optical output for the same channel current. Electron density perturbations associated with elves are also calculated, with contributions from attachment and ionization. Results presented as a function of parameters such as magnetic field direction, dipole current orientation, altitude and amplitude, and ambient ionospheric density profile demonstrate the highly nonlinear nature of the EMP-ionosphere interaction. Ionospheric effects of a sequence of in-cloud discharges are calculated, simulating a burst of in-cloud lightning activity and resulting in large density changes in the overlying ionosphere.

Slow, steady discharge regime for concentrated lead-acid cells with planar, cylindrical, and spherical electrodes

NASA Astrophysics Data System (ADS)

Yang, Yigang; Saslow, Wayne M.

1998-12-01

A recent theoretical study of slow, steady discharge for a lead-acid cell carrying current I, with planar electrodes, predicts a nonzero bulk charge distribution with an associated voltage profile within the electrolyte that is quadratic in space. A second theoretical study finds that the Ohmic voltage resistance R=ΔV/I across the electrolyte differs from the Joule heating resistance RJ=P/I2. The very different diffusion constants of the charge-carrying ions H+ and HSO4- is responsible for the quadratic voltage profile. The presence of changing chemical energies is responsible for the different resistances. In the present work we study this same chemical system for the cylindrical and spherical geometries, with Pb at inner radius a and PbO2 at outer radius b. For the cylindrical case, the voltage varies with radius as the sum of a logarithm and a quadratic. For the spherical case, the voltage varies with the radius as a sum of an inverse r and a quadratic. For both cases, the quadratic is the signature of a uniform nonzero bulk charge distribution. For both cases, R≠RJ. For large enough b/a, in both the spherical and cylindrical cases, we find that R<0; current flows from lower to higher electrical potential. This does not violate energy conservation when chemical as well as electrical energies are included.

Flood-inundation maps for North Fork Salt Creek at Nashville, Indiana

USGS Publications Warehouse

Martin, Zachary W.

2017-11-13

Digital flood-inundation maps for a 3.2-mile reach of North Fork Salt Creek at Nashville, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding that correspond to selected water levels (stages) at the North Fork Salt Creek at Nashville, Ind., streamgage (USGS station number 03371650). Real-time stages at this streamgage may be obtained from the USGS National Water Information System at http://waterdata.usgs.gov/nwis or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also shows observed USGS stages at the same site as the USGS streamgage (NWS site NFSI3).Flood profiles were computed for the stream reach by means of a one-dimensional, step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current (2015) stage-discharge rating at the USGS streamgage 03371650, North Fork Salt Creek at Nashville, Ind. The hydraulic model was then used to compute 12 water-surface profiles for flood stages at 1-foot (ft) intervals, except for the highest profile of 22.9 ft, referenced to the streamgage datum ranging from 12.0 ft (the NWS “action stage”) to 22.9 ft, which is the highest stage of the current (2015) USGS stage-discharge rating curve and 1.9 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.98-ft vertical accuracy and 4.9-ft horizontal resolution) to delineate the area flooded at each stage.The availability of these maps, along with information regarding current stage from the USGS streamgage, will provide emergency management personnel and residents with information that is critical for flood response activities, such as evacuations and road closures, as well as for postflood recovery efforts.

Saturated Widths of Magnetic Islands in Tokamak Discharges

NASA Astrophysics Data System (ADS)

Halpern, F.; Pankin, A. Y.

2005-10-01

The new ISLAND module described in reference [1] implements a quasi-linear model to compute the widths of multiple magnetic islands driven by saturated tearing modes in toroidal plasmas of arbitrary aspect ratio and cross sectional shape. The distortion of the island shape caused by the radial variation in the perturbation is computed in the new module. In transport simulations, the enhanced transport caused by the magnetic islands has the effect of flattening the pressure and current density profiles. This self consistent treatment of the magnetic islands alters the development of the plasma profiles. In addition, it is found that islands closer to the magnetic axis influence the evolution of islands further out in the plasma. In order to investigate such phenomena, the ISLAND module is used within the BALDUR predictive modeling code to compute the widths of multiple magnetic islands in tokamak discharges. The interaction between the islands and sawtooth crashes is examined in simulations of DIII-D and JET discharges. The module is used to compute saturated neoclassical tearing mode island widths for multiple modes in ITER. Preliminary results for island widths in ITER are consistent with those presented [2] by Hegna. [1] F.D. Halpern, G. Bateman, A.H. Kritz and A.Y. Pankin, ``The ISLAND Module for Computing Magnetic Island Widths in Tokamaks,'' submitted to J. Plasma Physics (2005). [2] C.C. Hegna, 2002 Fusion Snowmass Meeting.

Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

PubMed Central

Allagui, Anis; Freeborn, Todd J.; Elwakil, Ahmed S.; Maundy, Brent J.

2016-01-01

The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal SsC behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance Rs in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (Rs, Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical RsC model. We validate our formulae with the experimental measurements of different EDLCs. PMID:27934904

Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry

NASA Astrophysics Data System (ADS)

Allagui, Anis; Freeborn, Todd J.; Elwakil, Ahmed S.; Maundy, Brent J.

2016-12-01

The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal SsC behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance Rs in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (Rs, Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical RsC model. We validate our formulae with the experimental measurements of different EDLCs.

Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.R. Wilson; R.E. Bell; S. Bernabei

2003-02-11

High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the STmore » concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.« less

Reevaluation of Performance of Electric Double-layer Capacitors from Constant-current Charge/Discharge and Cyclic Voltammetry.

PubMed

Allagui, Anis; Freeborn, Todd J; Elwakil, Ahmed S; Maundy, Brent J

2016-12-09

The electric characteristics of electric-double layer capacitors (EDLCs) are determined by their capacitance which is usually measured in the time domain from constant-current charging/discharging and cyclic voltammetry tests, and from the frequency domain using nonlinear least-squares fitting of spectral impedance. The time-voltage and current-voltage profiles from the first two techniques are commonly treated by assuming ideal R s C behavior in spite of the nonlinear response of the device, which in turn provides inaccurate values for its characteristic metrics [corrected]. In this paper we revisit the calculation of capacitance, power and energy of EDLCs from the time domain constant-current step response and linear voltage waveform, under the assumption that the device behaves as an equivalent fractional-order circuit consisting of a resistance R s in series with a constant phase element (CPE(Q, α), with Q being a pseudocapacitance and α a dispersion coefficient). In particular, we show with the derived (R s , Q, α)-based expressions, that the corresponding nonlinear effects in voltage-time and current-voltage can be encompassed through nonlinear terms function of the coefficient α, which is not possible with the classical R s C model. We validate our formulae with the experimental measurements of different EDLCs.

Autonomous Method and System for Minimizing the Magnitude of Plasma Discharge Current Oscillations in a Hall Effect Plasma Device

NASA Technical Reports Server (NTRS)

Hruby, Vladimir (Inventor); Demmons, Nathaniel (Inventor); Ehrbar, Eric (Inventor); Pote, Bruce (Inventor); Rosenblad, Nathan (Inventor)

2014-01-01

An autonomous method for minimizing the magnitude of plasma discharge current oscillations in a Hall effect plasma device includes iteratively measuring plasma discharge current oscillations of the plasma device and iteratively adjusting the magnet current delivered to the plasma device in response to measured plasma discharge current oscillations to reduce the magnitude of the plasma discharge current oscillations.

Discharge and other hydraulic measurements for characterizing the hydraulics of Lower Congo River

USGS Publications Warehouse

Oberg, Kevin; Shelton, John M.; Gardiner, Ned; Jackson, P. Ryan

2009-01-01

The first direct measurements of discharge of the Lower Congo River below Malebo Pool and upstream from Kinganga, Democratic Republic of Congo (DRC) were made in July 2008 using acoustic Doppler current profilers, differential GPS, and echo sounders. These measurements were made in support of research that is attempting to understand the distribution of fish species in the Lower Congo River and reasons for separation of species within this large river. Analyses of these measurements show that the maximum depth in the Lower Congo River was in excess of 200 m and maximum water velocities were greater than 4 m/s. The discharge measured near Luozi, DRC was 35,800 m3/s, and decreased slightly beginning midway through the study. Local bedrock controls seem to have a large effect on the flow in the river, even in reaches without waterfalls and rapids. Dramatic changes in bed topography are evident in transects across the river.

The STPX Spheromak System: Recent Measurements and Observations

NASA Astrophysics Data System (ADS)

Williams, R. L.; Clark, J.; Richardson, M.; Williams, R. E.

2016-10-01

We present results of recent measurements made to characterize the plasma formed in the STPX* Spheromak plasma device installed at the Florida A. and M University. The toroidal plasma is formed using a pulsed cylindrical gun discharge and, when fully operational, is designed to approach a density of 1021 /m3 and electron temperatures in the range of 100-350 eV. The diagnostic devices used for these recent measurements include Langmuir probes, electrostatic triple probes, optical spectrometers, CCD detectors, laser probes and magnetic field coils. These probes have been tested using both a static and the pulsed discharges created in the device, and we report the latest measurements. The voltage and current profiles of the pulsed discharge as well as the pulsed magnetic field coils are discussed. Progress in modeling this spheromak using NIMROD and other simulation codes will be discussed. Our recent results of an ongoing study of the topology of magnetic helicity are presented in a separate poster. Spheromak Turbulent Physics Experiment.

Flood-inundation maps for the Big Blue River at Shelbyville, Indiana

USGS Publications Warehouse

Fowler, Kathleen K.

2017-02-13

Digital flood-inundation maps for a 4.1-mile reach of the Big Blue River at Shelbyville, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The floodinundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at https://water. usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Big Blue River at Shelbyville, Ind. (station number 03361500). Near-real-time stages at this streamgage may be obtained from the USGS National Water Information System at https://waterdata. usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at https://water.weather.gov/ ahps/, which also forecasts flood hydrographs at this site (SBVI3). Flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the most current stage-discharge relation at the Big Blue River at Shelbyville, Ind., streamgage. The calibrated hydraulic model was then used to compute 12 water-surface profiles for flood stages referenced to the streamgage datum and ranging from 9.0 feet, or near bankfull, to 19.4 feet, the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar] data having a 0.98-foot vertical accuracy and 4.9-foot horizontal resolution) to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage at the Big Blue River at Shelbyville, Ind., and forecasted stream stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures as well as for post-flood recovery efforts.

Is There an Association Between Markers of Cardiovascular Autonomic Dysfunction at Discharge From Rehabilitation and Participation 1 and 5 Years Later in Individuals With Spinal Cord Injury?

PubMed

Rianne Ravensbergen, H J; de Groot, Sonja; Post, Marcel W; Bongers-Janssen, Helma M; van der Woude, Lucas H; Claydon, Victoria E

2016-09-01

To determine whether physical activity and participation 1 and 5 years after discharge are associated with measures of cardiovascular autonomic function: prevalence of hypotension and reduced peak heart rate at discharge from initial inpatient spinal cord injury (SCI) rehabilitation. Prospective cohort study. Rehabilitation centers. Individuals with SCI (N=146). Not applicable. We recorded markers of cardiovascular autonomic dysfunction (resting blood pressure and peak heart rate) and personal and lesion characteristics at the time of discharge from rehabilitation. Parameters for participation (social health status dimension of the Sickness Impact Profile) and physical activity (Physical Activity Scale for Individuals with Physical Disabilities [PASIPD]) were measured 1 and 5 years after discharge. Effects of prevalence of cardiovascular autonomic dysfunction were analyzed using linear regression analysis while correcting for possible confounders. We found no significant association between hypotension and social health status dimension of the Sickness Impact Profile or PASIPD, either at 1 or at 5 years after discharge. A significant association between peak heart rate and social health status dimension of the Sickness Impact Profile was found at 1 year after discharge, showing poorer participation in individuals with low peak heart rate (ie, cardiovascular autonomic dysfunction). The unadjusted relation between peak heart rate and the social health status dimension of the Sickness Impact Profile was significant at 5 years, but not when adjusted for confounders. We found associations between peak heart rate and PASIPD for both 1 and 5 years after discharge; however, these were not significant after correction for potential confounding factors. Autonomic dysfunction after SCI is a crucial factor influencing quality of life. We found that cardiovascular autonomic impairment, assessed from low peak heart rate, was associated with reduced participation after 1 year. The results suggest that peak heart rate at discharge from rehabilitation after SCI should be used to identify those needing additional support to facilitate physical activity and participation after discharge. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Discharge current modes of high power impulse magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Zhongzhen, E-mail: wuzz@pkusz.edu.cn; Xiao, Shu; Ma, Zhengyong

2015-09-15

Based on the production and disappearance of ions and electrons in the high power impulse magnetron sputtering plasma near the target, the expression of the discharge current is derived. Depending on the slope, six possible modes are deduced for the discharge current and the feasibility of each mode is discussed. The discharge parameters and target properties are simplified into the discharge voltage, sputtering yield, and ionization energy which mainly affect the discharge plasma. The relationship between these factors and the discharge current modes is also investigated.

BAM: Bayesian AMHG-Manning Inference of Discharge Using Remotely Sensed Stream Width, Slope, and Height

NASA Astrophysics Data System (ADS)

Hagemann, M. W.; Gleason, C. J.; Durand, M. T.

2017-11-01

The forthcoming Surface Water and Ocean Topography (SWOT) NASA satellite mission will measure water surface width, height, and slope of major rivers worldwide. The resulting data could provide an unprecedented account of river discharge at continental scales, but reliable methods need to be identified prior to launch. Here we present a novel algorithm for discharge estimation from only remotely sensed stream width, slope, and height at multiple locations along a mass-conserved river segment. The algorithm, termed the Bayesian AMHG-Manning (BAM) algorithm, implements a Bayesian formulation of streamflow uncertainty using a combination of Manning's equation and at-many-stations hydraulic geometry (AMHG). Bayesian methods provide a statistically defensible approach to generating discharge estimates in a physically underconstrained system but rely on prior distributions that quantify the a priori uncertainty of unknown quantities including discharge and hydraulic equation parameters. These were obtained from literature-reported values and from a USGS data set of acoustic Doppler current profiler (ADCP) measurements at USGS stream gauges. A data set of simulated widths, slopes, and heights from 19 rivers was used to evaluate the algorithms using a set of performance metrics. Results across the 19 rivers indicate an improvement in performance of BAM over previously tested methods and highlight a path forward in solving discharge estimation using solely satellite remote sensing.

Effect of a direct current bias on the electrohydrodynamic performance of a surface dielectric barrier discharge actuator for airflow control

NASA Astrophysics Data System (ADS)

Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng

2015-02-01

The effect of a DC bias on the electrohydrodynamics (EHD) force induced by a surface dielectric barrier AC discharge actuator for airflow control at the atmospheric pressure is investigated. The measurement of the surface potential due to charge deposition at different DC biases is carried out by using a special designed corona like discharge potential probe. From the surface potential data, the plasma electromotive force is shown not affected much by the DC biases except for some reduction of the DC bias near the exposed electrode edge for the sheath-like configuration. The total thrust is measured by an analytical balance, and an almost linear relationship to the potential voltage at the exposed electrode edge is found for the direct thrust force. The temporally averaged ionic wind characteristics are investigated by Pitot tube sensor and schlieren visualization system. It is found that the ionic wind velocity profiles with different DC biases are almost the same in the AC discharge plasma area but gradually diversified in the further downstream area as well as the upper space away from the discharge plasma area. Also, the DC bias can significantly modify the topology of the ionic wind produced by the AC discharge actuator. These results can provide an insight into how the DC biases to affect the force generation.

Dynamic characteristics of a 30-centimeter mercury ion thruster

NASA Technical Reports Server (NTRS)

Serafini, J. S.; Mantenieks, M. A.; Rawlin, V. K.

1975-01-01

The present work reports on measurements of the fluctuations in the beam current, discharge current, neutralizer keeper current, and discharge voltage of a 30-cm ion thruster made with 60Hz laboratory-type power supplies. The intensities of the fluctuations (ratio of the root-mean-square magnitude to time-average quantity) were found to depend significantly on the beam and magnetic baffle currents. The shape of the frequency spectra of the discharge plasma fluctuations was related to the beam and magnetic baffle currents. The predominant peaks of the beam and discharge current spectra occurred at frequencies less than 30 kilohertz. This discharge chamber resonance could be attributable to ion-acoustic wave phenomena. Cross-correlations of the discharge and beam currents indicated that the dependence on the magnetic baffle current was strong. The measurements revealed that the discharge current fluctuations directly contribute to the beam current fluctuations and that the power supply characteristics can modify these fluctuations.

Characterization of pulsed metallic hydride vacuum arc discharge plasmas by optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Tang, Jian; Deng, Chunfeng; Wu, Chunlei; Lu, Biao; Hu, Yonghong

2017-12-01

The characteristics of plasmas in a titanium hydride vacuum arc ion source were experimentally investigated by a temporally- and spatially-integrated optical emission spectroscopy method. A plasma emission spectral fitting model was developed to calculate the plasmas temperature and relative density of each particle component, assuming plasmas were in local thermodynamic equilibrium state and optical thin in this study. The good agreement was founded between the predicted and measured spectra in the interesting regions of 330-340 nm and 498-503 nm for Ti+ ion and Ti atom respectively, while varying the plasma temperature and density. Compared with conventional Boltzmann plot method, this method, therefore, made a significant improvement on the plasma diagnosis in dealing with the spectral profile with many lines overlapped. At the same time, to understand the mechanism of the occluded-gas vacuum arc discharge plasmas, the plasmas emission spectra, ion relative density, and temperature with different discharge conditions were studied. The results indicated that the rate of Ti metal evaporation and H desorption from the electrode would be enhanced with arc current, and the ionization temperature increased with the feed-in power of arc discharge, leading more H+ and Ti+ ions, but reducing the H+ proportion in arc discharged plasmas.

Plasma oscillation effects on nested Hall thruster operation and stability

NASA Astrophysics Data System (ADS)

McDonald, M. S.; Sekerak, M. J.; Gallimore, A. D.; Hofer, R. R.

High-power Hall thrusters capable of throughput on the order of 100 kW are currently under development, driven by more demanding mission profiles and rapid growth in on-orbit solar power generation capability. At these power levels the nested Hall thruster (NHT), a new design that concentrically packs multiple thrusters into a single body with a shared magnetic circuit, offers performance and logistical advantages over conventional single-channel Hall thrusters. An important area for risk reduction in NHT development is quantifying inter-channel coupling between discharge channels. This work presents time- and frequency-domain discharge current and voltage measurements paired with high-speed video of the X2, a 10-kW class dual channel NHT. Two “ triads” of operating conditions at 150 V, 3.6 kW and 250 V, 8.6 kW were examined, including each channel in individual operation and both channels in joint operation. For both triads tested, dual-channel operation did not noticeably destabilize the discharge. Partial coupling of outer channel oscillations into the inner channel occurred at 150 V, though oscillation amplitudes did not change greatly. As a percentage of mean discharge current, RMS oscillations at 150 V increased from 8% to 13% on the inner channel and decreased from 10% to 8% on the outer channel from single- to dual-channel operation. At 250 V the RMS/mean level stayed steady at 13% on the inner channel and decreased from 7% to 6% on the outer channel. The only mean discharge parameter noticeably affected was the cathode floating potential, which decreased in magnitude below ground with increased absolute cathode flow rate in dual-channel mode. Rotating spokes were detected on high-speed video across all X2 operating cases with wavelength 12-18 cm, and spoke velocity generally increased from single- to dual-channel operation.

Self-pulsing in a low-current hollow cathode discharge: From Townsend to glow discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Yu; School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081; Xie, Kan, E-mail: xiekan@bit.edu.cn

We investigate the self-pulsing phenomenon of a low current cavity discharge in a cylindrical hollow cathode in pure argon. The waveforms of pulsed current and voltage are measured, and the time-averaged and time-resolved images of hollow cathode discharge are recorded by using high-speed intensified charge coupled device camera. The results show that the self-pulsing is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. During the self-pulsing, the current rising time relates to the dissipation of space charges, and the decay time relates to the reconstruction of the virtual anode by the accumulation ofmore » positive ions. Whether or not space charges can form and keep the virtual anode is responsible for the discharge mode and hence plays an important role in the self-pulsing phenomenon in low current hollow cathode discharge.« less

A thermal profile method to identify potential ground-water discharge areas and preferred salmonid habitats for long river reaches

USGS Publications Warehouse

Vaccaro, J.J.; Maloy, K.J.

2006-01-01

The thermal regime of riverine systems is a major control on aquatic ecosystems. Ground water discharge is an important abiotic driver of the aquatic ecosystem because it provides preferred thermal structure and habitat for different types of fish at different times in their life history. In large diverse river basins with an extensive riverine system, documenting the thermal regime and ground-water discharge is difficult and problematic. A method was developed to thermally profile long (5-25 kilometers) river reaches by towing in a Lagrangian framework one or two probes that measure temperature, depth, and conductivity. One probe is towed near the streambed and, if used, a second probe is towed near the surface. The probes continuously record data at 1-3-second intervals while a Global Positioning System logs spatial coordinates. The thermal profile provides valuable information about spatial and temporal variations in habitat, and, notably, indicates ground-water discharge areas. This method was developed and tested in the Yakima River Basin, Washington, in summer 2001 during low flows in an extreme drought year. The temperature profile comprehensively documents the longitudinal distribution of a river's temperature regime that cannot be captured by fixed station data. The example profile presented exhibits intra-reach diversity that reflects the many factors controlling the temperature of a parcel of water as it moves downstream. Thermal profiles provide a new perspective on riverine system temperature regimes that represent part of the aquatic habitat template for lotic community patterns.

Magnetic dipole discharges. II. Cathode and anode spot discharges and probe diagnostics

NASA Astrophysics Data System (ADS)

Stenzel, R. L.; Urrutia, J. M.; Ionita, C.; Schrittwieser, R.

2013-08-01

The high current regime of a magnetron-type discharge has been investigated. The discharge uses a permanent magnet as a cold cathode which emits secondary electrons while the chamber wall or a grounded electrode serves as the anode. As the discharge voltage is increased, the magnet develops cathode spots, which are short duration arcs that provide copious electrons to increase the discharge current dramatically. Short (1 μs), high current (200 A) and high voltage (750 V) discharge pulses are produced in a relaxation instability between the plasma and a charging capacitor. Spots are also observed on a negatively biased plane Langmuir probe. The probe current pulses are as large as those on the magnet, implying that the high discharge current does not depend on the cathode surface area but on the properties of the spots. The fast current pulses produce large inductive voltages, which can reverse the electrical polarity of the magnet and temporarily operate it as an anode. The discharge current may also oscillate at the frequency determined by the charging capacitor and the discharge circuit inductance. Each half cycle of high-current current pulses exhibits a fast (≃10 ns) current rise when a spot is formed. It induces high frequency (10-100 MHz) transients and ringing oscillations in probes and current circuits. Most probes behave like unmatched antennas for the electromagnetic pulses of spot discharges. Examples are shown to distinguish the source of oscillations and some rf characteristics of Langmuir probes.

A Study on Water Surface Profiles of Rivers with Constriction

NASA Astrophysics Data System (ADS)

Qian, Chaochao; Yamada, Tadashi

2013-04-01

Water surface profile of rivers with constrictions is precious in both classic hydraulics and river management practice. This study was conducted to clarify the essences of the water surface profiles. 3 cases of experiments and 1D numerical calculations with different discharges were made in the study and analysis solutions of the non-linear basic equation of surface profile in varied flow without considering friction were derived. The manning's number was kept in the same in each case by using crosspiece roughness. We found a new type of water surface profile of varied flow from the results of 1D numerical calculation and that of experiments and named it as Mc curve because of its mild condition with constriction segment. This kind of curves appears as a nature phenomenon ubiquitously. The process of water surface forming is dynamic and bore occurs at the upper side of constriction during increasing discharge before the surface profile formed. As a theoretical work, 3 analysis solutions were derived included 2 physical-meaning solutions in the study by using Man-Machine system. One of the derived physical-meaning solutions was confirmed that it is validity by comparing to the results of 1D numerical calculation and that of experiments. The solution represents a flow profile from under critical condition at the upper side to super critical condition at the down side of constriction segment. The other derived physical-meaning solution represents a flow profile from super critical condition at the upper side to under critical condition at the down side of constriction segment. These two kinds of flow profiles exist in the nature but no theoretical solution can express the phenomenon. We find the depth distribution only concerned with unit width discharge distribution and critical depth under a constant discharge from the derived solutions. Therefor, the profile can be gained simply and precisely by using the theoretical solutions instead of numerical calculation even in practice.

In Search of Easy-to-Use Methods for Calibrating ADCP's for Velocity and Discharge Measurements

USGS Publications Warehouse

Oberg, K.; ,

2002-01-01

A cost-effective procedure for calibrating acoustic Doppler current profilers (ADCP) in the field was presented. The advantages and disadvantages of various methods which are used for calibrating ADCP were discussed. The proposed method requires the use of differential global positioning system (DGPS) with sub-meter accuracy and standard software for collecting ADCP data. The method involves traversing a long (400-800 meter) course at a constant compass heading and speed, while collecting simultaneous DGPS and ADCP data.

Measurement of neoclassically predicted edge current density at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; McCarthy, P. J.; Wolfrum, E.; Fischer, R.; Giannone, L.; Burckhart, A.; the ASDEX Upgrade Team

2012-12-01

Experimental confirmation of neoclassically predicted edge current density in an ELMy H-mode plasma is presented. Current density analysis using the CLISTE equilibrium code is outlined and the rationale for accuracy of the reconstructions is explained. Sample profiles and time traces from analysis of data at ASDEX Upgrade are presented. A high time resolution is possible due to the use of an ELM-synchronization technique. Additionally, the flux-surface-averaged current density is calculated using a neoclassical approach. Results from these two separate methods are then compared and are found to validate the theoretical formula. Finally, several discharges are compared as part of a fuelling study, showing that the size and width of the edge current density peak at the low-field side can be explained by the electron density and temperature drives and their respective collisionality modifications.

Flood-inundation maps for the Iroquois River at Rensselaer, Indiana

USGS Publications Warehouse

Fowler, Kathleen K.; Bunch, Aubrey R.

2013-01-01

Digital flood-inundation maps for a 4.0-mile reach of the Iroquois River at Rensselaer, Indiana (Ind.), were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at USGS streamgage 05522500, Iroquois River at Rensselaer, Ind. Current conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the Internet at (http://waterdata.usgs.gov/in/nwis/uv?site_no=05522500). In addition, the National Weather Service (NWS) forecasts flood hydrographs at the Rensselaer streamgage. That forecasted peak-stage information, also available on the Internet (http://water.weather.gov/ahps/), may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation. For this study, flood profiles were computed for the Iroquois River reach by means of a one-dimensional step-backwater model developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated by using the most current (June 27, 2012) stage-discharge relations at USGS streamgage 05522500, Iroquois River at Rensselaer, Ind., and high-water marks from the flood of July 2003. The calibrated hydraulic model was then used to determine nine water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from Light Detection and Ranging (LiDAR) data) in order to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage at Rensselaer, Ind., and forecasted stream stages from the NWS, provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Interior and Exterior Laser-Induced Fluorescence and Plasma Potential Measurements on a Laboratory Hall Thruster (Postprint)

DTIC Science & Technology

1999-06-01

Hall thruster is provided by a 1 mm axial slot in the insulator outer wall. Axial ion velocity profiles for four discharge voltages (100 V, 160 V, 200 V, 250 V) are measured as are radial velocity profiles in the near field plume. Internal neutral xenon axial velocity profiles are also measured at these conditions. For comparison, the plume plasma potential profile is measured with an emissive probe. These probe based potential measurements extend from 50 mm outside the plume to the near anode region for all but the highest discharge voltage condition. For each condition,

An ionization region model of the reactive Ar/O2 high power impulse magnetron sputtering discharge

NASA Astrophysics Data System (ADS)

Gudmundsson, J. T.; Lundin, D.; Brenning, N.; Raadu, M. A.; Huo, Chunqing; Minea, T. M.

2016-12-01

A new reactive ionization region model (R-IRM) is developed to describe the reactive Ar/O2 high power impulse magnetron sputtering (HiPIMS) discharge with a titanium target. It is then applied to study the temporal behavior of the discharge plasma parameters such as electron density, the neutral and ion composition, the ionization fraction of the sputtered vapor, the oxygen dissociation fraction, and the composition of the discharge current. We study and compare the discharge properties when the discharge is operated in the two well established operating modes, the metal mode and the poisoned mode. Experimentally, it is found that in the metal mode the discharge current waveform displays a typical non-reactive evolution, while in the poisoned mode the discharge current waveform becomes distinctly triangular and the current increases significantly. Using the R-IRM we explore the current increase and find that when the discharge is operated in the metal mode Ar+ and Ti+ -ions contribute most significantly (roughly equal amounts) to the discharge current while in the poisoned mode the Ar+ -ions contribute most significantly to the discharge current and the contribution of O+ -ions, Ti+ -ions, and secondary electron emission is much smaller. Furthermore, we find that recycling of atoms coming from the target, that are subsequently ionized, is required for the current generation in both modes of operation. From the R-IRM results it is found that in the metal mode self-sputter recycling dominates and in the poisoned mode working gas recycling dominates. We also show that working gas recycling can lead to very high discharge currents but never to a runaway. It is concluded that the dominating type of recycling determines the discharge current waveform.

Measurements and modeling of transport and impurity radial profiles in the EXTRAP T2R reversed field pinch

NASA Astrophysics Data System (ADS)

Kuldkepp, M.; Brunsell, P. R.; Cecconello, M.; Dux, R.; Menmuir, S.; Rachlew, E.

2006-09-01

Radial impurity profiles of oxygen in the rebuilt reversed field pinch EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] have been measured with a multichannel spectrometer. Absolute ion densities for oxygen peak between 1-4×1010cm-3 for a central electron density of 1×1013cm-3. Transport simulations with the one-dimensional transport code STRAHL with a diffusion coefficient of 20m2 s-1 yield density profiles similar to those measured. Direct measurement of the ion profile evolution during pulsed poloidal current drive suggests that the diffusion coefficient is reduced by a factor ˜2 in the core but remains unaffected toward the edge. Core transport is not significantly affected by the radial magnetic field growth seen at the edge in discharges without feedback control. This indicates that the mode core amplitude remains the same while the mode eigenfunction increases at the edge.

Investigation of energy transport in DIII-D high- β P EAST-demonstration discharges with the TGLF turbulent and NEO neoclassical transport models [Investigation of energy transport in DIII-D high- β P EAST-demonstration discharges with turbulent and neoclassical transport models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Chengkang; Staebler, Gary M.; Lao, Lang L.

Here, energy transport analyses of DIII-D high-β P EAST-demonstration discharges have been performed using the TGYRO transport package with TGLF turbulent and NEO neoclassical transport models under the OMFIT integrated modeling framework. Ion energy transport is shown to be dominated by neoclassical transport and ion temperature profiles predicted by TGYRO agree closely with the experimental measured profiles for these high-β P discharges. Ion energy transport is largely insensitive to reductions in the E × B flow shear stabilization. The Shafranov shift is shown to play a role in the suppression of the ion turbulent energy transport below the neoclassical level.more » Electron turbulent energy transport is under-predicted by TGLF and a significant shortfall in the electron energy transport over the whole core plasma is found with TGLF predictions for these high-β P discharges. TGYRO can successfully predict the experimental ion and electron temperature profiles by artificially increasing the saturated turbulence level for ETG driven modes used in TGLF.« less

Investigation of energy transport in DIII-D high- β P EAST-demonstration discharges with the TGLF turbulent and NEO neoclassical transport models [Investigation of energy transport in DIII-D high- β P EAST-demonstration discharges with turbulent and neoclassical transport models

DOE PAGES

Pan, Chengkang; Staebler, Gary M.; Lao, Lang L.; ...

2017-01-11

Here, energy transport analyses of DIII-D high-β P EAST-demonstration discharges have been performed using the TGYRO transport package with TGLF turbulent and NEO neoclassical transport models under the OMFIT integrated modeling framework. Ion energy transport is shown to be dominated by neoclassical transport and ion temperature profiles predicted by TGYRO agree closely with the experimental measured profiles for these high-β P discharges. Ion energy transport is largely insensitive to reductions in the E × B flow shear stabilization. The Shafranov shift is shown to play a role in the suppression of the ion turbulent energy transport below the neoclassical level.more » Electron turbulent energy transport is under-predicted by TGLF and a significant shortfall in the electron energy transport over the whole core plasma is found with TGLF predictions for these high-β P discharges. TGYRO can successfully predict the experimental ion and electron temperature profiles by artificially increasing the saturated turbulence level for ETG driven modes used in TGLF.« less

Free surface profiles in river flows: Can standard energy-based gradually-varied flow computations be pursued?

NASA Astrophysics Data System (ADS)

Cantero, Francisco; Castro-Orgaz, Oscar; Garcia-Marín, Amanda; Ayuso, José Luis; Dey, Subhasish

2015-10-01

Is the energy equation for gradually-varied flow the best approximation for the free surface profile computations in river flows? Determination of flood inundation in rivers and natural waterways is based on the hydraulic computation of flow profiles. This is usually done using energy-based gradually-varied flow models, like HEC-RAS, that adopts a vertical division method for discharge prediction in compound channel sections. However, this discharge prediction method is not so accurate in the context of advancements over the last three decades. This paper firstly presents a study of the impact of discharge prediction on the gradually-varied flow computations by comparing thirteen different methods for compound channels, where both energy and momentum equations are applied. The discharge, velocity distribution coefficients, specific energy, momentum and flow profiles are determined. After the study of gradually-varied flow predictions, a new theory is developed to produce higher-order energy and momentum equations for rapidly-varied flow in compound channels. These generalized equations enable to describe the flow profiles with more generality than the gradually-varied flow computations. As an outcome, results of gradually-varied flow provide realistic conclusions for computations of flow in compound channels, showing that momentum-based models are in general more accurate; whereas the new theory developed for rapidly-varied flow opens a new research direction, so far not investigated in flows through compound channels.

Self-organized stationary states of inductively driven tokamaks

NASA Astrophysics Data System (ADS)

Jardin, S. C.; Ferraro, N.; Krebs, I.; Chen, J.

2014-10-01

We report on a mechanism for preventing the current and temperature profiles from peaking in a stationary state tokamak. For certain parameters, regardless of the initial state, the plasma profiles will evolve into a self-organized state with the safety factor q slightly above 1 and constant in a central volume. This large shear free region is unstable to interchange modes for any pressure gradient, and the instability drives a strong (1,1) helical flow. This flow has the property that V × B is the gradient of a potential, so it does not affect the magnetic field evolution. However, the driven flow appears in the temperature evolution equation and dominates over the thermal conductivity in the center of the discharge. The net effect is to keep the central temperature (and resistivity) profiles flat so that the resistive steady state preserves the self organized state with q slightly above 1 and constant in the central volume. This mechanism was discovered with the M3D-C1 toroidal 3D MHD code, and could possibly explain the mechanism at play in non-sawtoothing discharges with q0 just above 1 such as hybrid modes in DIII-D and ASDEX-U and long-lived modes in NSTX and MAST. This work was supported by US DOE Contract No. DE-AC02-09CHI1446, MPPC, and SciDAC CEMM.

Turbulence in high-beta ASDEX upgrade advanced scenarios

NASA Astrophysics Data System (ADS)

Doerk, H.; Bock, A.; Di Siena, A.; Fable, E.; Görler, T.; Jenko, F.; Stober, J.; The ASDEX Upgrade Team

2018-01-01

Recent experiments at ASDEX Upgrade achieve non-inductive operation in full tungsten wall conditions by applying electron cyclotron and neutral beam current drive. These discharges are characterised by a well-measured safety factor profile, which does not drop below one, and a good energy confinement. By reproducing the experimental heat fluxes, nonlinear gyrokinetic simulations suggest that the observed strong peaking of the ion temperature in the core is caused by the stabilising impact of a significant beam ion content, as well as strong electromagnetic effects on turbulent transport. Quasilinear transport models are not yet applicable in this interesting and reactor relevant parameter regime, but available simulation data may serve as a testbed for improvements. As the present plasma is close to the kinetic ballooning (KBM) threshold, elevating the safety factor profile under otherwise identical conditions is proposed to clarify, whether profiles are ultimately limited by KBM turbulence, or by global stability constraints.

The Detroit River, Michigan: an ecological profile

USGS Publications Warehouse

Manny, Bruce A.; Edsall, Thomas A.; Jaworski, Eugene

1988-01-01

A part of the connecting channel system between Lake Huron and Lake Erie, the Detroit River forms an integral link between the two lakes for both humans and biological resources such as fish, nutrients, and plant detritus. This profile summarizes existing scientific information on the ecological structure and functioning of this ecosystem. Topics include the geological history of the region, climatic influences, river hydrology, lower trophic-level biotic components, native and introduced fishes, waterfowl use, ecological interrelationships, commercial and recreational uses of the river, and current management issues. Despite urbanization, the river still supports diverse fish, waterfowl, and benthic populations. Management issues include sewer overflows; maintenance dredging for navigation and port activities; industrial discharges of potentially hazardous materials; and wetland, fishery, and waterfowl protection and enhancement.

High-beta, steady-state hybrid scenario on DIII-D

DOE PAGES

Petty, C. C.; Kinsey, J. E.; Holcomb, C. T.; ...

2015-12-17

Here, the potential of the hybrid scenario (first developed as an advanced inductive scenario for high fluence) as a regime for high-beta, steady-state plasmas is demonstrated on the DIII-D tokamak. These experiments show that the beneficial characteristics of hybrids, namely safety factor ≥1 with low central magnetic shear, high stability limits and excellent confinement, are maintained when strong central current drive (electron cyclotron and neutral beam) is applied to increase the calculated non-inductive fraction to ≈100% (≈50% bootstrap current). The best discharges achieve normalized beta of 3.4, IPB98(y,2) confinement factor of 1.4, surface loop voltage of 0.01 V, and nearlymore » equal electron and ion temperatures at low collisionality. A zero-dimensional physics model shows that steady-state hybrid operation with Q fus ~ 5 is feasible in FDF and ITER. The advantage of the hybrid scenario as an Advanced Tokamak regime is that the external current drive can be deposited near the plasma axis where the efficiency is high; additionally, good alignment between the current drive and plasma current profiles is not necessary as the poloidal magnetic flux pumping self-organizes the current density profile in hybrids with an m/n=3/2 tearing mode.« less

Rydberg gas theory of a glow discharge plasma: I. Application to the electrical behaviour of a fast flowing glow discharge plasma.

PubMed

Mason, Rod S; Mitchell, David J; Dickinson, Paul M

2010-04-21

Current-voltage (I-V) curves have been measured, independent of the main discharge, for electricity passing through the steady state fast flowing 'afterglow' plasma of a low power dc glow discharge in Ar. Voltage profiles along the axial line of conduction have been mapped using fixed probes and potentiometry, and the mass spectra of cations emerging from the downstream sampling Cone, also acting as a probe anode, were recorded simultaneously. Floating double probe experiments were also carried out. The electrical behavior is consistent with the well established I-V characteristics of such discharges, but does not comply with classical plasma theory predictions. The plasma decays along the line of conduction, with a lifetime of approximately 1 ms, despite carrying a steady state current, and its potential is below that of the large surface area anode voltage; a situation which cannot exist in the presence of a conventional free ion-electron plasma, unless the electron temperature is super cold. Currents, large by comparison with the main discharge current, and independent of it, are induced to flow through the downstream plasma, from the Anode (acting as a cathode) to the anodic ion exit Cone, induced by electron impact ionisation at the anode, but without necessarily increasing the plasma density. It appears to be conducted by direct charge transfer between a part of the anode surface (acting as cathode to the auxiliary circuit) and the plasma, without secondary electron emission or heating, which suggests the direct involvement of Rydberg atom intermediates. The reaction energy defect (= the work function of the electrode surface) fits with the plasma potential threshold observed for the cathodic reaction to occur. A true free ion-electron plasma is readily detected by the observation of cations at the anode surface, when induced at the downstream anode, at high bias voltages, by the electron impact ionisation in the boundary region. In contrast to the classical model, the complex electrical (and mass spectrometric) behaviour fits qualitatively, but can be understood well, with the Rydberg gas model described in papers II and III (R. S. Mason, and R. S. Mason and P. Douglas, PCCP, 2010, DOI: 10.1039/b918081h and b918083d) over a wide range of probe bias voltages. The full cycle of behavior is then described for the development of a true secondary discharge within the downstream plasma.

Mechanism of VHF H2 plasma production at high pressures

NASA Astrophysics Data System (ADS)

Chen, Kuan-Chen; Chiu, Kuo-Feng; Chen, Chia-Fu; Lien, Cheng-Yang; Tsai, Yu-Jer; Lien, Ting-Kuei; Ogiwara, Kohei; Uchino, Kiichiro; Kawai, Yoshinobu

2016-06-01

A VHF H2 plasma was produced by a narrow-gap discharge at high pressures, and the plasma parameters were examined with the Langmuir probe. A bi-Maxwellian electron distribution was observed near the discharge electrode at a discharge gap of 10 mm, while a Maxwellian distribution was seen near the center. When the discharge gap was 15 mm, electrons had a Maxwellian distribution independent of the position. It was found that there must be a threshold in the discharge gap for stochastic heating to occur. The plasma potential near the discharge electrode was higher than that near the center of the interelectrode gap, suggesting the existence of negative ions. The simulation using the plasma hybrid code was carried out. The spatial profiles of the density and temperature of electrons were similar to the experimental results. The plasma potential had a hill-like profile that was quite different from the measured one. The negative ion density was negligible.

Relation of morphology of electrodeposited zinc to ion concentration profile

NASA Technical Reports Server (NTRS)

May, C. E.; Kautz, H. E.; Sabo, B. B.

1977-01-01

The morphology of electrodeposited zinc was studied with special attention to the ion concentration profile. The initial concentrations were 9M hydroxide ion and 1.21M zincate. Current densities were 6.4 to 64 mA/sq cm. Experiments were run with a horizontal cathode which was observed in situ using a microscope. The morphology of the zinc deposit was found to be a function of time as well as current density; roughly, the log of the transition time from mossy to large crystalline type deposit is inversely proportional to current density. Probe electrodes indicated that the electrolyte in the cathode chamber was mixed by self inducted convection. However, relatively large concentration gradients of the involved species existed across the boundary layer of the cathode. Analysis of the data suggests that the morphology converts from mossy to large crystalline when the hydroxide activity on the cathode surface exceeds about 12 M. Other experiments show that the pulse discharge technique had no effect on the morphology in the system where the bulk concentration of the electrolyte was kept homogeneous via self induced convection.

Projecting High Beta Steady-State Scenarios from DIII-D Advanced Tokamk Discharges

NASA Astrophysics Data System (ADS)

Park, J. M.

2013-10-01

Fusion power plant studies based on steady-state tokamak operation suggest that normalized beta in the range of 4-6 is needed for economic viability. DIII-D is exploring a range of candidate high beta scenarios guided by FASTRAN modeling in a repeated cycle of experiment and modeling validation. FASTRAN is a new iterative numerical procedure coupled to the Integrated Plasma Simulator (IPS) that integrates models of core transport, heating and current drive, equilibrium and stability self-consistently to find steady state (d / dt = 0) solutions, and reproduces most features of DIII-D high beta discharges with a stationary current profile. Separately, modeling components such as core transport (TGLF) and off-axis neutral beam current drive (NUBEAM) show reasonable agreement with experiment. Projecting forward to scenarios possible on DIII-D with future upgrades, two self-consistent noninductive scenarios at βN > 4 are found: high qmin and high internal inductance li. Both have bootstrap current fraction fBS > 0 . 5 and rely on the planned addition of a second off-axis neutral beamline and increased electron cyclotron heating. The high qmin > 2 scenario achieves stable operation at βN as high as 5 by a very broad current density profile to improve the ideal-wall stabilization of low-n instabilities along with confinement enhancement from low magnetic shear. The li near 1 scenario does not depend on ideal-wall stabilization. Improved confinement from strong magnetic shear makes up for the lower pedestal needed to maintain li high. The tradeoff between increasing li and reduced edge pedestal determines the achievable βN (near 4) and fBS (near 0.5). This modeling identifies the necessary upgrades to achieve target scenarios and clarifies the pros and cons of particular scenarios to better inform the development of steady-state fusion. Supported by the US Department of Energy under DE-AC05-00OR22725 & DE-FC02-04ER54698.

Determination of the coefficient of reflection of metastable argon atoms from the discharge tube wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigorian, G. M.; Dyatko, N. A.; Kochetov, I. V., E-mail: kochet@triniti.ru

Radial profiles of the density of metastable atoms Ar({sup 3}P{sub 2}) in the positive column of a dc glow discharge in argon were measured. Gas-discharge glass tubes with clean inner surfaces and surfaces covered with a carbonitride or carbon film were utilized. The parameters of the discharge plasma under experimental conditions were calculated in the framework of a one-dimensional (along the tube radius) discharge model. The coefficient K of reflection of Ar({sup 3}P{sub 2}) atoms from the tube wall was estimated by comparing the measured and calculated density profiles. It is found that, for a clean tube wall, the coefficientmore » of reflection is K = 0.4 ± 0.2, whereas for a wall covered with a carbonitride or carbon film, it is K < 0.2.« less

Evidence cross-validation and Bayesian inference of MAST plasma equilibria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nessi, G. T. von; Hole, M. J.; Svensson, J.

2012-01-15

In this paper, current profiles for plasma discharges on the mega-ampere spherical tokamak are directly calculated from pickup coil, flux loop, and motional-Stark effect observations via methods based in the statistical theory of Bayesian analysis. By representing toroidal plasma current as a series of axisymmetric current beams with rectangular cross-section and inferring the current for each one of these beams, flux-surface geometry and q-profiles are subsequently calculated by elementary application of Biot-Savart's law. The use of this plasma model in the context of Bayesian analysis was pioneered by Svensson and Werner on the joint-European tokamak [Svensson and Werner,Plasma Phys. Controlledmore » Fusion 50(8), 085002 (2008)]. In this framework, linear forward models are used to generate diagnostic predictions, and the probability distribution for the currents in the collection of plasma beams was subsequently calculated directly via application of Bayes' formula. In this work, we introduce a new diagnostic technique to identify and remove outlier observations associated with diagnostics falling out of calibration or suffering from an unidentified malfunction. These modifications enable a good agreement between Bayesian inference of the last-closed flux-surface with other corroborating data, such as that from force balance considerations using EFIT++[Appel et al., ''A unified approach to equilibrium reconstruction'' Proceedings of the 33rd EPS Conference on Plasma Physics (Rome, Italy, 2006)]. In addition, this analysis also yields errors on the plasma current profile and flux-surface geometry as well as directly predicting the Shafranov shift of the plasma core.« less

Analysis of alternative modifications for reducing backwater flooding at the Honey Creek coal strip-mine reclamation site in Henry County, Missouri. Water Resources Investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexander, T.W.

Studies to determine the hydrologic conditions in mined and reclaimed mine areas, as well as areas of proposed mining, have become necessary with the enactment of the Surface Mining Control and Reclamation Act of 1977. Honey Creek in Henry County, Missouri, has been re-routed to flow through a series of former strip mining pits which lie within the Honey Creek coal strip mine reclamation site. During intense or long duration rainfalls within the Honey Creek basin, surface runoff has caused flooding on agricultural land near the upstream boundary of the reclamation site. The calculated existing design discharge (3,050 cubic feetmore » per second) water-surface profile is compared to the expected water-surface profiles from three assumed alternative channel modifcations within the Honey Creek study area. The alternative channel modifications used in these analyses include (1) improvement of channel bottom slope, (2) relocation of spoil material, and (3) improved by-pass channel flow conditions. The alternative 1, 2, and 3 design discharge increase will reduce the agricultural field current (1990) frequency of backwater flooding from a 3-year to a 6.5-year event.« less

Fast repetition rate (FRR) flasher

DOEpatents

Kolber, Zbigniew; Falkowski, Paul

1997-02-11

A fast repetition rate (FRR) flasher suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between Successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz.

Activity of dorsal raphe cells across the sleep–waking cycle and during cataplexy in narcoleptic dogs

PubMed Central

Wu, M-F; John, J; Boehmer, L N; Yau, D; Nguyen, G B; Siegel, J M

2004-01-01

Cataplexy, a symptom associated with narcolepsy, represents a unique dissociation of behavioural states. During cataplectic attacks, awareness of the environment is maintained, as in waking, but muscle tone is lost, as in REM sleep. We have previously reported that, in the narcoleptic dog, noradrenergic cells of the locus coeruleus cease discharge during cataplexy. In the current study, we report on the activity of serotonergic cells of the dorsal raphe nucleus. The discharge patterns of serotonergic dorsal raphe cells across sleep–waking states did not differ from those of dorsal raphe and locus coeruleus cells recorded in normal rats, cats and monkeys, with tonic discharge in waking, reduced activity in non-REM sleep and cessation of activity in REM sleep. However, in contrast with locus coeruleus cells, dorsal raphe REM sleep-off neurones did not cease discharge during cataplexy. Instead, discharge continued at a level significantly higher than that seen in REM sleep and comparable to that seen in non-REM sleep. We also identified several cells in the dorsal raphe whose pattern of activity was the opposite of that of the presumed serotonergic cells. These cells were maximally active in REM sleep and minimally active in waking and increased activity during cataplexy. The difference between noradrenergic and serotonergic cell discharge profiles in cataplexy suggests different roles for these cell groups in the normal regulation of environmental awareness and muscle tone and in the pathophysiology of narcolepsy. PMID:14678502

A Spectroscopic Study of Impurity Behavior in Neutral-beam and Ohmically Heated TFTR Discharges

DOE R&D Accomplishments Database

Stratton, B. C.; Ramsey, A. T.; Boody, F. P.; Bush, C. E.; Fonck, R. J.; Groenbner, R. J.; Hulse, R. A.; Richards, R. K.; Schivell, J.

1987-02-01

Quantitative spectroscopic measurements of Z{sub eff}, impurity densities, and radiated power losses have been made for ohmic- and neutral-beam-heated TFTR discharges at a plasma current of 2.2 MA and toroidal field of 4.7 T. Variations in these quantities with line-average plasma density (anti n{sub e}) and beam power up to 5.6 MW are presented for discharges on a graphite movable limiter. A detailed discussion of the use of an impurity transport model to infer absolute impurity densities and radiative losses from line intensity and visible continuum measurements is given. These discharges were dominated by low-Z impurities with carbon having a considerably higher density than oxygen, except in high-anti n{sub e} ohmic discharges, where the densities of carbon and oxygen were comparable. Metallic impurity concentrations and radiative losses were small, resulting in hollow radiated power profiles and fractions of the input power radiated being 30 to 50% for ohmic heating and 30% or less with beam heating. Spectroscopic estimates of the radiated power were in good agreement with bolometrically measured values. Due to an increase in the carbon density, Z{sub eff} rose from 2.0 to 2.8 as the beam power increased from 0 to 5.6 MW, pointing to a potentially serious dilution of the neutron-producing plasma ions as the beam power increased. Both the low-Z and metallic impurity concentrations were approximately constant with minor radius, indicating no central impurity accumulation in these discharges.

Effects of energetic particle phase space modifications by instabilities on integrated modeling

NASA Astrophysics Data System (ADS)

Podestà, M.; Gorelenkova, M.; Fredrickson, E. D.; Gorelenkov, N. N.; White, R. B.

2016-11-01

Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effective tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.

Effects of energetic particle phase space modifications by instabilities on integrated modeling

DOE PAGES

Podesta, M.; Gorelenkova, M.; Fredrickson, E. D.; ...

2016-07-22

Tokamak plasmas can feature a large population of energetic particles (EP) from neutral beam injection or fusion reactions. In turn, energetic particles can drive instabilities, which affect the driving EP population leading to a distortion of the original EP distribution function and of quantities that depend on it. The latter include, for example, neutral beam (NB) current drive and plasma heating through EP thermalization. Those effects must be taken into account to enable reliable and quantitative simulations of discharges for present devices as well as predictions for future burning plasmas. Reduced models for EP transport are emerging as an effectivemore » tool for long time-scale integrated simulations of tokamak plasmas, possibly including the effects of instabilities on EP dynamics. Available models differ in how EP distribution properties are modified by instabilities, e.g. in terms of gradients in real or phase space. It is therefore crucial to assess to what extent different assumptions in the transport models affect predicted quantities such as EP profile, energy distribution, NB driven current and energy/momentum transfer to the thermal populations. A newly developed kick model, which includes modifications of the EP distribution by instabilities in both real and velocity space, is used in this work to investigate these issues. Coupled to TRANSP simulations, the kick model is used to analyze NB-heated NSTX and DIII-D discharges featuring unstable Alfvén eigenmodes (AEs). Results show that instabilities can strongly affect the EP distribution function, and modifications propagate to macroscopic quantities such as NB-driven current profile and NB power transferred to the thermal plasma species. Furthermore, those important aspects are only qualitatively captured by simpler fast ion transport models that are based on radial diffusion of energetic ions only.« less

Experimental validation of a Lyapunov-based controller for the plasma safety factor and plasma pressure in the TCV tokamak

NASA Astrophysics Data System (ADS)

Mavkov, B.; Witrant, E.; Prieur, C.; Maljaars, E.; Felici, F.; Sauter, O.; the TCV-Team

2018-05-01

In this paper, model-based closed-loop algorithms are derived for distributed control of the inverse of the safety factor profile and the plasma pressure parameter β of the TCV tokamak. The simultaneous control of the two plasma quantities is performed by combining two different control methods. The control design of the plasma safety factor is based on an infinite-dimensional setting using Lyapunov analysis for partial differential equations, while the control of the plasma pressure parameter is designed using control techniques for single-input and single-output systems. The performance and robustness of the proposed controller is analyzed in simulations using the fast plasma transport simulator RAPTOR. The control is then implemented and tested in experiments in TCV L-mode discharges using the RAPTOR model predicted estimates for the q-profile. The distributed control in TCV is performed using one co-current and one counter-current electron cyclotron heating actuation.

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Culvert Analysis Program Graphical User Interface 1.0--A preprocessing and postprocessing tool for estimating flow through culvert

USGS Publications Warehouse

Bradley, D. Nathan

2013-01-01

The peak discharge of a flood can be estimated from the elevation of high-water marks near the inlet and outlet of a culvert after the flood has occurred. This type of discharge estimate is called an “indirect measurement” because it relies on evidence left behind by the flood, such as high-water marks on trees or buildings. When combined with the cross-sectional geometry of the channel upstream from the culvert and the culvert size, shape, roughness, and orientation, the high-water marks define a water-surface profile that can be used to estimate the peak discharge by using the methods described by Bodhaine (1968). This type of measurement is in contrast to a “direct” measurement of discharge made during the flood where cross-sectional area is measured and a current meter or acoustic equipment is used to measure the water velocity. When a direct discharge measurement cannot be made at a streamgage during high flows because of logistics or safety reasons, an indirect measurement of a peak discharge is useful for defining the high-flow section of the stage-discharge relation (rating curve) at the streamgage, resulting in more accurate computation of high flows. The Culvert Analysis Program (CAP) (Fulford, 1998) is a command-line program written in Fortran for computing peak discharges and culvert rating surfaces or curves. CAP reads input data from a formatted text file and prints results to another formatted text file. Preparing and correctly formatting the input file may be time-consuming and prone to errors. This document describes the CAP graphical user interface (GUI)—a modern, cross-platform, menu-driven application that prepares the CAP input file, executes the program, and helps the user interpret the output

Initial Edge Stability Observations in the PEGASUS Toroidal Experiment

NASA Astrophysics Data System (ADS)

Bongard, M. W.; Battaglia, D. J.; Garstka, G. D.; Sontag, A. C.; Unterberg, E. A.

2007-11-01

Edge stability is an important consideration for design of fusion experiments, as transient heat loads generated by edge instabilities may damage the first wall. Such instabilities are now believed to include peeling (current driven) and ballooning (pressure driven) components. Peeling instability may be expected for high values of edge j||/B and low edge pressure gradient. This matches the operating space of Pegasus, with typical ˜100 kA/m^2, |B|˜ 0.01 T, and an L-mode edge. A new camera system has observed filamentary structures in the edge of nearly all ohmically-heated discharges. Ideal stability analysis of these discharges with DCON indicates marginal stability to resistive interchange for ψN>= 0.95. Modification of triangularity during startup is observed to delay instability onset. A plasma control system based on that used on DIII-D will allow study of the influence of plasma shaping on mode stability characteristics. An array of magnetic probes capable of insertion into the scrape-off layer and plasma edge is being developed to provide a local constraint on the edge current profile.

Changes in Classes of Injury-Related Risks and Consequences of Risk-Level Drinking: a Latent Transition Analysis.

PubMed

Cochran, Gerald; Field, Craig; Caetano, Raul

2015-07-01

Risk-level drinking, drinking and driving, and alcohol-related violence are risk factors that result in injuries. The current study sought to identify which subgroups of patients experience the most behavioral change following a brief intervention. A secondary analysis of data from a brief alcohol intervention study was conducted. The sample (N = 664) includes at-risk drinkers who experienced an injury and were admitted for care to a Level 1 trauma center. Injury-related items from the Short Inventory of Problems+6 were used to perform a latent transition analysis to describe class transitions participants experienced following discharge. Four classes emerged for the year before and after the current injury. Most individuals transitioned from higher-risk classes into those with lower risk. Some participants maintained risky profiles, and others increased risks and consequences. Drinking and driving remained a persistent problem among the study participants. Although a large portion of intervention recipients improved risks and consequences of alcohol use following discharge, more intensive intervention services may be needed for a subset of patients who showed little or no improvement.

Adsorption contributions of graphene to sodium ion storage performance

NASA Astrophysics Data System (ADS)

Fu, Hao; Xu, Zhanwei; Guan, Weiwei; Shen, Xuetao; Cao, Liyun; Huang, Jianfeng

2018-05-01

Graphene derivates, including graphite, graphene oxide (GO), and reduced graphene oxide (rGO), are employed as sodium ion battery anodes to investigate the effect of adsorption reactions on their electrochemical performance. GO and rGO exhibit the reversible capacity of 230, 192 mAh g‑1 at a low current density of 100 mA g‑1. However, when tested at higher current densities of 200, 500, and 1000 mA g‑1, the GO electrodes deliver 136, 76, and 38 mAh g‑1, respectively. As a comparison, rGO exhibits capacity as high as 168, 133, and 117 mAh g‑1 at the same conditions—23.5%, 75.0%, and 207.9% higher, respectively, than the capacities of GO. These analyses, based on the cyclic voltammetry curves, discharge/charge voltage profiles, rate and cycle performance, as well as infrared spectroscopy analysis, show the contributions of the capacity from reversible physical and chemical adsorption. The main behavior type of rGO is physical adsorption, which meets the requirements of the fast charge/discharge process, while the predominant behavior of GO is chemical adsorption.

Microinstability properties of negative magnetic shear discharges in the Tokamak Fusion Test Reactor and DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rewoldt, G.; Tang, W.M.; Lao, L.L.

1997-03-01

The microinstability properties of discharges with negative (reversed) magnetic shear in the Tokamak Fusion Test Reactor (TFTR) and DIII-D experiments with and without confinement transitions are investigated. A comprehensive kinetic linear eigenmode calculation employing the ballooning representation is employed with experimentally measured profile data, and using the corresponding numerically computed magnetohydrodynamic (MHD) equilibria. The instability considered is the toroidal drift mode (trapped-electron-{eta}{sub i} mode). A variety of physical effects associated with differing q-profiles are explained. In addition, different negative magnetic shear discharges at different times in the discharge for TFTR and DIII-D are analyzed. The effects of sheared toroidal rotation,more » using data from direct spectroscopic measurements for carbon, are analyzed using comparisons with results from a two-dimensional calculation. Comparisons are also made for nonlinear stabilization associated with shear in E{sub r}/RB{sub {theta}}. The relative importance of changes in different profiles (density, temperature, q, rotation, etc.) on the linear growth rates is considered.« less

The effects of normal current density and the plasma spatial structuring in argon DBDs

NASA Astrophysics Data System (ADS)

Shkurenkov, I. A.; Mankelevich, Y. A.; Rakhimova, T. V.

2011-01-01

This paper presents the results of theoretical studies of high-pressure dielectric barrier discharges (DBD) in argon. Two different DBDs at the megahertz and the kilohertz power frequency range were simulated. The effect of normal current density was obtained in the numerical model for both types of the discharge. The discharge of megahertz range was uniform over the radius. The increase in the discharge current is accompanied by increase in the discharge area. The discharge of kilohertz range is not uniform over the radius. The concentric ring formation was observed during calculations. The increase in the discharge current occurs due to increase in the number of rings and as a result in the discharge area. The developed 2D model is able to describe only the first stage of the filament formation - the formation of concentric plasma rings. The filament formation starts at the edge of the current channel and spreads to its centre. Both the effect of normal current density and the filaments formation are caused by the nonstationarity at the current channel boundary.

Effects produced by iodine irradiation on high resistivity silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazanu, S.; Slav, A.; Lepadatu, A.-M.

2012-12-10

The effects of 5 Multiplication-Sign 10{sup 11} cm{sup -26+}I{sup 127} ions of 28 MeV kinetic energy on high resistivity (100) Si were studied. The profile of primary defects was simulated. The defects produced by irradiation which act as traps were investigated. Thermally stimulated current measurements without externally applied bias were used, and for this the traps were charged by illuminating samples with 1000, 800, and 400 nm wavelengths. The discharge currents were recorded and modeled, and therefore the parameters of the traps were determined. The presence of I ions, heavier than Si, stopped into the target was modeled as amore » temperature independent electric field.« less

Experimental study of heating scheme effect on the inner divertor power footprint widths in EAST lower single null discharges

NASA Astrophysics Data System (ADS)

Deng, G. Z.; Xu, J. C.; Liu, X.; Liu, X. J.; Liu, J. B.; Zhang, H.; Liu, S. C.; Chen, L.; Yan, N.; Feng, W.; Liu, H.; Xia, T. Y.; Zhang, B.; Shao, L. M.; Ming, T. F.; Xu, G. S.; Guo, H. Y.; Xu, X. Q.; Gao, X.; Wang, L.

2018-04-01

A comprehensive work of the effects of plasma current and heating schemes on divertor power footprint widths is carried out in the experimental advanced superconducting tokamak (EAST). The divertor power footprint widths, i.e., the scrape-off layer heat flux decay length λ q and the heat spreading S, are crucial physical and engineering parameters for fusion reactors. Strong inverse scaling of λ q and S with plasma current have been demonstrated for both neutral beam (NB) and lower hybrid wave (LHW) heated L-mode and H-mode plasmas at the inner divertor target. For plasmas heated by the combination of the two kinds of auxiliary heating schemes (NB and LHW), the divertor power widths tend to be larger in plasmas with higher ratio of LHW power. Comparison between experimental heat flux profiles at outer mid-plane (OMP) and divertor target for NB heated and LHW heated L-mode plasmas reveals that the magnetic topology changes induced by LHW may be the main reason to the wider divertor power widths in LHW heated discharges. The effect of heating schemes on divertor peak heat flux has also been investigated, and it is found that LHW heated discharges tend to have a lower divertor peak heat flux compared with NB heated discharges under similar input power. All these findings seem to suggest that plasmas with LHW auxiliary heating scheme are better heat exhaust scenarios for fusion reactors and should be the priorities for the design of next-step fusion reactors like China Fusion Engineering Test Reactor.

Ion Current Density Study of the NASA-300M and NASA-457Mv2 Hall Thrusters

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2012-01-01

NASA Glenn Research Center is developing a Hall thruster in the 15-50 kW range to support future NASA missions. As a part of the process, the performance and plume characteristics of the NASA-300M, a 20-kW Hall thruster, and the NASA-457Mv2, a 50-kW Hall thruster, were evaluated. The collected data will be used to improve the fidelity of the JPL modeling tool, Hall2De, which will then be used to aid the design of the 15-50 kW Hall thruster. This paper gives a detailed overview of the Faraday probe portion of the plume characterization study. The Faraday probe in this study is a near-field probe swept radially at many axial locations downstream of the thruster exit plane. Threshold-based integration limits with threshold values of 1/e, 1/e2, and 1/e3 times the local peak current density are tried for the purpose of ion current integration and divergence angle calculation. The NASA-300M is operated at 7 conditions and the NASA-457Mv2 at 14 conditions. These conditions span discharge voltages of 200 to 500 V and discharge power of 10 to 50 kW. The ion current density profiles of the near-field plume originating from the discharge channel are discovered to strongly resemble Gaussian distributions. A novel analysis approach involving a form of ray tracing is used to determine an effective point of origin for the near-field plume. In the process of performing this analysis, definitive evidence is discovered that showed the near-field plume is bending towards the thruster centerline.

Ion Current Density Study of the NASA-300M and NASA-457Mv2 Hall Thrusters

NASA Technical Reports Server (NTRS)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2012-01-01

NASA Glenn Research Center is developing a Hall thruster in the 15-50 kW range to support future NASA missions. As a part of the process, the performance and plume characteristics of the NASA-300M, a 20-kW Hall thruster, and the NASA-457Mv2, a 50-kW Hall thruster, were evaluated. The collected data will be used to improve the fidelity of the JPL modeling tool, Hall2De, which will then be used to aid the design of the 15-50 kW Hall thruster. This paper gives a detailed overview of the Faraday probe portion of the plume characterization study. The Faraday probe in this study is a near-field probe swept radially at many axial locations downstream of the thruster exit plane. Threshold-based integration limits with threshold values of 1/e, 1/e(sup 2), and 1/e(sup 3) times the local peak current density are tried for the purpose of ion current integration and divergence angle calculation. The NASA-300M is operated at 7 conditions and the NASA-457Mv2 at 14 conditions. These conditions span discharge voltages of 200 to 500 V and discharge power of 10 to 50 kW. The ion current density profiles of the near-field plume originating from the discharge channel are discovered to strongly resemble Gaussian distributions. A novel analysis approach involving a form of ray tracing is used to determine an effective point of origin for the near-field plume. In the process of performing this analysis, definitive evidence is discovered that showed the near-field plume is bending towards the thruster centerline.

Effect of KOH concentration and anions on the performance of an NiH 2 battery positive plate

NASA Astrophysics Data System (ADS)

Vaidyanathan, Hari; Robbins, Kathleen; Rao, Gopalakrishna M.

The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galvanostatic charging and discharging in a flooded electrolyte cell. Three different concentrations of potassium hydroxide (KOH) (40%,31% and 26%) and 31% KOH containing dissolved nitrate, sulfate, or silicate were investigated. The end-of-charge voltage at {C}/{10} charge and at 10°C showed the following order: 40% KOH > 31 % KOH alone, and in the presence of the anions > 26% KOH. The mid-discharge voltage at {C}/{2} discharge was higher in 26% KOH, almost the same for 31%Ao KOH with and without the added contaminants, and much lower for 40% KOH. The plate capacity was marginally affected by cycling in all cases except for 40% KOH, where the capacity declined after 1000 cycles at 80% depth-of-discharge (DOD). At the end of cycling all the plates tested experienced a weight loss, except in the case of 31% KOH, as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31% KOH showed that the cathodic peak potentials are less polarized at -5 °C (compared to 25 °C) in the presence and absence of silicate. This indicates a slightly higher voltage during discharge in an NiH 2 battery. Furthermore, the features of the current-potential profile were practically unchanged in the presence of silicate.

Mitigating the Problem of Unmeasured Outcomes in Quality Reports

PubMed Central

Glazer, Jacob; McGuire, Thomas; Normand, Sharon-Lise T.

2009-01-01

Quality reports or profiles of health care providers are inevitably based on only a measurable subset of the “outputs” of the organization. Hospitals, for example, are being profiled on their mortality in the cardiac area but not in some other areas where mortality does not seem to be the appropriate measure of quality. If inputs used for outputs included in the profile also affect outputs outside the scope of the profile, it can be taken into account in constructing a profile of the measured outputs. This paper presents a theory for how such a commonality in production should be taken into account in designing a profile for a hospital or other health care provider. We distinguish between “conventional” weights in a quality profile, and “optimal” weights that take into account a commonality in the production process. The basic idea is to increase the weights on discharges for which output is measured that use inputs that are important to other discharges whose outputs are not included in the profile. PMID:20490360

Properties of thermal air plasma with admixing of copper and carbon

NASA Astrophysics Data System (ADS)

Fesenko, S.; Veklich, A.; Boretskij, V.; Cressault, Y.; Gleizes, A.; Teulet, Ph

2014-11-01

This paper deals with investigations of air plasma with admixing of copper and carbon. Model plasma source unit with real breaking arc was used for the simulation of real discharges, which can be occurred during sliding of Cu-C composite electrodes on copper wire at electromotive vehicles. The complex technique of plasma property studies is developed. From one hand, the radial profiles of temperature and electron density in plasma of electric arc discharge in air between Cu-C composite and copper electrodes in air flow were measured by optical spectroscopy techniques. From another hand, the radial profiles of electric conductivity of plasma mixture were calculated by solution of energy balance equation. It was assumed that the thermal conductivity of air plasma is not depending on copper or carbon vapor admixtures. The electron density is obtained from electric conductivity profiles by calculation in assumption of local thermodynamic equilibrium in plasma. Computed in such way radial profiles of electron density in plasma of electric arc discharge in air between copper electrodes were compared with experimentally measured profiles. It is concluded that developed techniques of plasma diagnostics can be reasonably used in investigations of thermal plasma with copper and carbon vapors.

Improving H-Q rating curves in temprorary streams by using Acoustic Doppler Current meters

NASA Astrophysics Data System (ADS)

Marchand, P.; Salles, C.; Rodier, C.; Hernandez, F.; Gayrard, E.; Tournoud, M.-G.

2012-04-01

Intermittent rivers pose different challenges to stream rating due to high spatial and temporal gradients. Long dry periods, cut by short duration flush flood events explain the difficulty to obtain reliable discharge data, for low flows as well as for floods: problems occur with standard gauging, zero flow period, etc. Our study aims to test the use of an acoustic Doppler currentmeter (ADC) for improving stream rating curves in small catchments subject to large variations of discharge, solid transport and high eutrophication levels. The study is conducted at the outlet of the river Vène, a small coastal river (67 km2) located close to the city of Montpellier (France). The low flow period lasts for more than 6 month; during this period the river flow is sustained by effluents from urban sewage systems, which allows development of algae and macrophytes in the riverbed. The ADC device (Sontek ®Argonaut SW) is a pulsed Doppler current profiling system designed for measuring water velocity profiles and levels that are used to compute volumetric flow rates. It is designed for shallow waters (less than 4 meter depth). Its main advantages are its low cost and high accuracy (±1% of the measured velocity or ±0.05 m/sec, as reported by the manufacturer). The study will evaluate the improvement in rating curves in an intermittent flow context and the effect of differences in sensitivity between low and high water level, by comparing mean flow velocity obtained by ADC to direct discharges measurements. The study will also report long-term use of ADC device, by considering effects of biofilms, algae and macrophytes, as well as solid transport on the accuracy of the measurements. In conclusion, we show the possibility to improve stream rating and continuous data collection of an intermittent river by using a ADC with some precautions.

Study of runaway electrons using the conditional average sampling method in the Damavand tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pourshahab, B., E-mail: bpourshahab@gmail.com; Sadighzadeh, A.; Abdi, M. R., E-mail: r.abdi@phys.ui.ac.ir

2017-03-15

Some experiments for studying the runaway electron (RE) effects have been performed using the poloidal magnetic probes system installed around the plasma column in the Damavand tokamak. In these experiments, the so-called runaway-dominated discharges were considered in which the main part of the plasma current is carried by REs. The induced magnetic effects on the poloidal pickup coils signals are observed simultaneously with the Parail–Pogutse instability moments for REs and hard X-ray bursts. The output signals of all diagnostic systems enter the data acquisition system with 2 Msample/(s channel) sampling rate. The temporal evolution of the diagnostic signals is analyzedmore » by the conditional average sampling (CAS) technique. The CASed profiles indicate RE collisions with the high-field-side plasma facing components at the instability moments. The investigation has been carried out for two discharge modes—low-toroidal-field (LTF) and high-toroidal-field (HTF) ones—related to both up and down limits of the toroidal magnetic field in the Damavand tokamak and their comparison has shown that the RE confinement is better in HTF discharges.« less

Analysis of the Water Resources on Baseflow River Basin in Jeju Island, Korea

NASA Astrophysics Data System (ADS)

Yang, S.-K.; Jung, W.-Y.; Kang, M.-S.

2012-04-01

Jeju Island is a volcanic island located at the southernmost of Korea, and is the heaviest raining area in Korea, but due to its hydrological / geological characteristics different from those of inland areas, most streams are of the dry form, and it relies on groundwater for water resources. As for some streams, however, springwater is discharged at a point near the downstream of the final discharge to maintain the flow of the stream; this has been developed as the source for water supply since the past, but the studies on detail observations and analysis are yet inadequate. This study utilizes the ADCP (Acoustic Doppler Current Profiler) hydrometer to regularly observe the flow amount of base run-off stream, and the water resources of base discharge basin of Jeju Island were analyzed using the SWAT (Soil & Water Assessment Tool) model. The detail water resource analysis study using modeling and site observation with high precision for Jeju Island water resources is expected to become the foundation for efficient usage and security of water resources against future climate changes.

ELM Behavior in High- βp EAST-Demonstration Plasmas on DIII-D

NASA Astrophysics Data System (ADS)

Li, G. Q.; Gong, X. Z.; Garofalo, A. M.; Lao, L. L.; Meneghini, O.; Snyder, P. B.; Ren, Q. L.; Ding, S. Y.; Guo, W. F.; Qian, J. P.; Wan, B. N.; Xu, G. S.; Holcomb, C. T.; Solomon, W. M.

2015-11-01

In the DIII-D high- βp EAST-demonstration experiment, for several similar discharges when the experimental parameters such as the toroidal magnetic field or ECH power are varied slightly, the changes in ELM frequency response are observed to be much larger. Kinetic EFIT equilibrium reconstructions for these discharges have been performed, which suggest that the ELM frequency changes are likely due to the variations of pedestal width, height, and edge current density. Kinetic profile analyses further indicate that the strong ITB that are located at large minor radii (rho=0.6 ~0.7) in these discharges are affecting the pedestal structure. The ITB could broaden the pedestal width and decrease the pedestal height, thus changing the ELM frequency and size. With the GATO and ELITE MHD codes, the linear growth rates and mode structures of these ELMs are analyzed. The impact of ITB on the ELMs behavior will be discussed. Work supported by China MOST under 2014GB106001 and 2015GB102001 and US DOE under DE-FC02-04ER54698 and DE-FG03-95ER54309.

Mission simulator test data. [an overview of a real time mission simulation test program of a nickel cadmium battery

NASA Technical Reports Server (NTRS)

Hendee, E. A.

1980-01-01

A real time mission simulation test program of nickel cadmium cells, performed in conjunction with the Anik 1A2 satellite, is reviewed. Simulation of the temperature profiles, the electrical profiles, the depth of discharge, and the rate of charge and discharge is reported. The type of separator used in the cells and the transfer of electrolytes during overcharge are discussed.

Plans for a sensitivity analysis of bridge-scour computations

USGS Publications Warehouse

Dunn, David D.; Smith, Peter N.

1993-01-01

Plans for an analysis of the sensitivity of Level 2 bridge-scour computations are described. Cross-section data from 15 bridge sites in Texas are modified to reflect four levels of field effort ranging from no field surveys to complete surveys. Data from United States Geological Survey (USGS) topographic maps will be used to supplement incomplete field surveys. The cross sections are used to compute the water-surface profile through each bridge for several T-year recurrence-interval design discharges. The effect of determining the downstream energy grade-line slope from topographic maps is investigated by systematically varying the starting slope of each profile. The water-surface profile analyses are then used to compute potential scour resulting from each of the design discharges. The planned results will be presented in the form of exceedance-probability versus scour-depth plots with the maximum and minimum scour depths at each T-year discharge presented as error bars.

Characterization of peeling modes in a low aspect ratio tokamak

NASA Astrophysics Data System (ADS)

Bongard, M. W.; Thome, K. E.; Barr, J. L.; Burke, M. G.; Fonck, R. J.; Hinson, E. T.; Redd, A. J.; Schlossberg, D. J.

2014-11-01

Peeling modes are observed at the plasma edge in the Pegasus Toroidal Experiment under conditions of high edge current density (Jedge ˜ 0.1 MA m-2) and low magnetic field (B ˜ 0.1 T) present at near-unity aspect ratio. Their macroscopic properties are measured using external Mirnov coil arrays, Langmuir probes and high-speed visible imaging. The modest edge parameters and short pulse lengths of Pegasus discharges permit direct measurement of the internal magnetic field structure with an insertable array of Hall-effect sensors, providing the current profile and its temporal evolution. Peeling modes generate coherent, edge-localized electromagnetic activity with low toroidal mode numbers n ⩽ 3 and high poloidal mode numbers, in agreement with theoretical expectations of a low-n external kink structure. Coherent MHD fluctuation amplitudes are found to be strongly dependent on the experimentally measured Jedge/B peeling instability drive, consistent with theory. Peeling modes nonlinearly generate ELM-like, field-aligned filamentary structures that detach from the edge and propagate radially outward. The KFIT equilibrium code is extended with an Akima spline profile parameterization and an improved model for induced toroidal wall current estimation to obtain a reconstruction during peeling activity with its current profile constrained by internal Hall measurements. It is used to test the analytic peeling stability criterion and numerically evaluate ideal MHD stability. Both approaches predict instability, in agreement with experiment, with the latter identifying an unstable external kink.

MST's Programmable Power Supplies: Bt Update, Bp Prototype

NASA Astrophysics Data System (ADS)

Holly, D. J.; Chapman, B. E.; McCollam, K. J.; Morin, J. C.; Thomas, M. A.

2013-10-01

MST's toroidal field programmable power supply (Bt PPS) has now been in operation for several years and has provided important new capabilities. One of the primary goals for the Bt PPS is the partial optimization of inductive current profile control, involving control of the poloidal electric field. The Bt PPS has achieved fluctuation reduction over MST's entire range of Ip. At the largest Ip, the Bt PPS achieves fluctuation reduction with a smaller poloidal electric field than the previous passive system, implying that substantially longer periods of current profile control may be possible. The Bt PPS has also been used to produce Ohmic tokamak plasmas in MST. With an applied toroidal field of 0.135 T, and q(a) > 2, the estimated energy confinement time is roughly consistent with neo-Alcator scaling. Driving q(a) < 2 with larger Ip, the confinement time degrades, but the discharge duration does not terminate prematurely. To fully optimize current profile control and to test MST operational limits, a PPS is also needed for the Bp circuit. Currently in prototype stage, the Bp PPS will feature a number of innovations to increase its flexibility and performance. Isolated charging, control, and monitor systems will eliminate charging relays, reduce coupling between modules, and minimize capacitor heating. Seven-level pulse width modulation will reduce output ripple and switching losses. Solid state shorting bars will eliminate shorting relays and minimize wiring. A balanced switching algorithm will minimize capacitive noise generation. Work supported by U. S. D. o. E.

Fast repetition rate (FRR) flasher

DOEpatents

Kolber, Z.; Falkowski, P.

1997-02-11

A fast repetition rate (FRR) flasher is described suitable for high flash photolysis including kinetic chemical and biological analysis. The flasher includes a power supply, a discharge capacitor operably connected to be charged by the power supply, and a flash lamp for producing a series of flashes in response to discharge of the discharge capacitor. A triggering circuit operably connected to the flash lamp initially ionizes the flash lamp. A current switch is operably connected between the flash lamp and the discharge capacitor. The current switch has at least one insulated gate bipolar transistor for switching current that is operable to initiate a controllable discharge of the discharge capacitor through the flash lamp. Control means connected to the current switch for controlling the rate of discharge of the discharge capacitor thereby to effectively keep the flash lamp in an ionized state between successive discharges of the discharge capacitor. Advantageously, the control means is operable to discharge the discharge capacitor at a rate greater than 10,000 Hz and even up to a rate greater than about 250,000 Hz. 14 figs.

East Sea Spatial and Temporal Variability of Thermohaline Structure and Circulation Identified From Observational (T, S) Profiles

DTIC Science & Technology

2015-12-01

salinity effect caused by the Amur River’s discharge into the Tatar Strait, and a one- month delay after maximum discharge in September. The research...discovered another low salinity effect through the Korea Strait in summer by the Changjiang River’s discharge into the East China Sea, which identified... effect caused by the Amur River’s discharge into the Tatar Strait, and a one-month delay after maximum discharge in September. The research discovered

Transport and reconnection in tokamak sawteeth.

PubMed

Gentle, K W; Austin, M E; Phillips, P E

2003-12-19

The core of a tokamak discharge often undergoes periodic relaxation oscillations, sawteeth, as the steepening current and temperature profiles are flattened by fast reconnection events. Careful analysis of the electron temperature evolution over this cycle gives an estimate of the energy dissipated in the electrons during reconnection and a measure of the transport characteristic (energy flux versus temperature gradient) over the range of parameters occurring over the remainder of the cycle. The energy dissipated is consistent with estimates of the loss of poloidal magnetic energy. The transport characteristics exhibit a wide range of behaviors.

Flood-inundation maps for the Yellow River at Plymouth, Indiana

USGS Publications Warehouse

Menke, Chad D.; Bunch, Aubrey R.; Kim, Moon H.

2016-11-16

Digital flood-inundation maps for a 4.9-mile reach of the Yellow River at Plymouth, Indiana (Ind.), were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 05516500, Yellow River at Plymouth, Ind. Current conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/in/nwis/uv?site_no=05516500. In addition, information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood-warning system (http:/water.weather.gov/ahps/). The NWS AHPS forecasts flood hydrographs at many sites that are often collocated with USGS streamgages, including the Yellow River at Plymouth, Ind. NWS AHPS-forecast peak-stage information may be used in conjunction with the maps developed in this study to show predicted areas of flood and forecasts of flood hydrographs at this site.For this study, flood profiles were computed for the Yellow River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the current stage-discharge relations at the Yellow River streamgage, in combination with the flood-insurance study for Marshall County (issued in 2011). The calibrated hydraulic model was then used to determine eight water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The 1-percent annual exceedance probability flood profile elevation (flood elevation with recurrence intervals within 100 years) is within the calibrated water-surface elevations for comparison. The simulated water-surface profiles were then used with a geographic information system (GIS) digital elevation model (DEM, derived from Light Detection and Ranging [lidar]) in order to delineate the area flooded at each water level.The availability of these maps, along with Internet information regarding current stage from the USGS streamgage 05516500, Yellow River at Plymouth, Ind., and forecast stream stages from the NWS AHPS, provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for postflood recovery efforts.

Characterization of a suspected terrestrial deep groundwater discharge area on the Canadian Precambrian Shield

NASA Astrophysics Data System (ADS)

Sheppard, Marsha I.; Thibault, D. H.; Milton, G. M.; Reid, J. A. K.; Smith, P. A.; Stevens, K.

1995-03-01

Underground storage and disposal of hazardous wastes require an understanding of groundwater flow and the ability to locate recharge and discharge. Usually, recharge and discharge occur at a transition zone where dispersion/advection, molecular diffusion and biogeochemical processes control the fate of a contaminants leaving an underground facility. Appropriate landscape modelling for risk assessment cannot proceed until this interface is well defined and groundwater discharge can be mapped. Although discharge locations have traditionally been thought of as aquatic, the presence of animal licks suggests the possibility of terrestrial discharge. We have characterized a suspected terrestrial discharge, a well-used deer lick, (1) physically, through surficial mapping, and vegetation and soil profile analyses; (2) geophysically, through magnetic and very low-frequency electromagnetic tilt-angle surveys; (3) hydrogeologically, through water-table elevation measurements; (4) geochemically, through overburden analyses for 238U, 226Ra, 210Pb, Na, tritium, Cl and 36{Cl}/{Cl} atom ratios, as well as pore-water and groundwater analyses for pH, electrical conductivity (EC) and major anions and cations; and (5) thermally, through overburden-rock interface temperatures. Halophytic plants and sedges contained more Na, Cl and 238U than averages reported in the literature. Lineament alignment, coincident with elevated groundwater EC, supported the presence and position of a subsurface fracture. Groundwater chemistry suggested that interfering runoff from a nearby ridge masked the chemical signatures expected of deep groundwater but attest to the weak and possibly ephemeral nature of this discharge. Interpretation of the geochemical data was supported by solute transport modelling. Good agreement between the predictions using an unsaturated soil model, a simple wetland compartment model and the observed profile implied that evapotranspiration, seasonal water-table fluctuations and flooding, and sorption of 238U due to anoxia deep in the overburden are major processes shaping the overburden solute profile. This evidence strongly supported the hypothesis that the site is a location where deep groundwater (groundwater from depths of 500-1000 m) discharges.

Transport modeling of the DIII-D high $${{\\beta}_{p}}$$ scenario and extrapolations to ITER steady-state operation

DOE PAGES

McClenaghan, Joseph; Garofalo, Andrea M.; Meneghini, Orso; ...

2017-08-03

In this study, transport modeling of a proposed ITER steady-state scenario based on DIII-D high poloidal-beta (more » $${{\\beta}_{p}}$$ ) discharges finds that ITB formation can occur with either sufficient rotation or a negative central shear q-profile. The high $${{\\beta}_{p}}$$ scenario is characterized by a large bootstrap current fraction (80%) which reduces the demands on the external current drive, and a large radius internal transport barrier which is associated with excellent normalized confinement. Modeling predictions of the electron transport in the high $${{\\beta}_{p}}$$ scenario improve as $${{q}_{95}}$$ approaches levels similar to typical existing models of ITER steady-state and the ion transport is turbulence dominated. Typical temperature and density profiles from the non-inductive high $${{\\beta}_{p}}$$ scenario on DIII-D are scaled according to 0D modeling predictions of the requirements for achieving a $Q=5$ steady-state fusion gain in ITER with 'day one' heating and current drive capabilities. Then, TGLF turbulence modeling is carried out under systematic variations of the toroidal rotation and the core q-profile. A high bootstrap fraction, high $${{\\beta}_{p}}$$ scenario is found to be near an ITB formation threshold, and either strong negative central magnetic shear or rotation in a high bootstrap fraction are found to successfully provide the turbulence suppression required to achieve $Q=5$.« less

Kinetic description of large-scale low pressure glow discharges

NASA Astrophysics Data System (ADS)

Kortshagen, Uwe; Heil, Brian

1997-10-01

In recent years the so called ``nonlocal approximation'' to the solution of the electron Boltzmann equation has attracted considerable attention as an extremely efficient method for the kinetic modeling of low pressure discharges. However, it appears that modern discharges, which are optimized to provide large-scale plasma uniformity, are explicitly designed to work in a regime, in which the nonlocal approximation is no longer strictly valid. In the presentation we discuss results of a hybrid model, which is based on the natural division of the electron distribution function into a nonlocal body, which is determined by elastic collisions only, and a high energy part which requires a more complete treatment due to the action of inelastic collisions and wall losses of electrons. The method is applied to an inductively coupled low pressure discharge. We discuss the transition from plasma density profiles maximal on the discharge axis to plasma density profiles with off-center maxima, which has been observed in experiments. A positive feedback mechanism involved in this transition is pointed out.

Dependence of recycling and edge profiles on lithium evaporation in high triangularity, high performance NSTX H-mode discharges.

DOE PAGES

Maingi, R.; Osborne, T. H.; Bell, M. G.; ...

2014-11-04

In this paper, the effects of a pre-discharge lithium evaporation variation on highly shaped discharges in the National Spherical Torus Experiment (NSTX) are documented. Lithium wall conditioning (‘dose’) was routinely applied onto graphite plasma facing components between discharges in NSTX, partly to reduce recycling. Reduced D α emission from the lower and upper divertor and center stack was observed, as well as reduced midplane neutral pressure; the magnitude of reduction increased with the pre-discharge lithium dose. Improved energy confinement, both raw τ E and H-factor normalized to scalings, with increasing lithium dose was also observed. At the highest doses, wemore » also observed elimination of edge-localized modes. The midplane edge plasma profiles were dramatically altered, comparable to lithium dose scans at lower shaping, where the strike point was farther from the lithium deposition centroid. As a result, this indicates that the benefits of lithium conditioning should apply to the highly shaped plasmas planned in NSTX-U.« less

The development of shock wave overpressure driven by channel expansion of high current impulse discharge arc

NASA Astrophysics Data System (ADS)

Xiong, Jia-ming; Li, Lee; Dai, Hong-yu; Wu, Hai-bo; Peng, Ming-yang; Lin, Fu-chang

2018-03-01

During the formation of a high current impulse discharge arc, objects near the discharge arc will be strongly impacted. In this paper, a high power, high current gas switch is used as the site of the impulse discharge arc. The explosion wave theory and the arc channel energy balance equation are introduced to analyze the development of the shock wave overpressure driven by the high current impulse discharge arc, and the demarcation point of the arc channel is given, from which the energy of the arc channel is no longer converted into shock waves. Through the analysis and calculation, it is found that the magnitude of the shock wave overpressure caused by impulse discharge arc expansion is closely related to the arc current rising rate. The arc shock wave overpressure will undergo a slow decay process and then decay rapidly. The study of this paper will perform the function of deepening the understanding of the physical nature of the impulse arc discharge, which can be used to explain the damage effect of the high current impulse discharge arc.

Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai

2013-05-13

Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

Thermo-electrochemical analysis of lithium ion batteries for space applications using Thermal Desktop

NASA Astrophysics Data System (ADS)

Walker, W.; Ardebili, H.

2014-12-01

Lithium-ion batteries (LIBs) are replacing the Nickel-Hydrogen batteries used on the International Space Station (ISS). Knowing that LIB efficiency and survivability are greatly influenced by temperature, this study focuses on the thermo-electrochemical analysis of LIBs in space orbit. Current finite element modeling software allows for advanced simulation of the thermo-electrochemical processes; however the heat transfer simulation capabilities of said software suites do not allow for the extreme complexities of orbital-space environments like those experienced by the ISS. In this study, we have coupled the existing thermo-electrochemical models representing heat generation in LIBs during discharge cycles with specialized orbital-thermal software, Thermal Desktop (TD). Our model's parameters were obtained from a previous thermo-electrochemical model of a 185 Amp-Hour (Ah) LIB with 1-3 C (C) discharge cycles for both forced and natural convection environments at 300 K. Our TD model successfully simulates the temperature vs. depth-of-discharge (DOD) profiles and temperature ranges for all discharge and convection variations with minimal deviation through the programming of FORTRAN logic representing each variable as a function of relationship to DOD. Multiple parametrics were considered in a second and third set of cases whose results display vital data in advancing our understanding of accurate thermal modeling of LIBs.

Comparison between Trichel pulse in negative corona and self-pulsing in other configurations

NASA Astrophysics Data System (ADS)

Xia, Qing; Zhang, Yu; He, Feng; Qin, Yu; Jiang, Zhaorui; Ouyang, Jiting

2018-02-01

We present here a comparison study on self-pulsing phenomena in negative corona, hollow cathode discharges (HCD) and parallel-plate discharge in air. The voltage-current (V-I) curve, the waveforms of self-pulsed currents, and the time-resolved images of the pulsed discharge are measured under various operating conditions. It is experimentally evidenced that the Trichel pulse in a negative corona and the self-pulsing in HCD and/or parallel-plate discharge have similar features as well as spatial-temporal developing process. It is suggested that they should have a similar mechanism that the pulsing reflects the mode transition of discharge between the low-current Townsend and the high-current normal glow. The pulse rising corresponds to the breakdown and formation of temporal glow discharge in a background of low-current Townsend discharge, while the decay edge relates to the transition back to Townsend discharge. The pulse interval is the re-building process of the space charge layer of high density to ensure the glow breakdown.

Impact energy and retained dose uniformity in enhanced glow discharge plasma immersion ion implantation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Q. Y.; Fu, Ricky K. Y.; Chu, Paul K.

2009-08-10

The implantation energy and retained dose uniformity in enhanced glow discharge plasma immersion ion implantation (EGD-PIII) is investigated numerically and experimentally. Depth profiles obtained from different samples processed by EGD-PIII and traditional PIII are compared. The retained doses under different pulse widths are calculated by integrating the area under the depth profiles. Our results indicate that the improvement in the impact energy and retained dose uniformity by this technique is remarkable.

QRev—Software for computation and quality assurance of acoustic doppler current profiler moving-boat streamflow measurements—Technical manual for version 2.8

USGS Publications Warehouse

Mueller, David S.

2016-06-21

The software program, QRev applies common and consistent computational algorithms combined with automated filtering and quality assessment of the data to improve the quality and efficiency of streamflow measurements and helps ensure that U.S. Geological Survey streamflow measurements are consistent, accurate, and independent of the manufacturer of the instrument used to make the measurement. Software from different manufacturers uses different algorithms for various aspects of the data processing and discharge computation. The algorithms used by QRev to filter data, interpolate data, and compute discharge are documented and compared to the algorithms used in the manufacturers’ software. QRev applies consistent algorithms and creates a data structure that is independent of the data source. QRev saves an extensible markup language (XML) file that can be imported into databases or electronic field notes software. This report is the technical manual for version 2.8 of QRev.

Simulations of Atmospheric Plasma Arcs

NASA Astrophysics Data System (ADS)

Pearcy, Jacob; Chopra, Nirbhav; Jaworski, Michael

2017-10-01

We present the results of computer simulation of cylindrical plasma arcs with characteristics similar to those predicted to be relevant in magnetohydrodynamic (MHD) power conversion systems. These arcs, with core temperatures on the order of 1 eV, place stringent limitations on the lifetime of conventional electrodes used in such systems, suggesting that a detailed analysis of arc characteristics will be crucial in designing more robust electrode systems. Simulations utilize results from NASA's Chemical Equilibrium with Applications (CEA) program to solve the Elenbaas-Heller equation in a variety of plasma compositions, including approximations of coal-burning plasmas as well as pure gas discharges. The effect of carbon dioxide injection on arc characteristics, emulating discharges from molten carbonate salt electrodes, is also analyzed. Results include radial temperature profiles, composition maps, and current-voltage (IV) characteristics of these arcs. Work supported by DOE contract DE-AC02-09CH11466.

Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

NASA Astrophysics Data System (ADS)

Henderson, M. A.; Alberti, S.; Angioni, C.; Arnoux, G.; Behn, R.; Blanchard, P.; Bosshard, P.; Camenen, Y.; Coda, S.; Condrea, I.; Goodman, T. P.; Hofmann, F.; Hogge, J.-Ph.; Karpushov, A.; Manini, A.; Martynov, An.; Moret, J.-M.; Nikkola, P.; Nelson-Melby, E.; Pochelon, A.; Porte, L.; Sauter, O.; Ahmed, S. M.; Andrèbe, Y.; Appert, K.; Chavan, R.; Degeling, A.; Duval, B. P.; Etienne, P.; Fasel, D.; Fasoli, A.; Favez, J.-Y.; Furno, I.; Horacek, J.; Isoz, P.; Joye, B.; Klimanov, I.; Lavanchy, P.; Lister, J. B.; Llobet, X.; Magnin, J.-C.; Marlétaz, B.; Marmillod, P.; Martin, Y.; Mayor, J.-M.; Mylnar, J.; Paris, P. J.; Perez, A.; Peysson, Y.; Pitts, R. A.; Raju, D.; Reimerdes, H.; Scarabosio, A.; Scavino, E.; Seo, S. H.; Siravo, U.; Sushkov, A.; Tonetti, G.; Tran, M. Q.; Weisen, H.; Wischmeier, M.; Zabolotsky, A.; Yhuang, G.

2003-05-01

In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (τEe) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribution times. A linear dependence of the confinement improvement on the product of the global shear reversal factor (q0/qmin) and the reversed shear volume (ρq-min2) is shown. In other discharges heated with X2 the sawteeth are destabilized (respectively stabilized) when heating just inside (respectively outside) the q=1 surface. Control of the sawteeth may allow the avoidance of neoclassical tearing modes that can be seeded by the sawtooth instability. Results on H-mode and highly elongated plasmas using the newly completed third harmonic (X3) system and achieving up to 100% absorption are also discussed, along with comparison of experimental results with the TORAY-GA ray tracing code [K. Matsuda, IEEE Trans. Plasma Sci. PS-17, 6 (1989); R. H. Cohen, Phys. Fluids 30, 2442 (1987)].

On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prevosto, L., E-mail: prevosto@waycom.com.ar; Mancinelli, B.; Chamorro, J. C.

2015-02-15

Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V and a current density at the cathode surface of about 11 A/cm{sup 2}, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying themore » main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium.« less

Streamflow response from an ombrotrophic mire

Treesearch

E.S. Verry; K.N. Brooks; P.K. Barten

1988-01-01

Streamflow response to a rainstorm exceeding a 100-year return interval is documented in relation to the peat profile and microtopography. The water tab1e:discharge relation is corrected for specific yield and found to closely parallel the stage:discharge relationship for a level reservoir for flows up to a 25-year return interval. A faster water table:discharge...

High Frequency Radar Observations of Tidal Current Variability in the Lower Chesapeake Bay

NASA Astrophysics Data System (ADS)

Updyke, T. G.; Dusek, G.; Atkinson, L. P.

2016-02-01

Analysis of eight years of high frequency radar surface current observations in the lower Chesapeake Bay is presented with a focus on the variability of the tidal component of the surface circulation which accounts for a majority of the variance of the surface flow (typically 70-80% for the middle of the radar footprint). Variations in amplitude and phase of the major tidal constituents are examined in the context of water level, wind and river discharge data. Comparisons are made with harmonic analysis results from long-term records of current data measured by three current profilers operated by NOAA as part of the Chesapeake Bay Physical Oceanographic Real-Time System (PORTS). Preliminary results indicate that there is significant spatial variability in the M2 amplitude over the HF radar grid as well as temporal variability when harmonic analysis is performed using bi-monthly time segments over the course of the record.

Rectangular beam (5 X 40 cm multipole ion source). M.S. Thesis - Nov. 1979; [applications to electron bombardment in materials processing

NASA Technical Reports Server (NTRS)

Haynes, C. M.

1980-01-01

A 5 x 40 cm rectangular-beam ion source was designed and fabricated. A multipole field configuration was used to facilitate design of the modular rectangular chamber, while a three-grid ion optics system was used for increased ion current densities. For the multipole chamber, a magnetic integral of 0.000056 Tesla-m was used to contain the primary electrons. This integral value was reduced from the initial design value, with the reduction found necessary for discharge stability. The final value of magnetic integral resulted in discharge losses at typical operating conditions which ranged from 600 to 1000 eV/ion, in good agreement with the design value of 800 eV/ion. The beam current density at the ion optics was limited to about 3.2 mA/sq cm at 500 eV and to about 3.5 mA/sq cm at 1000 ev. The effects of nonuniform ion current, dimension tolerance, and grid thermal warping were considered. The use of multiple rectangular-beam ion sources to process wider areas than would be possible with a single source (approx. 40 cm) was also studied. Beam profiles were surveyed at a variety of operating conditions and the results of various amounts of beam overlap calculated.

Coarse-grained debris flow dynamics on erodible beds

NASA Astrophysics Data System (ADS)

Lanzoni, Stefano; Gregoretti, Carlo; Stancanelli, Laura Maria

2017-03-01

A systematic set of flume experiments is used to investigate the features of velocity profiles within the body of coarse-grained debris flows and the dependence of the transport sediment concentration on the relevant parameters (runoff discharge, bed slope, grain size, and form). The flows are generated in a 10 m long laboratory flume, initially filled with a layer consisting of loose debris. After saturation, a prescribed water discharge is suddenly supplied over the granular bed, and the runoff triggers a debris flow wave that reaches nearly steady conditions. Three types of material have been used in the tests: gravel with mean grain size of 3 and 5 mm, and 3 mm glass spheres. Measured parameters included: triggering water discharge, volumetric sediment discharge, sediment concentration, flow depth, and velocity profiles. The dynamic similarity with full-sized debris flows is discussed on the basis of the relevant dimensionless parameters. Concentration data highlight the dependence on the slope angle and the importance of the quasi-static friction angle. The effects of flow rheology on the shape of velocity profiles are analyzed with attention to the role of different stress-generating mechanisms. A remarkable collapse of the dimensionless profiles is obtained by scaling the debris flow velocity with the runoff velocity, and a power law characterization is proposed following a heuristic approach. The shape of the profiles suggests a smooth transition between the different rheological regimes (collisional and frictional) that establish in the upper and lower regions of the flow and is compatible with the presence of multiple length scales dictated by the type of contacts (instantaneous or long lasting) between grains.

Simulations of particle and heat fluxes in an ELMy H-mode discharge on EAST using BOUT++ code

NASA Astrophysics Data System (ADS)

Wu, Y. B.; Xia, T. Y.; Zhong, F. C.; Zheng, Z.; Liu, J. B.; team3, EAST

2018-05-01

In order to study the distribution and evolution of the transient particle and heat fluxes during edge-localized mode (ELM) bursts on the Experimental Advanced Superconducting Tokamak (EAST), the BOUT++ six-field two-fluid model is used to simulate the pedestal collapse. The profiles from the EAST H-mode discharge #56129 are used as the initial conditions. Linear analysis shows that the resistive ballooning mode and drift-Alfven wave are two dominant instabilities for the equilibrium, and play important roles in driving ELMs. The evolution of the density profile and the growing process of the heat flux at divertor targets during the burst of ELMs are reproduced. The time evolution of the poloidal structures of T e is well simulated, and the dominant mode in each stage of the ELM crash process is found. The studies show that during the nonlinear phase, the dominant mode is 5, and it changes to 0 when the nonlinear phase goes to saturation after the ELM crash. The time evolution of the radial electron heat flux, ion heat flux, and particle density flux at the outer midplane (OMP) are obtained, and the corresponding transport coefficients D r, χ ir, and χ er reach maximum around 0.3 ∼ 0.5 m2 s‑1 at ΨN = 0.9. The heat fluxes at outer target plates are several times larger than that at inner target plates, which is consistent with the experimental observations. The simulated profiles of ion saturation current density (j s) at the lower outboard (LO) divertor target are compared to those of experiments by Langmuir probes. The profiles near the strike point are similar, and the peak values of j s from simulation are very close to the measurements.

Ecton processes in the generation of pulsed runaway electron beams in a gas discharge

NASA Astrophysics Data System (ADS)

Mesyats, G. A.

2017-09-01

As was shown earlier for pulsed discharges that occur in electric fields rising with extremely high rates (1018 V/(cm s)) during the pulse rise time, the electron current in a vacuum discharge is lower than the current of runaway electrons in an atmospheric air discharge in a 1-cm-long gap. In this paper, this is explained by that the field emission current from cathode microprotrusions in a gas discharge is enhanced due to gas ionization. This hastens the initiation of explosive electron emission, which occurs within 10-11 s at a current density of up to 1010 A/cm2. Thereafter, a first-type cathode spot starts forming. The temperature of the cathode spot decreases due to heat conduction, and the explosive emission current ceases. Thus, the runaway electron current pulse is similar in nature to the ecton phenomenon in a vacuum discharge.

Computation of backwater and discharge at width constrictions of heavily vegetated flood plains

USGS Publications Warehouse

Schneider, V.R.; Board, J.W.; Colson, B.E.; Lee, F.N.; Druffel, Leroy

1977-01-01

The U.S. Geological Survey, cooperated with the Federal Highway Administration and the State Highway Departments of Mississippi, Alabama, and Louisiana, to develop a proposed method for computing backwater and discharge at width constrictions of heavily vegetated flood plains. Data were collected at 20 single opening sites for 31 floods. Flood-plain width varied from 4 to 14 times the bridge opening width. The recurrence intervals of peak discharge ranged from a 2-year flood to greater than a 100-year flood, with a median interval of 6 years. Measured backwater ranged from 0.39 to 3.16 feet. Backwater computed by the present standard Geological Survey method averaged 29 percent less than the measured, and that computed by the currently used Federal Highway Administration method averaged 47 percent less than the measured. Discharge computed by the Survey method averaged 21 percent more then the measured. Analysis of data showed that the flood-plain widths and the Manning 's roughness coefficient are larger than those used to develop the standard methods. A method to more accurately compute backwater and discharge was developed. The difference between the contracted and natural water-surface profiles computed using standard step-backwater procedures is defined as backwater. The energy loss terms in the step-backwater procedure are computed as the product of the geometric mean of the energy slopes and the flow distance in the reach was derived from potential flow theory. The mean error was 1 percent when using the proposed method for computing backwater and 3 percent for computing discharge. (Woodard-USGS)

Anomalous Transport in High Beta Poloidal DIII-D Discharges

NASA Astrophysics Data System (ADS)

Pankin, A.; Garofalo, A.; Kritz, A.; Rafiq, T.; Weiland, J.

2016-10-01

Dominant instabilities that drive anomalous transport in high beta poloidal DIII-D discharges are investigated using the MMM7.1, and TGLF models in the predictive integrated modeling TRANSP code. The ion thermal transport is found to be strongly reduced in these discharges, but turbulence driven by the ITG modes along with the neoclassical transport still play a role in determining the ion temperature profiles. The electron thermal transport driven by the ETG modes impact the electron temperature profiles. The E × B flow shear is found to have a small effect in reducing the electron thermal transport. The Shafranov shift is found to strongly reduce the anomalous transport in the high beta poloidal DIII-D discharges. The reduction of Shafranov shift can destroy the ion internal transport barrier and can result in significantly lower core temperatures. The MMM7.1 model predicts electron and ion temperature profiles reasonably well, but it fails to accurately predict the properties of electron internal transport barrier, which indicates that the ETG model in MMM7.1 needs to be improved in the high beta poloidal operational regime. Research supported by the Office of Science, US DOE.

Flood-inundation maps for the Wabash River at Lafayette, Indiana

USGS Publications Warehouse

Kim, Moon H.

2018-05-10

Digital flood-inundation maps for an approximately 4.8-mile reach of the Wabash River at Lafayette, Indiana (Ind.) were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science web site at https://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at USGS streamgage 03335500, Wabash River at Lafayette, Ind. Current streamflow conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the internet at https://waterdata.usgs.gov/in/nwis/uv?site_no=03335500. In addition, information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood-warning system (https://water.weather.gov/ahps/). The NWS AHPS forecasts flood hydrographs at many places that are often colocated with USGS streamgages, including the Wabash River at Lafayette, Ind. NWS AHPS-forecast peak-stage information may be used with the maps developed in this study to show predicted areas of flood inundation.For this study, flood profiles were computed for the Wabash River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the most current stage-discharge relations at USGS streamgage 03335500, Wabash River at Lafayette, Ind., and high-water marks from the flood of July 2003 (U.S. Army Corps of Engineers [USACE], 2007). The calibrated hydraulic model was then used to determine 23 water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a geographic information system digital elevation model derived from light detection and ranging to delineate the area flooded at each water level. The availability of these maps, along with internet information regarding current stage from the USGS streamgage 03335500, Wabash River at Lafayette, Ind., and forecasted high-flow stages from the NWS AHPS, will provide emergency management personnel and residents with information that is critical for flood-response activities such as evacuations and road closures, and for postflood recovery efforts.

Flood-inundation maps for the North Branch Elkhart River at Cosperville, Indiana

USGS Publications Warehouse

Kim, Moon H.; Johnson, Esther M.

2014-01-01

Digital flood-inundation maps for a reach of the North Branch Elkhart River at Cosperville, Indiana (Ind.), were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, Detroit District. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at USGS streamgage 04100222, North Branch Elkhart River at Cosperville, Ind. Current conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/in/nwis/uv?site_no=04100222. In addition, information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood warning system (http:/water.weather.gov/ahps/). The NWS AHPS forecasts flood hydrographs at many places that are often colocated with USGS streamgages, including the North Branch Elkhart River at Cosperville, Ind. NWS AHPS-forecast peak-stage information may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation. For this study, flood profiles were computed for the North Branch Elkhart River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the most current stage-discharge relations at USGS streamgage 04100222, North Branch Elkhart River at Cosperville, Ind., and preliminary high-water marks from the flood of March 1982. The calibrated hydraulic model was then used to determine four water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a geographic information system (GIS) digital elevation model (DEM, derived from Light Detection and Ranging [LiDAR]) in order to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage 04100222, North Branch Elkhart River at Cosperville, Ind., and forecast stream stages from the NWS AHPS, provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Flood-inundation maps for the East Fork White River near Bedford, Indiana

USGS Publications Warehouse

Fowler, Kathleen K.

2014-01-01

Digital flood-inundation maps for an 1.8-mile reach of the East Fork White River near Bedford, Indiana (Ind.) were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ depict estimates of the areal extent and depth of flooding corresponding to selectedwater levels (stages) at USGS streamgage 03371500, East Fork White River near Bedford, Ind. Current conditions for estimating near-real-time areas of inundation using USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/in/nwis/uv?site_no=03371500. In addition, information has been provided to the National Weather Service (NWS) for incorporation into their Advanced Hydrologic Prediction Service (AHPS) flood warning system (http://water.weather.gov/ahps/). The NWS forecasts flood hydrographs at many places that are often colocated with USGS streamgages, including the East Fork White River near Bedford, Ind. NWS-forecasted peak-stage information may be used in conjunction with the maps developed in this study to show predicted areas of flood inundation. For this study, flood profiles were computed for the East Fork White River reach by means of a one-dimensional step-backwater model. The hydraulic model was calibrated by using the most current stage-discharge relations at USGS streamgage 03371500, East Fork White River near Bedford, Ind., and documented high-water marks from the flood of June 2008. The calibrated hydraulic model was then used to determine 20 water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from bankfull to the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a geographic information system (GIS) digital elevation model (DEM, derived from Light Detection and Ranging (LiDAR) data having a 0.593-foot vertical accuracy) in order to delineate the area flooded at each water level. The availability of these maps, along with Internet information regarding current stage from the USGS streamgage near Bedford, Ind., and forecasted stream stages from the NWS, provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for postflood recovery eforts.

Oxygen saturation profile of term equivalent extreme preterm infants at discharge - comparison with healthy term counterparts.

PubMed

Rath, Chandra; Kluckow, Martin

2016-03-01

Compare the oxygen saturation profiles before discharge of neonates born extremely preterm (<28 weeks), now at term equivalent age, with healthy term neonates and assess the impact of feeding on this profile in each group. We prospectively evaluated and compared the oxygen saturation profile in 15 very low birthweight infants at term equivalent age, ready to be discharged home without any oxygen and 15 term newborns after 48 hours of life. We also evaluated and compared the saturations of these two groups during a one-hour period during and after feeding. Term equivalent preterm and term infants spent median 3% and 0%, respectively, of the time below 90% in a 12-hour saturation-recording period. Term infants spent a median 0.26% and 0.65% of the time in <90% saturation during feed time and no feed time, respectively. In contrast, preterm infants spent significantly more time <90% saturation (3.47% and 3.5% during feed time and no feed time, respectively). Term equivalent preterm infants spent significantly more time in a saturation range <90% compared to term infants. Feeding had little effect on saturation profile overall within each group. ©2015 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

Study of high field side/low field side asymmetry in the electron temperature profile with electron cyclotron emission

NASA Astrophysics Data System (ADS)

Gugliada, V. R.; Austin, M. E.; Brookman, M. W.

2017-10-01

Electron cyclotron emission (ECE) provides high resolution measurements of electron temperature profiles (Te(R , t)) in tokamaks. Calibration accuracy of this data can be improved using a sawtooth averaging technique. This improved calibration will then be utilized to determine the symmetry of Te profiles by comparing low field side (LFS) and high field side (HFS) measurements. Although Te is considered constant on flux surfaces, cases have been observed in which there are pronounced asymmetries about the magnetic axis, particularly with increased pressure. Trends in LFS/HFS overlap are examined as functions of plasma pressure, MHD mode presence, heating techniques, and other discharge conditions. This research will provide information on the accuracy of the current two-dimensional mapping of flux surfaces in the tokamak. Findings can be used to generate higher quality EFITs and inform ECE calibration. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER549698.

Formation of a spark discharge in an inhomogeneous electric field with current limitation by a large ballast Resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldanov, B. B., E-mail: baibat@mail.ru

2016-01-15

Results of studies of a spark discharge initiated in argon in a point–plane electrode gap with limitation of the discharge current by a large ballast resistance are presented. It is shown that the current flowing through the plasma channel of such a low-current spark has the form of periodic pulses. It is experimentally demonstrated that, when a low-current spark transforms into a constricted glow discharge, current pulses disappear, the spatial structure of the cathode glow changes abruptly, and a brightly glowing positive plasma column forms in the gap.

Dynamic characteristic of a 30-cm mercury ion thruster

NASA Technical Reports Server (NTRS)

Serafini, J. S.; Mantenieks, M. A.; Rawlin, V. K.

1975-01-01

Measurements of the fluctuations of the discharge and beam plasmas of a 30 centimeter ion thruster were performed using 60 Hertz laboratory type power supplies. The time-varying properties of the discharge voltage and current, the ion beam current, and neutralizer keeper current were measured. The intensities of the fluctuations were found to depend on the beam and magnetic baffle currents. The shape of the frequency spectra of the discharge plasma fluctuations was found to be related to the beam and magnetic baffle currents. The measurements indicated that the discharge current fluctuations directly contribute to the beam current fluctuations and that the power supply characteristics modify these fluctuations.

Construction and temporal behaviour study of multi RLC intense light pulses for dermatological applications.

PubMed

Hamoudi, Walid K; Ismail, Raid A; Shakir, Hussein A

2017-10-01

Driving a flash lamp in an intense pulsed light system requires a high-voltage DC power supply, capacitive energy storage and a flash lamp triggering unit. Single, double, triple and quadruple-mesh discharge and triggering circuits were constructed to provide intense light pulses of variable energy and time durations. The system was treated as [Formula: see text] circuit in some cases and [Formula: see text] circuit in others with a light pulse profile following the temporal behaviour of the exciting current pulse. Distributing the energy delivered to one lamp onto a number of LC meshes permitted longer current pulses, and consequently increased the light pulse length. Positive results were obtained when using the system to treat skin wrinkles.

Quench Detection and Protection of an HTS Coil

NASA Astrophysics Data System (ADS)

Sheehan, Evan; Pfotenhauer, John; Miller, Franklin; Christianson, Owen

2017-12-01

A pulsed, modular HTS magnet for energy storage applications was constructed and tested. Charge and discharge pulses were accomplished in about 1 second. A recuperative cryogenic cooling system supplies 42 to 80 Kelvin helium gas to the magnet. A practical solution to overvoltage and overcurrent protection has been implemented digitally using LabVIEW. Voltages as little as 46 μV greater than the expected value trigger the protection system, which stops the pulse profile and begins an immediate current ramp down to zero over 1 second. The protection system has displayed its effectiveness in HTS transition detection and damage prevention. Experimentation has demonstrated that current pulses on the order of seconds with amplitudes of up to 110 Amps can be achieved for extended periods. Higher currents produce joint heating in excess of the available cooling from the existing cryogenic system.

High-current discharge channel contraction in high density gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutberg, Ph. G.; Bogomaz, A. A.; Pinchuk, M. E.

Research results for discharges at current amplitudes of 0.5-1.6 MA and current rise rate of {approx}10{sup 10} A/s are presented. The discharge is performed in the hydrogen environment at the initial pressure of 5-35 MPa. Initiation is implemented by a wire explosion. The time length of the first half-period of the discharge current is 70-150 {mu}s. Under such conditions, discharge channel contraction is observed; the contraction is followed by soft x-ray radiation. The phenomena are discussed, which are determined by high density of the gas surrounding the discharge channel. These phenomena are increase of the current critical value, where themore » channel contraction begins and growth of temperature in the axis region of the channel, where the initial density of the gas increases.« less

On-line Monitoring Device for High-voltage Switch Cabinet Partial Discharge Based on Pulse Current Method

NASA Astrophysics Data System (ADS)

Y Tao, S.; Zhang, X. Z.; Cai, H. W.; Li, P.; Feng, Y.; Zhang, T. C.; Li, J.; Wang, W. S.; Zhang, X. K.

2017-12-01

The pulse current method for partial discharge detection is generally applied in type testing and other off-line tests of electrical equipment at delivery. After intensive analysis of the present situation and existing problems of partial discharge detection in switch cabinets, this paper designed the circuit principle and signal extraction method for partial discharge on-line detection based on a high-voltage presence indicating systems (VPIS), established a high voltage switch cabinet partial discharge on-line detection circuit based on the pulse current method, developed background software integrated with real-time monitoring, judging and analyzing functions, carried out a real discharge simulation test on a real-type partial discharge defect simulation platform of a 10KV switch cabinet, and verified the sensitivity and validity of the high-voltage switch cabinet partial discharge on-line monitoring device based on the pulse current method. The study presented in this paper is of great significance for switch cabinet maintenance and theoretical study on pulse current method on-line detection, and has provided a good implementation method for partial discharge on-line monitoring devices for 10KV distribution network equipment.

Torsional Eye Movements Evoked by Unilateral Labyrinthine Galvanic Polarizations in the Squirrel Monkey

NASA Technical Reports Server (NTRS)

Minor, Lloyd B.; Tomko, David L.; Paige, Gary D.

1995-01-01

Electrical stimulation of vestibular-nerve afferents innervating the semicircular canals has been used to identify the extraocular muscles receiving activation or inhibition by individual ampullary nerves. This technique was originally developed by Szentagothai (1950) and led to the description of three neuron reflex arcs that connect each semicircular canal through an interneuron traversing in the region of the medial longitudinal fasciculus to one ipsilateral and one contralateral eye muscle. Selective ampullary nerve stimulation was subsequently used by Cohen and colleagues (Cohen and Suzuki, 1963; Cohen et al., 1964; Suzuki et al., 1964; Cohen et al., 1966) to study movements of the eyes and activation of individual extraocular muscles in response to stimulation of combinations of ampullary nerves. This work led to a description of the now familiar relationships between activation of a semicircular canal ampullary nerves and the anticipated movement in each eye. Disconjugacy of eye movements induced by individual vertical canal stimulation and dependence of the pulling direction of vertical recti and oblique muscles on eye position were also defined in these experiments. Subsequent studies have defined the mechanisms by which externally applied galvanic currents result in a change in vestibular-nerve afferent discharge. The currents appear to act at the spike trigger site. Perilymphatic cathodal currents depolarize the trigger site and lead to excitation whereas anodal currents hyperpolarize and result in inhibition. Afferents innervating all five vestibular endorgans appear to be affected equally by the currents (Goldberg et al., 1984). Irregularly discharging afferents are about 5-10 times more sensitive than regularly discharging ones because of the steeper slope of the former's faster postspike recovery of excitability in encoder sensitivity (Smith and Goldberg, 1986). Response adaptation similar to that noted during acceleration steps is apparent for longer periods of current administration. This adaptation is manifested as a perstimulus return toward resting discharge and poststimulus after-response in the opposite direction (Goldberg et al., 1984; Minor and Goldberg, l991). Cathodal currents (with respect to the perilymphatic space of the vestibule) are excitatory whereas anodal currents are inhibitory. Horizontal eye movements evoked by unilateral galvanic polarizations administered through chronically implanted labyrinthine stimulating electrodes have been studied in alert squirrel monkeys (Minor and Goldberg, 1991). We sought to extend this analysis by recording three-dimensional eye movements during galvanic stimulation. As predicted based upon roughly equal stimulation of ampullary nerves innervating the vertical canals, a substantial torsional component to the nystagmus is noted. The trajectory of torsional slow phases and nystagmus profile after the polarization provide insight into the central mechanisms that influence these responses.

Dual-frequency glow discharges in atmospheric helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Xiaojiang; Guo, Ying; Magnetic Confinement Fusion Research Center, Ministry of Education of the People's Republic of China, Shanghai 201620

2015-10-15

In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

Effect of the charge surface distribution on the flow field induced by a dielectric barrier discharge actuator

NASA Astrophysics Data System (ADS)

Cristofolini, Andrea; Neretti, Gabriele; Borghi, Carlo A.

2013-08-01

The Electro-Hydro-Dynamics (EHD) interaction induced by a surface dielectric barrier discharge in the aerodynamic boundary layer at one atmosphere still air has been investigated. Three different geometrical configurations of the actuator have been utilized. In the first configuration, an electrode pair separated by a 2 mm dielectric sheet has been used. The second and the third configurations have been obtained by adding a third electrode on the upper side of the dielectric surface. This electrode has been placed downstream of the upper electrode and has been connected to ground or has been left floating. Three different dielectric materials have been utilized. The high voltage upper electrode was fed by an a.c. electric tension. Measurements of the dielectric surface potential generated by the charge deposition have been done. The discharge has been switched off after positive and negative phases of the plasma current (the current phase was characterized by a positive or a negative value, respectively). The measurements have been carried out after both phases. The charge distribution strongly depended on the switching off phase and was heavily affected by the geometrical configuration. A remarkable decrease of the charge deposited on the dielectric surface has been detected when the third electrode was connected to ground. Velocity profiles were obtained by using a Pitot probe. They showed that the presence of the third electrode limits the fluid dynamics performance of the actuator. A relation between the charge surface distribution and the EHD interaction phenomenon has been found. Imaging of the plasma has been done to evaluate the discharge structure and the extension of the plasma in the configurations investigated.

VRLA Ultrabattery for high-rate partial-state-of-charge operation

NASA Astrophysics Data System (ADS)

Lam, L. T.; Louey, R.; Haigh, N. P.; Lim, O. V.; Vella, D. G.; Phyland, C. G.; Vu, L. H.; Furukawa, J.; Takada, T.; Monma, D.; Kano, T.

The objective of this study is to produce and test the hybrid valve-regulated Ultrabattery designed specifically for hybrid-electric vehicle duty, i.e., high-rate partial-state-of-charge operation. The Ultrabattery developed by CSIRO Energy Technology is a hybrid energy-storage device, which combines an asymmetric supercapacitor, and a lead-acid battery in one unit cells, taking the best from both technologies without the need for extra, expensive electronic controls. The capacitor will enhance the power and lifespan of the lead-acid battery as it acts as a buffer during high-rate discharging and charging. Consequently, this hybrid technology is able to provide and absorb charge rapidly during vehicle acceleration and braking. The work programme of this study is divided into two main parts, namely, field trial of prototype Ultrabatteries in a Honda Insight HEV and laboratory tests of prototype batteries. In this paper, the performance of prototype Ultrabatteries under different laboratory tests is reported. The evaluation of Ultrabatteries in terms of initial performance and cycling performance has been conducted at both CSIRO and Furukawa laboratories. The initial performance of prototype Ultrabatteries, such as capacity, power, cold cranking and self-discharge has been evaluated based upon the US FreedomCAR Battery Test Manual (DOE/ID-11069, October 2003). Results show that the Ultrabatteries meet, or exceed, respective targets of power, available energy, cold cranking and self-discharge set for both minimum and maximum power-assist HEVs. The cycling performance of prototype Ultrabatteries has been evaluated using: (i) simplified discharge and charge profile to simulate the driving conditions of micro-HEV; (ii) 42-V profile to simulate the driving conditions of mild-HEV and (iii) EUCAR and RHOLAB profiles to simulate the driving conditions of medium-HEV. For comparison purposes, nickel-metal-hydride (Ni-MH) cells, which are presently used in the Honda Insight HEV, have also been subjected to some of the above profiles (i.e., simplified discharge and charge profile and EUCAR profile). Although the Ultrabattery and a Ni-MH cell under EUCAR test profile are still on cycling, the outcomes to date show that the performance of these batteries and cells has been at least four times longer than that of the state-of-the art lead-acid cells or batteries. Excitingly, the performance of Ultrabatteries is proven to be comparable with that of the Ni-MH cells.

Efficiency of lithium pacemaker batteries as a function of discharge rate and iodine:P2VP cathode composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helgeson, W.D.; Fester, K.E.

1980-01-01

Electrochemical discharge data for Li/I/sub 2/-P2VP pacemaker batteries at various discharge currents show the efficiency of the battery to be a function of discharge current. Depending on the iodine:P2VP cathode composition, the optimum current drain occurs between discharge currents of 100 to 200 /mu/a. As current drain is reduced to pacemaker application drains, 15-25 /mu/a, the efficiency of the Li/I/sub 2/-P2VP battery decreases. The loss in efficiency at pacemaker rates is attributed primarily to self-discharge. The efficiency of Li/I/sub 2/-P2VP batteries is improved by increasing the percent of iodine in the cathode. I/sub 2/:P2VP weight ratios of 10:1, 15:1 andmore » 20:1 have been discharged at various currents and the data indicate that there is significant improvement in efficiency at pacemaker rate in going from 10:1 to 20:1 cathode weight ratio. 2 refs.« less

Wave propagation and noncollisional heating in neutral loop and helicon discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celik, Y.; Crintea, D. L.; Luggenhoelscher, D.

2011-02-15

Heating mechanisms in two types of magnetized low pressure rf (13.56 MHz) discharges are investigated: a helicon discharge and a neutral loop discharge. Radial B-dot probe measurements demonstrate that the neutral loop discharge is sustained by helicon waves as well. Axial B-dot probe measurements reveal standing wave and beat patterns depending on the dc magnetic field strength and plasma density. In modes showing a strong wave damping, the plasma refractive index attains values around 100, leading to electron-wave interactions. In strongly damped modes, the radial plasma density profiles are mainly determined by power absorption of the propagating helicon wave, whereasmore » in weakly damped modes, inductive coupling dominates. Furthermore, an azimuthal diamagnetic drift is identified. Measurements of the helicon wave phase demonstrate that initial plane wave fronts are bent during their axial propagation due to the inhomogeneous density profile. A developed analytical standing wave model including Landau damping reproduces very well the damping of the axial helicon wave field. This comparison underlines the theory whereupon Landau damping of electrons traveling along the field lines at speeds close to the helicon phase velocity is the main damping mechanism in both discharges.« less

Stability of backwater-influenced river bifurcations: A study of the Mississippi-Atchafalaya system

NASA Astrophysics Data System (ADS)

Edmonds, D. A.

2012-04-01

In this paper I use numerical modeling to show that the hydraulic backwater profile creates a feedback that may stabilize river bifurcations. The numerical model simulates flow and sediment transport in the Mississippi-Atchafalaya River system without the Old River Control Structure. The results show that bifurcation evolution strongly depends on the discharge upstream of the bifurcation. At upstream discharges greater than 12600 m3 s-1 the Atchafalaya River discharge increases through time at the expense of the Mississippi River. Interestingly, at upstream discharges lower than 12600 m3 s-1 the opposite occurs and the Mississippi River discharge increases at the expense of the Atchafalaya River. The capture direction changes because the backwater profile of each river varies enough at high and low discharge to invert the water surface slope ratio. These results suggest that the capture direction would change at high and low flow, which would have a stabilizing effect by preventing the runaway growth of one channel. Accounting for this, I calculate that in the absence of the Old River Control Structure capture would not happen catastrophically, but rather the Atchafalaya River would capture the Mississippi River in ˜300 years from present day.

Effect of KOH Concentration and Anions on the Performance of a Ni-H2 Battery Positive Plate

NASA Technical Reports Server (NTRS)

Vaidyanathan, Hari; Robbins, Kathleen; Gopalakrishna, M. Rao

1996-01-01

The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galvanostatic charging and discharging in a flooded electrolyte cell. Three different concentrations of potassium hydroxide (KOH) (40, 31, and 26 percent) and 31 percent KOH containing dissolved nitrate, sulfate, or silicate were investigated. The end-of-charge voltage at C/10 charge and at 10 degrees C showed the following order: 40 percent KOH greater than 31 percent KOH alone and in the presence of the anions greater than 26 percent KOH. The mid discharge voltage at C/2 discharge was higher in 26 percent KOH, almost the same for 31 percent KOH with and without added contaminants, and much lower for 40 percent KOH. The plate capacity was marginally affected by cycling in all cases except for 40 percent KOH, where the capacity declined after 1,000 cycles at 80 percent depth of discharge (DOD). At the end of cycling, all the plates tested experienced a weight loss, except in the case of 31 percent KOH, as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31 percent KOH showed that the cathodic peak potentials are less polarized in the presence and absence of silicate at -5 degrees C compared to 25 degrees C indicating a slightly higher voltage during discharge in a Ni-H2 battery. Futhermore, the features of the current-potential profile were practically unchanged in the presence of silicate.

Development of a Specific Impulse Balance for a Pulsed Capillary Discharge (Preprint)

DTIC Science & Technology

2008-06-13

thrust stand [rad/s] I. Introduction A capillary discharge based coaxial , electrothermal pulsed plasma thruster (PPT) is currently under...20-23 July 2008. 14. ABSTRACT A capillary discharge based pulsed plasma thruster is currently under development at the Air Force Research...Edwards AFB, CA 93524 A capillary discharge based pulsed plasma thruster is currently under development at the Air Force Research Laboratory. A

Response of nickel to zinc cells to electric vehicle chopper discharge waveforms

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1981-01-01

The preliminary results of simulated electric vehicle chopper controlled discharge of a Nickel/Zinc battery shows delivered energy increases of 5 to 25 percent compared to constant current discharges of the same average current. The percentage increase was a function of chopper frequency, the ratio of peak to average current, and the magnitude of the discharge current. Because the chopper effects are of a complex nature, electric vehicle battery/speed controller interaction must be carefully considered in vehicle design to optimize battery performance.

Discharge mode transition and temporal-spatial evolution of an air-water plasma jet generated by pulsating DC power

NASA Astrophysics Data System (ADS)

Lei, J.; Geng, Y.; Liu, K.; Zhu, W.; Zheng, Z.; Hu, H.

2017-12-01

In this paper, pulsating direct current air-water plasma jet, which can increase the production of •OH and decrease the temperature, is studied. The results show that the discharge mode changes in one cycle from corona discharge with steep Trichel current pulse to glow-like discharge. It is unknown whether the different discharge modes and water ratio have an effect on the transient process of the excited O and •OH production and the mechanism of plasma propagation. So, a series of experiments are done in this paper. The results show that the changing rules of both the excited state O and the discharge current reach their two peak values synchronously. And its maximum appears at the time of the first peak current value in corona mode. However, the change of the excited state •OH is different. It increases to its maximum at the time of the second peak current value in glow-like mode. Besides, the intensified charge coupled device photographs show that the luminous intensity of the discharge zone at the first peak current value in corona mode is stronger than the second peak current value in glow-like mode. At the same time, the discharge area of the former is larger than the latter. Nevertheless, with the increase in water ratio, the discharge area change reversed. Additionally, the air plasma plume propagation depends on the gas flow. The initial propagation velocity decreases with the increase in water ratio.

Mobile Bay river plume mixing in the inner shelf

NASA Astrophysics Data System (ADS)

Parra, S. M.; Book, J. W.; Warner, S. J.; Moum, J.

2017-12-01

The microtidal region (0.5 m spring tides) of the inner shelf outside Mobile Bay presented a complex circulation pattern driven by the pulsed river discharge and winds. Currents, salinity, temperature, and turbulence profiles were measured for up to three weeks in April 2016 at six moorings outside Mobile Bay. Currents varied between locations and with depth. During neap and spring tides the currents were reliably >0.4 and <0.4 m/s, respectively. The outflow from Mobile Bay generated a complex density circulation, where two to three layers were normally present. Multiple density layers included a thicker brackish middle layer (5-10 m thickness), and a salty bottom layer (5-10 m thickness), with a thin ( 1-3 m) freshwater surface layer found intermittently. The multilayer currents were strongest at neap tides (>0.5 m/s) and toward deeper waters, concurrent with the strongest stratification. The possible flow drivers considered include tides, winds, inertial oscillations, waves, and stratification. Turbulent kinetic energy production and dissipation were calculated with multiple methods using data from bottom-mounted, upward-looking acoustic Doppler current profilers sampling at 1 Hz, and using data from line-moored chi-pod turbulent temperature microstructure instruments sampling at 100 Hz. This work explores different forcing mechanisms involved in modulating the circulation and turbulence in a multi-layered pulsed-river inner shelf region in the Gulf of Mexico.

Thermal island destabilization and the Greenwald limit

DOE PAGES

White, R. B.; Gates, D. A.; Brennan, D. P.

2015-02-24

Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. A magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration is evident in a fusion device. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Furthermore, modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturatedmore » island. Because field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. In addition destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

Thermal island destabilization and the Greenwald limit

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, R. B.; Gates, D. A.; Brennan, D. P.

Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. A magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration is evident in a fusion device. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Furthermore, modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturatedmore » island. Because field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. In addition destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

Thermal island destabilization and the Greenwald limit

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, R. B.; Gates, D. A.; Brennan, D. P.

Magnetic reconnection is ubiquitous in the magnetosphere, the solar corona, and in toroidal fusion research discharges. In a fusion device, a magnetic island saturates at a width which produces a minimum in the magnetic energy of the configuration. At saturation, the modified current density profile, a function of the flux in the island, is essentially flat, the growth rate proportional to the difference in the current at the O-point and the X-point. Further modification of the current density profile in the island interior causes a change in the island stability and additional growth or contraction of the saturated island. Becausemore » field lines in an island are isolated from the outside plasma, an island can heat or cool preferentially depending on the balance of Ohmic heating and radiation loss in the interior, changing the resistivity and hence the current in the island. A simple model of island destabilization due to radiation cooling of the island is constructed, and the effect of modification of the current within an island is calculated. An additional destabilization effect is described, and it is shown that a small imbalance of heating can lead to exponential growth of the island. A destabilized magnetic island near the plasma edge can lead to plasma loss, and because the radiation is proportional to plasma density and charge, this effect can cause an impurity dependent density limit.« less

Analysis of floods, including the tropical storm Irene inundation, of the Ottauquechee River in Woodstock, Bridgewater, and Killington and of Reservoir Brook in Bridgewater and Plymouth, Vermont

USGS Publications Warehouse

Flynn, Robert H.

2014-01-01

In addition to the two digital flood inundation maps, flood profiles were created that depict the study reach flood elevation of tropical storm Irene of August 2011 and the 10-, 2-, 1-, and 0.2-percent AEP floods, also known as the 10-, 50-, 100-, and 500-year floods, respectively. The 10-, 2-, 1-, and 0.2-percent AEP flood discharges were determined using annual peak flow data from the USGS Ottauquechee River near West Bridgewater, Vt. streamgage (station 01150900). Flood profiles were computed for the Ottauquechee River and Reservoir Brook by means of a one-dimensional step-backwater model. The model was calibrated using documented high-water marks of the peak of the tropical storm Irene flood of August 2011 as well as stage discharge data as determined for USGS Ottauquechee River near West Bridgewater, Vt. streamgage (station 01150900). The simulated water-surface profiles were combined with a digital elevation model within a geographic information system to delineate the areas flooded during tropical storm Irene and for the 1-percent AEP water-surface profile. The digital elevation model data were derived from light detection and ranging (lidar) data obtained for a 3,281-foot (1,000-meter) corridor along the Ottauquechee River study reach and were augmented with 33-foot (10- meter) contour interval data in the modeled flood-inundation areas outside the lidar corridor. The 33-foot (10-meter) contour interval USGS 15-minute quadrangle topographic digital raster graphics map used to augment lidar data was produced at a scale of 1:24,000. The digital flood inundation maps and flood profiles along with information regarding current stage from USGS streamgages on the Internet provide emergency management personnel and residents with information that is critical for flood response activities, such as evacuations and road closures, as well as for post-flood recovery efforts.

Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

NASA Astrophysics Data System (ADS)

Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

2017-10-01

The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

Optical emission spectroscopy of point-plane corona and back-corona discharges in air

NASA Astrophysics Data System (ADS)

Czech, T.; Sobczyk, A. T.; Jaworek, A.

2011-12-01

Results of spectroscopic investigations and current-voltage characteristics of corona discharge and back discharge on fly-ash layer, generated in point-plane electrode geometry in air at atmospheric pressure are presented in the paper. The characteristics of both discharges are similar but differ in the current and voltage ranges of all the discharge forms distinguished during the experiments. Three forms of back discharge, for positive and negative polarity, were investigated: glow, streamer and low-current back-arc. In order to characterize ionisation and excitation processes in back discharge, the emission spectra were measured and compared with those obtained for normal corona discharge generated in the same electrode configuration but with fly ash layer removed. The emission spectra were measured in two discharge zones: near the tip of needle electrode and near the plate. Visual forms of the discharge were recorded with digital camera and referred to current-voltage characteristics and emission spectra. The measurements have shown that spectral lines emitted by back discharge depend on the form of discharge and the discharge current. From the comparison of the spectral lines of back and normal discharges an effect of fly ash layer on the discharge morphology can be determined. The recorded emission spectra formed by ionised gas and plasma near the needle electrode and fly ash layer are different. It should be noted that in back arc emission, spectral lines of fly ash layer components can be distinguished. On the other hand, in needle zone, the emission of high intensity N2 second positive system and NO γ lines can be noticed. Regardless of these gaseous lines, also atomic lines of dust layer were present in the spectrum. The differences in spectra of back discharge for positive and negative polarities of the needle electrode have been explained by considering the kind of ions generated in the crater in fly ash layer. The aim of these studies is to better understand the discharge processes encountered in electrostatic precipitators.

Experimentally Determined Plasma Parameters in a 30 cm Ion Engine

NASA Technical Reports Server (NTRS)

Sengupta, Anita; Goebel, Dan; Fitzgerald, Dennis; Owens, Al; Tynan, George; Dorner, Russ

2004-01-01

Single planar Langmuir probes and fiber optic probes are used to concurrently measure the plasma properties and neutral density variation in a 30cm diameter ion engine discharge chamber, from the immediate vicinity of the keeper to the near grid plasma region. The fiber optic probe consists of a collimated optical fiber recessed into a double bore ceramic tube fitted with a stainless steel light-limiting window. The optical fiber probe is used to measure the emission intensity of excited neutral xenon for a small volume of plasma, at various radial and axial locations. The single Langmuir probes, are used to generate current-voltage characteristics at a total of 140 spatial locations inside the discharge chamber. Assuming a maxwellian distribution for the electron population, the Langmuir probe traces provide spatially resolved measurements of plasma potential, electron temperature, and plasma density. Data reduction for the NSTAR TH8 and TH15 throttle points indicates an electron temperature range of 1 to 7.9 eV and an electron density range of 4e10 to le13 cm(sup -3), throughout the discharge chamber, consistent with the results in the literature. Plasma potential estimates, computed from the first derivative of the probe characteristic, indicate potential from 0.5V to 11V above the discharge voltage along the thruster centerline. These values are believed to be excessively high due to the sampling of the primary electron population along the thruster centerline. Relative neutral density profiles are also obtained with a fiber optic probe sampling photon flux from the 823.1 nm excited to ground state transition. Plasma parameter measurements and neutral density profiles will be presented as a function of probe location and engine discharge conditions. A discussion of the measured electron energy distribution function will also be presented, with regards to variation from pure maxwellian. It has been found that there is a distinct primary population found along the thruster centerline, which causes estimates of electron temperature, electron density, and plasma potential, to err on the high side, due this energetic population. Computation of the energy distribution fimction of the plasma clearly indicates the presence of primaries, whose presence become less obvious with radial distance from the main discharge plume.

Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raizer, Yu. P.; Mokrov, M. S.

The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gasmore » as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time.« less

AC Glow Discharge Plasma in N2O

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yousif, F. B.; Martinez, H.; Robledo-Martinez, A.

2006-12-04

This paper considers the optical and electrical characterization of AC glow discharge plasma in the abnormal glow mode used for optical emission spectroscopy. The total discharge current and applied voltage are measured using conventional techniques. The electrical characteristics of the planer-cathode glow discharge confirmed that the plasma is operating at abnormal discharge mode characterized by the increases in the operating voltage as the current was raised under given pressure. Optical emission spectroscopy was used to determine the main emission lines of the glow discharge plasma of N2O at pressures between 0.5 and 4.0 Torr. It shows that the discharge emissionmore » range is mainly within 300-400 nm. The emission lines correspond to NO, O2, and O{sub 2}{sup +} are the dominant lines in the glow discharge plasma in the present study. Intensity of the emission lines show linear increase with the discharge current up to 0.4 A followed by saturation at higher currents. No emission lines were observed in this work corresponding to atomic oxygen or nitrogen.« less

Carbon microgranule injection into NSTX-U discharges for edge diagnostic research

NASA Astrophysics Data System (ADS)

Lunsford, Robert; Roquemore, A. Lane; Scotti, Filippo; Mansfield, Dennis; Bortolon, Alessandro; Kaita, Robert; Maingi, Rajesh

2016-10-01

Microgranule injection is a versatile means for investigating edge plasmas in fusion devices. Employing a dual bladed rotary turbine, carbon microgranules ranging in diameter from 300 - 700 microns are radially injected into NSTX-U discharges at approximately 50 m/sec. Utilizing multiple high speed camera views, a 3D reconstruction of the injection geometry is created which characterizes the ablation rate and granule trajectory. By coupling this with a neutral gas shielding (NGS) ablation model, the granule mass deposition profile can be determined. Simulation projects a depositional barycenter near the pedestal shoulder for H-mode discharges, and 20 cm inboard of the LCFS for L-mode discharges. Spectroscopic measurements of this localized particle source can be used to characterize impurity transport within the discharge, and potentially allows for direct measurement of the safety factor profile (q). In addition, the transient pressure peaking resultant from injection into H-mode plasmas can also result in the prompt triggering of an edge localized mode (ELM). Work supported by DOE Contract No. DE-AC02-09CH11466.

Outer midplane scrape-off layer profiles and turbulence in simulations of Alcator C-Mod inner-wall limited discharges

DOE PAGES

Halpern, Federico D.; LaBombard, Brian; Terry, James L.; ...

2017-06-27

A region of steep plasma gradients, the so-called ”narrow-feature”, has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [E.S. Marmar et al., Nucl. Fusion 55, (2015)] to study this phenomenon, allowing detailed observations of the plasma profiles and fluctuations. Langmuir probe (LP) measurements show a clear two decay length n e and T e profile structure at the outer midplane. The Gas-Puff Imaging (GPI) diagnostic shows large turbulent fluctuations across the last closed flux-surface, hence supporting the hypothesis that turbulent phenomena play a role in settingmore » the profile steepness. We have carried out the flux-driven non-linear turbulence simulations of two C-Mod discharges which allows a three-way comparison between LP, GPI, and simulation data. Observations and simulations correlate the steep gradient region characterizing the narrow feature with sheared poloidal flows and a deviation of the plasma potential from its floating value. Furthermore, the E x B shear rate exceeds the linear ballooning growth rate, indicating that the narrow feature could result from the effects of sheared flows, although causality could not be established. The fluctuation level in the narrow feature remains of order unity across the entire SOL, indicating that the transport reduction in the near-SOL cannot result from a simple quench rule.« less

Outer midplane scrape-off layer profiles and turbulence in simulations of Alcator C-Mod inner-wall limited discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halpern, Federico D.; LaBombard, Brian; Terry, James L.

A region of steep plasma gradients, the so-called ”narrow-feature”, has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [E.S. Marmar et al., Nucl. Fusion 55, (2015)] to study this phenomenon, allowing detailed observations of the plasma profiles and fluctuations. Langmuir probe (LP) measurements show a clear two decay length n e and T e profile structure at the outer midplane. The Gas-Puff Imaging (GPI) diagnostic shows large turbulent fluctuations across the last closed flux-surface, hence supporting the hypothesis that turbulent phenomena play a role in settingmore » the profile steepness. We have carried out the flux-driven non-linear turbulence simulations of two C-Mod discharges which allows a three-way comparison between LP, GPI, and simulation data. Observations and simulations correlate the steep gradient region characterizing the narrow feature with sheared poloidal flows and a deviation of the plasma potential from its floating value. Furthermore, the E x B shear rate exceeds the linear ballooning growth rate, indicating that the narrow feature could result from the effects of sheared flows, although causality could not be established. The fluctuation level in the narrow feature remains of order unity across the entire SOL, indicating that the transport reduction in the near-SOL cannot result from a simple quench rule.« less

Effect of Glycemic Control on Chylomicron Metabolism and Correlation between Postprandial Metabolism of Plasma Glucose and Chylomicron in Patients with Type 2 Diabetes Treated with Basal-bolus Insulin Therapy with or without Vildagliptin

PubMed Central

Emoto, Naoya; Kato, Katsuhito; Sugihara, Hitoshi

2017-01-01

Aim: Glucagon-like peptide-1 can reduce both postprandial plasma glucose (PG) and chylomicron (CM) levels in patients with type 2 diabetes. However, there have been no reports regarding the relationship between the postprandial metabolism of PG and CM. Methods: Patients with type 2 diabetes who were admitted for glycemic control were randomized to insulin alone (Ins; n = 16) or insulin plus vildagliptin 100 mg (InsV; n = 16) groups. The insulin dose was adjusted to maintain normal blood glucose levels. The daily profiles of serum TG, remnant lipoprotein cholesterol (RemL-C), and apolipoprotein B48 (ApoB48) were estimated by frequent blood collection on admission and before discharge, and the daily glucose fluctuation profile was also estimated using continuous glucose monitoring (CGM) before discharge. Results: The daily profiles of serum TG and RemL-C indicated a significant decrease before discharge compared with on admission; however, no significant changes in serum ApoB48 levels were observed in either group. At discharge, daily glucose fluctuation profile and the change in the serum ApoB48 level from fasting to the peak of the daily profile was significantly smaller in the InsV group than in the Ins group. The increment of serum ApoB48 level was significantly correlated with the mean amplitude of glycemic excursions calculated using CGM data only in the Ins group (R2 = 0.5242, P <0.001). Conclusions: Short-term glycemic control decreased serum TG and RemL-C levels, but not ApoB48 levels, and the postprandial metabolism of PG and CM might be regulated by the same mechanism except GLP-1 effect. PMID:27397060

Effect of Glycemic Control on Chylomicron Metabolism and Correlation between Postprandial Metabolism of Plasma Glucose and Chylomicron in Patients with Type 2 Diabetes Treated with Basal-bolus Insulin Therapy with or without Vildagliptin.

PubMed

Okajima, Fumitaka; Emoto, Naoya; Kato, Katsuhito; Sugihara, Hitoshi

2017-02-01

Glucagon-like peptide-1 can reduce both postprandial plasma glucose (PG) and chylomicron (CM) levels in patients with type 2 diabetes. However, there have been no reports regarding the relationship between the postprandial metabolism of PG and CM. Patients with type 2 diabetes who were admitted for glycemic control were randomized to insulin alone (Ins; n=16) or insulin plus vildagliptin 100 mg (InsV; n=16) groups. The insulin dose was adjusted to maintain normal blood glucose levels. The daily profiles of serum TG, remnant lipoprotein cholesterol (RemL-C), and apolipoprotein B48 (ApoB48) were estimated by frequent blood collection on admission and before discharge, and the daily glucose fluctuation profile was also estimated using continuous glucose monitoring (CGM) before discharge. The daily profiles of serum TG and RemL-C indicated a significant decrease before discharge compared with on admission; however, no significant changes in serum ApoB48 levels were observed in either group. At discharge, daily glucose fluctuation profile and the change in the serum ApoB48 level from fasting to the peak of the daily profile was significantly smaller in the InsV group than in the Ins group. The increment of serum ApoB48 level was significantly correlated with the mean amplitude of glycemic excursions calculated using CGM data only in the Ins group (R 2 = 0.5242,P＜0.001). Short-term glycemic control decreased serum TG and RemL-C levels, but not ApoB48 levels, and the postprandial metabolism of PG and CM might be regulated by the same mechanism except GLP-1 effect.

Quality Profiling at the TCM Hospital Bad Kötzting - Examples from an Ongoing Systematic Patient Documentation.

PubMed

Weidenhammer, Wolfgang; Melchart, Dieter

2016-01-01

Quality profiling is practiced at the TCM hospital Bad Kötzting since its establishment 25 years ago. The profiling comprises assessment of treatment effectiveness andsafety, structural features, staff qualification as well as diagnostic and therapeutic processes. Findings regarding patients, intervention and outcome profiles are presented by appropriate examples. Data of each in-patient were systematically collected by physicians and via self-reports at admission, discharge and follow-up. Over the years the system was adjusted several times resulting in a data pool of about 19,000 in-patients by end of 2014. Patients are 52 years old on average, 70% are female, and suffering from the main complaint since 7 years (median). The diagnostic spectrum changed over the years according to the development towards a psychosomatic focus. For TCM acupuncture therapy 222 different acupoints were used in 7.7 different localisations on average per individual treatment. The mean intensity of the main complaint decreased clinically relevant (Cohen's d = 1.11 at discharge and 0.93 at follow-up). After the hospital stay the number of days of sick leave declined from 51.3 days by 40% per patient and year. Depressive disorders as most common mental illness decreased significantly decreased significantly at discharge (ICD symptom rating; Cohen's d = -1.01). 29.8% of patients met the criteria for a metabolic syndrome diagnosis according to the International Diabetes Federation (IDF). In this group of cases, triglycerides, cholesterol and blood glucose improved markedly at discharge. The presented quality control measures clearly contribute to an enhanced transparency in terms of a comprehensive quality profile. The findings from various outcome parameters indicate that patients benefit from the treatment. © 2016 S. Karger GmbH, Freiburg.

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

DOE PAGES

Boyer, M. D.; Battaglia, D. J.; Mueller, D.; ...

2018-01-25

Here, the upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgradedmore » to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.« less

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyer, M. D.; Battaglia, D. J.; Mueller, D.

Here, the upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgradedmore » to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.« less

Symptom changes in five dimensions of the Positive and Negative Syndrome Scale in refractory psychosis.

PubMed

Woodward, Todd S; Jung, Kwanghee; Smith, Geoffrey N; Hwang, Heungsun; Barr, Alasdair M; Procyshyn, Ric M; Flynn, Sean W; van der Gaag, Mark; Honer, William G

2014-12-01

Refractory psychosis units currently have little information regarding which symptoms profiles should be expected to respond to treatment. In the current study, we provide this information using structural equation modeling of Positive and Negative Syndrome Scale (PANSS) ratings at admission and discharge on a sample of 610 patients admitted to a treatment refractory psychosis program at a Canadian tertiary care unit between 1990 and 2011. The hypothesized five-dimensional structure of the PANSS fit the data well at both admission and discharge, and the latent variable scores are reported as a function of symptom dimension and diagnostic category. The results suggest that, overall, positive symptoms (POS) responded to treatment better than all other symptoms dimensions, but for the schizoaffective and bipolar groups, greater response on POS was observed relative to the schizophrenia and major depression groups. The major depression group showed the most improvement on negative symptoms and emotional distress, and the bipolar group showed the most improvement on disorganization. Schizophrenia was distinct from schizoaffective disorder in showing reduced treatment response on all symptom dimensions. These results can assist refractory psychosis units by providing information on how PANSS symptom dimensions respond to treatment and how this depends on diagnostic category.

Experimental Results from a Laser-Triggered, Gas-Insulated, Spark-Gap Switch

NASA Astrophysics Data System (ADS)

Camacho, J. F.; Ruden, E. L.; Domonkos, M. T.

2017-10-01

We are performing experiments on a laser-triggered spark-gap switch with the goal of studying the transition from photoionization to current conduction. The discharge of current through the switch is triggered by a focused 532-nm wavelength beam from a Q-switched Nd:YAG laser with a pulse duration of about 10 ns. The trigger pulse is delivered along the longitudinal axis of the switch, and the focal spot can be placed anywhere along the axis of the 5-mm, gas-insulated gap between the switch electrodes. The switch test bed is designed to support a variety of working gases (e.g., Ar, N2) over a range of pressures. Electrical and optical diagnostics are used to measure switch performance as a function of parameters such as charge voltage, trigger pulse energy, insulating gas pressure, and gas species. A Mach-Zehnder imaging interferometer system operating at 532 nm is being used to obtain interferograms of the discharge plasma in the switch. We are also developing a 1064-nm interferometry diagnostic in an attempt to measure plasma free electron and neutral gas density profiles simultaneously within the switch gap. Results from our most recent experiments will be presented.

Plasma boundary shape control and real-time equilibrium reconstruction on NSTX-U

NASA Astrophysics Data System (ADS)

Boyer, M. D.; Battaglia, D. J.; Mueller, D.; Eidietis, N.; Erickson, K.; Ferron, J.; Gates, D. A.; Gerhardt, S.; Johnson, R.; Kolemen, E.; Menard, J.; Myers, C. E.; Sabbagh, S. A.; Scotti, F.; Vail, P.

2018-03-01

The upgrade to the National Spherical Torus eXperiment (NSTX-U) included two main improvements: a larger center-stack, enabling higher toroidal field and longer pulse duration, and the addition of three new tangentially aimed neutral beam sources, which increase available heating and current drive, and allow for flexibility in shaping power, torque, current, and particle deposition profiles. To best use these new capabilities and meet the high-performance operational goals of NSTX-U, major upgrades to the NSTX-U control system (NCS) hardware and software have been made. Several control algorithms, including those used for real-time equilibrium reconstruction and shape control, have been upgraded to improve and extend plasma control capabilities. As part of the commissioning phase of first plasma operations, the shape control system was tuned to control the boundary in both inner-wall limited and diverted discharges. It has been used to accurately track the requested evolution of the boundary (including the size of the inner gap between the plasma and central solenoid, which is a challenge for the ST configuration), X-point locations, and strike point locations, enabling repeatable discharge evolutions for scenario development and diagnostic commissioning.

An Overview of NSTX Research Facility and Recent Experimental Results

NASA Astrophysics Data System (ADS)

Ono, Masayuki

2006-10-01

The 2006 NSTX experimental campaign yielded significant new experimental results in many areas. Improved plasma control achieved the highest elongation of 2.9 and plasma shape factor q95Ip/aBT = 42 MA/m.T. Active feedback correction of error fields sustained the plasma rotation and increased the pulse length of high beta discharges. Active feedback stabilization of the resistive wall mode in high-beta, low-rotation plasmas was demonstrated for ˜100 resistive wall times. Operation at higher toroidal field showed favorable plasma confinement and HHFW heating efficiency trends with the field. A broader current profile, measured by the 12-channel MSE diagnostic in high beta discharges revealed an outward anomalous diffusivity of energetic ions due to the n=1 MHD modes. A tangential microwave scattering diagnostic measured localized electron gyro-scale fluctuations in L-mode, H-mode and reversed-shear plasmas. Evaporation of lithium onto plasma facing surfaces yielded lower density, higher temperature and improved confinement. A strong dependence of the divertor heat load and ELM behavior on the plasma triangularity was observed. Coaxial helicity injection produced a start-up current of 160 kA on closed flux surfaces.

Chopper-controlled discharge life cycling studies on lead-acid batteries

NASA Technical Reports Server (NTRS)

Kraml, J. J.; Ames, E. P.

1982-01-01

State-of-the-art 6 volt lead-acid golf car batteries were tested. A daily charge/discharge cycling to failure points under various chopper controlled pulsed dc and continuous current load conditions was undertaken. The cycle life and failure modes were investigated for depth of discharge, average current chopper frequency, and chopper duty cycle. It is shown that battery life is primarily and inversely related to depth of discharge and discharge current. Failure mode is characterized by a gradual capacity loss with consistent evidence of cell element aging.

Response of lead-acid batteries to chopper-controlled discharge: Preliminary results

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1978-01-01

The preliminary results of simulated electric vehicle, chopper, speed controller discharge of a battery show energy output losses up to 25 percent compared to constant current discharges at the same average discharge current of 100 amperes. These energy losses are manifested as temperature rises during discharge, amounting to a two-fold increase for a 400-ampere pulse compared to the constant current case. Because of the potentially large energy inefficiency, the results suggest that electric vehicle battery/speed controller interaction must be carefully considered in vehicle design.

Response of lead-acid batteries to chopper-controlled discharge

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1978-01-01

The preliminary results of simulated electric vehicle, chopper, speed controller discharge of a battery show energy output losses at up to 25 percent compared to constant current discharges at the same average discharge current of 100 A. These energy losses are manifested as temperature rises during discharge, amounting to a two-fold increase for a 400-A pulse compared to the constant current case. Because of the potentially large energy inefficiency, the results suggest that electric vehicle battery/speed controller interaction must be carefully considered in vehicle design.

Tearing Mode Stability of Evolving Toroidal Equilibria

NASA Astrophysics Data System (ADS)

Pletzer, A.; McCune, D.; Manickam, J.; Jardin, S. C.

2000-10-01

There are a number of toroidal equilibrium (such as JSOLVER, ESC, EFIT, and VMEC) and transport codes (such as TRANSP, BALDUR, and TSC) in our community that utilize differing equilibrium representations. There are also many heating and current drive (LSC and TORRAY), and stability (PEST1-3, GATO, NOVA, MARS, DCON, M3D) codes that require this equilibrium information. In an effort to provide seamless compatibility between the codes that produce and need these equilibria, we have developed two Fortran 90 modules, MEQ and XPLASMA, that serve as common interfaces between these two classes of codes. XPLASMA provides a common equilibrium representation for the heating and current drive applications while MEQ provides common equilibrium and associated metric information needed by MHD stability codes. We illustrate the utility of this approach by presenting results of PEST-3 tearing stability calculations of an NSTX discharge performed on profiles provided by the TRANSP code. Using the MEQ module, the TRANSP equilibrium data are stored in a Fortran 90 derived type and passed to PEST3 as a subroutine argument. All calculations are performed on the fly, as the profiles evolve.

Dependency of Tearing Mode Stability on Current and Pressure Profiles in DIII-D Hybrid Discharges

NASA Astrophysics Data System (ADS)

Kim, K.; Park, J. M.; Murakami, M.; La Haye, R. J.; Na, Y.-S.; SNU/ORAU; ORNL; Atomics, General; SNU; DIII-D Team

2016-10-01

Understanding the physics of the onset and evolution of tearing modes (TMs) in tokamak plasmas is important for high- β steady-state operation. Based on DIII-D steady-state hybrid experiments with accurate equilibrium reconstruction and well-measured plasma profiles, the 2/1 tearing mode can be more stable with increasing local current and pressure gradient at rational surface and with lower pressure peaking and plasma inductance. The tearing stability index Δ', estimated by the Rutherford equation with experimental mode growth rate was validated against Δ' calculated by linear eigenvalue solver (PEST3); preliminary comprehensive MHD modeling by NIMROD reproduced the TM onset reasonably well. We present a novel integrated modeling for the purpose of predicting TM onset in experiment by combining a model equilibrium reconstruction using IPS/FASTRAN, linear stability Δ' calculation using PEST3, and fitting formula for critical Δ' from NIMROD. Work supported in part by the US DoE under DE-AC05-06OR23100, DE-AC05-00OR22725, and DEFC02-04ER54698.

Effects of neutral gas releases on electron beam injection from electrically tethered spacecraft

NASA Technical Reports Server (NTRS)

Winglee, R. M.

1990-01-01

The presence of high neutral densities at low altitudes and/or during thruster firings is known to modify the spacecraft potential during active electron beam injection. Two-dimensional (three velocity) particle simulations are used to investigate the ionization processes including the neutral density required, the modification of the spacecraft potential, beam profile and spatial distribution of the return current into the spacecraft. Three processes are identified: (1) beam-induced ionization, (2) vehicle-induced ionization, and (3) beam plasma discharge. Only in the first two cases does the beam propagate away with little distortion.

An averaging battery model for a lead-acid battery operating in an electric car

NASA Technical Reports Server (NTRS)

Bozek, J. M.

1979-01-01

A battery model is developed based on time averaging the current or power, and is shown to be an effective means of predicting the performance of a lead acid battery. The effectiveness of this battery model was tested on battery discharge profiles expected during the operation of an electric vehicle following the various SAE J227a driving schedules. The averaging model predicts the performance of a battery that is periodically charged (regenerated) if the regeneration energy is assumed to be converted to retrievable electrochemical energy on a one-to-one basis.

River self-organisation inhibits discharge control on waterfall migration.

PubMed

Baynes, Edwin R C; Lague, Dimitri; Attal, Mikaël; Gangloff, Aurélien; Kirstein, Linda A; Dugmore, Andrew J

2018-02-05

The action of rivers within valleys is fundamentally important in controlling landscape morphology, and how it responds to tectonic or climate change. The response of landscapes to external forcing usually results in sequential changes to river long profiles and the upstream migration of waterfalls. Currently, models of this response assume a relationship between waterfall retreat rate and drainage area at the location of the waterfall. Using an experimental study, we show that this assumption has limited application. Due to a self-regulatory response of channel geometry to higher discharge through increasing channel width, the bed shear stress at the lip of the experimental waterfall remains almost constant, so there was no observed change in the upstream retreat rate despite an order of magnitude increase in discharge. Crucially, however, the strength of the bedrock material exhibits a clear control on the magnitude of the mean retreat rate, highlighting the importance of lithology in setting the rate at which landscapes respond to external forcing. As a result existing numerical models of landscape evolution that simulate the retreat of waterfalls as a function of drainage area with a fixed erodibility constant should be re-evaluated to consider spatial heterogeneity in erodibility and channel self-organisation.

Assessment of velocity fields through open-channel flows with an empiric law.

PubMed

Bardiaux, J B; Vazquez, J; Mosé, R

2008-01-01

Most sewer managers are currently confronted with the evaluation of the water discharges, that flow through their networks or go to the discharge system, i.e. rivers in the majority of cases. In this context, the Urban Hydraulic Systems laboratory of the ENGEES is working on the relation between velocity fields and metrology assessment through a partnership with the Fluid and Solid Mechanics Institute of Strasbourg (IMFS). The responsibility is clearly to transform a velocity profile measurement, given by a Doppler sensor developed by the IMFS team, into a water discharge evaluation. The velocity distribution in a cross section of the flow in a channel has attracted the interests of many researchers over the years, due to its practical applications. In the case of free surface flows in narrow open channels the maximum velocity is below the free surface. This phenomenon, usually called "dip-phenomenon", amongst other things, raises the problem of the area explored in the section of measurements. The work presented here tries to create a simple relation making possible to associate the flow with the velocity distribution. This step allows to insert the sensor position into the flow calculation.

The evolution of discharge current and channel radius in cloud-to-ground lightning return stroke process

NASA Astrophysics Data System (ADS)

Fan, Tingting; Yuan, Ping; Wang, Xuejuan; Cen, Jianyong; Chang, Xuan; Zhao, Yanyan

2017-09-01

The spectra of two negative cloud-to-ground lightning discharge processes with multi-return strokes are obtained by a slit-less high-speed spectrograph, which the temporal resolution is 110 μs. Combined with the synchronous electrical observation data and theoretical calculation, the physical characteristics during return strokes process are analysed. A positive correlation between discharge current and intensity of ionic lines in the spectra is verified, and based on this feature, the current evolution characteristics during four return strokes are investigated. The results show that the time from peak current to the half-peak value estimated by multi point-fitting is about 101 μs-139 μs. The Joule heat in per unit length of four return strokes channel is in the order of 105J/m-106 J/m. The radius of arc discharge channel is positively related to the discharge current, and the more intense the current is, the greater the radius of channel is. Furthermore, the evolution for radius of arc core channel in the process of return stroke is consistent with the change trend of discharge current after the peak value. Compared with the decay of the current, the temperature decreases more slowly.

Generation of a pulsed low-energy electron beam using the channel spark device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elgarhy, M. A. I., E-mail: elgarhy@azhar.edu.eg; Hassaballa, S. E.; Rashed, U. M.

2015-12-15

For the generation of low-energy electron beam, the design and characteristics of channel spark discharge (CSD) operating at a low voltage are presented in this paper. The discharge voltage, discharge current, X-ray emissions, and electron beam current were experimentally determined. The effects of the applied voltage, working gas pressure, and external capacitance on the CSD and beam parameters were measured. At an applied voltage of 11 kV, an oxygen gas pressure of 25 mTorr, and an external capacitance of 16.45 nF, the maximum measured current was 900 A. The discharge current increased with the increase in the pressure and capacitance,more » while its periodic time decreased with the increase in the pressure. Two types of the discharge were identified and recorded: the hollow cathode discharge and the conduction discharge. A Faraday cup was used to measure the beam current. The maximum measured beam current was 120 A, and the beam signal exhibited two peaks. The increase in both the external capacitance and the applied discharge voltage increased the maximum electron beam current. The electron-beam pulse time decreased with the increase in the gas pressure at a constant voltage and increased with the decrease in the applied discharge voltage. At an applied voltage of 11 kV and an oxygen gas pressure of 15 mTorr, the maximum beam energy was 2.8 keV. The X-ray signal intensity decreased with the increase in the gas pressure and increased with the increase in the capacitance.« less

Suspended sediment transport in the freshwater reach of the Hudson river estuary in eastern New York

USGS Publications Warehouse

Wall, G.R.; Nystrom, E.A.; Litten, S.

2008-01-01

Deposition of Hudson River sediment into New York Harbor interferes with navigation lanes and requires continuous dredging. Sediment dynamics at the Hudson estuary turbidity maximum (ETM) have received considerable study, but delivery of sediment to the ETM through the freshwater reach of the estuary has received relatively little attention and few direct measurements. An acoustic Doppler current profiler was positioned at the approximate limit of continuous freshwater to develop a 4-year time series of water velocity, discharge, suspended sediment concentration, and suspended sediment discharge. This data set was compared with suspended sediment discharge data collected during the same period at two sites just above the Hudson head-of-tide (the Federal Dam at Troy) that together represent the single largest source of sediment entering the estuary. The mean annual suspended sediment-discharge from the freshwater reach of the estuary was 737,000 metric tons. Unexpectedly, the total suspended sediment discharge at the study site in November and December slightly exceeded that observed during March and April, the months during which rain and snowmelt typically result in the largest sediment discharge to the estuary. Suspended sediment discharge at the study site exceeded that from the Federal Dam, even though the intervening reach appears to store significant amounts of sediment, suggesting that 30-40% of sediment discharge observed at the study site is derived from tributaries to the estuary between the Federal Dam and study site. A simple model of sediment entering and passing through the freshwater reach on a timescale of weeks appears reasonable during normal hydrologic conditions in adjoining watersheds; however, this simple model may dramatically overestimate sediment delivery during extreme tributary high flows, especially those at the end of, or after, the "flushing season" (October through April). Previous estimates of annual or seasonal sediment delivery from tributaries and the Federal Dam to the ETM and harbor may be high for those years with extreme tributary high-flow events. ?? 2008 Coastal and Estuarine Research Federation.

Characterizing severe and enduring anorexia nervosa: An empirical approach.

PubMed

Wildes, Jennifer E; Forbush, Kelsie T; Hagan, Kelsey E; Marcus, Marsha D; Attia, Evelyn; Gianini, Loren M; Wu, Wei

2017-04-01

Targeted approaches for the treatment of severe and enduring anorexia nervosa (SE-AN) have been recommended, but there is no consensus definition of SE-AN to inform research and clinical practice. This study aimed to take initial steps toward developing an empirically based definition of SE-AN by characterizing associations among putative indicators of severity and chronicity in eating disorders. Patients with AN (N = 355) completed interviews and questionnaires at treatment admission and discharge; height and weight were assessed to calculate body mass index (BMI). Structural equation mixture modeling was used to test whether associations among potential indicators of SE-AN (illness duration, treatment history, BMI, binge eating, purging, quality-of-life) formed distinct subgroups, a single group with one or more dimensions, or a combination of subgroups and dimensions. A three-factor (dimensional), two-profile (categorical) mixture model provided the best fit to the data. Factor 1 included eating disorder behaviors; Factor 2 comprised quality-of-life domains; Factor 3 was characterized by illness duration, number of hospitalizations, and admission BMI. Profiles differed on eating disorder behaviors and quality-of-life, but not on indicators of chronicity or BMI. Factor scores, but not profile membership, predicted outcome at discharge from treatment. Data suggest that patients with AN can be classified on the basis of eating disorder behaviors and quality-of-life, but there was no evidence for a chronic subgroup of AN. Rather, indices of chronicity varied dimensionally within each class. Given that current definitions of SE-AN rely on illness duration, these findings have implications for research and clinical practice. © 2016 Wiley Periodicals, Inc.

Nonlinear standing wave excitation by series resonance-enhanced harmonics in low pressure capacitive discharges

NASA Astrophysics Data System (ADS)

Lieberman, M. A.; Lichtenberg, A. J.; Kawamura, Emi; Marakhtanov, A. M.

2015-09-01

It is well known that standing waves having radially center-high rf voltage profiles exist in high frequency capacitive discharges. It is also known that in radially uniform discharges, the capacitive sheath nonlinearities excite strong nonlinear series resonance harmonics that enhance the electron power deposition. In this work, we consider the coupling of the series resonance-enhanced harmonics to the standing waves. A one-dimensional, asymmetric radial transmission line model is developed incorporating the wave and nonlinear sheath physics and a self-consistent dc potential. The resulting coupled pde equation set is solved numerically to determine the discharge voltages and currents. A 10 mT argon base case is chosen with plasma density 2 ×1016 m-3, gap width 2 cm and conducting electrode radius 15 cm, driven by a high frequency 500 V source with source resistance 0.5 ohms. We find that nearby resonances lead to an enhanced ratio of 4.5 of the electron power per unit area on axis, compared to the average. The radial dependence of electron power with frequency shows significant variations, with the central enhancement and sharpness of the spatial resonances depending in a complicated way on the harmonic structure. Work supported by DOE Fusion Energy Science Contract DE-SC000193 and by a gift from the Lam Research Corporation.

External heating and current drive source requirements towards steady-state operation in ITER

NASA Astrophysics Data System (ADS)

Poli, F. M.; Kessel, C. E.; Bonoli, P. T.; Batchelor, D. B.; Harvey, R. W.; Snyder, P. B.

2014-07-01

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities, reducing the no-wall limit. The E × B flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of heating and current drive (H/CD) sources that sustain reversed magnetic shear profiles throughout the discharge are the focus of this work. Time-dependent transport simulations indicate that a combination of electron cyclotron (EC) and lower hybrid (LH) waves is a promising route towards steady state operation in ITER. The LH forms and sustains expanded barriers and the EC deposition at mid-radius freezes the bootstrap current profile stabilizing the barrier and leading to confinement levels 50% higher than typical H-mode energy confinement times. Using LH spectra with spectrum centred on parallel refractive index of 1.75-1.85, the performance of these plasma scenarios is close to the ITER target of 9 MA non-inductive current, global confinement gain H98 = 1.6 and fusion gain Q = 5.

Validation of a coupled core-transport, pedestal-structure, current-profile and equilibrium model

NASA Astrophysics Data System (ADS)

Meneghini, O.

2015-11-01

The first workflow capable of predicting the self-consistent solution to the coupled core-transport, pedestal structure, and equilibrium problems from first-principles and its experimental tests are presented. Validation with DIII-D discharges in high confinement regimes shows that the workflow is capable of robustly predicting the kinetic profiles from on axis to the separatrix and matching the experimental measurements to within their uncertainty, with no prior knowledge of the pedestal height nor of any measurement of the temperature or pressure. Self-consistent coupling has proven to be essential to match the experimental results, and capture the non-linear physics that governs the core and pedestal solutions. In particular, clear stabilization of the pedestal peeling ballooning instabilities by the global Shafranov shift and destabilization by additional edge bootstrap current, and subsequent effect on the core plasma profiles, have been clearly observed and documented. In our model, self-consistency is achieved by iterating between the TGYRO core transport solver (with NEO and TGLF for neoclassical and turbulent flux), and the pedestal structure predicted by the EPED model. A self-consistent equilibrium is calculated by EFIT, while the ONETWO transport package evolves the current profile and calculates the particle and energy sources. The capabilities of such workflow are shown to be critical for the design of future experiments such as ITER and FNSF, which operate in a regime where the equilibrium, the pedestal, and the core transport problems are strongly coupled, and for which none of these quantities can be assumed to be known. Self-consistent core-pedestal predictions for ITER, as well as initial optimizations, will be presented. Supported by the US Department of Energy under DE-FC02-04ER54698, DE-SC0012652.

Impact of river discharge on the California coastal ocean circulation and variability

NASA Astrophysics Data System (ADS)

Leiva, J.; Chao, Y.; Farrara, J. D.; Zhang, H.

2016-12-01

A real-time California coastal ocean nowcast and forecast system is used to quantify the impact of river discharge on the California coastal ocean circulation and variability. River discharge and freshwater runoff is monitored by an extensive network of stream gages maintained through the U.S. Geological Survey, that offers archived stream flow records as well as real-time datasets. Of all the rivers monitored by the USGS, 25 empty into the Pacific Ocean and contribute a potential source of runoff data. Monthly averages for the current water year yield discharge estimates as high as 6,000 cubic meters per second of additional freshwater input into our present model. Using Regional Ocean Modeling System (ROMS), we performed simulations from October 2015 to May 2016 with and without the river discharge. Results of these model simulations are compared with available observations including both in situ and satellite. Particular attention is paid to the salinity simulation. Validation is done with comparisons to sea glider data available through Oregon State University and UC San Diego, which provides depth profiles along the California coast during this time period. Additional validation is performed through comparisons with sea surface salinity measurements from the Soil Moisture and Ocean Salinity (SMOS) mission. Continued testing for previous years, e.g. between 2011 and 2015, is being made using the Aquarius sea surface salinity data. Discharge data collected by the USGS stream gages provides a necessary source of freshwater input that must be accounted for. Incorporating a new runoff source produces a more robust model that generates improved forecasts. Following validation with available sea glider and satellite data, the enhanced model can be adapted to real-time forecasting.

The influence of groundwater currents on diffusion processes in a lake bottom: an old report reviewed

NASA Astrophysics Data System (ADS)

Volker, A.; van der Molen, W. H.

1991-09-01

An internal report by the senior author, brought out in 1942, is presented and reviewed with the intention to show the historical developments made around 1940. The diffusion process from a clayey and saline lake bottom towards fresh supernatant water proved to be influenced by slow upward or downward groundwater currents. The deviations from the expected diffusion profiles, as observed during the period 1936-1938, could be used to find the velocities of such currents, even if they are as low as 10 mm year -1. There were areas where water from the underlying Pleistocene aquifier discharged into the lake, and elsewhere lake water infiltrated to recharge the aquifier. The conclusions of the study were in accordance with the geohydrology of the area as existed at that time. The theoretical formulation was originally not in closed form, but it is shown to be equivalent to a recent analytical solution.

Stage-discharge rating curves based on satellite altimetry and modeled discharge in the Amazon basin

NASA Astrophysics Data System (ADS)

Paris, Adrien; Dias de Paiva, Rodrigo; Santos da Silva, Joecila; Medeiros Moreira, Daniel; Calmant, Stephane; Garambois, Pierre-André; Collischonn, Walter; Bonnet, Marie-Paule; Seyler, Frederique

2016-05-01

In this study, rating curves (RCs) were determined by applying satellite altimetry to a poorly gauged basin. This study demonstrates the synergistic application of remote sensing and watershed modeling to capture the dynamics and quantity of flow in the Amazon River Basin, respectively. Three major advancements for estimating basin-scale patterns in river discharge are described. The first advancement is the preservation of the hydrological meanings of the parameters expressed by Manning's equation to obtain a data set containing the elevations of the river beds throughout the basin. The second advancement is the provision of parameter uncertainties and, therefore, the uncertainties in the rated discharge. The third advancement concerns estimating the discharge while considering backwater effects. We analyzed the Amazon Basin using nearly one thousand series that were obtained from ENVISAT and Jason-2 altimetry for more than 100 tributaries. Discharge values and related uncertainties were obtained from the rain-discharge MGB-IPH model. We used a global optimization algorithm based on the Monte Carlo Markov Chain and Bayesian framework to determine the rating curves. The data were randomly allocated into 80% calibration and 20% validation subsets. A comparison with the validation samples produced a Nash-Sutcliffe efficiency (Ens) of 0.68. When the MGB discharge uncertainties were less than 5%, the Ens value increased to 0.81 (mean). A comparison with the in situ discharge resulted in an Ens value of 0.71 for the validation samples (and 0.77 for calibration). The Ens values at the mouths of the rivers that experienced backwater effects significantly improved when the mean monthly slope was included in the RC. Our RCs were not mission-dependent, and the Ens value was preserved when applying ENVISAT rating curves to Jason-2 altimetry at crossovers. The cease-to-flow parameter of our RCs provided a good proxy for determining river bed elevation. This proxy was validated against Acoustic Doppler current profiler (ADCP) cross sections with an accuracy of more than 90%. Altimetry measurements are routinely delivered within a few days, and this RC data set provides a simple and cost-effective tool for predicting discharge throughout the basin in nearly real time.

Static current-voltage characteristics for radio-frequency induction discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budyansky, A.; Zykov, A.

1995-12-31

The aim of this work was to obtain experimentally such characteristic of Radio-Frequency Induction Discharge (RFID) that can play the role of its current-voltage characteristic (CVC) and to explain the nature of current and voltage jumps arising in RF coils at exciting of discharge. Experiments were made in quartz 5.5, 11, 20 cm diam tubes with outer RF coil at pressures 10--100 mTorr, at frequency 13.56 MHz and discharge power to 500 W. In case of outer coil as analogue of discharge voltage it`s convenient to use the value of the RF voltage U{sub R}, induced around outer perimeter ofmore » discharge tube. It is evident that current and voltage jumps arising at exciting of discharge are due to low output resistance of standard generators and negative slope of initial part of CVC. Three sets of such dependencies for different pressures were obtained for each diameter of tubes. The influence of different metal electrodes placed into discharge volume on CVC`s shape has been studied also. Experimental results can explain the behavior of HFI discharge as a load of RF generator and give data for calculation of RF circuit.« less

Illegal discharges in Spanish waters. Analysis of the profile of the Alleged Offending Vessel.

PubMed

Martín Alonso, J M; Ortega Piris, Andrés; Pérez Labajos, Carlos

2015-08-15

There is at present a growing concern, on an international level, over environmental offences caused by oil discharges into the sea from vessels. The objective of the Spanish Maritime Administration is to prevent the illegal discharges of polluting substances in Spanish maritime waters by vessels in transit. To combat such discharges, since 2007 Spain has reinforced its means of response with the use of aircrafts that provide services of maritime surveillance, identifying the Alleged Offending Vessels and acting as a deterrent. The objective of the present study is both to introduce the concept and to analyze certain aspects of the so-called "Alleged Offending Vessel" (AOV) that have been detected within Spanish Search and Rescue (SAR) jurisdiction waters in the period 2008-2012, in order to build a profile of such a vessel. For this purpose, an analysis methodology is formalized based on the GINI index and Lorenz curves, associated with certain aspects of vessels: type, flag and sailing area. Copyright © 2015 Elsevier Ltd. All rights reserved.

Depth elemental characterization of 1D self-aligned TiO2 nanotubes using calibrated radio frequency glow discharge optical emission spectroscopy (GDOES)

NASA Astrophysics Data System (ADS)

Mohajernia, Shiva; Mazare, Anca; Hwang, Imgon; Gaiaschi, Sofia; Chapon, Patrick; Hildebrand, Helga; Schmuki, Patrik

2018-06-01

In this work we study the depth composition of anodic TiO2 nanotube layers. We use elemental depth profiling with Glow Discharge Optical Emission Spectroscopy and calibrate the results of this technique with X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). We establish optimized sputtering conditions for nanotubular structures using the pulsed RF mode, which causes minimized structural damage during the depth profiling of the nanotubular structures. This allows to obtain calibrated sputter rates that account for the nanotubular "porous" morphology. Most importantly, sputter-artifact free compositional profiles of these high aspect ratio 3D structures are obtained, as well as, in combination with SEM, elegant depth sectional imaging.

Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes

NASA Astrophysics Data System (ADS)

Cecconello, M.; Menmuir, S.; Brunsell, P. R.; Kuldkepp, M.

2006-09-01

Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the 'slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non-resonant RWMs. This may be due to an indirect positive effect, through non-linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma-wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.

Transmission of electric fields due to distributed cloud charges in the atmosphere-ionosphere system

NASA Astrophysics Data System (ADS)

Paul, Suman; De, S. S.; Haldar, D. K.; Guha, G.

2017-10-01

The transmission of electric fields in the lower atmosphere by thunder clouds with a suitable charge distribution profile has been modeled. The electromagnetic responses of the atmosphere are presented through Maxwell's equations together with a time-varying source charge distribution. The conductivities are taken to be exponentially graded function of altitude. The radial and vertical electric field components are derived for isotropic, anisotropic and thundercloud regions. The analytical solutions for the total Maxwell's current which flows from the cloud into the ionosphere under DC and quasi-static conditions are obtained for isotropic region. We found that the effect of charge distribution in thunderclouds produced by lightning discharges diminishes rapidly with increasing altitudes. Also, it is found that time to reach Maxwell's currents a maximum is higher for higher altitudes.

The DIII-D Plasma Control System as a Scientific Research Tool

NASA Astrophysics Data System (ADS)

Hyatt, A. W.; Ferron, J. R.; Humphreys, D. A.; Leuer, J. A.; Walker, M. L.; Welander, A. S.

2006-10-01

The digital plasma control system (PCS) is an essential element of the DIII-D tokamak as a scientific research instrument, providing experimenters with real-time measurement and control of the plasma equilibrium, heating, current drive, transport, stability, and plasma-wall interactions. A wide range of sensors and actuators allow feedback control not only of global quantities such as discharge shape, plasma energy, and toroidal rotation, but also of non-axisymmetric magnetic fields and features of the internal profiles of temperature and current density. These diverse capabilities of the PCS improve the effectiveness of tokamak operation and enable unique physics experiments. We will present an overview of the PCS and the systems it controls and interacts with, and show examples of various plasma parameters controlled by the PCS and its actuators.

Maintenance of improved lipid levels following attendance at a cardiovascular risk reduction clinic: a 10-year experience

PubMed Central

Pearson, Glen J; Olson, Kari L; Panich, Nicole E; Majumdar, Sumit R; Tsuyuki, Ross T; Gilchrist, Dawna M; Damani, Ali; Francis, Gordon A

2008-01-01

Background: Specialty cardiovascular risk reduction clinics (CRRC) increase the proportion of patients attaining recommended lipid targets; however, it is not known if the benefits are sustained after discharge. We evaluated the impact of a CRRC on lipid levels and assessed the long-term effect of a CRRC in maintaining improved lipid levels following discharge. Methods: The medical records of consecutive dyslipidemic patients discharged ×6 months from a tertiary hospital CRRC from January 1991 to January 2001 were retrospectively reviewed. The primary outcome was the change in patients’ lipid levels between the final CRRC visit and the most recent primary care follow-up. A worst-case analysis was conducted to evaluate the potential impact of the patients in whom the follow-up lipid profiles post-discharge from the CRRC were not obtained. Results: Within the CRRC (median follow-up = 1.28 years in 1064 patients), we observed statistically significant improvements in all lipid parameters. In the 411 patients for whom post-discharge lipid profiles were available (median follow-up = 2.41 years), there were no significant differences observed in low-density lipoprotein-cholesterol, total cholesterol (TC), or triglycerides since CRRC discharge; however, there were small improvements in high-density lipoprotein-cholesterol (HDL-C) and TC:HDL ratio (p < 0.05 for both). The unadjusted worst-case analysis (653 patients with no follow-up lipid profiles) demonstrated statistically significant worsening of all lipid parameters between CRRC discharge and the most recent follow-up. However, when the change in lipid parameters between the baseline and the most recent follow-up was assessed in this analysis, the changes in all lipid parameters were significantly improved (p < 0.05). Conclusions: This study demonstrates that a CRRC can improve lipid levels and suggests that these benefits are sustained once patients are returned to the care of their primary physician. PMID:19183763

Transport of light, trace impurities in Alcator C-Mod

NASA Astrophysics Data System (ADS)

Rowan, W. L.; Bespamyatnov, I. O.; Liao, K. T.; Horton, W.; Fu, X. R.; Hughes, J. W.

2012-10-01

Light impurity profiles for boron were measured in ITB, H-mode, L-mode, and I-mode discharges in Alcator C-Mod. Within this wide range of modes, the profiles varied from peaked to hollow to flat. Specifically, hollow profiles are often observed in H-mode, while ITBs produce strong peaking, and L-mode produces moderate peaking. I-mode discharges are characterized by flat impurity profiles. For the study reported here, the profiles were measured with charge exchange recombination spectroscopy. The dependences of Rv/D were sought on dimensionless quantities including ion density scale length, effective charge, collisionality, and temperature scale length. We find that neoclassical transport consistently underestimates the measured transport. The excess measured transport is assumed to be turbulent. The strongest dependence of Rv/D is with temperature scale length. In addition, the measured transport was compared with the prediction of an analytical theory of drift wave turbulence that identifies transport implications for drift waves driven by ion and impurity density gradients.

Modelling the fate of the Tijuana River discharge plume

NASA Astrophysics Data System (ADS)

van Ormondt, M.; Terrill, E.; Hibler, L. F.; van Dongeren, A. R.

2010-12-01

After rainfall events, the Tijuana River discharges excess runoff into the ocean in a highly turbid plume. The runoff waters contain large suspended solids concentrations, as well as high levels of toxic contaminants, bacteria, and hepatitis and enteroviruses. Public health hazards posed by the effluent often result in beach closures for several kilometers northward along the U.S. shoreline. A Delft3D model has been set up to predict the fate of the Tijuana River plume. The model takes into account the effects of tides, wind, waves, salinity, and temperature stratification. Heat exchange with the atmosphere is also included. The model consists of a relatively coarse outer domain and a high-resolution surf zone domain that are coupled with Domain Decomposition. The offshore boundary conditions are obtained from the larger NCOM SoCal model (operated by the US Navy) that spans the entire Southern California Bight. A number of discharge events are investigated, in which model results are validated against a wide range of field measurements in the San Diego Bight. These include HF Radar surface currents, REMUS tracks, drifter deployments, satellite imagery, as well as current and temperature profile measurements at a number of locations. The model is able to reproduce the observed current and temperature patterns reasonably well. Under calm conditions, the model results suggest that the hydrodynamics in the San Diego Bight are largely governed by internal waves. During rainfall events, which are typically accompanied by strong winds and high waves, wind and wave driven currents become dominant. An analysis will be made of what conditions determine the trapping and mixing of the plume inside the surfzone and/or the propagation of the plume through the breakers and onto the coastal shelf. The model is now also running in operational mode. Three day forecasts are made every 24 hours. This study was funded by the Office of Naval Research.

Water temperature and baseflow discharge of streams throughout the range of Rio Grande cutthroat trout in Colorado and New Mexico—2010 and 2011

USGS Publications Warehouse

Zeigler, Matthew P.; Todd, Andrew S.; Caldwell, Colleen A.

2013-01-01

This study characterized the thermal regime in a number of Colorado and New Mexico streams that contain populations of Rio Grande cutthroat trout (Oncorhynchus clarkii virginalis) and had no previous record of continual temperature records. When compared to Colorado’s water temperature criteria (Cold Tier 1), a portion of these populations appeared to be at risk from elevated stream temperatures, as indicated by exceedance of both acute (17–22 percent) and chronic (2–9 percent) water quality metrics. Summer water temperature profiles recorded at sites within current Rio Grande cutthroat trout habitat indicated that although the majority of currently occupied conservation streams have temperatures that fall well below these biologically based acute and chronic thermal thresholds, several sites may be at or approaching water temperatures considered stressful to cutthroat trout. Further, water temperatures should be considered in decisions regarding the current and future thermal suitability of potential Rio Grande cutthroat trout restoration sites. Additionally, baseflow discharge sampling indicated that a majority of the sampled stream segments containing Rio Grande cutthroat trout have flows less than 1.0 cubic feet per second (cfs) in both 2010 (74 percent) and 2011 (77 percent). The relative drought sensitivity of these low baseflow streams containing Rio Grande cutthroat trout could be further evaluated to assess their probable sustainability under possible future drought conditions.

Assessment of the Electrification of the Road Transport Sector on Net System Emissions

NASA Astrophysics Data System (ADS)

Miller, James

As worldwide environmental consciousness grows, electric vehicles (EVs) are becoming more common and despite the incredible potential for emissions reduction, the net emissions of the power system supply side plus the transportation system are dependent on the generation matrix. Current EV charging patterns tend to correspond directly with the peak consumption hours and have the potential to increase demand sharply allowing for only a small penetration of Electric Vehicles. Using the National Household Travel Survey (NHTS) data a model is created for vehicle travel patterns using trip chaining. Charging schemes are modeled to include uncontrolled residential, uncontrolled residential/industrial charging, optimized charging and optimized charging with vehicle to grid discharging. A charging profile is then determined based upon the assumption that electric vehicles would directly replace a percentage of standard petroleum-fueled vehicles in a known system. Using the generation profile for the specified region, a unit commitment model is created to establish not only the generation dispatch, but also the net CO2 profile for variable EV penetrations and charging profiles. This model is then used to assess the impact of the electrification of the road transport sector on the system net emissions.

Active core profile and transport modification by application of ion Bernstein wave power in the Princeton Beta Experiment-Modification

NASA Astrophysics Data System (ADS)

LeBlanc, B.; Batha, S.; Bell, R.; Bernabei, S.; Blush, L.; de la Luna, E.; Doerner, R.; Dunlap, J.; England, A.; Garcia, I.; Ignat, D.; Isler, R.; Jones, S.; Kaita, R.; Kaye, S.; Kugel, H.; Levinton, F.; Luckhardt, S.; Mutoh, T.; Okabayashi, M.; Ono, M.; Paoletti, F.; Paul, S.; Petravich, G.; Post-Zwicker, A.; Sauthoff, N.; Schmitz, L.; Sesnic, S.; Takahashi, H.; Talvard, M.; Tighe, W.; Tynan, G.; von Goeler, S.; Woskov, P.; Zolfaghari, A.

1995-03-01

Application of Ion Bernstein Wave Heating (IBWH) into the Princeton Beta Experiment-Modification (PBX-M) [Phys. Fluids B 2, 1271 (1990)] tokamak stabilizes sawtooth oscillations and generates peaked density profiles. A transport barrier, spatially correlated with the IBWH power deposition profile, is observed in the core of IBWH-assisted neutral beam injection (NBI) discharges. A precursor to the fully developed barrier is seen in the soft x-ray data during edge localized mode (ELM) activity. Sustained IBWH operation is conducive to a regime where the barrier supports large ∇ne, ∇Te, ∇νφ, and ∇Ti, delimiting the confinement zone. This regime is reminiscent of the H(high) mode, but with a confinement zone moved inward. The core region has better than H-mode confinement while the peripheral region is L(low)-mode-like. The peaked profile enhances NBI core deposition and increases nuclear reactivity. An increase in central Ti results from χi reduction (compared to the H mode) and better beam penetration. Bootstrap current fractions of up to 0.32-0.35 locally and 0.28 overall were obtained when an additional NBI burst is applied to this plasma.

Creating Hybrid Plasmas With Off-Axis ECCD for Radiating Divertor Studies in DIII-D

NASA Astrophysics Data System (ADS)

Petty, C. C.; Ferron, J. R.; Luce, T. C.; Osborne, T. H.; Petrie, T. W.; Turco, F.; Holcomb, C. T.; Thome, K. E.

2017-10-01

A long duration, high density, high power hybrid scenario has been developed for use in radiative divertor studies in DIII-D. Using 11.2 MW of co-NBI power and 3.4 MW of ECCD, with a total injected energy of up to 56 MJ, high performance hybrid plasmas with βN = 3.7 and H98y2 = 1.5 were created. The hybrid plasmas were fully non-inductive at densities of n 4.2 ×1019 m-3 with central ECCD, but the EC deposition needed to be moved to ρ = 0.45 to avoid the right-hand cutoff when the density was raised to n 5.8 ×1019 m-3 for radiative divertor studies. Although moving the EC deposition to ρ = 0.45 had the effect of dropping τE by 10%, the energy confinement time increased with higher density like τE n0.4, allowing high beta to be maintained. While the plasma current profile displays the usual self-organizing properties of hybrids - an anomalously broad profile with qmin >1 - local current drive can still have a measurable effect on stability, either positively or negatively. For example, hybrid discharges with radial ECH deposited at ρ = 0.45 proved to be more robustly stable to n = 1 modes (can be either a 1/1 or 2/1 mode) than similar discharges with co-ECCD at the same location. Interestingly, the large 1/1 mode had almost no effect on energy confinement but strongly degraded particle confinement; thus this mode needed to be suppressed to achieve the high pedestal densities required for radiative divertor studies. Work supported by USDOE under DE-FC02-04ER54698.

Initiation of long, free-standing z discharges by CO2 laser gas heating

NASA Astrophysics Data System (ADS)

Niemann, C.; Tauschwitz, A.; Penache, D.; Neff, S.; Knobloch, R.; Birkner, R.; Presura, R.; Hoffmann, D. H. H.; Yu, S. S.; Sharp, W. M.

2002-01-01

High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft für Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser-gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge.

Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

NASA Astrophysics Data System (ADS)

Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro

2014-12-01

Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating current (AC) power source. The plasma column extended beyond the water-cooled stainless steel electrodes and was stabilized by matching the flow speed of the turbulent air jet with the rated output power. Comprehensive investigations were performed using high-speed movies measured over the plasma column, synchronized with simultaneously recorded current and voltage waveforms. Dynamic details of the novel non-equilibrium discharge are revealed, which is characterized by a sinusoidal current waveform with amplitude stabilized at around 200 mA intermediate between thermal arc and glow discharge, shedding light to the governing mechanism of the sustained spark-suppressed AC gliding arc discharge.

Integrated fusion simulation with self-consistent core-pedestal coupling

DOE PAGES

Meneghini, O.; Snyder, P. B.; Smith, S. P.; ...

2016-04-20

In this study, accurate prediction of fusion performance in present and future tokamaks requires taking into account the strong interplay between core transport, pedestal structure, current profile and plasma equilibrium. An integrated modeling workflow capable of calculating the steady-state self- consistent solution to this strongly-coupled problem has been developed. The workflow leverages state-of-the-art components for collisional and turbulent core transport, equilibrium and pedestal stability. Validation against DIII-D discharges shows that the workflow is capable of robustly pre- dicting the kinetic profiles (electron and ion temperature and electron density) from the axis to the separatrix in good agreement with the experiments.more » An example application is presented, showing self-consistent optimization for the fusion performance of the 15 MA D-T ITER baseline scenario as functions of the pedestal density and ion effective charge Z eff.« less

Plasma Flow During RF Discharges in VASIMR

NASA Technical Reports Server (NTRS)

Jacobson, V. T.; Chang Diaz, F. R.; Squire, J. P.; Ilin, A. V.; Bengtson, R. D.; Carter, M. D.; Goulding, R. H.

1999-01-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) plasma source consists of a helical antenna, driven at frequencies of 4 to 19 MHz with powers up to 1 kW, in a magnetic field up to 3 kG. Helium is the current test gas, and future experiments with hydrogen are planned. Plasma density and temperature profiles were measured by a reciprocating Langmuir probe, and plasma flow profiles were measured with a reciprocating Mach probe. Both probes were located about 0.5 m downstream from the helical antenna. The plasma source operated in capacitive and inductive modes in addition to a helicon mode. During capacitive and inductive modes, densities were low and plasma flow was < 0.5 Cs. When the plasma operated in a helicon mode, the densities measured downstream from the source were higher [10(exp 12) / cubic cm ] and plasma flow along the magnetic field was of the order Mach 1. Details of the measurements will be shown.

Characterization of electrical discharges on Teflon dielectrics used as spacecraft thermal control

NASA Technical Reports Server (NTRS)

Yadlowsky, E. J.; Hazelton, R. C.; Churchill, R. J.

1979-01-01

The dual effects of system degradation and reduced life of synchronous-orbit satellites as a result of differential spacecraft charging underscore the need for a clearer understanding of the prevailing electrical discharge phenomena. In a laboratory simulation, the electrical discharge current, surface voltage, emitted particle fluxes, and photo-emission associated with discharge events on electron beam irradiated silver-backed Teflon samples were measured. Sample surface damage was examined with optical and electron beam microscopes. The results are suggestive of a model in which the entire sample surface is discharged by lateral sub-surface currents flowing from a charge deposition layer through a localized discharge channel to the back surface of the sample. The associated return current pulse appears to have a duration which may be a signature by which different discharge processes may be characterized.

Development of a high current 60 keV neutral lithium beam injector for beam emission spectroscopy measurements on fusion experiments.

PubMed

Anda, G; Dunai, D; Lampert, M; Krizsanóczi, T; Németh, J; Bató, S; Nam, Y U; Hu, G H; Zoletnik, S

2018-01-01

A 60 keV neutral lithium beam system was designed and built up for beam emission spectroscopy measurement of edge plasma on the KSTAR and EAST tokamaks. The electron density profile and its fluctuation can be measured using the accelerated lithium beam-based emission spectroscopy system. A thermionic ion source was developed with a SiC heater to emit around 4-5 mA ion current from a 14 mm diameter surface. The ion optic is following the 2 step design used on other devices with small modifications to reach about 2-3 cm beam diameter in the plasma at about 4 m from the ion source. A newly developed recirculating sodium vapour neutralizer neutralizes the accelerated ion beam at around 260-280 °C even during long (<20 s) discharges. A set of new beam diagnostic and manipulation techniques are applied to allow optimization, aiming, cleaning, and beam modulation. The maximum 60 keV beam energy with 4 mA ion current was successfully reached at KSTAR and at EAST. Combined with an efficient observation system, the Li-beam diagnostic enables the measurement of the density profile and fluctuations on the plasma turbulence time scale.

Development of a high current 60 keV neutral lithium beam injector for beam emission spectroscopy measurements on fusion experiments

NASA Astrophysics Data System (ADS)

Anda, G.; Dunai, D.; Lampert, M.; Krizsanóczi, T.; Németh, J.; Bató, S.; Nam, Y. U.; Hu, G. H.; Zoletnik, S.

2018-01-01

A 60 keV neutral lithium beam system was designed and built up for beam emission spectroscopy measurement of edge plasma on the KSTAR and EAST tokamaks. The electron density profile and its fluctuation can be measured using the accelerated lithium beam-based emission spectroscopy system. A thermionic ion source was developed with a SiC heater to emit around 4-5 mA ion current from a 14 mm diameter surface. The ion optic is following the 2 step design used on other devices with small modifications to reach about 2-3 cm beam diameter in the plasma at about 4 m from the ion source. A newly developed recirculating sodium vapour neutralizer neutralizes the accelerated ion beam at around 260-280 °C even during long (<20 s) discharges. A set of new beam diagnostic and manipulation techniques are applied to allow optimization, aiming, cleaning, and beam modulation. The maximum 60 keV beam energy with 4 mA ion current was successfully reached at KSTAR and at EAST. Combined with an efficient observation system, the Li-beam diagnostic enables the measurement of the density profile and fluctuations on the plasma turbulence time scale.

Effect of the collector tube profile on Pitot pump performances

NASA Astrophysics Data System (ADS)

Komaki, K.; Kanemoto, T.; Sagara, K.; Umekage, T.

2013-12-01

The pitot pump is composed of the rotating casing with the impeller channel and the pitot tube type collector as the discharge line. The radial impeller feeds water to the rotating casing. The water rotating together with the casing is caught by the stationary pitot tube type collector, and then discharges to the outside. This type pump, as the extra high head pump, is provided mainly for boiler feed systems, and has been designed by trial and error. To optimize the pump profiles, it is desirable to investigate not only performances but also internal flow conditions. This paper discusses experimentally and numerically the relation between the pump performances and the flow conditions in the rotating casing. The moderately larger dimensions of the collector make the pump head and the discharge high with the higher hydraulic efficiency. The flow in the casing is almost the forced vortex type whose velocity is in proportion to the radius but the core velocity is affected with the drag force of the stationary collector. Based upon the above results, the profile of the pitot tube type collector was optimized with the numerical simulation.

Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matlis, N. H., E-mail: nmatlis@gmail.com; Gonsalves, A. J.; Steinke, S.

We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function ofmore » the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.« less

Designable ultra-smooth ultra-thin solid-electrolyte interphases of three alkali metal anodes.

PubMed

Gu, Yu; Wang, Wei-Wei; Li, Yi-Juan; Wu, Qi-Hui; Tang, Shuai; Yan, Jia-Wei; Zheng, Ming-Sen; Wu, De-Yin; Fan, Chun-Hai; Hu, Wei-Qiang; Chen, Zhao-Bin; Fang, Yuan; Zhang, Qing-Hong; Dong, Quan-Feng; Mao, Bing-Wei

2018-04-09

Dendrite growth of alkali metal anodes limited their lifetime for charge/discharge cycling. Here, we report near-perfect anodes of lithium, sodium, and potassium metals achieved by electrochemical polishing, which removes microscopic defects and creates ultra-smooth ultra-thin solid-electrolyte interphase layers at metal surfaces for providing a homogeneous environment. Precise characterizations by AFM force probing with corroborative in-depth XPS profile analysis reveal that the ultra-smooth ultra-thin solid-electrolyte interphase can be designed to have alternating inorganic-rich and organic-rich/mixed multi-layered structure, which offers mechanical property of coupled rigidity and elasticity. The polished metal anodes exhibit significantly enhanced cycling stability, specifically the lithium anodes can cycle for over 200 times at a real current density of 2 mA cm -2 with 100% depth of discharge. Our work illustrates that an ultra-smooth ultra-thin solid-electrolyte interphase may be robust enough to suppress dendrite growth and thus serve as an initial layer for further improved protection of alkali metal anodes.

Impurity transport in enhanced confinement regimes in RFX-mod Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Carraro, Lorella; Menmuir, Sheena; Fassina, Alessandro

2010-11-01

The results of impurity transport studies in RFX-mod enhanced confinement quasi-single helicity (QSH) and single helical axis (SHAx) regimes are presented and discussed. The impurity diffusion coefficient and pinch velocity are obtained through comparing experimental emission pattern (line emission and SXR time evolutions, SXR profiles) with the results of a 1-D impurity transport code. Previous analysis [S. Menmuir et al. to be published in Plasma Phys. Contr. Fus.] of impurity transport in RFX-mod standard discharges showed that the impurity pinch velocity, always directed outwards, features a barrier with high values around r/a = 0.8, where the diffusion coefficient decreases by one order of magnitude. In the QSH regime, the transition region in D and v is more internal and the barrier in velocity is wider and stronger. New results have been obtained in experiments with Ni laser blow-off (LBO) injection in high current discharges (Ip>1.5 MA) with long lasting QSH, to better characterize the Ni behavior inside the helical magnetic topology.

The business of palliative medicine--part 4: Potential impact of an acute-care palliative medicine inpatient unit in a tertiary care cancer center.

PubMed

Walsh, Declan

2004-01-01

In this study, a hematology/oncology computerized discharge database was qualitatively and quantitatively reviewed using an empirical methodology. The goal was to identify potential patients for admission to a planned acute-care, palliative medicine inpatient unit. Patients were identified by the International Classifications of Disease (ICD-9) codes. A large heterogenous population, comprising up to 40 percent of annual discharges from the Hematology/Oncology service, was identified. If management decided to add an acute-care, palliative medicine unit to the hospital, these are the patients who would benefit. The study predicted a significant change in patient profile, acuity, complexity, and resource utilization in current palliative care services. This study technique predicted the actual clinical load of the acute-care unit when it opened and was very helpful in program development. Our model predicted that 695 patients would be admitted to the acute-care palliative medicine unit in the first year of operation; 655 patients were actually admitted during this time.

Groundwater inflow measurements in wetland systems

USGS Publications Warehouse

Hunt, Randy J.; Krabbenhoft, David P.; Anderson, Mary P.

1996-01-01

Our current understanding of wetlands is insufficient to assess the effects of past and future wetland loss. While knowledge of wetland hydrology is crucial, groundwater flows are often neglected or uncertain. In this paper, groundwater inflows were estimated in wetlands in southwestern Wisconsin using traditional Darcy's law calculations and three independent methods that included (1) stable isotope mass balances, (2) temperature profile modeling, and (3) numerical water balance modeling techniques. Inflows calculated using Darcy's law were lower than inflows estimated using the other approaches and ranged from 0.02 to 0.3 cm/d. Estimates obtained using the other methods generally were higher (0.1 to 1.1 cm/d) and showed similar spatial trends. An areal map of groundwater flux generated by the water balance model demonstrated that areas of both recharge and discharge exist in what is considered a regional discharge area. While each method has strengths and weaknesses, the use of more than one method can reduce uncertainty in the estimates.

Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment

NASA Astrophysics Data System (ADS)

Reusch, J. A.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Perry, J. M.; Pierren, C.; Rhodes, A. T.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Weberski, J. D.

2018-05-01

A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio ( R0/a ˜1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/a BT>14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ˜100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN˜7.

Sea Surface Salinity Variability in Response to the Congo River Discharge

NASA Astrophysics Data System (ADS)

Moller, D.; Chao, Y.; Farrara, J. D.; Schumann, G.; Andreadis, K.

2014-12-01

Sea surface salinity (SSS) variability associated with the Congo River discharge is examined using Aquarius satellite-retrieved SSS data and vertical profiles of salinity measured by the Argo floats. The Congo River plume can be clearly identified in the Aquarius SSS data with a westward extension of 500 to 1000 km off the coast of the Democratic Republic of Congo (DRC). The peak amplitude of the SSS variability associated with the Congo River discharge exceeds 2.0 psu. Using the first two years of Aquarius data, a well-defined seasonal cycle is described: maximum fresh-water anomalies are found in the boreal winter and spring seasons. The fresh-water anomalies during the 2012-2013 winter and spring seasons are significantly fresher than the 2011-2012 winter and spring seasons. Vertical profiles of salinity derived from the Argo floats reveal that these fresh-water anomalies can be traced to 40 meters below the sea surface. Combining the Aquarius SSS data with the Argo vertical profiles of salinity, the 3D volume of these fresh-water anomalies can be inferred and used to estimate the Congo River discharge. Reasonably good agreement is found between the Congo River discharge as observed by a stream gauge at Kinshasa and that estimated from the combined Aquarius and Argo data, indicating that Aquarius data can be used to close the fresh-water budget between the coastal ocean and the Congo River. The precipitation minus evaporation portion of the freshwater flux is found to play a secondary role in this region.

Synthesis and electrochemical properties of Li2/3Ni1/3Mn2/3O2 as a novel 5 V class positive electrode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Chiba, Kazuki; Shikano, Masahiro; Sakaebe, Hikari

2016-02-01

A lithium nickel manganese oxide, O3-Li2/3Ni1/3Mn2/3O2, is synthesized from the precursor, P3-Na2/3Ni1/3Mn2/3O2, by a Na+/Li+ ion exchange reaction using molten salt. Post-heating at 300, 400, 500, 600, and 700 °C is carried out for 5 h in air. The products are characterized by powder XRD, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), SEM, 6Li-magic-angle-spinning-NMR, and electrochemical measurements. The charge/discharge profiles of O3-Li2/3Ni1/3Mn2/3O2, thermally treated at 500 °C, show a high-potential plateau region at 4.8 V. Furthermore, sloping voltage profiles are observed at an average voltage of 3.21 V. An initial discharge capacity of 257 mA h g-1 is obtained between 2.0 and 4.8 V with a current density of 15 mA g-1 at 25 °C. This capacity corresponds to 0.90 electron transfers per formula unit. This study shows that Post-heating of O3-Li2/3Ni1/3Mn2/3O2 is effective to improve its electrochemical properties.

The 15 cm mercury ion thruster research 1975

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1975-01-01

Doubly charged ion current measurements in the beam of a SERT II thruster are shown to introduce corrections which bring its calculated thrust into close agreement with that measured during flight testing. A theoretical model of doubly charged ion production and loss in mercury electron bombardment thrusters is discussed and is shown to yield doubly-to-singly charged ion density ratios that agree with experimental measurements obtained on a 15 cm diameter thruster over a range of operating conditions. Single cusp magnetic field thruster operation is discussed and measured ion beam profiles, performance data, doubly charged ion densities, and discharge plasma characteristics are presented for a range of operating conditions and thruster geometries. Variations in the characteristics of this thruster are compared to those observed in the divergent field thruster and the cusped field thruster is shown to yield flatter ion beam profiles at about the same discharge power and propellant utilization operating point. An ion optics test program is described and the measured effects of grid system dimensions on ion beamlet half angle and diameter are examined. The effectiveness of hollow cathode startup using a thermionically emitting filament within the cathode is examined over a range of mercury flow rates and compared to results obtained with a high voltage tickler startup technique. Results of cathode plasma property measurement tests conducted within the cathode are presented.

On the shape of the glow discharge channel

NASA Astrophysics Data System (ADS)

Dmitriev, A. L.; Nikushchenko, E. M.

2017-05-01

Examples of the shapes of the glow discharge channel are presented. The discharge has been initiated in air at a pressure of 0.1 atm. The effective value and frequency of the discharge current are 30-70 mA and 50 Hz, respectively. It has been shown that, for these values of the current and pressure, thermal convection in a vacuum chamber and buoyancy (Archimedes force) are not major reasons for the specific parabolic shape of glow discharge.

Association Between Hospital Admission Risk Profile Score and Skilled Nursing or Acute Rehabilitation Facility Discharges in Hospitalized Older Adults.

PubMed

Liu, Stephen K; Montgomery, Justin; Yan, Yu; Mecchella, John N; Bartels, Stephen J; Masutani, Rebecca; Batsis, John A

2016-10-01

To evaluate whether the Hospital Admission Risk Profile (HARP) score is associated with skilled nursing or acute rehabilitation facility discharge after an acute hospitalization. Retrospective cohort study. Inpatient unit of a rural academic medical center. Hospitalized individuals aged 70 and older from October 1, 2013 to June 1, 2014. Participant age at the time of admission, modified Folstein Mini-Mental State Examination score, and self-reported instrumental activities of daily living 2 weeks before admission were used to calculate HARP score. The primary predictor was HARP score, and the primary outcome was discharge disposition (home, facility, deceased). Multivariate analysis was used to evaluate the association between HARP score and discharge disposition, adjusting for age, sex, comorbidities, and length of stay. Four hundred twenty-eight individuals admitted from home were screened and their HARP scores were categorized as low (n = 162, 37.8%), intermediate (n = 157, 36.7%), or high (n = 109, 25.5%). Participants with high HARP scores were significantly more likely to be discharged to a facility (55%) than those with low HARP scores (20%) (P < .001). After adjustment, participants with high HARP scores were more than four times as likely as those with low scores to be discharged to a facility (odds ratio = 4.58, 95% confidence interval = 2.42-8.66). In a population of older hospitalized adults, HARP score (using readily available admission information) identifies individuals at greater risk of skilled nursing or acute rehabilitation facility discharge. Early identification for potential facility discharges may allow for targeted interventions to prevent functional decline, improve informed shared decision-making about post-acute care needs, and expedite discharge planning. © 2016, Copyright the Authors Journal compilation © 2016, The American Geriatrics Society.

Machine Learning Based Diagnosis of Lithium Batteries

NASA Astrophysics Data System (ADS)

Ibe-Ekeocha, Chinemerem Christopher

The depletion of the world's current petroleum reserve, coupled with the negative effects of carbon monoxide and other harmful petrochemical by-products on the environment, is the driving force behind the movement towards renewable and sustainable energy sources. Furthermore, the growing transportation sector consumes a significant portion of the total energy used in the United States. A complete electrification of this sector would require a significant development in electric vehicles (EVs) and hybrid electric vehicles (HEVs), thus translating to a reduction in the carbon footprint. As the market for EVs and HEVs grows, their battery management systems (BMS) need to be improved accordingly. The BMS is not only responsible for optimally charging and discharging the battery, but also monitoring battery's state of charge (SOC) and state of health (SOH). SOC, similar to an energy gauge, is a representation of a battery's remaining charge level as a percentage of its total possible charge at full capacity. Similarly, SOH is a measure of deterioration of a battery; thus it is a representation of the battery's age. Both SOC and SOH are not measurable, so it is important that these quantities are estimated accurately. An inaccurate estimation could not only be inconvenient for EV consumers, but also potentially detrimental to battery's performance and life. Such estimations could be implemented either online, while battery is in use, or offline when battery is at rest. This thesis presents intelligent online SOC and SOH estimation methods using machine learning tools such as artificial neural network (ANN). ANNs are a powerful generalization tool if programmed and trained effectively. Unlike other estimation strategies, the techniques used require no battery modeling or knowledge of battery internal parameters but rather uses battery's voltage, charge/discharge current, and ambient temperature measurements to accurately estimate battery's SOC and SOH. The developed algorithms are evaluated experimentally using two different batteries namely lithium iron phosphate (LiFePO 4) and lithium titanate (LTO), both subjected to constant and dynamic current profiles. Results highlight the robustness of these algorithms to battery's nonlinear dynamic nature, hysteresis, aging, dynamic current profile, and parametric uncertainties. Consequently, these methods are susceptible and effective if incorporated with the BMS of EVs', HEVs', and other battery powered devices.

Discharge processes and an electrical model of atmospheric pressure plasma jets in argon

NASA Astrophysics Data System (ADS)

Fang, Zhi; Shao, Tao; Yang, Jing; Zhang, Cheng

2016-01-01

In this paper, an atmospheric pressure plasma discharge in argon was generated using a needle-to-ring electrode configuration driven by a sinusoidal excitation voltage. The electric discharge processes and discharge characteristics were investigated by inspecting the voltage-current waveforms, Lissajous curves and lighting emission images. The change in discharge mode with applied voltage amplitude was studied and characterised, and three modes of corona discharge, dielectric barrier discharge (DBD) and jet discharge were identified, which appeared in turn with increasing applied voltage and can be distinguished clearly from the measured voltage-current waveforms, light-emission images and the changing gradient of discharge power with applied voltage. Based on the experimental results and discharge mechanism analysis, an equivalent electrical model and the corresponding equivalent circuit for characterising the whole discharge processes accurately was proposed, and the three discharge stages were characterised separately. A voltage-controlled current source (VCCS) associated with a resistance and a capacitance were used to represent the DBD stage, and the plasma plume and corona discharge were modelled by a variable capacitor in series with a variable resistor. Other factors that can influence the discharge, such as lead and stray capacitance values of the circuit, were also considered in the proposed model. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

Simulation of the electric potential and plasma generation coupling in magnetron sputtering discharges

NASA Astrophysics Data System (ADS)

Trieschmann, Jan; Krueger, Dennis; Schmidt, Frederik; Brinkmann, Ralf Peter; Mussenbrock, Thomas

2016-09-01

Magnetron sputtering typically operated at low pressures below 1 Pa is a widely applied deposition technique. For both, high power impulse magnetron sputtering (HiPIMS) as well as direct current magnetron sputtering (dcMS) the phenomenon of rotating ionization zones (also referred to as spokes) has been observed. A distinct spatial profile of the electric potential has been associated with the latter, giving rise to low, mid, and high energy groups of ions observed at the substrate. The adherent question of which mechanism drives this process is still not fully understood. This query is approached using Monte Carlo simulations of the heavy particle (i.e., ions and neutrals) transport consistently coupled to a pre-specified electron density profile via the intrinsic electric field. The coupling between the plasma generation and the electric potential, which establishes correspondingly, is investigated. While the system is observed to strive towards quasi-neutrality, distinct mechanisms governing the shape of the electric potential profile are identified. This work is supported by the German Research Foundation (DFG) in the frame of the transregional collaborative research centre TRR 87.

Flood-inundation maps for the White River at Noblesville, Indiana

USGS Publications Warehouse

Martin, Zachary W.

2017-11-02

Digital flood-inundation maps for a 7.5-mile reach of the White River at Noblesville, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Department of Transportation. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the White River at Noblesville, Ind., streamgage (USGS station number 03349000). Real-time stages at this streamgage may be obtained from the USGS National Water Information System at https://waterdata.usgs.gov/nwis or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at the same site as the USGS streamgage (NWS site NBLI3).Flood profiles were computed for the stream reach by means of a one-dimensional, step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current (2016) stage-discharge rating at the USGS streamgage 03349000, White River at Noblesville, Ind., and documented high-water marks from the floods of September 4, 2003, and May 6, 2017. The hydraulic model was then used to compute 15 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 10.0 ft (the NWS “action stage”) to 24.0 ft, which is the highest stage interval of the current (2016) USGS stage-discharge rating curve and 2 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.98-ft vertical accuracy and 4.9-ft horizontal resolution) to delineate the area flooded at each stage.The availability of these maps, along with internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities, such as evacuations and road closures, as well as for postflood recovery efforts.

Flood-inundation maps for the Saddle River in Ho-Ho-Kus Borough, the Village of Ridgewood, and Paramus Borough, New Jersey, 2013

USGS Publications Warehouse

Watson, Kara M.; Niemoczynski, Michal J.

2014-01-01

Digital flood-inundation maps for a 5.4-mile reach of the Saddle River in New Jersey from Hollywood Avenue in Ho-Ho-Kus Borough downstream through the Village of Ridgewood and Paramus Borough to the confluence with Hohokus Brook in the Village of Ridgewood were created by the U.S. Geological Survey (USGS) in cooperation with the New Jersey Department of Environmental Protection (NJDEP). The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Saddle River at Ridgewood, New Jersey (station 01390500). Current conditions for estimating near real-time areas of inundation using USGS streamgage information may be obtained on the Internet at http://waterdata.usgs.gov/nwis/uv?site_no=01390500 or at the National Weather Services (NWS) Advanced Hydrologic Prediction Service (AHPS) at http://water.weather.gov/ahps2/hydrograph.php?wfo=okx&gage=rwdn4. In this study, flood profiles were computed for the stream reach by means of a one-dimensional step-backwater model. The model was calibrated by using the most current stage-discharge relation (March 11, 2011) at the USGS streamgage 01390500, Saddle River at Ridgewood, New Jersey. The hydraulic model was then used to compute 10 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum, North American Vertical Datum of 1988 (NAVD 88), and ranging from 5 ft, the NWS “action and minor flood stage”, to 14 ft, which is the maximum extent of the stage-discharge rating and 0.6 ft higher than the highest recorded water level at the streamgage. The simulated water-surface profiles were then combined with a geographic information system 3-meter (9.84-ft) digital elevation model derived from Light Detection and Ranging (lidar) data in order to delineate the area flooded at each water level. The availability of these maps along with information on the Internet regarding current stage from the USGS streamgage provides emergency management personnel and residents with information that is critical for flood response activities, such as evacuations and road closures as well as for post-flood recovery efforts.

Flood-inundation maps for the Wabash River at Memorial Bridge at Vincennes, Indiana

USGS Publications Warehouse

Fowler, Kathleen K.; Menke, Chad D.

2017-08-23

Digital flood-inundation maps for a 10.2-mile reach of the Wabash River from Sevenmile Island to 3.7 mile downstream of Memorial Bridge (officially known as Lincoln Memorial Bridge) at Vincennes, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at USGS streamgage 03343010, Wabash River at Memorial Bridge at Vincennes, Ind. Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site.For this study, flood profiles were computed for the Wabash River reach by means of a one-dimensional stepbackwater model. The hydraulic model was calibrated by using the most current stage-discharge relations at USGS streamgage 03343010, Wabash River at Memorial Bridge at Vincennes, Ind., and preliminary high-water marks from a high-water event on April 27, 2013. The calibrated hydraulic model was then used to determine 19 water-surface profiles for flood stages at 1-foot intervals referenced to the streamgage datum and ranging from 10 feet (ft) or near bankfull to 28 ft, the highest stage of the current stage-discharge rating curve. The simulated water-surface profiles were then combined with a Geographic Information System (GIS) digital elevation model (DEM, derived from Light Detection and Ranging [lidar] data having a 0.98-ft vertical accuracy and 4.9-ft horizontal resolution) in order to delineate the area flooded at each water level.The availability of these maps—along with Internet information regarding current stage from the USGS streamgage 03343010, and forecast stream stages from the NWS AHPS—provides emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Flood-inundation maps for the St. Joseph River at Elkhart, Indiana

USGS Publications Warehouse

Martin, Zachary W.

2017-02-01

Digital flood-inundation maps for a 6.6-mile reach of the St. Joseph River at Elkhart, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at https://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind. Real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at https://waterdata.usgs.gov/nwis or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS site EKMI3).Flood profiles were computed for the stream reach by means of a one-dimensional, step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current stage-discharge rating at the USGS streamgage 04101000, St. Joseph River at Elkhart, Ind., and the documented high-water marks from the flood of March 1982. The hydraulic model was then used to compute six water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 23.0 ft (the NWS “action stage”) to 28.0 ft, which is the highest stage interval of the current USGS stage-discharge rating curve and 1 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar] data having a 0.49-ft root mean squared error and 4.9-ft horizontal resolution, resampled to a 10-ft grid) to delineate the area flooded at each stage.The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Flood-Inundation Maps for Sugar Creek at Crawfordsville, Indiana

USGS Publications Warehouse

Martin, Zachary W.

2016-06-06

Digital flood-inundation maps for a 6.5-mile reach of Sugar Creek at Crawfordsville, Indiana, were created by the U.S. Geological Survey (USGS) in cooperation with the Indiana Office of Community and Rural Affairs. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/, depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage 03339500, Sugar Creek at Crawfordsville, Ind. Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http://water.weather.gov/ahps/, which also forecasts flood hydrographs at this site (NWS site CRWI3).Flood profiles were computed for the USGS streamgage 03339500, Sugar Creek at Crawfordsville, Ind., reach by means of a one-dimensional step-backwater hydraulic modeling software developed by the U.S. Army Corps of Engineers. The hydraulic model was calibrated using the current stage-discharge rating at the USGS streamgage 03339500, Sugar Creek at Crawfordsville, Ind., and high-water marks from the flood of April 19, 2013, which reached a stage of 15.3 feet. The hydraulic model was then used to compute 13 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum ranging from 4.0 ft (the NWS “action stage”) to 16.0 ft, which is the highest stage interval of the current USGS stage-discharge rating curve and 2 ft higher than the NWS “major flood stage.” The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging [lidar]) data having a 0.49-ft root mean squared error and 4.9-ft horizontal resolution) to delineate the area flooded at each stage.The availability of these maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for post-flood recovery efforts.

Flood profiles for lower Brooker Creek, west-central Florida

USGS Publications Warehouse

Murphy, W.R.

1978-01-01

Flood heights are computed for a range of recurrence intervals for a 12.6 mile reach of Brooker Creek, beginning at the mouth at Lake Tarpon. A Geological Survey step-backwater computer program, E431, was used in these analyses using: (1) Stream and valley cross-section geometry and roughness data; (2) Recurrence interval flood-peak discharges; (3) Recurrence interval starting elevations; (4) Gaging station stage-discharge relations. Flood heights may be plotted versus distance above stream mouth and connected to construct flood profiles. They may also be used to indicate areas of inundation on detailed topographic maps.

Sediment Characteristics and Transport in the Kootenai River White Sturgeon Critical Habitat near Bonners Ferry, Idaho

USGS Publications Warehouse

Fosness, Ryan L.; Williams, Marshall L.

2009-01-01

Recovery efforts for the endangered Kootenai River population of white sturgeon require an understanding of the characteristics and transport of suspended and bedload sediment in the critical habitat reach of the river. In 2007 and 2008, the U.S. Geological Survey in cooperation with the Kootenai Tribe of Idaho, conducted suspended- and bedload-sediment sampling in the federally designated critical habitat of the endangered Kootenai River white sturgeon population. Three sediment-sampling sites were selected that represent the hydraulic differences in the critical habitat. Suspended- and bedload-sediment samples along with acoustic Doppler current profiles were collected at these sites during specific river discharges. Samples were analyzed to determine suspended- and bedload-sediment characteristics and transport rates. Sediment transport data were analyzed to provide total loading estimates for suspended and bedload sediment in the critical habitat reach. Total suspended-sediment discharge primarily occurred as fine material that moved through the system in suspension. Total suspended-sediment discharge ranged from about 300 metric tons per day to more than 23,000 metric tons per day. Total suspended sediment remained nearly equal throughout the critical habitat, with the exception of a few cases where mass wasting of the banks may have caused sporadic spikes in total suspended sediment. Bedload-sediment discharge averaged 0-3 percent of the total loading. These bedload discharges ranged from 0 to 271 tons per day. The bedload discharge in the upper part of the critical habitat primarily consisted of fine to coarse gravel. A decrease in river competence in addition to an armored channel may be the cause of this limited bedload discharge. The bedload discharge in the middle part of the white sturgeon critical habitat varied greatly, depending on the extent of the backwater from Kootenay Lake. A large quantity of fine-to-coarse gravel is present in the braided reach, but the duration of transport for these gravels is limited by the encroaching backwater of Kootenay Lake. Bedload discharge in the lower part of the white sturgeon critical habitat primarily consisted of fine to coarse sand due to decreased velocities as a result of the backwater from Kootenay Lake.

Production of atmospheric-pressure glow discharge in nitrogen using needle-array electrode

NASA Astrophysics Data System (ADS)

Takaki, K.; Hosokawa, M.; Sasaki, T.; Mukaigawa, S.; Fujiwara, T.

2005-04-01

An atmospheric pressure glow discharge was generated using a needle-array electrode in nitrogen, and the voltage-current characteristics of the glow discharge were obtained in a range from 1 mA to 60 A. A pulsed high voltage with short rise time under 10 ns was employed to generate streamer discharges simultaneously at all needle tips. The large number of streamer discharges prevented the glow-to-arc transition caused by inhomogeneous thermalization. Semiconductor opening switch diodes were employed as an opening switch to shorten the rise time. The glow voltage was almost constant until the discharge current became 0.3 A, whereas the voltage increased with the current higher than 0.3 A. Electron density and temperature in a positive column of the glow discharge at 60 A were obtained to 1.4×1012cm-3 and 1.3 eV from calculation based on nitrogen swarm data.

Groundwater and surface-water interactions and impacts of human activities in the Hailiutu catchment, northwest China

NASA Astrophysics Data System (ADS)

Yang, Zhi; Zhou, Yangxiao; Wenninger, Jochen; Uhlenbrook, Stefan; Wang, Xusheng; Wan, Li

2017-08-01

The interactions between groundwater and surface water have been significantly affected by human activities in the semi-arid Hailiutu catchment, northwest China. Several methods were used to investigate the spatial and temporal interactions between groundwater and surface water. Isotopic and chemical analyses of water samples determined that groundwater discharges to the Hailiutu River, and mass balance equations were employed to estimate groundwater seepage rates along the river using chemical profiles. The hydrograph separation method was used to estimate temporal variations of groundwater discharges to the river. A numerical groundwater model was constructed to simulate groundwater discharges along the river and to analyze effects of water use in the catchment. The simulated seepage rates along the river compare reasonably well with the seepage estimates derived from a chemical profile in 2012. The impacts of human activities (river-water diversion and groundwater abstraction) on the river discharge were analyzed by calculating the differences between the simulated natural groundwater discharge and the measured river discharge. Water use associated with the Hailiutu River increased from 1986 to 1991, reached its highest level from 1992 to 2000, and decreased from 2001 onwards. The reduction of river discharge might have negative impacts on the riparian ecosystem and the water availability for downstream users. The interactions between groundwater and surface water as well as the consequences of human activities should be taken into account when implementing sustainable water resources management in the Hailiutu catchment.

Enhanced submarine ground water discharge form mixing of pore water and estuarine water

USGS Publications Warehouse

Martin, Jonathan B.; Cable, Jaye E.; Swarzenski, Peter W.; Lindenberg, Mary K.

2004-01-01

Submarine ground water discharge is suggested to be an important pathway for contaminants from continents to coastal zones, but its significance depends on the volume of water and concentrations of contaminants that originate in continental aquifers. Ground water discharge to the Banana River Lagoon, Florida, was estimated by analyzing the temporal and spatial variations of Cl− concentration profiles in the upper 230 cm of pore waters and was measured directly by seepage meters. Total submarine ground water discharge consists of slow discharge at depths > ∼70 cm below seafloor (cmbsf) of largely marine water combined with rapid discharge of mixed pore water and estuarine water above ∼70 cmbsf. Cl− profiles indicate average linear velocities of ∼0.014 cm/d at depths > ∼70 cmbsf. In contrast, seepage meters indicate water discharges across the sediment-water interface at rates between 3.6 and 6.9 cm/d. The discrepancy appears to be caused by mixing in the shallow sediment, which may result from a combination of bioirrigation, wave and tidal pumping, and convection. Wave and tidal pumping and convection would be minor because the tidal range is small, the short fetch of the lagoon limits wave heights, and large density contacts are lacking between lagoon and pore water. Mixing occurs to ∼70 cmbsf, which represents depths greater than previously reported. Mixing of oxygenated water to these depths could be important for remineralization of organic matter.

Experimental study of low-temperature plasma of electrical discharges with liquid electrodes

NASA Astrophysics Data System (ADS)

Zheltukhin, Viktor; Gaisin, Almaz

2016-09-01

Results of the experimental research of discharge between the liquid jet cathode (LJC) and the metal anode are presented. The discharge was studied over the voltage range U = 100 - 600 V, discharge current range I = 0 . 1 - 0 . 25 A, external pressure range P =105 Pa, discharge power Pd = 10 - 150 W. We used the techniques of infrared thermography and spectral measurements. Schlieren's photography is applied for describing the processes in liquid and gas phase. Results of the experimental researches of discharge current-voltage characteristic (CVC), the surface temperature distribution both on the LJC and the metal anode, a spectral measurements are showed. Effects of action both of breakdown and discharge on the jet flow as well as on the air flow near the discharge are described. It is found that the discharge CVC has an ascending behavior due to increase of plasma current density. The discharge is generated on the borders between the LJC and the metal anode as well as along the LJC misshaping this one. It is established that both the convection streams and an electrolyte drops are formed during the discharge burn. It is found that the discharge temperature in the vicinity of electrode surface reaches T 348 K. The work was funded by RFBR, according to the research projects No.,14-01-0755.

Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Jiang, Weiman; Wang, Yishan

2015-08-24

A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

Integrating unmanned aerial systems and LSPIV for rapid, cost-effective stream gauging

NASA Astrophysics Data System (ADS)

Lewis, Quinn W.; Lindroth, Evan M.; Rhoads, Bruce L.

2018-05-01

Quantifying flow in rivers is fundamental to assessments of water supply, water quality, ecological conditions, hydrological responses to storm events, and geomorphological processes. Image-based surface velocity measurements have shown promise in extending the range of discharge conditions that can be measured in the field. The use of Unmanned Aerial Systems (UAS) in image-based measurements of surface velocities has the potential to expand applications of this method. Thus far, few investigations have assessed this potential by evaluating the accuracy and repeatability of discharge measurements using surface velocities obtained from UAS. This study uses large-scale particle image velocimetry (LSPIV) derived from videos captured by cameras on a UAS and a fixed tripod to obtain discharge measurements at ten different stream locations in Illinois, USA. Discharge values are compared to reference values measured by an acoustic Doppler current profiler, a propeller meter, and established stream gauges. The results demonstrate the effects of UAS flight height, camera steadiness and leveling accuracy, video sampling frequency, and LSPIV interrogation area size on surface velocities, and show that the mean difference between fixed and UAS cameras is less than 10%. Differences between LSPIV-derived and reference discharge values are generally less than 20%, not systematically low or high, and not related to site parameters like channel width or depth, indicating that results are relatively insensitive to camera setup and image processing parameters typically required of LSPIV. The results also show that standard velocity indices (between 0.85 and 0.9) recommended for converting surface velocities to depth-averaged velocities yield reasonable discharge estimates, but are best calibrated at specific sites. The study recommends a basic methodology for LSPIV discharge measurements using UAS that is rapid, cost-efficient, and does not require major preparatory work at a measurement location, pre- and post-processing of imagery, or extensive background in image analysis and PIV.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korolev, Yu. D.; Landl, N. V., E-mail: landl@lnp.hcei.tsc.ru; Geyman, V. G.

Results from studies of a low-current glow discharge with a hollow cathode are presented. A specific feature of the discharge conditions was that a highly emissive tablet containing cesium carbonate was placed in the cathode cavity. In the absence of a tablet, the discharge ignition voltage was typically ≥3.5 kV, while the burning voltage was in the range of 500–600 V. The use of the tablet made it possible to decrease the ignition voltage to 280 V and maintain the discharge burning voltage at a level of about 130 V. A model of the current sustainment in a hollow-cathode dischargemore » is proposed. Instead of the conventional secondary emission yield, the model uses a generalized emission yield that takes into account not only ion bombardment of the cathode, but also the emission current from an external source. The model is used to interpret the observed current−voltage characteristics. The results of calculations agree well with the experimental data. It is shown that, in some discharge modes, the external emission current from the cathode can reach 25% of the total discharge current.« less

Development of V2G and G2V Power Profiles and Their Implications on Grid Under Varying Equilibrium of Aggregated Electric Vehicles

NASA Astrophysics Data System (ADS)

Jain, Prateek; Jain, Trapti

2016-04-01

The objective of this paper is to examine the vehicle-to-grid (V2G) power capability of aggregated electric vehicles (EV) in the manner that they are being adopted by the consumers with their growing infiltration in the vehicles market. The proposed modeling of V2G and grid-to-vehicle (G2V) energy profiles blends the heterogeneous attributes namely, driven mileages, arrival and departure times, travel and parking durations, and speed dependent energy consumption of mobility trends. Three penetration percentages of 25 %, 50 % and 100 % resulting in varied compositions of battery electric vehicle (BEV) and plug-in hybrid electric vehicle (PHEV) in the system, as determined by the consumers' acceptance, have been considered to evaluate the grid capacity for V2G. Distinct charge-discharge powers have been selected as per charging standards to match contemporary vehicles and infrastructure requirements. Charging and discharging approaches have been devised to replicate non-linear characteristics of Li-ion battery. Effects of simultaneous conjunction of V2G and G2V power curves with daily conventional load profile are quantified drawn upon workplace-discharging home-charging scheme. Results demonstrated a marked drop in load and hence in market price during morning hours which is hurriedly overcompensated by the hike during evening hours with rising penetration level and charge-discharge power.

Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Peterson, Peter Y.; Williams, George J.; Gilland, James; Hofer, Richard; Mikellides, Ioannis

2016-01-01

NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front magnetic pole cover thruster configuration with the thruster body electrically tied to cathode, and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68% and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the discharge current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability were mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 1×10-5 Torr-Xe (for thruster flow rates of 20.5 mg/s). Power spectral density analysis of the discharge current waveforms showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant breathing mode frequency. Finally, IVB maps of the TDU-1 thruster indicated that the discharge current became more oscillatory with higher discharge current peak-to-peak and RMS values with increased facility background pressure at lower thruster mass flow rates; thruster operation at higher flow rates resulted in less change to the thruster's IVB characteristics with elevated background pressure.

NEXT Ion Thruster Thermal Model

NASA Technical Reports Server (NTRS)

VanNoord, Jonathan L.

2010-01-01

As the NEXT ion thruster progresses towards higher technology readiness, it is necessary to develop the tools that will support its implementation into flight programs. An ion thruster thermal model has been developed for the latest prototype model design to aid in predicting thruster temperatures for various missions. This model is comprised of two parts. The first part predicts the heating from the discharge plasma for various throttling points based on a discharge chamber plasma model. This model shows, as expected, that the internal heating is strongly correlated with the discharge power. Typically, the internal plasma heating increases with beam current and decreases slightly with beam voltage. The second is a model based on a finite difference thermal code used to predict the thruster temperatures. Both parts of the model will be described in this paper. This model has been correlated with a thermal development test on the NEXT Prototype Model 1 thruster with most predicted component temperatures within 5 to 10 C of test temperatures. The model indicates that heating, and hence current collection, is not based purely on the footprint of the magnet rings, but follows a 0.1:1:2:1 ratio for the cathode-to-conical-to-cylindrical-to-front magnet rings. This thermal model has also been used to predict the temperatures during the worst case mission profile that is anticipated for the thruster. The model predicts ample thermal margin for all of its components except the external cable harness under the hottest anticipated mission scenario. The external cable harness will be re-rated or replaced to meet the predicted environment.

The association of military discharge variables with smoking status among homeless Veterans.

PubMed

Hammett, Patrick; Fu, Steven S; Lando, Harry A; Owen, Greg; Okuyemi, Kolawale S

2015-12-01

There is a dearth of research examining the health correlates of tobacco use within the homeless population, particularly with respect to homeless Veterans. An aim of the present study was to compare homeless Veteran and homeless non-Veteran smokers across a series of socio-demographic and health variables, and to determine whether any of these variables were independently associated with Veteran status. A subsequent aim was to compare the socio-demographic and health profiles of Veteran smokers and Veteran nonsmokers, and to determine whether any of these variables were independently associated with current smoking. Data were obtained from the 2009 Homelessness in Minnesota survey conducted by the Wilder Research Foundation. The final sample included 4750 homeless individuals living throughout Minnesota. The prevalence of smoking was greater among homeless Veterans (74%) than homeless non-Veterans (70%). The prevalence of physical and mental health problems was higher among homeless Veteran smokers than homeless non-Veteran smokers, although these variables were not independently associated with Veteran status after controlling for socio-demographics. Analyses of the homeless Veteran sample indicated that receipt of Veterans' benefits, type of discharge, and alcohol and/or chemical dependence were independently associated with current smoking. Homeless Veteran smokers exhibit heightened rates of physical and mental health problems compared to homeless non-Veteran smokers. Military service and discharge characteristics may contribute to this high smoking prevalence. Future efforts should focus on increasing Veterans' access to and knowledge of Veterans' health resources, and on developing innovative strategies to boost cessation in this population. Copyright © 2015 Elsevier Inc. All rights reserved.

Nanoscale discharge electrode for minimizing ozone emission from indoor corona devices.

PubMed

Bo, Zheng; Yu, Kehan; Lu, Ganhua; Mao, Shun; Chen, Junhong; Fan, Fa-Gung

2010-08-15

Ground-level ozone emitted from indoor corona devices poses serious health risks to the human respiratory system and the lung function. Federal regulations call for effective techniques to minimize the indoor ozone production. In this work, stable atmospheric corona discharges from nanomaterials are demonstrated using horizontally suspended carbon nanotubes (CNTs) as the discharge electrode. Compared with the conventional discharges employing micro- or macroscale electrodes, the corona discharge from CNTs could initiate and operate at a much lower voltage due to the small electrode diameter, and is thus energy-efficient. Most importantly, the reported discharge is environmentally friendly since no ozone (below the detection limit of 0.5 ppb) was detected for area current densities up to 0.744 A/m(2) due to the significantly reduced number of electrons and plasma volume generated by CNT discharges. The resulting discharge current density depends on the CNT loading. Contrary to the conventional wisdom, negative CNT discharges should be used to enhance the current density owing to the efficient field emission of electrons from the CNT surface.

Surveys of water velocities in the vicinity of the discharge-release gates of Salamonie Lake Dam, northeastern Indiana, spring and winter 1998

USGS Publications Warehouse

Morlock, Scott E.; Stewart, James A.

2000-01-01

An acoustic Doppler current profiler (ADCP) mounted on a boat was used to collect velocity and depth data and to compute positions of the velocity and depth data relative to the boat track. A global positioning system (GPS) was used to collect earth-referenced position data, and a GPS base station receiver was used to improve the accuracy of the earth-referenced position data. The earth-referenced position data were used to transform the ADCP-computed positions (which were relative to boat tracks) to positions referenced to a point on the spillway tower.

Current Density Measurements of an Annular-Geometry Ion Engine

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

2012-01-01

The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential nonuniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to 10% of the average current density in the discharge and 5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

Current Density Measurements of an Annular-Geometry Ion Engine

NASA Technical Reports Server (NTRS)

Shastry, Rohit; Patterson, Michael J.; Herman, Daniel A.; Foster, John E.

2012-01-01

The concept of the annular-geometry ion engine, or AGI-Engine, has been shown to have many potential benefits when scaling electric propulsion technologies to higher power. However, the necessary asymmetric location of the discharge cathode away from thruster centerline could potentially lead to non-uniformities in the discharge not present in conventional geometry ion thrusters. In an effort to characterize the degree of this potential non-uniformity, a number of current density measurements were taken on a breadboard AGI-Engine. Fourteen button probes were used to measure the ion current density of the discharge along a perforated electrode that replaced the ion optics during conditions of simulated beam extraction. Three Faraday probes spaced apart in the vertical direction were also used in a separate test to interrogate the plume of the AGI-Engine during true beam extraction. It was determined that both the discharge and the plume of the AGI-Engine are highly uniform, with variations under most conditions limited to +/-10% of the average current density in the discharge and +/-5% of the average current density in the plume. Beam flatness parameter measured 30 mm from the ion optics ranged from 0.85 - 0.95, and overall uniformity was shown to generally increase with increasing discharge and beam currents. These measurements indicate that the plasma is highly uniform despite the asymmetric location of the discharge cathode.

Study of the homogeneity of the current distribution in a dielectric barrier discharge in air by means of a segmented electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malashin, M. V., E-mail: m-malashin@mail.ru; Moshkunov, S. I.; Khomich, V. Yu.

2016-02-15

The current distribution in a dielectric barrier discharge in atmospheric-pressure air at a natural humidity of 40–60% was studied experimentally with a time resolution of 200 ps. The experimental results are interpreted by means of numerically simulating the discharge electric circuit. The obtained results indicate that the discharge operating in the volumetric mode develops simultaneously over the entire transverse cross section of the discharge gap.

Dynamics of laser-guided alternating current high voltage discharges

NASA Astrophysics Data System (ADS)

Daigle, J.-F.; Théberge, F.; Lassonde, P.; Kieffer, J.-C.; Fujii, T.; Fortin, J.; Châteauneuf, M.; Dubois, J.

2013-10-01

The dynamics of laser-guided alternating current high voltage discharges are characterized using a streak camera. Laser filaments were used to trigger and guide the discharges produced by a commercial Tesla coil. The streaking images revealed that the dynamics of the guided alternating current high voltage corona are different from that of a direct current source. The measured effective corona velocity and the absence of leader streamers confirmed that it evolves in a pure leader regime.

Steady-state sustainment of high-β plasmas through stability control in Japan Atomic Energy Research Institute Tokamak-60 Upgradea)

NASA Astrophysics Data System (ADS)

Isayama, A.

2005-05-01

Recent results from steady-state sustainment of high-β plasma experiments in the Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U) tokamak [A. Kitsunezaki et al., Fusion Sci. Technol. 42, 179 (2002)] are described. Extension of discharge duration to 65s (formerly 15s) has enabled physics research with long time scale. In long-duration high-β research, the normalized beta βN=2.5, which is comparable to that in the steady-state operation in International Thermonuclear Experimental Reactor (ITER) [R. Aymar, P. Barabaschi, and Y. Shimomura, Plasma Phys. Controlled Fusion 44, 519 (2002)], has been sustained for about 15s with confinement enhancement factor H89PL above 2, where the duration is about 80 times energy confinement time and ˜10 times current diffusion time (τR). In the scenario aiming at longer duration with βN˜1.9, which is comparable to that in the ITER standard operation scenario, duration has been extended to 24s (˜15τR). Also, from the viewpoint of collisionality and Larmor radius of the plasmas, these results are obtained in the ITER-relevant regime with a few times larger than the ITER values. No serious effect of current diffusion on instabilities is observed in the region of βN≲2.5, and in fact neoclassical tearing modes (NTMs), which limit the achievable β in the stationary high-βp H-mode discharges, are suppressed throughout the discharge. In high-β research with the duration of several times τR, a high-β plasma with βN˜2.9-3 has been sustained for 5-6s with two scenarios for NTM suppression: (a) NTM avoidance by modification of pressure and current profiles, and (b) NTM stabilization with electron cyclotron current drive (ECCD)/electron cyclotron heating (ECH). NTM stabilization with the second harmonic X-mode ECCD/ECH has been performed, and it is found that EC current density comparable to bootstrap current density at the mode location is required for complete stabilization. Structure of a magnetic island associated with an m /n=3/2 NTM has been measured in detail (m and n are poloidal and toroidal mode numbers, respectively). By applying newly developed analysis method using motional Stark effect (MSE) diagnostic, where change in current density is directly evaluated from change in MSE pitch angle without equilibrium reconstruction, localized decrease/increase in current density at the mode rational surface is observed for NTM growth/suppression. In addition, it is found that characteristic structure of electron temperature perturbation profile is deformed during NTM stabilization. Hypothesis that temperature increase inside the magnetic island well explains the experimental observations. It is also found that the characteristic structure is not formed for the case of ECCD/ECH before the mode, while the structure is seen for the case with ECCD/ECH just after the mode onset, suggesting the stronger stabilization effect of the early EC wave injection.

On the road to self-sputtering in high power impulse magnetron sputtering: particle balance and discharge characteristics

NASA Astrophysics Data System (ADS)

Huo, Chunqing; Lundin, Daniel; Raadu, Michael A.; Anders, André; Tomas Gudmundsson, Jon; Brenning, Nils

2014-04-01

The onset and development of self-sputtering (SS) in a high power impulse magnetron sputtering (HiPIMS) discharge have been studied using a plasma chemical model and a set of experimental data, taken with an aluminum target and argon gas. The model is tailored to duplicate the discharge in which the data are taken. The pulses are long enough to include both an initial transient and a following steady state. The model is used to unravel how the internal discharge physics evolves with pulse power and time, and how it is related to features in the discharge current-voltage-time characteristics such as current densities, maxima, kinks and slopes. The connection between the self-sputter process and the discharge characteristics is quantified and discussed in terms of three parameters: a critical target current density Jcrit based on the maximum refill rate of process (argon) gas above the target, an SS recycling factor ΠSS-recycle, and an approximation \\tilde{\\alpha} of the probabilities of ionization of species that come from the target (both sputtered metal and embedded argon atoms). For low power pulses, discharge voltages UD ⩽ 380 V with peak current densities below ≈ 0.2 A cm-2, the discharge is found to be dominated by process gas sputtering. In these pulses there is an initial current peak in time, associated with partial gas rarefaction, which is followed by a steady-state-like plateau in all parameters similar to direct current magnetron sputtering. In contrast, high power pulses, with UD ⩾ 500 V and peak current densities above JD ≈ 1.6 A cm-2, make a transition to a discharge mode where SS dominates. The transition is found not to be driven by process gas rarefaction which is only about 10% at this time. Maximum gas rarefaction is found later in time and always after the initial peak in the discharge current. With increasing voltage, and pulse power, the discharge can be described as following a route where the role of SS increases in four steps: process gas sputtering, gas-sustained SS, self-sustained SS and SS runaway. At the highest voltage, 1000 V, the discharge is very close to, but does not go into, the SS runaway mode. This absence of runaway is proposed to be connected to an unexpected finding: that twice ionized ions of the target species play almost no role in this discharge, not even at the highest powers. This reduces ionization by secondary-emitted energetic electrons almost to zero in the highest power range of the discharge.

Electric characteristics of a surface barrier discharge with a plasma induction electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alemskii, I. N.; Lelevkin, V. M.; Tokarev, A. V.

2006-07-15

Static and dynamic current-voltage and charge-voltage characteristics of a surface barrier discharge with a plasma induction electrode have been investigated experimentally. The dependences of the discharge current on both the gas pressure in the induction electrode tube and the winding pitch of the corona electrode, as well as of the discharge power efficiency on the applied voltage, have been measured.

Influence of Sample Size of Polymer Materials on Aging Characteristics in the Salt Fog Test

NASA Astrophysics Data System (ADS)

Otsubo, Masahisa; Anami, Naoya; Yamashita, Seiji; Honda, Chikahisa; Takenouchi, Osamu; Hashimoto, Yousuke

Polymer insulators have been used in worldwide because of some superior properties; light weight, high mechanical strength, good hydrophobicity etc., as compared with porcelain insulators. In this paper, effect of sample size on the aging characteristics in the salt fog test is examined. Leakage current was measured by using 100 MHz AD board or 100 MHz digital oscilloscope and separated three components as conductive current, corona discharge current and dry band arc discharge current by using FFT and the current differential method newly proposed. Each component cumulative charge was estimated automatically by a personal computer. As the results, when the sample size increased under the same average applied electric field, the peak values of leakage current and each component current increased. Especially, the cumulative charges and the arc discharge length of dry band arc discharge increased remarkably with the increase of gap length.

Collisional radiative model of an argon atmospheric capillary surface-wave discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanguas-Gil, A.; Cotrino, J.; Gonzalez-Elipe, A.R.

2004-12-01

The characteristics of a microwave surface-wave sustained plasma operated at atmospheric pressure in an open-ended dielectric tube are investigated theoretically as a first step in the development of a self-consistent model for these discharges. The plasma column is sustained in flowing argon. A surface-wave discharge that fills the whole radial cross section of the discharge tube is considered. With experimental electron temperature profiles [Garcia et al., Spectrochim. Acta, Part B 55, 1733 (2000)] the numerical model is used to test the validity of the different approximations and to study the influence of the different kinetic processes and power loss mechanismsmore » on the discharge.« less

On transition from diffuse mode to the constricted one with high-current cathode spot in overvoltage open discharge in D2

NASA Astrophysics Data System (ADS)

Akishev, Yu S.; Karalnik, V. B.; Medvedev, M. A.; Petryakov, A. V.; Trushkin, N. I.; Shafikov, A. G.

2017-11-01

So called “open discharges” in a narrow gap between the solid cathode and grid anode are widely used for generation of the pulsed high-current electron beams with energy up to 100 keV. The need to get high-energy e-beams leads to the necessity in using of strong overvoltage of the short gas gap with the reduced electric field of the order of 105 Td or higher. The discharge under strong overvoltage is unstable and tends to transit into high-current regime with low voltage. In the case of the open discharge in D2 at low pressure (about 0.5-2 Torr) and powered by stepwise voltage with amplitude up to 25 kV we revealed that this discharge exhibits two diffuse regimes which follow one by one and finally transits into the constricted mode with formation of high-current spots on the cathode. The physical properties of these gas discharge regimes have been explored in detail with the usage of the fast multi-frame camera synchronized with the current and voltage of discharge. Our findings promote more insight into physics of the overvoltage open discharge generating the e-beams with energy up to 25 keV.

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study.

PubMed

Shifman, Aaron R; Longtin, André; Lewis, John E

2015-10-30

Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways.

Effect of Pulsed Plasma Jets on the Recovering Boundary Layer Downstream of a Reflected Shock Interaction

NASA Astrophysics Data System (ADS)

Greene, Benton; Clemens, Noel; Magari, Patrick; Micka, Daniel; Ueckermann, Mattheus

2015-11-01

Shock-induced turbulent boundary layer separation can have many detrimental effects in supersonic inlets including flow distortion and instability, structural fatigue, poor pressure recovery, and unstart. The current study investigates the effect of pulsed plasma jets on the recovering boundary layer downstream of a reflected shock wave-boundary layer interaction. The effects of pitch and skew angle of the jet as well as the heating parameter and discharge time scale are tested using several pulsing frequencies. In addition, the effect of the plasma jets on the undisturbed boundary layer at 6 mm and 11 mm downstream of the jets is measured. A pitot-static pressure probe is used to measure the velocity profile of the boundary layer 35 mm downstream of the plasma jets, and the degree of boundary layer distortion is compared between the different models and run conditions. Additionally, the effect of each actuator configuration on the shape of the mean separated region is investigated using surface oil flow visualization. Previous studies with lower energy showed a weak effect on the downstream boundary layer. The current investigation will attempt to increase this effect using a higher-energy discharge. Funded by AFRL through and SBIR in collaboration with Creare, LLC.

Ultrafast traveling wave dominates the electric organ discharge of Apteronotus leptorhynchus: an inverse modelling study

PubMed Central

Shifman, Aaron R.; Longtin, André; Lewis, John E.

2015-01-01

Identifying and understanding the current sources that give rise to bioelectric fields is a fundamental problem in the biological sciences. It is very difficult, for example, to attribute the time-varying features of an electroencephalogram recorded from the head surface to the neural activity of specific brain areas; model systems can provide important insight into such problems. Some species of fish actively generate an oscillating (c. 1000 Hz) quasi-dipole electric field to communicate and sense their environment in the dark. A specialized electric organ comprises neuron-like cells whose collective signal underlies this electric field. As a step towards understanding the detailed biophysics of signal generation in these fish, we use an anatomically-detailed finite-element modelling approach to reverse-engineer the electric organ signal over one oscillation cycle. We find that the spatiotemporal profile of current along the electric organ constitutes a travelling wave that is well-described by two spatial Fourier components varying in time. The conduction velocity of this wave is faster than action potential conduction in any known neuronal axon (>200 m/s), suggesting that the spatiotemporal features of high-frequency electric organ discharges are not constrained by the conduction velocities of spinal neuron pathways. PMID:26514932

History dependence of human muscle-fiber conduction velocity during voluntary isometric contractions.

PubMed

McGill, Kevin C; Lateva, Zoia C

2011-09-01

The conduction velocity (CV) of a muscle fiber is affected by the fiber's discharge history going back ∼1 s. We investigated this dependence by measuring CV fluctuations during voluntary isometric contractions of the human brachioradialis muscle. We recorded electromyogram (EMG) signals simultaneously from multiple intramuscular electrodes, identified potentials belonging to the same motor unit using EMG decomposition, and estimated the CV of each discharge from the interpotential interval. In 12 of 14 subjects, CV increased by ∼10% during the first second after recruitment and then fluctuated by about ±2% in a way that mirrored the fluctuations in the instantaneous firing rate. The CV profile could be precisely described in terms of the discharge history by a simple mathematical model. In the other two subjects, and one subject retested after cooling the arm, the CV fluctuations were inversely correlated with instantaneous firing rate. In all subjects, CV was additionally affected by very short interdischarge intervals (<25 ms): it was increased in doublets at recruitment, but decreased in doublets during continuous firing and after short interdischarge intervals in doubly innervated fibers. CV also exhibited a slow trend of about -0.05%/s that did not depend on the immediate discharge history. We suggest that measurements of CV fluctuations during voluntary contractions, or during stimulation protocols that involve longer and more complex stimulation patterns than are currently being used, may provide a sensitive approach for estimating the dynamic characteristics of ion channels in the human muscle-fiber membrane.

History dependence of human muscle-fiber conduction velocity during voluntary isometric contractions

PubMed Central

Lateva, Zoia C.

2011-01-01

The conduction velocity (CV) of a muscle fiber is affected by the fiber's discharge history going back ∼1 s. We investigated this dependence by measuring CV fluctuations during voluntary isometric contractions of the human brachioradialis muscle. We recorded electromyogram (EMG) signals simultaneously from multiple intramuscular electrodes, identified potentials belonging to the same motor unit using EMG decomposition, and estimated the CV of each discharge from the interpotential interval. In 12 of 14 subjects, CV increased by ∼10% during the first second after recruitment and then fluctuated by about ±2% in a way that mirrored the fluctuations in the instantaneous firing rate. The CV profile could be precisely described in terms of the discharge history by a simple mathematical model. In the other two subjects, and one subject retested after cooling the arm, the CV fluctuations were inversely correlated with instantaneous firing rate. In all subjects, CV was additionally affected by very short interdischarge intervals (<25 ms): it was increased in doublets at recruitment, but decreased in doublets during continuous firing and after short interdischarge intervals in doubly innervated fibers. CV also exhibited a slow trend of about −0.05%/s that did not depend on the immediate discharge history. We suggest that measurements of CV fluctuations during voluntary contractions, or during stimulation protocols that involve longer and more complex stimulation patterns than are currently being used, may provide a sensitive approach for estimating the dynamic characteristics of ion channels in the human muscle-fiber membrane. PMID:21565985

Experimental investigation on a vectorized aerodynamic dielectric barrier discharge plasma actuator array

NASA Astrophysics Data System (ADS)

Neretti, Gabriele; Cristofolini, Andrea; Borghi, Carlo A.

2014-04-01

The Electro-Hydro-Dynamics (EHD) interaction, induced in atmospheric pressure still air by a surface dielectric barrier discharge (DBD) actuator, had been experimentally studied. A plasma aerodynamic actuator array, able to produce a vectorized jet, with the induced airflow oriented toward the desired direction, had been developed. The array was constituted by a sequence of single surface DBD actuators with kapton as dielectric material. An ac voltage in the range of 0-6 kV peak at 15 kHz had been used. The vectorization had been obtained by feeding the upper electrodes with different voltages and by varying the electrical connections. The lower electrodes had been connected either to ground or to the high voltage source, to produce the desired jet orientation and to avoid plasma formation acting in an undesired direction. Voltage and current measurements had been carried out to evaluate waveforms and to estimate the active power delivered to the discharge. Schlieren imaging allowed to visualize the induced jet and to estimate its orientation. Pitot measurements had been performed to obtain velocity profiles for all jet configurations. A proportional relation between the jet deflection angle and the applied voltage had been found. Moreover, a linear relation had been obtained between the maximum speed in the jet direction and the applied voltage. The active power of the discharge is approximated by both a power law function and an exponential function of the applied voltage.

Simultaneous influence of Stark effect and excessive line broadening on the Hα line

NASA Astrophysics Data System (ADS)

Cvetanović, Nikola; Ivković, Saša S.; Obradović, Bratislav M.; Kuraica, Milorad M.

2017-12-01

The aim of this paper is to study the combined influence of the Stark effect and the excessive Doppler broadening on the Balmer alpha line in hydrogen discharges. Since this line is a good candidate for measuring electric field in various types of discharges with different gas compositions, a simple method for field measurement based on polarization spectroscopy is developed, that includes all the excitation mechanisms. To simultaneously test the flexibility of the fitting procedure and investigate the excessive broadening, we applied the fitting procedure on line profiles obtained at a range of conditions from two different discharges. The range of pressures and voltages was examined in an abnormal glow and in dielectric barrier discharge operating with hydrogen gas. The model fitting function was able to respond and follow the change in the line profile caused by the change of conditions. This procedure can therefore be recommended for electric field measurement. Contribution to the "Topical Issue: Physics of Ionized Gases (SPIG 2016)", edited by Goran Poparic, Bratislav Obradovic, Dragana Maric and Aleksandar Milosavljevic.

Thermal modeling of a Ni-H2 battery cell

NASA Technical Reports Server (NTRS)

Ryu, Si-Ok; Dewitt, K. J.; Keith, T. G.

1991-01-01

The nickel-hydrogen secondary battery has many desirable features which make it attractive for satellite power systems. It can provide a significant improvement over the energy density of present spacecraft nickel-cadnium batteries, combined with longer life, tolerance to overcharge and possibility of state-of-charge indication. However, to realize these advantages, accurate thermal modeling of nickel-hydrogen cells is required in order to properly design the battery pack so that it operates within a specified temperature range during the operation. Maintenance of a low operating temperature and a uniform temperature profile within the cell will yield better reliability, improved cycle life and better charge/discharge efficiencies. This research has the objective of developing and testing a thermal model which can be used to characterize battery operation. Primarily, temperature distribution with the heat generation rates as a function of position and time will be evaluated for a Ni-H2 cell in the three operating modes: (1) charge cycle, (2) discharge cycle, and (3) overcharge condition, if applicable. Variables to be examined include charging current, discharge rates, state of charge, pressure and temperature. Once the thermal model has been developed, this resulting model will predict the actual operating temperature and temperature gradient for the specific cell geometry to be used.

Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Weiman; Tang, Jie; Wang, Yishan

2013-07-15

A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. Theremore » is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization.« less

Apparatus for producing voltage and current pulses

DOEpatents

Kirbie, Hugh; Dale, Gregory E.

2010-12-21

An apparatus having one or more modular stages for producing voltage and current pulses. Each module includes a diode charging means to charge a capacitive means that stores energy. One or more charging impedance means are connected to the diode charging means to provide a return current pathway. A solid-state switch discharge means, with current interruption capability, is connected to the capacitive means to discharge stored energy. Finally, a control means is provided to command the switching action of the solid-state switch discharge means.

Measured and simulated electron thermal transport in the Madisom symmetric torus reversed field pinch

NASA Astrophysics Data System (ADS)

Rodrigue Mbombo, Brice

New high time resolution measurements of the evolution of the electron temperature profile through a sawtooth event in high current reversed-field pinch (RFP) discharges in the Madison Symmetric Torus (MST) have been made using the enhanced capabilities of the multipoint, multi-pulse Thomson scattering system. Using this and other data, the electron thermal diffusion chie determined and is found to vary by orders of magnitude over the course of the sawtooth cycle. This experimental data is compared directly to simulations run at experimentally relevant parameters. This includes zero beta, single fluid, nonlinear, resistive magnetohydrodynamic (MHD) simulations run with the aspect ratio, resistivity profile, and Lundquist number (S ˜ 4 x 106) of high current RFP discharges in MST. These simulations display MHD activity and sawtooth like behavior similar to that observed in the MST. This includes both the sawtooth period and the duration of the sawtooth crash. The radial shape of the magnetic mode amplitudes, scaled to match edge measurements made in MST, are then used to compute the expected level of thermal diffusion due to parallel losses along diffusing magnetic field lines, chiMD = upsilon∥Dmag. The evolution of the Dmag profile was determined for over 20 sawteeth so that the ensemble averaged evolution could be compared to the sawtooth ensembled data from MST. The resulting comparison to the measured chi e shows that chiMD is larger than chi e at most times. However, if electrons are trapped in a magnetic well, they cannot carry energy along the diffusing magnetic field lines, reducing the thermal transport. Accounting for trapped particles brings chi MD to within uncertainty of chie in the mid radius at most times throughout the sawtooth cycle. In the core, the measured chie is greater than chi MD leading up to and including the sawtooth crash, suggesting other transport mechanisms are important at these times. Additionally, in a simulation including pressure evolution, a striking agreement is found between the temperature fluctuations seen in the simulation and those previously measured in MST. This work supported by the US DOE and NSF.

Modeling streamflow from coupled airborne laser scanning and acoustic Doppler current profiler data

USGS Publications Warehouse

Norris, Lam; Kean, Jason W.; Lyon, Steve

2016-01-01

The rating curve enables the translation of water depth into stream discharge through a reference cross-section. This study investigates coupling national scale airborne laser scanning (ALS) and acoustic Doppler current profiler (ADCP) bathymetric survey data for generating stream rating curves. A digital terrain model was defined from these data and applied in a physically based 1-D hydraulic model to generate rating curves for a regularly monitored location in northern Sweden. Analysis of the ALS data showed that overestimation of the streambank elevation could be adjusted with a root mean square error (RMSE) block adjustment using a higher accuracy manual topographic survey. The results of our study demonstrate that the rating curve generated from the vertically corrected ALS data combined with ADCP data had lower errors (RMSE = 0.79 m3/s) than the empirical rating curve (RMSE = 1.13 m3/s) when compared to streamflow measurements. We consider these findings encouraging as hydrometric agencies can potentially leverage national-scale ALS and ADCP instrumentation to reduce the cost and effort required for maintaining and establishing rating curves at gauging station sites similar to the Röån River.

Three-dimensional modeling of a negative ion source with a magnetic filter: impact of biasing the plasma electrode on the plasma asymmetry

NASA Astrophysics Data System (ADS)

Fubiani, G.; Boeuf, J. P.

2015-10-01

The effect on the plasma characteristics of biasing positively the plasma electrode (PE) in negative ion sources with a magnetic filter is analysed using a 3D particle-in-cell model with Monte-Carlo collisions (PIC-MCC). We specialize to the one driver (i.e. one inductively coupled radio-frequency discharge) BATMAN negative ion source and the 4-drivers (large volume) ELISE device. Both are ITER prototype high power tandem-type negative ion sources developed for the neutral beam injector (NBI) system. The plasma is generated in the driver and diffuses inside the second chamber which is magnetized. Asymmetric plasma profiles originate from the formation of an electric field transverse to the electron current flowing through the magnetic filter (Hall effect). The model shows that the importance of the asymmetry increases with the PE bias potential, i.e. with the electron flow from the driver to the extraction region and depends on the shape of the magnetic filter field. We find that although the plasma density and potential profiles may be more or less asymmetric depending on the filter field configuration, the electron current to the plasma grid is always strongly asymmetric.

Field evaluation of boat-mounted acoustic Doppler instruments used to measure streamflow

USGS Publications Warehouse

Mueller, D.S.; ,

2003-01-01

The use of instruments based on the Doppler principle for measuring water velocity and computing discharge is common within the U.S. Geological Survey (USGS). The instruments and software have changed appreciably during the last 5 years; therefore, the USGS has begun field validation of the instruments used to make discharge measurements from a moving boat. Instruments manufactured by SonTek/YSI and RD Instruments, Inc. were used to collect discharge data at five different sites. One or more traditional discharge measurements were made using a Price AA current meter and standard USGS procedures concurrent with the acoustic instruments at each site. Discharges measured with the acoustic instruments were compared with discharges measured with Price AA current meters and the USGS stage-discharge rating for each site. The mean discharges measured by each acoustic instrument were within 5 percent of the Price AA-based measurement and (or) discharge from the stage-discharge rating.

An experimental system for controlled exposure of biological samples to electrostatic discharges.

PubMed

Marjanovič, Igor; Kotnik, Tadej

2013-12-01

Electrostatic discharges occur naturally as lightning strokes, and artificially in light sources and in materials processing. When an electrostatic discharge interacts with living matter, the basic physical effects can be accompanied by biophysical and biochemical phenomena, including cell excitation, electroporation, and electrofusion. To study these phenomena, we developed an experimental system that provides easy sample insertion and removal, protection from airborne particles, observability during the experiment, accurate discharge origin positioning, discharge delivery into the sample either through an electric arc with adjustable air gap width or through direct contact, and reliable electrical insulation where required. We tested the system by assessing irreversible electroporation of Escherichia coli bacteria (15 mm discharge arc, 100 A peak current, 0.1 μs zero-to-peak time, 0.2 μs peak-to-halving time), and gene electrotransfer into CHO cells (7 mm discharge arc, 14 A peak current, 0.5 μs zero-to-peak time, 1.0 μs peak-to-halving time). Exposures to natural lightning stroke can also be studied with this system, as due to radial current dissipation, the conditions achieved by a stroke at a particular distance from its entry are also achieved by an artificial discharge with electric current downscaled in magnitude, but similar in time course, correspondingly closer to its entry. © 2013.

Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Venkattraman, Ayyaswamy

2013-11-15

The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential andmore » the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.« less

Thermal profiles for reaches of Snee-Oosh and Fornsby Creeks, Swinomish Indian Reservation, northwestern Washington, July 2013

USGS Publications Warehouse

Gendaszek, Andrew S.; Opatz, Chad C.

2013-01-01

Longitudinal profiles of streambed temperatures were measured in approximately 225-m-long reaches of the Snee-Oosh and Fornsby Creeks in the Swinomish Indian Reservation, northwestern Washington, during July 2013, to provide information about areas of groundwater discharge to streams. During summer, groundwater discharge is a source of cold water to streams and typically cools the surface water into which it discharges and buffers diurnal temperature fluctuations. Near-streambed temperatures were averaged over 1-m-long sections of cable during 1-minute periods every 30 minutes for 1-week periods using a fiber-optic distributed temperature sensor positioned on top of the streambed. The position of the fiber-optic cable was surveyed with a Global Positioning System. Stream temperatures and survey data are presented as Microsoft Excel® files consisting of date and time, water temperature, and geographical coordinates.

Self-similar magnetohydrodynamic model for direct current discharge fireball experiments

NASA Astrophysics Data System (ADS)

Tsui, K. H.; Navia, C. E.; Robba, M. B.; Carneiro, L. T.; Emelin, S. E.

2006-11-01

Ball lightning models and corresponding laboratory efforts in generating fireballs are briefly summarized to give an overview of the current status. In particular, emphasis is given to direct current discharge experiments at atmospheric pressure such as capillary discharge with a plasma plume in front of the anode opening [Emelin et al., Tech. Phys. Letters 23, 758 (1997)] and water resistor discharge with fluttering fireball overhead [Egorov and Stepanov, Tech. Phys. 47, 1584 (2002)]. These fireballs are interpreted as laboratory demonstrations of the self-similar magnetohydrodynamic (MHD) model of ball lightning [Tsui, Phys. Plasmas 13, 072102 (2006)].

Floods of September 15-16, 1992, in the Thompson, Weldon, and Chariton River basins, south-central Iowa

USGS Publications Warehouse

Eash, D.A.; Koppensteiner, B.A.

1997-01-01

Water-surface-elevation profiles and peak discharges for the floods of September 15-16, 1992, in the Thompson, Weldon, and Chariton River Basins, south-central Iowa, are presented in this report. The profiles illustrate the 1992 floods along the Thompson, Weldon, Chariton, and South Fork Chariton Rivers and along Elk Creek in the south-central Iowa counties of Adair, Clarke, Decatur, Lucas, Madison, Ringgold, Union, and Wayne. Water-surface-elevation profiles for the floods of July 4, 1981, along the Chariton River in Lucas County and along the South Fork Chariton River in Wayne County also are included in the report for comparative purposes. The September 15-16, 1992, floods are the largest known peak discharges at gaging stations Thompson River at Davis City (station number 06898000) 57,000 cubic feet per second, Weldon River near Leon (station number 06898400) 76,200 cubic feet per second, Chariton River near Chariton (station number 06903400) 37,700 cubic feet per second, and South Fork Chariton River near Promise City (station number 06903700) 70,600 cubic feet per second. The peak discharges were, respectively, 1.7, 2.6, 1.4, and 2.1 times larger than calculated 100-year recurrence-interval discharges. The report provides information on flood stages and discharges and floodflow frequencies for streamflow-gaging stations in the Thompson, Weldon, and Chariton River Basins using flood information collected through 1995. Information on temporary bench marks and reference points established in the Thompson and Weldon River Basins during 1994-95, and in the Chariton River Basin during 1983-84 and 1994-95, also is included in the report. A flood history summarizes rainfall conditions and damages for floods that occurred during 1947, 1959, 1981, 1992, and 1993.

Flood of July 9-11, 1993, in the Raccoon River basin, west-central Iowa

USGS Publications Warehouse

Eash, D.A.; Koppensteiner, B.A.

1997-01-01

Water-surface-elevation profiles and peak discharges for the flood of July 9-11, 1993, in the Raccoon River Basin, west-central Iowa, are presented in this report. The profiles illustrate the 1993 flood along the Raccoon, North Raccoon, South Raccoon, and Middle Raccoon Rivers and along Brushy and Storm Creeks in the west-central Iowa counties of Carroll, Dallas, Greene, Guthrie, and Polk. Water-surface-elevation profiles for the floods of June 1947, March 1979, and June 29- July 1, 1986, in the Raccoon River Basin also are included in the report for comparative purposes. The July 9-11, 1993, flood is the largest known peak discharge at gaging stations Brushy Creek near Templeton (station number 05483318) 19,000 cubic feet per second, Middle Raccoon River near Bayard (station number 05483450) 27,500 cubic feet per second, Middle Raccoon River at Panora (station number 05483600) 22,400 cubic feet per second, South Raccoon River at Redfield (station number 05484000) 44,000 cubic feet per second, and Raccoon River at Van Meter (station number 05484500) 70,100 cubic feet per second. The peak discharges were, respectively, 1.5, 1.3, 1.1,1.2, and 1.3 times larger than calculated 100-year recurrence-interval discharges. The report provides information on flood stages and discharges and floodflow frequencies for streamflow-gaging stations in the Raccoon River Basin using flood information collected through 1996. A flood history summarizes rainfall conditions and damages for floods that occurred during 1947, 1958, 1979, 1986, 1990, and 1993. Information on temporary bench marks and reference points established in the Raccoon River Basin during 1976-79 and 1995-97 also is included in the report.

Alternate charging and discharging of capacitor to enhance the electron production of bioelectrochemical systems.

PubMed

Liang, Peng; Wu, Wenlong; Wei, Jincheng; Yuan, Lulu; Xia, Xue; Huang, Xia

2011-08-01

A bioelectrochemical system (BES) can be operated in both "microbial fuel cell" (MFC) and "microbial electrolysis cell" (MEC) modes, in which power is delivered and invested respectively. To enhance the electric current production, a BES was operated in MFC mode first and a capacitor was used to collect power from the system. Then the charged capacitor discharged electrons to the system itself, switching into MEC mode. This alternate charging and discharging (ACD) mode helped the system produce 22-32% higher average current compared to an intermittent charging (IC) mode, in which the capacitor was first charged from an MFC and then discharged to a resistor, at 21.6 Ω external resistance, 3.3 F capacitance and 300 mV charging voltage. The effects of external resistance, capacitance and charging voltage on average current were studied. The average current reduced as the external resistance and charging voltage increased and was slightly affected by the capacitance. Acquisition of higher average current in the ACD mode was attributed to the shorter discharging time compared to the charging time, as well as a higher anode potential caused by discharging the capacitor. Results from circuit analysis and quantitatively calculation were consistent with the experimental observations.

Silo discharge of binary granular mixtures.

PubMed

Madrid, M; Asencio, K; Maza, D

2017-08-01

We present numerical and experimental results on the mass flow rate during the discharge of three-dimensional silos filled with a bidisperse mixture of grains of different sizes. We analyzed the influence of the ratio between coarse and fine particles on the profile of volume fraction and velocity across the orifice. By using numerical simulations, we have shown that the velocity profile has the same shape as that in the monodisperse case and is insensitive to the composition of the mixture. On the contrary, the volume fraction profile is strongly affected by the composition of the mixture. Assuming that an effective particle size can be introduced to characterize the mixture, we have shown that previous expression for the mass flow rate of monodisperse particles can be used for binary mixtures. A comparison with Beverloo's correlation is also presented.

Feasibility of Estimating Constituent Concentrations and Loads Based on Data Recorded by Acoustic Instrumentation

USGS Publications Warehouse

Lietz, A.C.

2002-01-01

The acoustic Doppler current profiler (ADCP) and acoustic Doppler velocity meter (ADVM) were used to estimate constituent concentrations and loads at a sampling site along the Hendry-Collier County boundary in southwestern Florida. The sampling site is strategically placed within a highly managed canal system that exhibits low and rapidly changing water conditions. With the ADCP and ADVM, flow can be gaged more accurately rather than by conventional field-data collection methods. An ADVM velocity rating relates measured velocity determined by the ADCP (dependent variable) with the ADVM velocity (independent variable) by means of regression analysis techniques. The coefficient of determination (R2) for this rating is 0.99 at the sampling site. Concentrations and loads of total phosphorus, total Kjeldahl nitrogen, and total nitrogen (dependent variables) were related to instantaneous discharge, acoustic backscatter, stage, or water temperature (independent variables) recorded at the time of sampling. Only positive discharges were used for this analysis. Discharges less than 100 cubic feet per second generally are considered inaccurate (probably as a result of acoustic ray bending and vertical temperature gradients in the water column). Of the concentration models, only total phosphorus was statistically significant at the 95-percent confidence level (p-value less than 0.05). Total phosphorus had an adjusted R2 of 0.93, indicating most of the variation in the concentration can be explained by the discharge. All of the load models for total phosphorus, total Kjeldahl nitrogen, and total nitrogen were statistically significant. Most of the variation in load can be explained by the discharge as reflected in the adjusted R2 for total phosphorus (0.98), total Kjeldahl nitrogen (0.99), and total nitrogen (0.99).

The influence of the N(2D) and N(2P) states in the ionization of the pink afterglow of the nitrogen flowing DC discharge

NASA Astrophysics Data System (ADS)

Levaton, J.; Klein, A. N.; Binder, C.

2018-01-01

In the present work, we extensively discuss the role of N(2D) and N(2P) atoms in the ionization processes of pink afterglow based on optical emission spectroscopy analysis and kinetic numerical modelling. We studied the pink afterglow generated by a nitrogen DC discharge operating at 0.6 Slm-1 flow rate, 45 mA discharge current and pressures ranging from 250 to 1050 Pa. The 391.4 nm nitrogen band was monitored along the afterglow furnishing the relative density of the N2+(B2Σ+u, v = 0) state. A numerical model developed to calculate the nitrogen species densities in the afterglow fits the excited ion density profiles well for the experimental conditions. From the modelling results, we determine the densities of the N+, N2+, N3+, and N4+ ions; the calculations show that the N3+ ion density predominates in the afterglow at the typical residence times of the pink afterglow. This behaviour has been observed experimentally and reported in the literature. Furthermore, we calculate the fractional contribution in the ionization for several physical-chemical mechanisms in the post-discharge. Even with the N3+ ion density being dominant in the afterglow, we find through the calculations that the ionization is dominated by the reactions N(2D) + N(2P) → N2+(X2Σ+g) + e and N2(a'1Σ-u) + N2(X 1Σg+, v > 24) → N4+ + e. The ion conversion mechanisms, or ion transfer reactions, which are responsible for the fact that the N3+ density dominates in the post-discharge, are investigated.

Inter-machine validation study of neoclassical transport modelling in medium- to high-density stellarator-heliotron plasmas

NASA Astrophysics Data System (ADS)

Dinklage, A.; Yokoyama, M.; Tanaka, K.; Velasco, J. L.; López-Bruna, D.; Beidler, C. D.; Satake, S.; Ascasíbar, E.; Arévalo, J.; Baldzuhn, J.; Feng, Y.; Gates, D.; Geiger, J.; Ida, K.; Isaev, M.; Jakubowski, M.; López-Fraguas, A.; Maaßberg, H.; Miyazawa, J.; Morisaki, T.; Murakami, S.; Pablant, N.; Kobayashi, S.; Seki, R.; Suzuki, C.; Suzuki, Y.; Turkin, Yu.; Wakasa, A.; Wolf, R.; Yamada, H.; Yoshinuma, M.; LHD Exp. Group; TJ-II Team; W7-AS Team

2013-06-01

A comparative study of energy transport for medium- to high-density discharges in the stellarator-heliotrons TJ-II, W7-AS and LHD is carried out. The specific discharge parameters are chosen to apply a recently concluded benchmarking study of neoclassical (NC) transport coefficients (Beidler et al 2011 Nucl. Fusion 51 076001) to perform this validation study. In contrast to previous experiments at low densities for which electron transport was predominant (Yokoyama et al 2007 Nucl. Fusion 47 1213), the current discharges also exhibit significant ion energy transport. As it affects the energy transport in 3D devices, the ambipolar radial electric field is addressed as well. For the discharges described, ion-root conditions, i.e. a small negative radial electric field were found. The energy transport in the peripheral region cannot be explained by NC theory. Within a ‘core region’(r/a < 1/2 ˜ 2/3), the predicted NC energy fluxes comply with experimental findings for W7-AS. For TJ-II, compliance in the core region is found for the particle transport and the electron energy transport. For the specific LHD discharges, the core energy transport complied with NC theory except for the electron energy transport in the inward-shifted magnetic configuration. The NC radial electric field tends to agree with experimental results for all devices but is measured to be more negative in the core of both LHD and TJ-II. As a general observation, the energy confinement time approaches the gyro-Bohm-type confinement scaling ISS04 (Yamada et al 2005 Nucl. Fusion 45 1684). This work is carried out within the International Stellarator-Heliotron Profile Database (www.ipp.mpg.de/ISS and http://ishpdb.nifs.ac.jp/index.html).

DC corona discharge ozone production enhanced by magnetic field

NASA Astrophysics Data System (ADS)

Pekárek, S.

2010-01-01

We have studied the effect of a stationary magnetic field on the production of ozone from air at atmospheric pressure by a negative corona discharge in a cylindrical electrode configuration. We used a stainless steel hollow needle placed at the axis of the cylindrical discharge chamber as a cathode. The outer wall of the cylinder was used as an anode. The vector of magnetic induction was perpendicular to the vector of current density. We found that: (a) the magnetic field extends the current voltage range of the discharge; (b) for the discharge in the Trichel pulses regime and in the pulseless glow regime, the magnetic field has no substantial effect on the discharge voltage or on the concentration of ozone that is produced; (c) for the discharge in the filamentary streamer regime for a particular current, the magnetic field increases the discharge voltage and consequently an approximately 30% higher ozone concentration can be obtained; (d) the magnetic field does not substantially increase the maximum ozone production yield. A major advantage of using a magnetic field is that the increase in ozone concentration produced by the discharge can be obtained without additional energy requirements.

Distribution of E/N and N/e/ in a cross-flow electric discharge laser. [electric field to neutral gas density and electron number density

NASA Technical Reports Server (NTRS)

Dunning, J. W., Jr.; Lancashire, R. B.; Manista, E. J.

1976-01-01

Measurements have been conducted of the effect of the convection of ions and electrons on the discharge characteristics in a large scale laser. The results are presented for one particular distribution of ballast resistance. Values of electric field, current density, input power density, ratio of electric field to neutral gas density (E/N), and electron number density were calculated on the basis of measurements of the discharge properties. In a number of graphs, the E/N ratio, current density, power density, and electron density are plotted as a function of row number (downstream position) with total discharge current and gas velocity as parameters. From the dependence of the current distribution on the total current, it appears that the electron production in the first two rows significantly affects the current flowing in the succeeding rows.

Heating and current drive requirements for ideal MHD stability and ITB sustainment in ITER steady state scenarios

NASA Astrophysics Data System (ADS)

Poli, Francesca

2012-10-01

Steady state scenarios envisaged for ITER aim at optimizing the bootstrap current, while maintaining sufficient confinement and stability to provide the necessary fusion yield. Non-inductive scenarios will need to operate with Internal Transport Barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. However, the large pressure gradients associated with ITBs in regions of weak or negative magnetic shear can be conducive to ideal MHD instabilities in a wide range of βN, reducing the no-wall limit. Scenarios are established as relaxed flattop states with time-dependent transport simulations with TSC [1]. Fully non-inductive configurations with current in the range of 7-10 MA and various heating mixes (NB, EC, IC and LH) have been studied against variations of the pressure profile peaking and of the Greenwald fraction. It is found that stable equilibria have qmin> 2 and moderate ITBs at 2/3 of the minor radius [2]. The ExB flow shear from toroidal plasma rotation is expected to be low in ITER, with a major role in the ITB dynamics being played by magnetic geometry. Combinations of H&CD sources that maintain reverse or weak magnetic shear profiles throughout the discharge and ρ(qmin)>=0.5 are the focus of this work. The ITER EC upper launcher, designed for NTM control, can provide enough current drive off-axis to sustain moderate ITBs at mid-radius and maintain a non-inductive current of 8-9MA and H98>=1.5 with the day one heating mix. LH heating and current drive is effective in modifying the current profile off-axis, facilitating the formation of stronger ITBs in the rampup phase, their sustainment at larger radii and larger bootstrap fraction. The implications for steady state operation and fusion performance are discussed.[4pt] [1] Jardin S.C. et al, J. Comput. Phys. 66 (1986) 481[0pt] [2] Poli F.M. et al, Nucl. Fusion 52 (2012) 063027.

Profile patterns, consistency, and change in the Millon Clinical Multiaxial Inventory-II in cocaine abusers.

PubMed

McMahon, R C; Richards, S K

1996-01-01

This study examined the MCMI-II in samples of cocaine-dependent subjects who were receiving treatment in three separate residential facilities. Profile characteristics, patterns of scale stability, and change are reported. MCMI-II elevations are found in all three samples on the Antisocial, Aggressive/Sadistic, Narcissistic, Passive-Aggressive, Borderline, Drug Dependence, and Alcohol Dependence scales at both intake into treatment and discharge. Moderate stability coefficients are found on Basic Personality, Pathological Personality, and Symptom scales. Although some statistically significant mean scale changes between intake and discharge are noted in each sample, few involve change from clinically elevated to below clinical levels.

A technique for measuring hypersonic flow velocity profiles

NASA Technical Reports Server (NTRS)

Gartrell, L. R.

1973-01-01

A technique for measuring hypersonic flow velocity profiles is described. This technique utilizes an arc-discharge-electron-beam system to produce a luminous disturbance in the flow. The time of flight of this disturbance was measured. Experimental tests were conducted in the Langley pilot model expansion tube. The measured velocities were of the order of 6000 m/sec over a free-stream density range from 0.000196 to 0.00186 kg/cu m. The fractional error in the velocity measurements was less than 5 percent. Long arc discharge columns (0.356 m) were generated under hypersonic flow conditions in the expansion-tube modified to operate as an expansion tunnel.

Subsurface thermal regime to delineate the paleo-groundwater flow system in an arid area, Al Kufra, Libya

NASA Astrophysics Data System (ADS)

Salem, Zenhom El-Said

2016-12-01

The purpose of this study was to understand the groundwater flow system in Al Kufra basin, Libya, as a case study of arid areas using subsurface temperature. The temperature-depth profiles and water levels were measured in eight boreholes in the area. Well 6 is considered a recharge type profile with low geothermal gradient (0.0068 °C/m) and an estimated paleo-temperature around 19.5 °C. The other profiles are of discharge type with higher geothermal gradient (0.0133 to 0.0166 °C/m). The constructed horizontal 2D distribution maps of the hydraulic heads and the subsurface temperature measurements reveal that the main recharge area is located to the south with low temperature while the main discharge area is located to the north with higher temperature. Vertical 2D distribution maps show that location of well 4 has low hydraulic heads and higher temperature indicating that the fault defined in the area may have affected the groundwater flow system. The estimated groundwater flux ranges from 0.001 to 0.1 mm/day for the recharge area and from -0.3 to -0.7 mm/day in average in the discharge area.

Monitoring of well-controlled turbidity currents using the latest technology and a dredger

NASA Astrophysics Data System (ADS)

Vellinga, A. J.; Cartigny, M.; Clare, M. A.; Mastbergen, D. R.; Van den Ham, G.; Koelewijn, A. R.; de Kleine, M.; Hizzett, J. L.; Azpiroz, M.; Simmons, S.; Parsons, D. R.

2017-12-01

Recent advances in technology enable monitoring of turbidity currents at field scale. This now allows us to test models developed at small-scale in the laboratory. However, interpretation of field measurements is complicated, as the instruments used are not bespoke for monitoring turbidity currents. For example, Acoustic Doppler Current Profiles (ADCPs) are developed to measure clear water flows, and 3D multimode multibeam echosounders (M3s) are made to find shoals of fish. Calibration of field-scale measurements is complicated, as we often do not know fundamental information about the measured flows, such as grain size and initial sediment volume. We present field-scale measurements of two turbidity currents for which the pre- and post-flow bathymetry, grain size and initial sediment volume is known precisely. A dredger created two turbidity currents by twice discharging 500m3 of sediment on a slope in the Western Scheldt Estuary, the Netherlands. Flow velocity and echo intensity were directly measured using three frequencies of ADCPs, and two M3 sonars imaged the flow morphology in 3D. This experiment was part of the IJkdijk research program. The turbidity currents formed upstream-migrating crescentic shaped bedforms. The ADCPs measured peak flow velocities of 1-1.5 m/s. The M3s however suggest head velocities are 2-4 m/s. The two measured turbidity currents have thicknesses of about 3m, are up to 50m in width and travel downslope for about 150m. Flow dimensions, duration, and sediment discharge indicate a mean sediment concentration of 1-5 vol. %. Flow morphology evolves from a fast but thin, snout-like head, to a thicker body, and a dilute tail. The initial flow dynamics contrast with many laboratory experiments, but are coherent with direct measurements of much larger flows in the Congo Canyon. Well-constrained field studies, like this one, thus help to understand the validity of scaling from the laboratory to the deep sea.

Sex differences in lipid profiles and treatment utilization among young adults with acute myocardial infarction: Results from the VIRGO study.

PubMed

Lu, Yuan; Zhou, Shengfan; Dreyer, Rachel P; Caulfield, Michael; Spatz, Erica S; Geda, Mary; Lorenze, Nancy P; Herbert, Peter; D'Onofrio, Gail; Jackson, Elizabeth A; Lichtman, Judith H; Bueno, Héctor; Spertus, John A; Krumholz, Harlan M

2017-01-01

Young women with acute myocardial infarction (AMI) have higher mortality risk than similarly aged men. An adverse lipid profile is an important risk factor for cardiovascular outcomes after AMI, but little is known about whether young women with AMI have a higher-risk lipid pattern than men. We characterized sex differences in lipid profiles and treatment utilization among young adults with AMI. A total of 2,219 adults with AMI (1,494 women) aged 18-55 years were enrolled from 103 hospitals in the United States (2008-2012). Serum lipids and lipoprotein subclasses were measured 1 month after discharge. More than 90% of adults were discharged on a statin, but less than half received a high-intensity dose and 12% stopped taking treatments by 1 month. For both men and women, the median of low-density lipoprotein (LDL) cholesterol was reduced to <100 mg/dL 1 month after discharge for AMI, but high-density lipoprotein (HDL) cholesterol remained <40 mg/dL. Multivariate regression analyses showed that young women had favorable lipoprotein profiles compared with men: women had higher HDL cholesterol and HDL large particle, but lower total cholesterol-to-HDL cholesterol ratio and LDL small particle. Young women with AMI had slightly favorable lipid and lipoprotein profiles compared with men, suggesting that difference in lipid and lipoprotein may not be a major contributor to sex differences in outcomes after AMI. In both men and women, statin remained inadequately used, and low HDL cholesterol level was a major lipid abnormality. Copyright © 2016 Elsevier Inc. All rights reserved.

Characterization of magnetic field profiles at RFX-mod by Faraday rotation measurements

NASA Astrophysics Data System (ADS)

Auriemma, Fulvio; Brombin, Matteo; Canton, Alessandra; Giudicotti, Leonardo; Innocente, Paolo; Zilli, Enrico

2009-11-01

A multichannel far-infrared (FIR, λ=118.8 μm) polarimeter has been recently upgraded and re-installed on RFX-mod to measure the Faraday rotation angle along five vertical chords. Polarimetric data, associated with electron density profile, allow the reconstruction of the poloidal magnetic field profile. In this work the setup of the diagnostic is presented and the first Faraday rotation measurements are analyzed. The measurements have been performed at plasma current above 1.2 MA and electron density between 2 and 6x10^19 m-3. The actual S/N ratio is slightly lower than the expected one, due to electromagnetic coupling of the detectors with the saddle coils close to the polarimeter position. Due to this limit, only average information in the flat-top phase of the discharge could be so far obtained. The experimental data have been compared with the result of the μ&p equilibrium model [1], showing a good agreement between experiment and model, whereas the main differences are in the external region of the plasma. A different parameterization of the μ=μ0 J.B/B^2 profile has been proposed to enhance the agreement between model and experiment. [0pt] [1] Ortolani and Snack, World Scientific (1993) Singapore

Institutionalization, Involuntary Sterilization, and Mental Retardation: Profiles from the History of the Practice.

ERIC Educational Resources Information Center

Smith, David J.; Polloway, Edward A.

1993-01-01

This study analyzes data on 212 individuals with mental retardation who were sterilized while residents of the Central Virginia Training Center and discharged from the facility between 1969 and 1989. The analysis includes gender, age at and date of sterilization, level of mental retardation, and location of subsequent discharge. (Author/JDD)

Simulation of the effect of an oil refining project on the water environment using the MIKE 21 model

NASA Astrophysics Data System (ADS)

Jia, Peng; Wang, Qinggai; Lu, Xuchuan; Zhang, Beibei; Li, Chen; Li, Sa; Li, Shibei; Wang, Yaping

2018-02-01

A case study of the Caofeidian oil refining project is conducted. A two-dimensional convective dispersion mathematical model is established to simulate the increase in the concentration of pollutants resulting from the wastewater discharge from the Caofeidian oil refining project and to analyze the characteristics of the dispersion of pollutants after wastewater is discharged and the effect of the wastewater discharge on the surrounding sea areas. The results demonstrate the following: (1) The Caofeidian sea area has strong tidal currents, which are significantly affected by the terrain. There are significant differences in the tidal current velocity and the direction between the deep-water areas and the shoals. The direction of the tidal currents in the deep-water areas is essentially parallel to the contour lines of the sea areas. Onshore currents and rip currents submerging the shoals are the dominant currents in the shoals. (2) The pollutant concentration field in the offshore areas changes periodically with the movement of the tidal current. The dilution and dispersion of pollutants are affected by the ocean currents in different tidal periods. The turbulent dispersion of pollutants is the most intense when a neap tide ebbs, followed by when a neap tide rises, when a spring tide ebbs and when a spring tide rises. (3) There are relatively good hydrodynamic conditions near the project's wastewater discharge outlet. Wastewater is well diluted after being discharged. Areas with high concentrations of pollutants are concentrated near the wastewater discharge outlet and the offshore areas. These pollutants migrate southwestward with the flood tidal current and northeastward with the ebb tidal current and have no significant impact on the protection targets in the open sea areas and nearby sea areas.

Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

NASA Astrophysics Data System (ADS)

Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy

2017-04-01

The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

Transition from edge-localized to center-localized power deposition in helicon discharges

NASA Astrophysics Data System (ADS)

Curreli, D.

2011-11-01

In radiofrequency (RF) helicon discharges the electromagnetic power is transferred from the RF field irradiated by the antenna to the plasma medium by means of plasma-wave coupling of the electromagnetic wave with the electrons. For the common industrial frequencies of tens of MHz, and for typical pressures of few Pascals, the power deposition occurs mostly at the edge of the discharge. In these conditions, ionization and electron heating occur in a layer close to the chamber walls, where a consistent fraction of the plasma is rapidly lost by diffusion toward the surface. The remaining fraction of plasma diffuses inward toward the center of the discharge, setting up a uniform and almost flat density profile, used in applications. A one-dimensional model considering both the plasma-wave coupling of the electrons with the RF wave and the macroscopic transport of ions and neutrals along the radial dimension of a cylindrical processing chamber has been derived and used to evaluate the profiles at equilibrium. The model has been validated through Langmuir probe measurements in helicon processing chambers. The numerical model has then been used to study the power-coupling behavior of the discharge when the pressure of the neutral gas is decreased. When the Knudsen number of the neutral gas approaches unity and in conditions of slightly magnetized discharge, the power deposition shifts from being edge-localized to center-localized, thus reducing the particle fluxes toward the walls and increasing the efficiency of the coupling.

Effects of insulator ablation on the operation of a quasi-steady MPD arc

NASA Technical Reports Server (NTRS)

Boyle, M. J.; Jahn, R. G.

1973-01-01

Multimegawatt operation of quasi-steady MPD arcjets can involve serious ablation of the insulator surfaces within the arc discharge chamber. Various degrees of insulator ablation manifest themselves by significantly perturbing the voltage-current characteristics and the exhaust velocity profiles. Voltage-current characteristics for two different insulator materials, Plexiglas and boron nitride, are interpreted in terms of an empirical Ohm's law. Use of the refractory insulator material eliminates the ablation-dominated nature of the terminal voltage, but the exhaust stream is still disturbed by insulator material. An Alfven critical velocity model can be applied to this influence of insulator ablation on exhaust velocity. Appropriate changes in the propellant injection geometry eliminate this influence and result in arcjet operation which is independent of insulator material. A particular combination of propellant injection geometries reduces the terminal voltage for a given current and mass flow while maintaining insulator-independent operation, thus implying an improvement in the overall efficiency of the device.

Magnetless magnetic fusion

NASA Astrophysics Data System (ADS)

Beklemishev, A. D.; Tajima, T.

1994-02-01

The authors propose a concept of thermonuclear fusion reactor in which the plasma pressure is balanced by direct gas-wall interaction in a high-pressure vessel. The energy confinement is achieved by means of the self-contained toroidal magnetic configuration sustained by an external current drive or charged fusion products. This field structure causes the plasma pressure to decrease toward the inside of the discharge and thus it should be magnetohydrodynamically stable. The maximum size, temperature and density profiles of the reactor are estimated. An important feature of confinement physics is the thin layer of cold gas at the wall and the adjacent transitional region of dense arc-like plasma. The burning condition is determined by the balance between these nonmagnetized layers and the current-carrying plasma. They suggest several questions for future investigation, such as the thermal stability of the transition layer and the possibility of an effective heating and current drive behind the dense edge plasma. The main advantage of this scheme is the absence of strong external magnets and, consequently, potentially cheaper design and lower energy consumption.

Low-flow characteristics and profiles for the Rocky River in the Yadkin-Pee Dee River basin, North Carolina, through 2002

USGS Publications Warehouse

Weaver, J. Curtis; Fine, Jason M.

2003-01-01

An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 12 continuous-record gaging stations and 44 partial-record measuring sites in the Rocky River basin in North Carolina. Records of discharge collected through the 2002 water year at continuous-record gaging stations and through the 2001 water year at partial-record measuring sites were used. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, which is similar to 7Q10 discharge but is based only on flow during the winter months of November through March; and (5) 7Q2 low-flow discharge. The Rocky River basin drains 1,413 square miles (mi2) of the southern Piedmont Province in North Carolina. The Rocky River is about 91 miles long and merges with the Yadkin River in eastern Stanly County to form the Pee Dee River, which discharges into the Atlantic Ocean in South Carolina. Low-flow characteristics compiled for selected sites in the Rocky River basin indicated that the potential for sustained base flows in the upper half of the basin is relatively higher than for streams in the lower half of the basin. The upper half of the basin is underlain by the Charlotte Belt, where streams have been identified as having moderate potentials for sustained base flows. In the lower half of the basin, many streams were noted as having little to no potential for sustained base flows. Much of the decrease in base-flow potential is attributed to the underlying rock types of the Carolina Slate Belt. Of the 19 sites in the basin having minimal (defined as less than 0.05 cubic foot per second) or zero 7Q10 discharges, 18 sites are located in the lower half of the basin underlain by the Carolina Slate Belt. Assessment of these 18 sites indicates that streams that have drainage areas less than about 25 square miles are likely to have minimal or zero 7Q10 discharges. No drainage-area threshold for minimal or zero 7Q10 discharges was identified for the upper half of the basin, which is underlain by the Charlotte Belt. Tributaries to the Rocky River include the West Branch Rocky River (22.8 mi2), Clarke Creek (28.2 mi2), Mallard Creek (41.2 mi2), Coddle Creek (78.8 mi2), Reedy Creek (43.0 mi2), Irish Buffalo/Coldwater Creeks (110 mi2), Dutch Buffalo Creek (99 mi2), Long Creek (200 mi2), Richardson Creek (234 mi2), and Lanes Creek (135 mi2). In the 20-mile reach upstream from the mouth (about 22 percent of the river length), the drainage area increases by 648 mi2, or about 46 percent of the total drainage area as a result of the confluences with Long Creek, Richardson Creek, and Lanes Creek. Low-flow discharge profiles for the Rocky River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included. At the gaging stations above Irish Buffalo Creek and near Stanfield, the 7Q10 discharges are 25.2 and 42.3 cubic feet per second, corresponding to 0.09 and 0.07 cubic feet per second per square mile, respectively. At the gaging station near Norwood, the 7Q10 discharge is 45.8 cubic feet per second, equivalent to 0.03 cubic foot per second per square mile. Low-flow discharge profiles reflect the presence of several major flow diversions in the reaches upstream from Stanfield and an apparent losing reach between the continuous-record gaging stations near Stanfield and Norwood, North Carolina.

Tidal currents and bedload transport at the mouth of a rock-bound estuary during low river discharge conditions (Guadiana Estuary, Portugal)

NASA Astrophysics Data System (ADS)

Garel, E.; Pacheco, A.; Ferreira, Ó.

2009-04-01

The present study documents the poorly-described hydro-sediment dynamics of narrow bedrock-controlled estuaries during periods of low-river discharge. The results also contribute to assess the geomorphological evolution of these systems, when affected by drastic flow regulation. The Guadiana Estuary is a narrow rock-bound mesotidal estuary, 80 km in length, located at the southern border between Spain and Portugal. Until recently, the river inputs to the estuary displayed high (annual and seasonal) variability, characterized by periods of droughts, and episodic flood events with (monthly-averaged) fluvial discharge as high as 5,000 m3s-1 (160 m3s-1 in average, for the period 1947/2001). This pattern has ceased in February 2002, with the impoundment of the main river by the large Alqueva dam, 60 km upstream from the estuary head. At present, the daily-averaged river discharge is generally kept low throughout the year (< 50 m3s-1). In the absence of significant flood events to expel massively sediment out of the estuary, concerns have been raised about sand infilling at the mouth and increased erosion at the adjacent coastline. For the assessment of the sediment balance of the estuary under present hydrodynamic conditions, this study examines the tidal currents and bedload transport at the entrance of the estuarine channel. Current measurement transects were performed across the 600 m-wide channel entrance using a ship borne Acoustic Doppler Profiler (ADP, operating at 1.5 MHz frequency) during 2 entire tidal cycles, at spring (17 September 2008, 3.0 m tidal range) and at neap tide (21 October 2008, 1.6 m tidal range). Surficial sediment samples were also collected across the channel during the spring tidal cycle. The bed sediment consists of well-sorted medium sand with mean grain size ranging from 0.5 to 0.3 mm (with coarser material at the deepest part of the channel cross-section). Tidal currents were analysed along 6 sub-sections to take into account these grain size variations. The friction velocity and bed shear stress were computed based on the mean depth-averaged velocities of each sub-sections and considering a power law vertical velocity profile. The transport rate of sand was then estimated using Nielsen (1992) formula for bedload transport. The transport of sand in suspension was not considered in the study, as the skin friction velocities were lesser than the estimated settling velocities of the grains. Maximum velocity values (about 1.2 and 0.8 m.s-1 at spring and neap, respectively) were observed near the surface of the deepest sub-section of the channel. The tidal prism was about 1.5 times larger at spring (39x106 m3) than at neap (25x106m3), whereas the fresh water inputs during both tidal cycles were comparatively negligible. Maximum depth-averaged, bed and surface current velocities were ebb-directed at both neap and spring tides, for each of the 6 channel sub-sections. No significant lateral variation of the tidal flow was observed, in relation with the narrowness of the channel. Vertical residual velocity profiles were also directed downstream at both neap and spring tide. At neap, however, the (ebb-directed) residual velocities were slower near the bed and faster near the surface, when compared to the spring tide. These differences were induced by the reinforcement of the estuarine circulation, in relation with enhanced stratified conditions during neap periods (weak currents and reduced mixing). The net bedload transport of sand was also directed downstream for all channel sub-sections. The transport rates of the entire channel were estimated to be of about 30 and 10 m3 for the spring and neap tidal cycles, respectively. Extrapolation of these extreme (i.e. neap and spring) rates yielded a potential seaward export of sand of approximately 15,000 m3yr-1. This study suggests that the Guadiana estuary departs from typical estuaries where landward net transport of sediment is generally described. The outputs of the study are important with respect to the long-term (decades) geomorphological evolution and sustainable management of the estuary mouth and adjacent coastline.

Study on residual discharge time of lead-acid battery based on fitting method

NASA Astrophysics Data System (ADS)

Liu, Bing; Yu, Wangwang; Jin, Yueqiang; Wang, Shuying

2017-05-01

This paper use the method of fitting to discuss the data of C problem of mathematical modeling in 2016, the residual discharge time model of lead-acid battery with 20A,30A,…,100A constant current discharge is obtained, and the discharge time model of discharge under arbitrary constant current is presented. The mean relative error of the model is calculated to be about 3%, which shows that the model has high accuracy. This model can provide a basis for optimizing the adaptation of power system to the electrical motor vehicle.

Influence of driving frequency on discharge modes in the dielectric barrier discharge excited by a triangle voltage

NASA Astrophysics Data System (ADS)

Li, Xuechen; Liu, Rui; Jia, Pengying; Wu, Kaiyue; Ren, Chenhua; Yin, Zengqian

2018-01-01

A one-dimensional fluid model in atmospheric pressure argon is employed to investigate the influence of the driving frequency on dielectric barrier discharge modes excited by a triangle voltage. Results indicate that a stepped discharge mode is obtained with a low driving frequency of 35 kHz. The current amplitude increases, while its plateau duration decreases with increasing the frequency. The stepped discharge transits into a multi-pulsed mode when the frequency is increased to 80 kHz. With its further increment, the pulse number decreases, and a double-pulsed discharge is realized at 90 kHz, which finally transits to a single-pulsed discharge. Through analyzing spatial distributions of electron density, ion density, and electric field, it can be concluded that the discharge regime transits from a Townsend-like discharge to a glow discharge with increasing the frequency. The regime transition is further verified by analyzing voltage-current curves. These simulated results are consistent with the experimental phenomena.

Feature Profile Evolution of SiO2 Trenches In Fluorocarbon Plasmas

NASA Technical Reports Server (NTRS)

Hwang, Helen; Govindan, T. R.; Meyyappan, M.; Arunachalam, Valli; Rauf, Shahid; Coronell, Dan; Carroll, Carol W. (Technical Monitor)

1999-01-01

Etching of silicon microstructures for semiconductor manufacturing in chlorine plasmas has been well characterized. The etching proceeds in a two-part process, where the chlorine neutrals passivate the Si surface and then the ions etch away SiClx. However, etching in more complicated gas mixtures and materials, such as etching of SiO2 in Ar/C4F8, requires knowledge of the ion and neutral distribution functions as a function of angle and velocity, in addition to modeling the gas surface reactions. In order to address these needs, we have developed and integrated a suite of models to simulate the etching process from the plasma reactor level to the feature profile evolution level. This arrangement allows for a better understanding, control, and prediction of the influence of equipment level process parameters on feature profile evolution. We are currently using the HPEM (Hybrid Plasma Equipment Model) and PCMCM (Plasma Chemistry Monte Carlo Model) to generate plasma properties and ion and neutral distribution functions for argon/fluorocarbon discharges in a GEC Reference Cell. These quantities are then input to the feature scale model, Simulation of Profile Evolution by Level Sets (SPELS). A surface chemistry model is used to determine the interaction of the incoming species with the substrate material and simulate the evolution of the trench profile. The impact of change of gas pressure and inductive power on the relative flux of CFx and F to the wafer, the etch and polymerization rates, and feature profiles will be examined. Comparisons to experimental profiles will also be presented.

ANTHROPOGENIC COPPER INVENTORIES AND MERCURY PROFILES FROM LAKE SUPERIOR: EVIDENCE FOR MINING IMPACTS

EPA Science Inventory

During the past 150 years, the mining indstry discharged more than a billion tons of tailings along Lake Superior shorelines and constructed numerous smelters in the watershed. Given the vast size of Lake Superior, were sediment profiles at locations far offshore impacted by near...