Biased low differential input impedance current receiver/converter device and method for low noise readout from voltage-controlled detectors

DOEpatents

Degtiarenko, Pavel V [Williamsburg, VA; Popov, Vladimir E [Newport News, VA

2011-03-22

A first stage electronic system for receiving charge or current from voltage-controlled sensors or detectors that includes a low input impedance current receiver/converter device (for example, a transimpedance amplifier), which is directly coupled to the sensor output, a source of bias voltage, and the device's power supply (or supplies), which use the biased voltage point as a baseline.

Control of Analyte Electrolysis in Electrospray Ionization Mass Spectrometry Using Repetitively Pulsed High Voltage

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

Kertesz, Vilmos; Van Berkel, Gary J

2011-01-01

Analyte electrolysis using a repetitively pulsed high voltage ion source was investigated and compared to that using a regular, continuously operating direct current high voltage ion source in electrospray ionization mass spectrometry. The extent of analyte electrolysis was explored as a function of the length and frequency of the high voltage pulse using the model compound reserpine in positive ion mode. Using +5 kV as the maximum high voltage amplitude, reserpine was oxidized to its 2, 4, 6 and 8-electron oxidation products when direct current high voltage was employed. In contrast, when using a pulsed high voltage, oxidation of reserpinemore » was eliminated by employing the appropriate high voltage pulse length and frequency. This effect was caused by inefficient mass transport of the analyte to the electrode surface during the duration of the high voltage pulse and the subsequent relaxation of the emitter electrode/ electrolyte interface during the time period when the high voltage was turned off. This mode of ESI source operation allows for analyte electrolysis to be quickly and simply switched on or off electronically via a change in voltage pulse variables.« less

Measurement and analysis of time-domain characteristics of corona-generated radio interference from a single positive corona source

NASA Astrophysics Data System (ADS)

Li, Xuebao; Li, Dayong; Chen, Bo; Cui, Xiang; Lu, Tiebing; Li, Yinfei

2018-04-01

The corona-generated electromagnetic interference commonly known as radio interference (RI) has become a limiting factor for the design of high voltage direct current transmission lines. In this paper, a time-domain measurement system is developed to measure the time-domain characteristics of corona-generated RI from a single corona source under a positive corona source. In the experiments, the corona current pulses are synchronously measured through coupling capacitors. The one-to-one relationship between the corona current pulse and measured RI voltage pulse is observed. The statistical characteristics of pulse parameters are analyzed, and the correlations between the corona current pulse and RI voltage pulse in the time-domain and frequency-domain are analyzed. Depending on the measured corona current pulses, the time-domain waveform of corona-generated RI is calculated on the basis of the propagation model of corona current on the conductor, the dipolar model for electric field calculation, and the antenna model for inducing voltage calculation. The well matched results between measured and simulated waveforms of RI voltage can show the validity of the measurement and calculation method presented in this paper, which also further show the close correlation between corona current and corona-generated RI.

Power supply system for negative ion source at IPR

NASA Astrophysics Data System (ADS)

Gahlaut, Agrajit; Sonara, Jashwant; Parmar, K. G.; Soni, Jignesh; Bandyopadhyay, M.; Singh, Mahendrajit; Bansal, Gourab; Pandya, Kaushal; Chakraborty, Arun

2010-02-01

The first step in the Indian program on negative ion beams is the setting up of Negative ion Experimental Assembly - RF based, where 100 kW of RF power shall be coupled to a plasma source producing plasma of density ~5 × 1012 cm-3, from which ~ 10 A of negative ion beam shall be produced and accelerated to 35 kV, through an electrostatic ion accelerator. The experimental system is modelled similar to the RF based negative ion source, BATMAN presently operating at IPP, Garching, Germany. The mechanical system for Negative Ion Source Assembly is close to the IPP source, remaining systems are designed and procured principally from indigenous sources, keeping the IPP configuration as a base line. High voltage (HV) and low voltage (LV) power supplies are two key constituents of the experimental setup. The HV power supplies for extraction and acceleration are rated for high voltage (~15 to 35kV), and high current (~ 15 to 35A). Other attributes are, fast rate of voltage rise (< 5ms), good regulation (< ±1%), low ripple (< ±2%), isolation (~50kV), low energy content (< 10J) and fast cut-off (< 100μs). The low voltage (LV) supplies required for biasing and providing heating power to the Cesium oven and the plasma grids; have attributes of low ripple, high stability, fast and precise regulation, programmability and remote operation. These power supplies are also equipped with over-voltage, over-current and current limit (CC Mode) protections. Fault diagnostics, to distinguish abnormal rise in currents (breakdown faults) with over-currents is enabled using fast response breakdown and over-current protection scheme. To restrict the fault energy deposited on the ion source, specially designed snubbers are implemented in each (extraction and acceleration) high voltage path to swap the surge energy. Moreover, the monitoring status and control signals from these power supplies are required to be electrically (~ 50kV) isolated from the system. The paper shall present the design basis, topology selection, manufacturing, testing, commissioning, integration and control strategy of these HVPS. A complete power interconnection scheme, which includes all protective devices and measuring devices, low & high voltage power supplies, monitoring and control signals etc. shall also be discussed. The paper also discusses the protocols involved in grounding and shielding, particularly in operating the system in RF environment.

Load insensitive electrical device. [power converters for supplying direct current at one voltage from a source at another voltage

NASA Technical Reports Server (NTRS)

Schwarz, F. C. (Inventor)

1974-01-01

A class of power converters is described for supplying direct current at one voltage from a source at another voltage. It includes a simple passive circuit arrangement of solid-state switches, inductors, and capacitors by which the output voltage of the converter tends to remain constant in spite of changes in load. The switches are sensitive to the current flowing in the circuit and are employed to permit the charging of capacitance devices in accordance with the load requirements. Because solid-state switches (such as SCR's) may be used with relatively high voltage and because of the inherent efficiency of the invention that permits relatively high switching frequencies, power supplies built in accordance with the invention, together with their associated cabling, can be substantially lighter in weight for a given output power level and efficiency of operation than systems of the prior art.

High voltage DC power supply

DOEpatents

Droege, T.F.

1989-12-19

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively. 7 figs.

High voltage DC power supply

DOEpatents

Droege, Thomas F.

1989-01-01

A high voltage DC power supply having a first series resistor at the output for limiting current in the event of a short-circuited output, a second series resistor for sensing the magnitude of output current, and a voltage divider circuit for providing a source of feedback voltage for use in voltage regulation is disclosed. The voltage divider circuit is coupled to the second series resistor so as to compensate the feedback voltage for a voltage drop across the first series resistor. The power supply also includes a pulse-width modulated control circuit, having dual clock signals, which is responsive to both the feedback voltage and a command voltage, and also includes voltage and current measuring circuits responsive to the feedback voltage and the voltage developed across the second series resistor respectively.

Module Five: Relationships of Current, Voltage, and Resistance; Basic Electricity and Electronics Individualized Learning System.

ERIC Educational Resources Information Center

Bureau of Naval Personnel, Washington, DC.

This module covers the relationships between current and voltage; resistance in a series circuit; how to determine the values of current, voltage, resistance, and power in resistive series circuits; the effects of source internal resistance; and an introduction to the troubleshooting of series circuits. This module is divided into five lessons:…

A Smart Voltage and Current Monitoring System for Three Phase Inverters Using an Android Smartphone Application

PubMed Central

Mnati, Mohannad Jabbar; Van den Bossche, Alex; Chisab, Raad Farhood

2017-01-01

In this paper, a new smart voltage and current monitoring system (SVCMS) technique is proposed. It monitors a three phase electrical system using an Arduino platform as a microcontroller to read the voltage and current from sensors and then wirelessly send the measured data to monitor the results using a new Android application. The integrated SVCMS design uses an Arduino Nano V3.0 as the microcontroller to measure the results from three voltage and three current sensors and then send this data, after calculation, to the Android smartphone device of an end user using Bluetooth HC-05. The Arduino Nano V3.0 controller and Bluetooth HC-05 are a cheap microcontroller and wireless device, respectively. The new Android smartphone application that monitors the voltage and current measurements uses the open source MIT App Inventor 2 software. It allows for monitoring some elementary fundamental voltage power quality properties. An effort has been made to investigate what is possible using available off-the-shelf components and open source software. PMID:28420132

A Smart Voltage and Current Monitoring System for Three Phase Inverters Using an Android Smartphone Application.

PubMed

Mnati, Mohannad Jabbar; Van den Bossche, Alex; Chisab, Raad Farhood

2017-04-15

In this paper, a new smart voltage and current monitoring system (SVCMS) technique is proposed. It monitors a three phase electrical system using an Arduino platform as a microcontroller to read the voltage and current from sensors and then wirelessly send the measured data to monitor the results using a new Android application. The integrated SVCMS design uses an Arduino Nano V3.0 as the microcontroller to measure the results from three voltage and three current sensors and then send this data, after calculation, to the Android smartphone device of an end user using Bluetooth HC-05. The Arduino Nano V3.0 controller and Bluetooth HC-05 are a cheap microcontroller and wireless device, respectively. The new Android smartphone application that monitors the voltage and current measurements uses the open source MIT App Inventor 2 software. It allows for monitoring some elementary fundamental voltage power quality properties. An effort has been made to investigate what is possible using available off-the-shelf components and open source software.

Low noise constant current source for bias dependent noise measurements

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

Talukdar, D.; Bose, Suvendu; Bardhan, K. K.

2011-01-15

A low noise constant current source used for measuring the 1/f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 {mu}A to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noisemore » voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described.« less

A new mathematical model and control of a three-phase AC-DC voltage source converter

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

Blasko, V.; Kaura, V.

1997-01-01

A new mathematical model of the power circuit of a three-phase voltage source converter (VSC) was developed in the stationary and synchronous reference frames. The mathematical model was then used to analyze and synthesize the voltage and current control loops for the VSC. Analytical expressions were derived for calculating the gains and time constants of the current and voltage regulators. The mathematical model was used to control a 140-kW regenerative VSC. The synchronous reference frame model was used to define feedforward signals in the current regulators to eliminate the cross coupling between the d and q phases. It allowed themore » reduction of the current control loop to first-order plants and improved their tracking capability. The bandwidths of the current and voltage-control loops were found to be approximately 20 and 60 times (respectively) smaller than the sampling frequency. All control algorithms were implemented in a digital-signal processor. All results of the analysis were experimentally verified.« less

Multijunction high-voltage solar cell

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr.; Goradia, C.; Chai, A. T.

1981-01-01

Multijunction cell allows for fabrication of high-voltage solar cell on single semiconductor wafer. Photovoltaic energy source using cell is combined on wafer with circuit it is to power. Cell consists of many voltage-generating regions internally or externally interconnected to give desired voltage and current combination. For computer applications, module is built on silicon wafer with energy for internal information processing and readouts derived from external light source.

Power-control switch

NASA Technical Reports Server (NTRS)

Kessler, L. L.

1976-01-01

Constant-current source creates drive current independent of input-voltage variations, 50% reduction in power loss in base drive circuitry, maintains essentially constant charge rate, and improves rise-time consistency over input voltage range.

Influence of the electrode gap separation on the pseudospark-sourced electron beam generation

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

Zhao, J., E-mail: junping.zhao@qq.com; State Key Laboratory of Electrical Insulation and Power Equipment, West Xianning Road, Xi'an 710049; Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG Scotland

Pseudospark-sourced electron beam is a self-focused intense electron beam which can propagate without any external focusing magnetic field. This electron beam can drive a beam-wave interaction directly or after being post-accelerated. It is especially suitable for terahertz radiation generation due to the ability of a pseudospark discharge to produce small size in the micron range and very high current density and bright electron beams. In this paper, a single-gap pseudospark discharge chamber has been built and tested with several electrode gap separations to explore the dependence of the pseudospark-sourced electron beam current on the discharge voltage and the electrode gapmore » separation. Experimental results show that the beam pulses have similar pulse width and delay time from the distinct drop of the applied voltage for smaller electrode gap separations but longer delay time for the largest gap separation used in the experiment. It has been found that the electron beam only starts to occur when the charging voltage is above a certain value, which is defined as the starting voltage of the electron beam. The starting voltage is different for different electrode gap separations and decreases with increasing electrode gap separation in our pseudospark discharge configuration. The electron beam current increases with the increasing discharge voltage following two tendencies. Under the same discharge voltage, the configuration with the larger electrode gap separation will generate higher electron beam current. When the discharge voltage is higher than 10 kV, the beam current generated at the electrode gap separation of 17.0 mm, is much higher than that generated at smaller gap separations. The ionization of the neutral gas in the main gap is inferred to contribute more to the current increase with increasing electrode gap separation.« less

Series Connected Buck-Boost Regulator

NASA Technical Reports Server (NTRS)

Birchenough, Arthur G. (Inventor)

2006-01-01

A Series Connected Buck-Boost Regulator (SCBBR) that switches only a fraction of the input power, resulting in relatively high efficiencies. The SCBBR has multiple operating modes including a buck, a boost, and a current limiting mode, so that an output voltage of the SCBBR ranges from below the source voltage to above the source voltage.

Operation of a voltage source converter at increased utility voltage

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

Kaura, V.; Blasko, V.

1997-01-01

The operation of a voltage source converter (VSC) with regeneration capability, controllable power factor, and low distortion of utility currents is analyzed at increased utility voltage. Increase in the utility voltage causes a VSC to saturate and enter a nonlinear mode of operation. To operate under elevated utility, two steps are taken: (1) a pulse width modulation (PWM) algorithm is implemented which extends the linear region of operation by 15% and (2) a PWM saturation regulator is used to control the reactive current at higher utility voltages. The PWM algorithm reduces the switching losses by at least 33% and themore » effect of blanking time by one-third. All analytical results are experimentally verified on a 100 kW three-phase VSC.« less

The Most Energy Efficient Way to Charge the Capacitor in an RC Circuit

ERIC Educational Resources Information Center

Wang, Dake

2017-01-01

The voltage waveform that minimizes the energy loss in the resistance when charging the capacitor in a resistor-capacitor circuit is investigated using the calculus of variation. A linear voltage ramp gives the best efficiency, which means a constant current source should be used for charging. Comparison between constant current source and…

Performance improvement of doped TFET by using plasma formation concept

NASA Astrophysics Data System (ADS)

Soni, Deepak; Sharma, Dheeraj; Yadav, Shivendra; Aslam, Mohd.; Sharma, Neeraj

2018-01-01

Formation of abrupt doping profile at tunneling junction for the nanoscale tunnel field effect transistor (TFET) is a critical issue for attaining improved electrical behaviour. The realization of abrupt doping profile is more difficult in the case of physically doped TFETs due to material solubility limit. In this concern, we propose a novel design of TFET. For this, P+ (source)-I (channel)-N (drain) type structure has been considered, wherein a metal electrode is deposited over the source region. In addition to this, a negative voltage is applied to the source electrode (SE). It induces the surface plasma layer of holes in the source region, which is responsible for steepness in the bands at source/channel junction and provides the advantage of higher doping in source region without any addition of the physical impurity. The proposed modification is helpful for achieving steeper band bending at the source/channel interface, which enables higher tunneling generation rate of charge carriers at this interface and overcomes the issue of low ON-state current. Thus, the proposed device shows the increment of 2 decades in drain current and 252 mV reduction in threshold voltage compared with conventional device. The optimization of spacer length (LSG) between source/gate (LSG) and applied negative voltage (Vpg) over source electrode have been performed to obtain optimum drain current and threshold voltage (Vth). Further, for the suppression of ambipolar current, drain region is kept lightly doped, which reduces the ambipolar current up to level of Off state current. Moreover, in the proposed device gate electrode is underlapped for improving RF performance. It also reduces gate to drain capacitances (Cgd) and increases cut-off-frequency (fT), fmax, GBP, TFP. In addition to these, linearity analysis has been performed to validate the applicability of the device.

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source.

PubMed

Wang, T; Yang, Z; Dong, P; long, J D; He, X Z; Wang, X; Zhang, K Z; Zhang, L W

2012-06-01

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

Performance of unified power quality conditioner (UPQC) based on fuzzy controller for attenuating of voltage and current harmonics

NASA Astrophysics Data System (ADS)

Milood Almelian, Mohamad; Mohd, Izzeldin I.; Asghaiyer Omran, Mohamed; Ullah Sheikh, Usman

2018-04-01

Power quality-related issues such as current and voltage distortions can adversely affect home and industrial appliances. Although several conventional techniques such as the use of passive and active filters have been developed to increase power quality standards, these methods have challenges and are inadequate due to the increasing number of applications. The Unified Power Quality Conditioner (UPQC) is a modern strategy towards correcting the imperfections of voltage and load current supply. A UPQC is a combination of both series and shunt active power filters in a back-to-back manner with a common DC link capacitor. The control of the voltage of the DC link capacitor is important in achieving a desired UPQC performance. In this paper, the UPQC with a Fuzzy logic controller (FLC) was used to precisely eliminate the imperfections of voltage and current harmonics. The results of the simulation studies using MATLAB/Simulink and Simpower system programming for R-L load associated through an uncontrolled bridge rectifier was used to assess the execution process. The UPQC with FLC was simulated for a system with distorted load current and a system with distorted source voltage and load current. The outcome of the comparison of %THD in the load current and source voltage before and after using UPQC for the two cases was presented.

A Current Source Method For t(sub q) Measurement of Fast Switching Thyristors

NASA Technical Reports Server (NTRS)

Niedra, Janis M.

2006-01-01

A current source driven circuit has been constructed to measure the turn-off time (t(sub q)) of fast-switching SiC thyristors. This circuit operates from a single power supply and a dual channel pulse generator to provide adjustment of forward current, magnitude and duration of reverse applied voltage, and rate of rise of reapplied forward voltage. Values of t(sub q) down to 100 ns can be resolved.

Design and Development of High Voltage Direct Current (DC) Sources for the Solar Array Module Plasma Interaction Experiment

NASA Technical Reports Server (NTRS)

Bibyk, Irene K.; Wald, Lawrence W.

1995-01-01

Two programmable, high voltage DC power supplies were developed as part of the flight electronics for the Solar Array Module Plasma Interaction Experiment (SAMPIE). SAMPIE's primary objectives were to study and characterize the high voltage arcing and parasitic current losses of various solar cells and metal samples within the space plasma of low earth orbit (LEO). High voltage arcing can cause large discontinuous changes in spacecraft potential which lead to damage of the power system materials and significant Electromagnetic Interference (EMI). Parasitic currents cause a change in floating potential which lead to reduced power efficiency. These primary SAMPIE objectives were accomplished by applying artificial biases across test samples over a voltage range from -600 VDC to +300 VDC. This paper chronicles the design, final development, and test of the two programmable high voltage sources for SAMPIE. The technical challenges to the design for these power supplies included vacuum, space plasma effects, thermal protection, Shuttle vibrations and accelerations.

Analysis of spacecraft battery charger systems

NASA Astrophysics Data System (ADS)

Kim, Seong J.; Cho, Bo H.

In spacecraft battery charger systems, switching regulators are widely used for bus voltage regulation, charge current regulation, and peak power tracking. Small-signal dynamic characteristics of the battery charging subsystem of direct energy transfer (DET) and peak power tracking (PPT) systems are analyzed to facilitate design of the control loop for optimum performance and stability. Control loop designs of the charger in various modes of operation are discussed. Analyses are verified through simulations. It is shown that when the charger operates in the bus voltage regulation mode, the control-to-voltage transfer function has a negative DC gain and two LHP zeros in both the DET and PPT systems. The control-to-inductor current transfer function also has a negative DC gain and a RHP zero. Thus, in the current-mode control, the current loop can no longer be used to stabilize the system. When the system operates in the charge current regulation mode, the charger operates with a fixed duty cycle which is determined by the regulated bus voltage and the battery voltage. Without an input filter, the converter becomes a first-order system. When the peak power tracker is inactive, the operating point of the solar array output moves to the voltage source region. Thus, the solar array behaves as a stiff voltage source to a constant power load.

Inverter for Interchangeable Use as Current Source Inverter and Voltage Source Inverter for Interconnecting to Grid

NASA Astrophysics Data System (ADS)

Teruya, Daisuke; Masukawa, Shigeo; Iida, Shoji

We propose a novel inverter that can be operated either as a Current Source Inverter (CSI) or as a Voltage Source Inverter (VSI) by changing only the control signals. It is proper to apply it to the interconnecting system with renewal energy, such as photovoltaic cells or wind generation systems, to a grid. This inverter is usually operated as the CSI connected to the grid. Even if the energy source has a lower voltage than the grid, the energy can be supplied to the grid through the proposed inverter. The power factor can be briefly maintained at almost unity. When power supply from the grid is interrupted, the proposed circuit should be operated as the VSI in the stand-alone operation mode. In this way, the circuit can maintain a constant output voltage to the loads. In this paper, the proposed circuit configuration and the control schemes for both the CSI and the VSI are described. Further, the circuit characteristics for both are discussed experimentally.

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

Wang, T.; Yang, Z.; Dong, P.

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H{sup -}) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H{sup -} beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H{sup -} beam current of aboutmore » 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.« less

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.

Coordinated single-phase control scheme for voltage unbalance reduction in low voltage network.

PubMed

Pullaguram, Deepak; Mishra, Sukumar; Senroy, Nilanjan

2017-08-13

Low voltage (LV) distribution systems are typically unbalanced in nature due to unbalanced loading and unsymmetrical line configuration. This situation is further aggravated by single-phase power injections. A coordinated control scheme is proposed for single-phase sources, to reduce voltage unbalance. A consensus-based coordination is achieved using a multi-agent system, where each agent estimates the averaged global voltage and current magnitudes of individual phases in the LV network. These estimated values are used to modify the reference power of individual single-phase sources, to ensure system-wide balanced voltages and proper power sharing among sources connected to the same phase. Further, the high X / R ratio of the filter, used in the inverter of the single-phase source, enables control of reactive power, to minimize voltage unbalance locally. The proposed scheme is validated by simulating a LV distribution network with multiple single-phase sources subjected to various perturbations.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).

Deducing noninductive current profile from surface voltage evolution

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

Litwin, C.; Wukitch, S.; Hershkowitz, N.

Solving the resistive diffusion equation in the presence of a noninductive current source determines the time-evolution of the surface voltage. By inverting the problem the current drive profile can be determined from the surface voltage evolution. We show that under wide range of conditions the deduced profile is unique. If the conductivity profile is known, this method can be employed to infer the noninductive current profile, and, ipso facto, the profile of the total current. We discuss the application of this method to analyze the Alfven wave current drive experiments in Phaedrus-T.

Testing the Auroral Current-Voltage Relation in Multiple Arcs

NASA Astrophysics Data System (ADS)

Cameron, T. G.; Knudsen, D. J.; Cully, C. M.

2013-12-01

The well-known current-voltage relation within auroral inverted-V regions [Knight, Planet. Space Sci., 21, 741, 1973] predicts current carried by an auroral flux tube given the total potential drop between a plasma-sheet source region and the ionosphere. Numerous previous studies have tested this relation using spacecraft that traverse auroral arcs at low (ionospheric) or mid altitudes. Typically, the potential drop is estimated at the peak of the inverted-V, and field-aligned current is estimated from magnetometer data; statistical information is then gathered over many arc crossings that occur over a wide range of source conditions. In this study we use electron data from the FAST satellite to examine the current-voltage relation in multiple arc sets, in which the key source parameters (plasma sheet density and temperature) are presumed to be identical. We argue that this approach provides a more sensitive test of the Knight relation, and we seek to explain remaining variability with factors other than source variability. This study is supported by a grant from the Natural Sciences and Engineering Research Council of Canada.

Modelling of illuminated current-voltage characteristics to evaluate leakage currents in long wavelength infrared mercury cadmium telluride photovoltaic detectors

NASA Astrophysics Data System (ADS)

Gopal, Vishnu; Qiu, WeiCheng; Hu, Weida

2014-11-01

The current-voltage characteristics of long wavelength mercury cadmium telluride infrared detectors have been studied using a recently suggested method for modelling of illuminated photovoltaic detectors. Diodes fabricated on in-house grown arsenic and vacancy doped epitaxial layers were evaluated for their leakage currents. The thermal diffusion, generation-recombination (g-r), and ohmic currents were found as principal components of diode current besides a component of photocurrent due to illumination. In addition, both types of diodes exhibited an excess current component whose growth with the applied bias voltage did not match the expected growth of trap-assisted-tunnelling current. Instead, it was found to be the best described by an exponential function of the type, Iexcess = Ir0 + K1 exp (K2 V), where Ir0, K1, and K2 are fitting parameters and V is the applied bias voltage. A study of the temperature dependence of the diode current components and the excess current provided the useful clues about the source of origin of excess current. It was found that the excess current in diodes fabricated on arsenic doped epitaxial layers has its origin in the source of ohmic shunt currents. Whereas, the source of excess current in diodes fabricated on vacancy doped epitaxial layers appeared to be the avalanche multiplication of photocurrent. The difference in the behaviour of two types of diodes has been attributed to the difference in the quality of epitaxial layers.

PV source based high voltage gain current fed converter

NASA Astrophysics Data System (ADS)

Saha, Soumya; Poddar, Sahityika; Chimonyo, Kudzai B.; Arunkumar, G.; Elangovan, D.

2017-11-01

This work involves designing and simulation of a PV source based high voltage gain, current fed converter. It deals with an isolated DC-DC converter which utilizes boost converter topology. The proposed converter is capable of high voltage gain and above all have very high efficiency levels as proved by the simulation results. The project intends to produce an output of 800 V dc from a 48 V dc input. The simulation results obtained from PSIM application interface were used to analyze the performance of the proposed converter. Transformer used in the circuit steps up the voltage as well as to provide electrical isolation between the low voltage and high voltage side. Since the converter involves high switching frequency of 100 kHz, ultrafast recovery diodes are employed in the circuitry. The major application of the project is for future modeling of solar powered electric hybrid cars.

Inductive Position Sensor

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor); Simmons, Stephen M. (Inventor)

2015-01-01

An inductive position sensor uses three parallel inductors, each of which has an axial core that is an independent magnetic structure. A first support couples first and second inductors and separate them by a fixed distance. A second support coupled to a third inductor disposed between the first and second inductors. The first support and second support are configured for relative movement as distance changes from the third inductor to each of the first and second inductors. An oscillating current is supplied to the first and second inductors. A device measures a phase component of a source voltage generating the oscillating current and a phase component of voltage induced in the third inductor when the oscillating current is supplied to the first and second inductors such that the phase component of the voltage induced overlaps the phase component of the source voltage.

Method and system for a gas tube switch-based voltage source high voltage direct current transmission system

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

She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui

A voltage source converter based high-voltage direct-current (HVDC) transmission system includes a voltage source converter (VSC)-based power converter channel. The VSC-based power converter channel includes an AC-DC converter and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and a DC-AC inverter include at least one gas tube switching device coupled in electrical anti-parallel with a respective gas tube diode. The VSC-based power converter channel includes a commutating circuit communicatively coupled to one or more of the at least one gas tube switching devices. The commutating circuit is configured to "switch on" a respective one of themore » one or more gas tube switching devices during a first portion of an operational cycle and "switch off" the respective one of the one or more gas tube switching devices during a second portion of the operational cycle.« less

Electrophysiology of connection current spikes.

PubMed

Fish, Raymond M; Geddes, Leslie A

2008-12-01

Connection to a 60-Hz or other voltage source can result in cardiac dysrhythmias, a startle reaction, muscle contractions, and a variety of other physiological responses. Such responses can lead to injury, especially if significant ventricular cardiac dysrhythmias occur, or if a person is working at some height above ground and falls as a result of a musculoskeletal response. Physiological reactions are known to relate to intensity and duration of current exposure. The connection current that flows is a function of the applied voltage at the instant of connection, and the electrical impedance encountered by the voltage source in contact with the skin or other body tissues. In this article we describe a rarely investigated phenomenon, namely a contact, or connection, current spike that is many times higher than the steady-state current. This current spike occurs when an electrical connection is made at a non-zero voltage time in a sine wave or other waveform. Such current spikes may occur when electronic or manual switching or connecting of conductors occurs in electronic instrumentation connected to a patient. These findings are relevant to medical devices and instrumentation and to electrical safety in general.

Comparison of gate and drain current detection of hydrogen at room temperature with AlGaN /GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Wang, Hung-Ta; Kang, B. S.; Ren, F.; Fitch, R. C.; Gillespie, J. K.; Moser, N.; Jessen, G.; Jenkins, T.; Dettmer, R.; Via, D.; Crespo, A.; Gila, B. P.; Abernathy, C. R.; Pearton, S. J.

2005-10-01

Pt-gated AlGaN /GaN high electron mobility transistors can be used as room-temperature hydrogen gas sensors at hydrogen concentrations as low as 100ppm. A comparison of the changes in drain and gate current-voltage (I-V) characteristics with the introduction of 500ppm H2 into the measurement ambient shows that monitoring the change in drain-source current provides a wider gate voltage operation range for maximum detection sensitivity and higher total current change than measuring the change in gate current. However, over a narrow gate voltage range, the relative sensitivity of detection by monitoring the gate current changes is up to an order of magnitude larger than that of drain-source current changes. In both cases, the changes are fully reversible in <2-3min at 25°C upon removal of the hydrogen from the ambient.

40 CFR 63.11454 - What are the monitoring requirements for new and existing sources?

Code of Federal Regulations, 2011 CFR

2011-07-01

... must monitor the secondary voltage and secondary electrical current to each field of the ESP according... this subpart and is controlled with an ESP, you must monitor the voltage and electrical current to each...

40 CFR 63.11454 - What are the monitoring requirements for new and existing sources?

Code of Federal Regulations, 2014 CFR

2014-07-01

... must monitor the secondary voltage and secondary electrical current to each field of the ESP according... this subpart and is controlled with an ESP, you must monitor the voltage and electrical current to each...

40 CFR 63.11454 - What are the monitoring requirements for new and existing sources?

Code of Federal Regulations, 2012 CFR

2012-07-01

... must monitor the secondary voltage and secondary electrical current to each field of the ESP according... this subpart and is controlled with an ESP, you must monitor the voltage and electrical current to each...

40 CFR 63.11454 - What are the monitoring requirements for new and existing sources?

Code of Federal Regulations, 2013 CFR

2013-07-01

... must monitor the secondary voltage and secondary electrical current to each field of the ESP according... this subpart and is controlled with an ESP, you must monitor the voltage and electrical current to each...

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2007-01-09

A high voltage power supply for use in a system such as a microfluidics system, uses a DC--DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC--DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2010-05-04

A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

Modular high voltage power supply for chemical analysis

DOEpatents

Stamps, James F [Livermore, CA; Yee, Daniel D [Dublin, CA

2008-07-15

A high voltage power supply for use in a system such as a microfluidics system, uses a DC-DC converter in parallel with a voltage-controlled resistor. A feedback circuit provides a control signal for the DC-DC converter and voltage-controlled resistor so as to regulate the output voltage of the high voltage power supply, as well as, to sink or source current from the high voltage supply.

The most energy efficient way to charge the capacitor in a RC circuit

NASA Astrophysics Data System (ADS)

Wang, Dake

2017-11-01

The voltage waveform that minimize the energy loss in the resistance when charging the capacitor in a resistor-capacitor circuit is investigated using the calculus of variation. A linear voltage ramp gives the best efficiency, which means a constant current source should be used for charging. Comparison between constant current source and battery-powered system is made to illustrate the energy advantage of the former.

Spectrometer system for optical reflectance measurements

NASA Technical Reports Server (NTRS)

Phillipps, Patrick G. (Inventor); Soller, Babs R. (Inventor); Parker, Michael S. (Inventor)

2007-01-01

A spectrometer system includes a thermal light source for illuminating a sample, where the thermal light source includes a filament that emits light when heated. The system additionally includes a spectrograph for measuring a light spectrum from the sample and an electrical circuit for supplying electrical current to the filament to heat the filament and for controlling a resistance of the filament. The electrical circuit includes a power supply that supplies current to the filament, first electrical components that sense a current through the filament, second electrical components that sense a voltage drop across the filament, third electrical components that compare a ratio of the sensed voltage drop and the sensed current with a predetermined value, and fourth electrical components that control the current through the filament or the voltage drop across the filament to cause the ratio to equal substantially the predetermined value.

Inrush Current Suppression Circuit and Method for Controlling When a Load May Be Fully Energized

NASA Technical Reports Server (NTRS)

Schwerman, Paul (Inventor)

2017-01-01

A circuit and method for controlling when a load may be fully energized includes directing electrical current through a current limiting resistor that has a first terminal connected to a source terminal of a field effect transistor (FET), and a second terminal connected to a drain terminal of the FET. The gate voltage magnitude on a gate terminal of the FET is varied, whereby current flow through the FET is increased while current flow through the current limiting resistor is simultaneously decreased. A determination is made as to when the gate voltage magnitude on the gate terminal is equal to or exceeds a predetermined reference voltage magnitude, and the load is enabled to be fully energized when the gate voltage magnitude is equal to or exceeds the predetermined reference voltage magnitude.

A new balancing three level three dimensional space vector modulation strategy for three level neutral point clamped four leg inverter based shunt active power filter controlling by nonlinear back stepping controllers.

PubMed

Chebabhi, Ali; Fellah, Mohammed Karim; Kessal, Abdelhalim; Benkhoris, Mohamed F

2016-07-01

In this paper is proposed a new balancing three-level three dimensional space vector modulation (B3L-3DSVM) strategy which uses a redundant voltage vectors to realize precise control and high-performance for a three phase three-level four-leg neutral point clamped (NPC) inverter based Shunt Active Power Filter (SAPF) for eliminate the source currents harmonics, reduce the magnitude of neutral wire current (eliminate the zero-sequence current produced by single-phase nonlinear loads), and to compensate the reactive power in the three-phase four-wire electrical networks. This strategy is proposed in order to gate switching pulses generation, dc bus voltage capacitors balancing (conserve equal voltage of the two dc bus capacitors), and to switching frequency reduced and fixed of inverter switches in same times. A Nonlinear Back Stepping Controllers (NBSC) are used for regulated the dc bus voltage capacitors and the SAPF injected currents to robustness, stabilizing the system and to improve the response and to eliminate the overshoot and undershoot of traditional PI (Proportional-Integral). Conventional three-level three dimensional space vector modulation (C3L-3DSVM) and B3L-3DSVM are calculated and compared in terms of error between the two dc bus voltage capacitors, SAPF output voltages and THDv, THDi of source currents, magnitude of source neutral wire current, and the reactive power compensation under unbalanced single phase nonlinear loads. The success, robustness, and the effectiveness of the proposed control strategies are demonstrated through simulation using Sim Power Systems and S-Function of MATLAB/SIMULINK. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Magneto-acousto-electrical tomography: a potential method for imaging current density and electrical impedance.

PubMed

Haider, S; Hrbek, A; Xu, Y

2008-06-01

Primarily this report outlines our investigation on utilizing magneto-acousto-electrical-tomography (MAET) to image the lead field current density in volume conductors. A lead field current density distribution is obtained when a current/voltage source is applied to a sample via a pair of electrodes. This is the first time a high-spatial-resolution image of current density is presented using MAET. We also compare an experimental image of current density in a sample with its corresponding numerical simulation. To image the lead field current density, rather than applying a current/voltage source directly to the sample, we place the sample in a static magnetic field and focus an ultrasonic pulse on the sample to simulate a point-like current dipole source at the focal point. Then by using electrodes we measure the voltage/current signal which, based on the reciprocity theorem, is proportional to a component of the lead field current density. In the theory section, we derive the equation relating the measured voltage to the lead field current density and the displacement velocity caused by ultrasound. The experimental data include the MAET signal and an image of the lead field current density for a thin sample. In addition, we discuss the potential improvements for MAET especially to overcome the limitation created by the observation that no signal was detected from the interior of a region having a uniform conductivity. As an auxiliary we offer a mathematical formula whereby the lead field current density may be utilized to reconstruct the distribution of the electrical impedance in a piecewise smooth object.

Method and system for operating an electric motor

DOEpatents

Gallegos-Lopez, Gabriel; Hiti, Silva; Perisic, Milun

2013-01-22

Methods and systems for operating an electric motor having a plurality of windings with an inverter having a plurality of switches coupled to a voltage source are provided. A first plurality of switching vectors is applied to the plurality of switches. The first plurality of switching vectors includes a first ratio of first magnitude switching vectors to second magnitude switching vectors. A direct current (DC) current associated with the voltage source is monitored during the applying of the first plurality of switching vectors to the plurality of switches. A second ratio of the first magnitude switching vectors to the second magnitude switching vectors is selected based on the monitoring of the DC current associated with the voltage source. A second plurality of switching vectors is applied to the plurality of switches. The second plurality of switching vectors includes the second ratio of the first magnitude switching vectors to the second magnitude switching vectors.

The negative hydrogen Penning ion gauge ion source for KIRAMS-13 cyclotron

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

An, D. H.; Jung, I. S.; Kang, J.

2008-02-15

The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 {mu}A from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This papermore » presents the results of the dc H-extraction measurement and the expansion gap experiment.« less

A Method of Maximum Power Control in Single-phase Utility Interactive Photovoltaic Generation System by using PWM Current Source Inverter

NASA Astrophysics Data System (ADS)

Neba, Yasuhiko

This paper deals with a maximum power point tracking (MPPT) control of the photovoltaic generation with the single-phase utility interactive inverter. The photovoltaic arrays are connected by employing the PWM current source inverter to the utility. The use of the pulsating dc current and voltage allows the maximum power point to be searched. The inverter can regulate the array voltage and keep the arrays to the maximum power. This paper gives the control method and the experimental results.

Modelling of illuminated current–voltage characteristics to evaluate leakage currents in long wavelength infrared mercury cadmium telluride photovoltaic detectors

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

Gopal, Vishnu, E-mail: vishnu-46@yahoo.com, E-mail: wdhu@mail.sitp.ac.cn; Qiu, WeiCheng; Hu, Weida, E-mail: vishnu-46@yahoo.com, E-mail: wdhu@mail.sitp.ac.cn

2014-11-14

The current–voltage characteristics of long wavelength mercury cadmium telluride infrared detectors have been studied using a recently suggested method for modelling of illuminated photovoltaic detectors. Diodes fabricated on in-house grown arsenic and vacancy doped epitaxial layers were evaluated for their leakage currents. The thermal diffusion, generation–recombination (g-r), and ohmic currents were found as principal components of diode current besides a component of photocurrent due to illumination. In addition, both types of diodes exhibited an excess current component whose growth with the applied bias voltage did not match the expected growth of trap-assisted-tunnelling current. Instead, it was found to be themore » best described by an exponential function of the type, I{sub excess} = I{sub r0} + K{sub 1} exp (K{sub 2} V), where I{sub r0}, K{sub 1}, and K{sub 2} are fitting parameters and V is the applied bias voltage. A study of the temperature dependence of the diode current components and the excess current provided the useful clues about the source of origin of excess current. It was found that the excess current in diodes fabricated on arsenic doped epitaxial layers has its origin in the source of ohmic shunt currents. Whereas, the source of excess current in diodes fabricated on vacancy doped epitaxial layers appeared to be the avalanche multiplication of photocurrent. The difference in the behaviour of two types of diodes has been attributed to the difference in the quality of epitaxial layers.« less

Megawatt-Scale Power Hardware-in-the-Loop Simulation Testing of a Power Conversion Module for Naval Applications

DTIC Science & Technology

2015-06-21

problem was detected . Protection elements were implemented to trigger on over- voltage , over-current, over/under-frequency, and zero-sequence voltage ...power hardware in the loop simulation of distribution networks with photovoltaic generation,” International Journal of Renewable Energy Research...source modules were intended to support both emulation of a representative gas turbine generator set, as well as a flexible, controllable voltage source

Complementary power output characteristics of electromagnetic generators and triboelectric generators.

PubMed

Fan, Feng-Ru; Tang, Wei; Yao, Yan; Luo, Jianjun; Zhang, Chi; Wang, Zhong Lin

2014-04-04

Recently, a triboelectric generator (TEG) has been invented to convert mechanical energy into electricity by a conjunction of triboelectrification and electrostatic induction. Compared to the traditional electromagnetic generator (EMG) that produces a high output current but low voltage, the TEG has different output characteristics of low output current but high output voltage. In this paper, we present a comparative study regarding the fundamentals of TEGs and EMGs. The power output performances of the EMG and the TEG have a special complementary relationship, with the EMG being a voltage source and the TEG a current source. Utilizing a power transformed and managed (PTM) system, the current output of a TEG can reach as high as ∼3 mA, which can be coupled with the output signal of an EMG to enhance the output power. We also demonstrate a design to integrate a TEG and an EMG into a single device for simultaneously harvesting mechanical energy. In addition, the integrated NGs can independently output a high voltage and a high current to meet special needs.

Performance analyses of Z-source and quasi Z-source inverter for photovoltaic applications

NASA Astrophysics Data System (ADS)

Himabind, S.; Priya, T. Hari; Manjeera, Ch.

2018-04-01

This paper presents the comparative analysis of Z-source and Quasi Z-source converter for renewable energy applications. Due to the dependency of renewable energy sources on external weather conditions the output voltage, current changes accordingly which effects the performance of traditional voltage source and current source inverters connected across it. To overcome the drawbacks of VSI and CSI, Z-source and Quasi Z-source inverter (QZSI) are used, which can perform multiple tasks like ac-to-dc, dc-to-ac, ac-to-ac, dc-to-dc conversion. They can be used for both buck and boost operations, by utilizing the shoot-through zero state. The QZSI is derived from the ZSI topology, with a slight change in the impedance network and it overcomes the drawbacks of ZSI. The QZSI draws a constant current from the source when compared to ZSI. A comparative analysis is performed between Z-source and Quasi Z-source inverter, simulation is performed in MATLAB/Simulink environment.

Ultra-short ion and neutron pulse production

DOEpatents

Leung, Ka-Ngo; Barletta, William A.; Kwan, Joe W.

2006-01-10

An ion source has an extraction system configured to produce ultra-short ion pulses, i.e. pulses with pulse width of about 1 .mu.s or less, and a neutron source based on the ion source produces correspondingly ultra-short neutron pulses. To form a neutron source, a neutron generating target is positioned to receive an accelerated extracted ion beam from the ion source. To produce the ultra-short ion or neutron pulses, the apertures in the extraction system of the ion source are suitably sized to prevent ion leakage, the electrodes are suitably spaced, and the extraction voltage is controlled. The ion beam current leaving the source is regulated by applying ultra-short voltage pulses of a suitable voltage on the extraction electrode.

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

NASA Astrophysics Data System (ADS)

Reisgen, Uwe; Schleser, Markus; Mokrov, Oleg; Zabirov, Alexander

2011-06-01

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.

Versatile plasma ion source with an internal evaporator

NASA Astrophysics Data System (ADS)

Turek, M.; Prucnal, S.; Drozdziel, A.; Pyszniak, K.

2011-04-01

A novel construction of an ion source with an evaporator placed inside a plasma chamber is presented. The crucible is heated to high temperatures directly by arc discharge, which makes the ion source suitable for substances with high melting points. The compact ion source enables production of intense ion beams for wide spectrum of solid elements with typical separated beam currents of ˜100-150 μA for Al +, Mn +, As + (which corresponds to emission current densities of 15-25 mA/cm 2) for the extraction voltage of 25 kV. The ion source works for approximately 50-70 h at 100% duty cycle, which enables high ion dose implantation. The typical power consumption of the ion source is 350-400 W. The paper presents detailed experimental data (e.g. dependences of ion currents and anode voltages on discharge and filament currents and magnetic flux densities) for Cr, Fe, Al, As, Mn and In. The discussion is supported by results of Monte Carlo method based numerical simulation of ionisation in the ion source.

Broad-beam high-current dc ion source based on a two-stage glow discharge plasma.

PubMed

Vizir, A V; Oks, E M; Yushkov, G Yu

2010-02-01

We have designed, made, and demonstrated a broad-beam, dc, ion source based on a two-stage, hollow-cathode, and glow discharges plasma. The first-stage discharge (auxiliary discharge) produces electrons that are injected into the cathode cavity of a second-stage discharge (main discharge). The electron injection causes a decrease in the required operating pressure of the main discharge down to 0.05 mTorr and a decrease in required operating voltage down to about 50 V. The decrease in operating voltage of the main discharge leads to a decrease in the fraction of impurity ions in the ion beam extracted from the main gas discharge plasma to less than 0.2%. Another feature of the source is a single-grid accelerating system in which the ion accelerating voltage is applied between the plasma itself and the grid electrode. The source has produced steady-state Ar, O, and N ion beams of about 14 cm diameter and current of more than 2 A at an accelerating voltage of up to 2 kV.

The Application of Auto-Disturbance Rejection Control Optimized by Least Squares Support Vector Machines Method and Time-Frequency Representation in Voltage Source Converter-High Voltage Direct Current System.

PubMed

Liu, Ying-Pei; Liang, Hai-Ping; Gao, Zhong-Ke

2015-01-01

In order to improve the performance of voltage source converter-high voltage direct current (VSC-HVDC) system, we propose an improved auto-disturbance rejection control (ADRC) method based on least squares support vector machines (LSSVM) in the rectifier side. Firstly, we deduce the high frequency transient mathematical model of VSC-HVDC system. Then we investigate the ADRC and LSSVM principles. We ignore the tracking differentiator in the ADRC controller aiming to improve the system dynamic response speed. On this basis, we derive the mathematical model of ADRC controller optimized by LSSVM for direct current voltage loop. Finally we carry out simulations to verify the feasibility and effectiveness of our proposed control method. In addition, we employ the time-frequency representation methods, i.e., Wigner-Ville distribution (WVD) and adaptive optimal kernel (AOK) time-frequency representation, to demonstrate our proposed method performs better than the traditional method from the perspective of energy distribution in time and frequency plane.

The Application of Auto-Disturbance Rejection Control Optimized by Least Squares Support Vector Machines Method and Time-Frequency Representation in Voltage Source Converter-High Voltage Direct Current System

PubMed Central

Gao, Zhong-Ke

2015-01-01

In order to improve the performance of voltage source converter-high voltage direct current (VSC-HVDC) system, we propose an improved auto-disturbance rejection control (ADRC) method based on least squares support vector machines (LSSVM) in the rectifier side. Firstly, we deduce the high frequency transient mathematical model of VSC-HVDC system. Then we investigate the ADRC and LSSVM principles. We ignore the tracking differentiator in the ADRC controller aiming to improve the system dynamic response speed. On this basis, we derive the mathematical model of ADRC controller optimized by LSSVM for direct current voltage loop. Finally we carry out simulations to verify the feasibility and effectiveness of our proposed control method. In addition, we employ the time-frequency representation methods, i.e., Wigner-Ville distribution (WVD) and adaptive optimal kernel (AOK) time-frequency representation, to demonstrate our proposed method performs better than the traditional method from the perspective of energy distribution in time and frequency plane. PMID:26098556

Threshold Voltage Instability in A-Si:H TFTS and the Implications for Flexible Displays and Circuits

DTIC Science & Technology

2008-12-01

and negative gate voltages with and without elevated drain voltages for FDC TFTs. Extending techniques used to localize hot electron degradation...in MOSFETs, experiments in our lab have localized the degradation of a-Si:H to the gate dielectric/a-Si:H channel interface [Shringarpure, et al...saturation, increased drain source current measured with the source and drain reversed indicates localization of ΔVth to the gate dielectric/amorphous

Optical voltage reference

DOEpatents

Rankin, Richard; Kotter, Dale

1994-01-01

An optical voltage reference for providing an alternative to a battery source. The optical reference apparatus provides a temperature stable, high precision, isolated voltage reference through the use of optical isolation techniques to eliminate current and impedance coupling errors. Pulse rate frequency modulation is employed to eliminate errors in the optical transmission link while phase-lock feedback is employed to stabilize the frequency to voltage transfer function.

A Passive EMI Filter with Access to the Ungrounded Motor Neutral Line-The Case that a General-Purpose Inverter is Directly Connected to a Three-Phase Grounded Voltage Source-

NASA Astrophysics Data System (ADS)

Doumoto, Takafumi; Akagi, Hirofumi

This paper proposes a small-sized passive EMI filter for the purpose of eliminating high-frequency shaft voltage and ground leakage current from an ac motor. The motor is driven by a general-purpose PWM inverter connected to a three-phase grounded voltage source. The passive EMI filter requires access to the ungrounded neutral point of the motor. This unique circuit configuration makes the common-mode inductor effective in reducing the high-frequency common-mode voltage generated by the PWM inverter with a carrier frequency of 15kHz. As a result, both high-frequency shaft voltage and ground leakage current can be eliminated very efficiently. However, the common-mode inductor may not play any role in reducing the low-frequency common-mode voltage generated by the diode rectifier, so that a low-frequency component still remains in the shaft voltage. Such a low-frequency shaft voltage may not produce any bad effect on motor bearings. The validity and effectiveness of the EMI filter is verified by experimental results obtained from a 200-V 5-kVA laboratory system.

Use of a wire scanner for monitoring residual gas ionization in Soreq Applied Research Accelerator Facility 20 keV/u proton/deuteron low energy beam transport beam line

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

Vainas, B.; Eliyahu, I.; Weissman, L.

2012-02-15

The ion source end of the Soreq Applied Research Accelerator Facility accelerator consists of a proton/deuteron ECR ion source and a low energy beam transport (LEBT) beam line. An observed reduction of the radio frequency quadrupole transmission with increase of the LEBT current prompted additional study of the LEBT beam properties. Numerous measurements have been made with the LEBT bream profiler wire biased by a variable voltage. Current-voltage characteristics in presence of the proton beam were measured even when the wire was far out of the beam. The current-voltage characteristic in this case strongly resembles an asymmetric diodelike characteristic, whichmore » is typical of Langmuir probes monitoring plasma. The measurement of biased wire currents, outside the beam, enables us to estimate the effective charge density in vacuum.« less

Microsecond Electron Beam Source with Electron Energy Up to 400 Kev and Plasma Anode

NASA Astrophysics Data System (ADS)

Abdullin, É. N.; Basov, G. F.; Shershnev, S.

2017-12-01

A new high-power source of electrons with plasma anode for producing high-current microsecond electron beams with electron energy up to 400 keV has been developed, manufactured, and put in operation. To increase the cross section and pulse current duration of the beam, a multipoint explosive emission cathode is used in the electron beam source, and the beam is formed in an applied external guiding magnetic field. The Marx generator with vacuum insulation is used as a high-voltage source. Electron beams with electron energy up to 300-400 keV, current of 5-15 kA, duration of 1.5-3 μs, energy up to 4 kJ, and cross section up to 150 cm2 have been produced. The operating modes of the electron beam source are realized in which the applied voltage is influenced weakly on the current. The possibility of source application for melting of metal surfaces is demonstrated.

Stable Extraction of Threshold Voltage Using Transconductance Change Method for CMOS Modeling, Simulation and Characterization

NASA Astrophysics Data System (ADS)

Choi, Woo Young; Woo, Dong-Soo; Choi, Byung Yong; Lee, Jong Duk; Park, Byung-Gook

2004-04-01

We proposed a stable extraction algorithm for threshold voltage using transconductance change method by optimizing node interval. With the algorithm, noise-free gm2 (=dgm/dVGS) profiles can be extracted within one-percent error, which leads to more physically-meaningful threshold voltage calculation by the transconductance change method. The extracted threshold voltage predicts the gate-to-source voltage at which the surface potential is within kT/q of φs=2φf+VSB. Our algorithm makes the transconductance change method more practical by overcoming noise problem. This threshold voltage extraction algorithm yields the threshold roll-off behavior of nanoscale metal oxide semiconductor field effect transistor (MOSFETs) accurately and makes it possible to calculate the surface potential φs at any other point on the drain-to-source current (IDS) versus gate-to-source voltage (VGS) curve. It will provide us with a useful analysis tool in the field of device modeling, simulation and characterization.

Quasi-multi-pulse voltage source converter design with two control degrees of freedom

NASA Astrophysics Data System (ADS)

Vural, A. M.; Bayindir, K. C.

2015-05-01

In this article, the design details of a quasi-multi-pulse voltage source converter (VSC) switched at line frequency of 50 Hz are given in a step-by-step process. The proposed converter is comprised of four 12-pulse converter units, which is suitable for the simulation of single-/multi-converter flexible alternating current transmission system devices as well as high voltage direct current systems operating at the transmission level. The magnetic interface of the converter is originally designed with given all parameters for 100 MVA operation. The so-called two-angle control method is adopted to control the voltage magnitude and the phase angle of the converter independently. PSCAD simulation results verify both four-quadrant converter operation and closed-loop control of the converter operated as static synchronous compensator (STATCOM).

Methods and apparatus for measurement of the resistivity of geological formations from within cased wells in presence of acoustic and magnetic energy sources

DOEpatents

Vail, W.B. III.

1991-08-27

Methods and apparatus are provided for measuring the acoustically modulated electronic properties of geological formations and cement layers adjacent to cased boreholes. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. Voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the leakage current conducted into formation in the vicinity of those electrodes. Simultaneously subjecting the casing and formation to an acoustic source acoustically modulates the leakage current measured thereby providing a measure of the acoustically modulated electronic properties of the adjacent formation. Similarly, methods and apparatus are also described which measure the leakage current into formation while simultaneously subjecting the casing to an applied magnetic field which therefore allows measurement of the magnetically modulated electronic properties of the casing and the adjacent formation. 9 figures.

Methods and apparatus for measurement of the resistivity of geological formations from within cased wells in presence of acoustic and magnetic energy sources

DOEpatents

Vail, III, William B.

1991-01-01

Methods and apparatus are provided for measuring the acoustically modulated electronic properties of geological formations and cement layers adjacent to cased boreholes. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. Voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the leakage current conducted into formation in the vicinity of those electrodes. Simultaneously subjecting the casing and formation to an acoustic source acoustically modulates the leakage current measured thereby providing a measure of the acoustically modulated electronic properties of the adjacent formation. Similarly, methods and apparatus are also described which measure the leakage current into formation while simultaneously subjecting the casing to an applied magnetic field which therefore allows measurement of the magnetically modulated electronic properties of the casing and the adjacent formation.

An Unsolved Electric Circuit: A Common Misconception

ERIC Educational Resources Information Center

Harsha, N. R. Sree; Sreedevi, A.; Prakash, Anupama

2015-01-01

Despite a number of theories in circuit analysis, little is known about the behaviour of ideal equal voltage sources in parallel, connected across a resistive load. We neither have any theory that can predict the voltage source that provides the load current, nor is there any method to test it experimentally. In a series of experiments performed…

Implications of Pulser Voltage Ripple

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

Barnard, J J

In a recent set of measurements obtained by G. Kamin, W. Manning, A. Molvik, and J. Sullivan, the voltage waveform of the diode pulser had a ripple of approximately {+-}1.3% of the 65 kV flattop voltage, and the beam current had a larger corresponding ripple of approximately {+-}8.4% of the 1.5 mA average current at the location of the second Faraday cup, approximately 1.9 m downstream from the ion source. The period of the ripple was about 1 {mu}s. It was initially unclear whether this large current ripple was in fact a true measurement of the current or a spuriousmore » measurement of noise produced by the pulser electronics. The purpose of this note is to provide simulations which closely match the experimental results and thereby corroborate the physical nature of those measurements, and to provide predictions of the amplitude of the current ripples as they propagate to the end of linear transport section. Additionally analytic estimates are obtained which lend some insight into the nature of the current fluctuations and to provide an estimate of what the maximum amplitude of the current fluctuations are expected to be, and conversely what initial ripple in the voltage source is allowed, given a smaller acceptable tolerance on the line charge density.« less

Optical voltage reference

DOEpatents

Rankin, R.; Kotter, D.

1994-04-26

An optical voltage reference for providing an alternative to a battery source is described. The optical reference apparatus provides a temperature stable, high precision, isolated voltage reference through the use of optical isolation techniques to eliminate current and impedance coupling errors. Pulse rate frequency modulation is employed to eliminate errors in the optical transmission link while phase-lock feedback is employed to stabilize the frequency to voltage transfer function. 2 figures.

Nitrate removal from pharmaceutical wastewater using microbial electrochemical system supplied through low frequency-low voltage alternating electric current.

PubMed

Hoseinzadeh, Edris; Rezaee, Abbas; Farzadkia, Mahdi

2018-04-01

In this study, a microbial electrochemical system (MES) was designed to evaluate the effects of a low frequency-low voltage alternating electrical current on denitrification efficacy in the presence of ibuprofen as a low biodegradable organic carbon source. Cylindrical carbon cloth and stainless steel mesh electrodes containing a consortium of heterotrophic and autotrophic bacteria were mounted in the wall of the designed laboratory-scale bioreactor. The effects of inlet nitrate concentration (50-800mgL -1 ), retention time (2.5-24h), waveform magnitude (0.1-9.6V p-p ), adjustable direct current voltage added to offset voltage (0.1-4.9V), alternating current frequency (10-60Hz), and waveforms (sinusoidal, square, and ramp) were studied in this work. The results showed that the proposed system removes 800mgL -1 nitrate up to 95% during 6.5h. Optimum conditions were obtained in the 8V p-p using a frequency of 10Hz of a sinusoidal waveform. The morphology studies confirmed bacterial morphology change when applying the alternating current. Dehydrogenase activity of biofilms formed on surface of stainless steel electrodes increased to 15.24μgTFmg biomass cm -2 d. The maximum bacterial activity was obtained at a voltage of 8V p-p . The experimental results revealed that the MES using a low frequency-low voltage alternating electrical current is a promising technique for nitrate removal from pharmaceutical wastewaters in the presence of low biodegradability of carbon sources such as ibuprofen. Copyright © 2017 Elsevier B.V. All rights reserved.

ESD robustness improving for the low-voltage triggering silicon-controlled rectifier by adding NWell at cathode

NASA Astrophysics Data System (ADS)

Jin, Xiangliang; Zheng, Yifei; Wang, Yang; Guan, Jian; Hao, Shanwan; Li, Kan; Luo, Jun

2018-01-01

The low-voltage triggering silicon-controlled rectifier (LVTSCR) device is widely used in on-chip electrostatic discharge (ESD) protection owing to its low trigger voltage and strong current-tolerating capability per area. In this paper, an improved LVTSCR by adding a narrow NWell (NW2) under the source region of NMOS is discussed, which is realized in a 0.5-μm CMOS process. A 2-dimension (2D) device simulation platform and a transmission line pulse (TLP) testing system are used to predict and characterize the proposed ESD protection devices. According to the measurement results, compared with the preliminary LVTSCR, the improved LVTSCR elevates the second breakdown current (It2) from 2.39 A to 5.54 A and increases the holding voltage (Vh) from 3.04 V to 4.09 V without expanding device area or sacrificing any ESD performances. Furthermore, the influence of the size of the narrow NWell under the source region of NMOS on holding voltage is also discussed.

Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments.

PubMed

Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

2012-08-01

We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 10(17) m(-3), i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

Modeling, Development and Control of Multilevel Converters for Power System Application =

NASA Astrophysics Data System (ADS)

Vahedi, Hani

The main goal of this project is to develop a multilevel converter topology to be useful in power system applications. Although many topologies are introduced rapidly using a bunch of switches and isolated dc sources, having a single-dc-source multilevel inverter is still a matter of controversy. In fact, each isolated dc source means a bulky transformer and a rectifier that have their own losses and costs forcing the industries to avoid entering in this topic conveniently. On the other hand, multilevel inverters topologies with single-dc-source require associated controllers to regulate the dc capacitors voltages in order to have multilevel voltage waveform at the output. Thus, a complex controller would not interest investors properly. Consequently, developing a single-dc-source multilevel inverter topology along with a light and reliable voltage control is still a challenging topic to replace the 2-level inverters in the market effectively. The first effort in this project was devoted to the PUC7 inverter to design a simple and yet efficient controller. A new modelling is performed on the PUC7 inverter and it has been simplified to first order system. Afterwards, a nonlinear cascaded controller is designed and applied to regulate the capacitor voltage at 1/3 of the DC source amplitude and to generate 7 identical voltage levels at the output supplying different type of loads such as RL or rectifier harmonic ones. In next work, the PUC5 topology is proposed as a remedy to the PUC7 that requires a complicated controller to operate properly. The capacitor voltage is regulated at half of dc source amplitude to generate 5 voltage levels at the output. Although the 7-level voltage waveform is replaced by a 5-level one in PUC5 topology, it is shown that the PUC5 needs a very simple and reliable voltage balancing technique due to having some redundant switching states. Moreover, a sensor-less voltage balancing technique is designed and implemented on the PUC5 inverter successfully to work in both stand-alone and gridconnected mode of operation. Eventually, a modified configuration of the PUC5 topology is presented to work as a buck PFC rectifier. The internal performance of the rectifier is like a buck converter to generate stepped down DC voltages at the two output terminals while the grid sees a boost converter externally. As well, a decoupled voltage/current controller is designed and applied to balance the output voltages identically and synchronize the input current with grid voltage to have a PFC operation acceptably. A power balance analysis is done to show the load variation range limit. All the theoretical and simulation studies are validated by experimental results completely.

A Complete Multimode Equivalent-Circuit Theory for Electrical Design

PubMed Central

Williams, Dylan F.; Hayden, Leonard A.; Marks, Roger B.

1997-01-01

This work presents a complete equivalent-circuit theory for lossy multimode transmission lines. Its voltages and currents are based on general linear combinations of standard normalized modal voltages and currents. The theory includes new expressions for transmission line impedance matrices, symmetry and lossless conditions, source representations, and the thermal noise of passive multiports. PMID:27805153

Generation of electrical power

DOEpatents

Hursen, Thomas F.; Kolenik, Steven A.; Purdy, David L.

1976-01-01

A heat-to-electricity converter is disclosed which includes a radioactive heat source and a thermoelectric element of relatively short overall length capable of delivering a low voltage of the order of a few tenths of a volt. Such a thermoelectric element operates at a higher efficiency than longer higher-voltage elements; for example, elements producing 6 volts. In the generation of required power, thermoelectric element drives a solid-state converter which is controlled by input current rather than input voltage and operates efficiently for a high signal-plus-noise to signal ratio of current. The solid-state converter has the voltage gain necessary to deliver the required voltage at the low input of the thermoelectric element.

Light intensity-voltage correlations and leakage-current excess noise in a single-mode semiconductor laser

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

Maurin, I.; Bramati, A.; Giacobino, E.

2005-09-15

Semiconductor lasers are particularly well suited for the implementation of pump-noise suppression, yielding a reduction of the intensity noise in the laser. In this simple picture, the maximal amount of squeezing is equal to the quantum efficiency. However, experimental results on intensity noise reduction by pump-noise suppression are usually above this limit. This discrepancy suggests that additional noise sources must be involved. Here we successful y interpret the full noise behavior of a single-mode laser diode far above threshold by considering two excess noise sources: the leakage current fluctuations across the laser and the Petermann excess noise. We have estimatedmore » the contribution of each noise source using the results of the correlations between the laser output intensity noise and the voltage fluctuations across the laser diode (light-voltage correlations) and obtained good agreement between our theory and experimental results.« less

Method and system for a gas tube-based current source high voltage direct current transmission system

DOEpatents

She, Xu; Chokhawala, Rahul Shantilal; Bray, James William; Sommerer, Timothy John; Zhou, Rui; Zhang, Di

2017-08-29

A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to "switch on" one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and "switch off" the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

Performance Analysis of a Static Synchronous Compensator (STATCOM)

NASA Astrophysics Data System (ADS)

Kambey, M. M.; Ticoh, J. D.

2018-02-01

Reactive power and voltage are some of the problems in electric power supply and A Gate Turn Off (GTO) Static Synchronous Compensator (STATCOM) is one of the type of FACTS with shunt which can supply variable reactive power and regulate the voltage of the bus where it is connected. This study only discuss about the performance characteristic of the three phase six-pulse STATCOM by analysing the current wave flowing through DC Capacitor which depend on switching current and capacitor voltage wave. Simulation methods used in this research is started with a mathematical analysis of the ac current, dc voltage and current equations that pass STATCOM from a literature. The result shows the presence of the capacitor voltage ripple also alters the ac current waveform, even though the errors to be not very significant and the constraint of the symmetry circuit is valid if the source voltages have no zero sequence components and the impedances in all the three phases are identical. There for to improve STATCOM performance it is necessary to use multi-pulse 12, 24, 36, 48 or more, and/or with a multilevel converter.

Current-voltage characteristics influenced by the nanochannel diameter and surface charge density in a fluidic field-effect-transistor.

PubMed

Singh, Kunwar Pal; Guo, Chunlei

2017-06-21

The nanochannel diameter and surface charge density have a significant impact on current-voltage characteristics in a nanofluidic transistor. We have simulated the effect of the channel diameter and surface charge density on current-voltage characteristics of a fluidic nanochannel with positive surface charge on its walls and a gate electrode on its surface. Anion depletion/enrichment leads to a decrease/increase in ion current with gate potential. The ion current tends to increase linearly with gate potential for narrow channels at high surface charge densities and narrow channels are more effective to control the ion current at high surface charge densities. The current-voltage characteristics are highly nonlinear for wide channels at low surface charge densities and they show different regions of current change with gate potential. The ion current decreases with gate potential after attaining a peak value for wide channels at low values of surface charge densities. At low surface charge densities, the ion current can be controlled by a narrow range of gate potentials for wide channels. The current change with source drain voltage shows ohmic, limiting and overlimiting regions.

3-D time-domain induced polarization tomography: a new approach based on a source current density formulation

NASA Astrophysics Data System (ADS)

Soueid Ahmed, A.; Revil, A.

2018-04-01

Induced polarization (IP) of porous rocks can be associated with a secondary source current density, which is proportional to both the intrinsic chargeability and the primary (applied) current density. This gives the possibility of reformulating the time domain induced polarization (TDIP) problem as a time-dependent self-potential-type problem. This new approach implies a change of strategy regarding data acquisition and inversion, allowing major time savings for both. For inverting TDIP data, we first retrieve the electrical resistivity distribution. Then, we use this electrical resistivity distribution to reconstruct the primary current density during the injection/retrieval of the (primary) current between the current electrodes A and B. The time-lapse secondary source current density distribution is determined given the primary source current density and a distribution of chargeability (forward modelling step). The inverse problem is linear between the secondary voltages (measured at all the electrodes) and the computed secondary source current density. A kernel matrix relating the secondary observed voltages data to the source current density model is computed once (using the electrical conductivity distribution), and then used throughout the inversion process. This recovered source current density model is in turn used to estimate the time-dependent chargeability (normalized voltages) in each cell of the domain of interest. Assuming a Cole-Cole model for simplicity, we can reconstruct the 3-D distributions of the relaxation time τ and the Cole-Cole exponent c by fitting the intrinsic chargeability decay curve to a Cole-Cole relaxation model for each cell. Two simple cases are studied in details to explain this new approach. In the first case, we estimate the Cole-Cole parameters as well as the source current density field from a synthetic TDIP data set. Our approach is successfully able to reveal the presence of the anomaly and to invert its Cole-Cole parameters. In the second case, we perform a laboratory sandbox experiment in which we mix a volume of burning coal and sand. The algorithm is able to localize the burning coal both in terms of electrical conductivity and chargeability.

Power flow controller with a fractionally rated back-to-back converter

DOEpatents

Divan, Deepakraj M.; Kandula, Rajendra Prasad; Prasai, Anish

2016-03-08

A power flow controller with a fractionally rated back-to-back (BTB) converter is provided. The power flow controller provide dynamic control of both active and reactive power of a power system. The power flow controller inserts a voltage with controllable magnitude and phase between two AC sources at the same frequency; thereby effecting control of active and reactive power flows between the two AC sources. A transformer may be augmented with a fractionally rated bi-directional Back to Back (BTB) converter. The fractionally rated BTB converter comprises a transformer side converter (TSC), a direct-current (DC) link, and a line side converter (LSC). By controlling the switches of the BTB converter, the effective phase angle between the two AC source voltages may be regulated, and the amplitude of the voltage inserted by the power flow controller may be adjusted with respect to the AC source voltages.

Fuzzy Logic Controlled Solar Module for Driving Three- Phase Induction Motor

NASA Astrophysics Data System (ADS)

Afiqah Zainal, Nurul; Sooi Tat, Chan; Ajisman

2016-02-01

Renewable energy produced by solar module gives advantages for generated three- phase induction motor in remote area. But, solar module's ou tput is uncertain and complex. Fuzzy logic controller is one of controllers that can handle non-linear system and maximum power of solar module. Fuzzy logic controller used for Maximum Power Point Tracking (MPPT) technique to control Pulse-Width Modulation (PWM) for switching power electronics circuit. DC-DC boost converter used to boost up photovoltaic voltage to desired output and supply voltage source inverter which controlled by three-phase PWM generated by microcontroller. IGBT switched Voltage source inverter (VSI) produced alternating current (AC) voltage from direct current (DC) source to control speed of three-phase induction motor from boost converter output. Results showed that, the output power of solar module is optimized and controlled by using fuzzy logic controller. Besides that, the three-phase induction motor can be drive and control using VSI switching by the PWM signal generated by the fuzzy logic controller. This concluded that the non-linear system can be controlled and used in driving three-phase induction motor.

Recent Developments in High Voltage Research in the United Kingdom

NASA Astrophysics Data System (ADS)

Haddad, A. Manu

This paper gives an overview of research activities in the area of high voltage engineering in UK universities. It summarises the main activities of all active high voltage research groups. Furthermore, current research drivers and funding sources for research in the area are described, and the main initiatives to safeguard the health of the discipline are presented.

The fabrication of carbon nanotube field-effect transistors with semiconductors as the source and drain contact materials.

PubMed

Xiao, Z; Camino, F E

2009-04-01

Sb(2)Te(3) and Bi(2)Te(2)Se semiconductor materials were used as the source and drain contact materials in the fabrication of carbon nanotube field-effect transistors (CNTFETs). Ultra-purified single-walled carbon nanotubes (SWCNTs) were ultrasonically dispersed in N-methyl pyrrolidone solvent. Dielectrophoresis was used to deposit and align SWCNTs for fabrication of CNTFETs. The Sb(2)Te(3)- and Bi(2)Te(2)Se-based CNTFETs demonstrate p-type metal-oxide-silicon-like I-V curves with high on/off drain-source current ratio at large drain-source voltages and good saturation of drain-source current with increasing drain-source voltage. The fabrication process developed is novel and has general meaning, and could be used for the fabrication of SWCNT-based integrated devices and systems with semiconductor contact materials.

Control method for peak power delivery with limited DC-bus voltage

DOEpatents

Edwards, John; Xu, Longya; Bhargava, Brij B.

2006-09-05

A method for driving a neutral point-clamped multi-level voltage source inverter supplying a synchronous motor is provided. A DC current is received at a neutral point-clamped multi-level voltage source inverter. The inverter has first, second, and third output nodes. The inverter also has a plurality of switches. A desired speed of a synchronous motor connected to the inverter by the first second and third nodes is received by the inverter. The synchronous motor has a rotor and the speed of the motor is defined by the rotational rate of the rotor. A position of the rotor is sensed, current flowing to the motor out of at least two of the first, second, and third output nodes is sensed, and predetermined switches are automatically activated by the inverter responsive to the sensed rotor position, the sensed current, and the desired speed.

Method and apparatus for measuring low currents in capacitance devices

DOEpatents

Kopp, M.K.; Manning, F.W.; Guerrant, G.C.

1986-06-04

A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.

The Studies of a Vacuum Gap Breakdown after High-Current Arc Interruption with Increasing the Voltage

NASA Astrophysics Data System (ADS)

Schneider, A. V.; Popov, S. A.; Batrakov, A. V.; Dubrovskaya, E. L.; Lavrinovich, V. A.

2017-12-01

Vacuum-gap breakdown has been studied after high-current arc interruption with a subsequent increase in the transient recovery voltage across a gap. The effects of factors, such as the rate of the rise in the transient voltage, the potential of the shield that surrounds a discharge gap, and the arc burning time, have been determined. It has been revealed that opening the contacts earlier leads to the formation of an anode spot, which is the source of electrode material vapors into the discharge gap after current zero moment. Under the conditions of increasing voltage, this fact results in the breakdown. Too late opening leads to the breakdown of a short gap due to the high electric fields.

Controllable Bidirectional dc Power Sources For Large Loads

NASA Technical Reports Server (NTRS)

Tripp, John S.; Daniels, Taumi S.

1995-01-01

System redesigned for greater efficiency, durability, and controllability. Modern electronically controlled dc power sources proposed to supply currents to six electromagnets used to position aerodynamic test model in wind tunnel. Six-phase bridge rectifier supplies load with large current at voltage of commanded magnitude and polarity. Current-feedback circuit includes current-limiting feature giving some protection against overload.

Wind Farm Stabilization by using DFIG with Current Controlled Voltage Source Converters Taking Grid Codes into Consideration

NASA Astrophysics Data System (ADS)

Okedu, Kenneth Eloghene; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

Recent wind farm grid codes require wind generators to ride through voltage sags, which means that normal power production should be re-initiated once the nominal grid voltage is recovered. However, fixed speed wind turbine generator system using induction generator (IG) has the stability problem similar to the step-out phenomenon of a synchronous generator. On the other hand, doubly fed induction generator (DFIG) can control its real and reactive powers independently while being operated in variable speed mode. This paper proposes a new control strategy using DFIGs for stabilizing a wind farm composed of DFIGs and IGs, without incorporating additional FACTS devices. A new current controlled voltage source converter (CC-VSC) scheme is proposed to control the converters of DFIG and the performance is verified by comparing the results with those of voltage controlled voltage source converter (VC-VSC) scheme. Another salient feature of this study is to reduce the number of proportionate integral (PI) controllers used in the rotor side converter without degrading dynamic and transient performances. Moreover, DC-link protection scheme during grid fault can be omitted in the proposed scheme which reduces overall cost of the system. Extensive simulation analyses by using PSCAD/EMTDC are carried out to clarify the effectiveness of the proposed CC-VSC based control scheme of DFIGs.

Low-cost wireless voltage & current grid monitoring

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

Hines, Jacqueline

This report describes the development and demonstration of a novel low-cost wireless power distribution line monitoring system. This system measures voltage, current, and relative phase on power lines of up to 35 kV-class. The line units operate without any batteries, and without harvesting energy from the power line. Thus, data on grid condition is provided even in outage conditions, when line current is zero. This enhances worker safety by detecting the presence of voltage and current that may appear from stray sources on nominally isolated lines. Availability of low-cost power line monitoring systems will enable widespread monitoring of the distributionmore » grid. Real-time data on local grid operating conditions will enable grid operators to optimize grid operation, implement grid automation, and understand the impact of solar and other distributed sources on grid stability. The latter will enable utilities to implement eneygy storage and control systems to enable greater penetration of solar into the grid.« less

Investigation and optimization of low-frequency noise performance in readout electronics of dc superconducting quantum interference device

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

Zhao, Jing; Peter Grünberg Institute; Zhang, Yi

2014-05-15

We investigated and optimized the low-frequency noise characteristics of a preamplifier used for readout of direct current superconducting quantum interference devices (SQUIDs). When the SQUID output was detected directly using a room-temperature low-voltage-noise preamplifier, the low-frequency noise of a SQUID system was found to be dominated by the input current noise of the preamplifiers in case of a large dynamic resistance of the SQUID. To reduce the current noise of the preamplifier in the low-frequency range, we investigated the dependence of total preamplifier noise on the collector current and source resistance. When the collector current was decreased from 8.4 mAmore » to 3 mA in the preamplifier made of 3 parallel SSM2220 transistor pairs, the low-frequency total voltage noise of the preamplifier (at 0.1 Hz) decreased by about 3 times for a source resistance of 30 Ω whereas the white noise level remained nearly unchanged. Since the relative contribution of preamplifier's input voltage and current noise is different depending on the dynamic resistance or flux-to-voltage transfer of the SQUID, the results showed that the total noise of a SQUID system at low-frequency range can be improved significantly by optimizing the preamplifier circuit parameters, mainly the collector current in case of low-noise bipolar transistor pairs.« less

Investigation and optimization of low-frequency noise performance in readout electronics of dc superconducting quantum interference device

NASA Astrophysics Data System (ADS)

Zhao, Jing; Zhang, Yi; Lee, Yong-Ho; Krause, Hans-Joachim

2014-05-01

We investigated and optimized the low-frequency noise characteristics of a preamplifier used for readout of direct current superconducting quantum interference devices (SQUIDs). When the SQUID output was detected directly using a room-temperature low-voltage-noise preamplifier, the low-frequency noise of a SQUID system was found to be dominated by the input current noise of the preamplifiers in case of a large dynamic resistance of the SQUID. To reduce the current noise of the preamplifier in the low-frequency range, we investigated the dependence of total preamplifier noise on the collector current and source resistance. When the collector current was decreased from 8.4 mA to 3 mA in the preamplifier made of 3 parallel SSM2220 transistor pairs, the low-frequency total voltage noise of the preamplifier (at 0.1 Hz) decreased by about 3 times for a source resistance of 30 Ω whereas the white noise level remained nearly unchanged. Since the relative contribution of preamplifier's input voltage and current noise is different depending on the dynamic resistance or flux-to-voltage transfer of the SQUID, the results showed that the total noise of a SQUID system at low-frequency range can be improved significantly by optimizing the preamplifier circuit parameters, mainly the collector current in case of low-noise bipolar transistor pairs.

Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

DOEpatents

Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

2012-02-14

A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.

Thermally-induced voltage alteration for analysis of microelectromechanical devices

DOEpatents

Walraven, Jeremy A.; Cole, Jr., Edward I.

2002-01-01

A thermally-induced voltage alteration (TIVA) apparatus and method are disclosed for analyzing a microelectromechanical (MEM) device with or without on-board integrated circuitry. One embodiment of the TIVA apparatus uses constant-current biasing of the MEM device while scanning a focused laser beam over electrically-active members therein to produce localized heating which alters the power demand of the MEM device and thereby changes the voltage of the constant-current source. This changing voltage of the constant-current source can be measured and used in combination with the position of the focused and scanned laser beam to generate an image of any short-circuit defects in the MEM device (e.g. due to stiction or fabrication defects). In another embodiment of the TIVA apparatus, an image can be generated directly from a thermoelectric potential produced by localized laser heating at the location of any short-circuit defects in the MEM device, without any need for supplying power to the MEM device. The TIVA apparatus can be formed, in part, from a scanning optical microscope, and has applications for qualification testing or failure analysis of MEM devices.

Identification of linearised RMS-voltage dip patterns based on clustering in renewable plants

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

García-Sánchez, Tania; Gómez-Lázaro, Emilio; Muljadi, Edward

Generation units connected to the grid are currently required to meet low-voltage ride-through (LVRT) requirements. In most developed countries, these requirements also apply to renewable sources, mainly wind power plants and photovoltaic installations connected to the grid. This study proposes an alternative characterisation solution to classify and visualise a large number of collected events in light of current limits and requirements. The authors' approach is based on linearised root-mean-square-(RMS)-voltage trajectories, taking into account LRVT requirements, and a clustering process to identify the most likely pattern trajectories. The proposed solution gives extensive information on an event's severity by providing a simplemore » but complete visualisation of the linearised RMS-voltage patterns. In addition, these patterns are compared to current LVRT requirements to determine similarities or discrepancies. A large number of collected events can then be automatically classified and visualised for comparative purposes. Real disturbances collected from renewable sources in Spain are used to assess the proposed solution. Extensive results and discussions are also included in this study.« less

Multiple high voltage output DC-to-DC power converter

NASA Technical Reports Server (NTRS)

Cronin, Donald L. (Inventor); Farber, Bertrand F. (Inventor); Gehm, Hartmut K. (Inventor); Goldin, Daniel S. (Inventor)

1977-01-01

Disclosed is a multiple output DC-to-DC converter. The DC input power is filtered and passed through a chopper preregulator. The chopper output is then passed through a current source inverter controlled by a squarewave generator. The resultant AC is passed through the primary winding of a transformer, with high voltages induced in a plurality of secondary windings. The high voltage secondary outputs are each solid-state rectified for passage to individual output loads. Multiple feedback loops control the operation of the chopper preregulator, one being responsive to the current through the primary winding and another responsive to the DC voltage level at a selected output.

Measurement system for determination of current-voltage characteristics of PV modules

NASA Astrophysics Data System (ADS)

Idzkowski, Adam; Walendziuk, Wojciech; Borawski, Mateusz; Sawicki, Aleksander

2015-09-01

The realization of a laboratory stand for testing photovoltaic panels is presented here. The project of the laboratory stand was designed in SolidWorks software. The aim of the project was to control the electrical parameters of a PV panel. For this purpose a meter that measures electrical parameters i.e. voltage, current and power, was realized. The meter was created with the use of LabJack DAQ device and LabVIEW software. The presented results of measurements were obtained in different conditions (variable distance from the source of light, variable tilt angle of the panel). Current voltage characteristics of photovoltaic panel were created and all parameters could be detected in different conditions. The standard uncertainties of sample voltage, current, power measurements were calculated. The paper also gives basic information about power characteristics and efficiency of a solar cell.

Alpha-Particle Gas-Pressure Sensor

NASA Technical Reports Server (NTRS)

Buehler, M. C.; Bell, L. D.; Hecht, M. H.

1996-01-01

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

A universal procedure for evaluation and application of surge-protective devices

NASA Technical Reports Server (NTRS)

1980-01-01

The source, nature, and frequency of occurrence of transients must be identified and a representative standard test wave chosen for proof testing. The performance of candidate suppressor devices then can be evaluated against the withstand goals set for the equipment. The various suppressors divide into two classes of generic behavior. The key to a universal procedure for evaluating both classes lies in representing transients as quasi-current sources of defined current impulse duration. The available surge current is established by the Thevenin equivalent transient voltage and source impedance. A load line drawn on the V-I characteristic graph of the suppressor quickly determines the clamping voltage and peak current. These values then can be compared to the requirement. The deposited energy and average power dissipation for multiple transients also can be calculated. The method is illustrated with a design example for motor vehicle alternator load dump suppression.

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

DOEpatents

Kikta, Thomas J.; Mitchell, Ronald D.

1992-01-01

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

Method and apparatus for remote tube crevice detection by current and voltage probe resistance measurement

DOEpatents

Kikta, T.J.; Mitchell, R.D.

1992-11-24

A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet. 4 figs.

Four-point probe measurements using current probes with voltage feedback to measure electric potentials

NASA Astrophysics Data System (ADS)

Lüpke, Felix; Cuma, David; Korte, Stefan; Cherepanov, Vasily; Voigtländer, Bert

2018-02-01

We present a four-point probe resistance measurement technique which uses four equivalent current measuring units, resulting in minimal hardware requirements and corresponding sources of noise. Local sample potentials are measured by a software feedback loop which adjusts the corresponding tip voltage such that no current flows to the sample. The resulting tip voltage is then equivalent to the sample potential at the tip position. We implement this measurement method into a multi-tip scanning tunneling microscope setup such that potentials can also be measured in tunneling contact, allowing in principle truly non-invasive four-probe measurements. The resulting measurement capabilities are demonstrated for \

Modularized multilevel and z-source power converter as renewable energy interface for vehicle and grid-connected applications

NASA Astrophysics Data System (ADS)

Cao, Dong

Due the energy crisis and increased oil price, renewable energy sources such as photovoltaic panel, wind turbine, or thermoelectric generation module, are used more and more widely for vehicle and grid-connected applications. However, the output of these renewable energy sources varies according to different solar radiation, wind speed, or temperature difference, a power converter interface is required for the vehicle or grid-connected applications. Thermoelectric generation (TEG) module as a renewable energy source for automotive industry is becoming very popular recently. Because of the inherent characteristics of TEG modules, a low input voltage, high input current and high voltage gain dc-dc converters are needed for the automotive load. Traditional high voltage gain dc-dc converters are not suitable for automotive application in terms of size and high temperature operation. Switched-capacitor dc-dc converters have to be used for this application. However, high voltage spike and EMI problems exist in traditional switched-capacitor dc-dc converters. Huge capacitor banks have to be utilized to reduce the voltage ripple and achieve high efficiency. A series of zero current switching (ZCS) or zero voltage switching switched-capacitor dc-dc converters have been proposed to overcome the aforementioned problems of the traditional switched-capacitor dc-dc converters. By using the proposed soft-switching strategy, high voltage spike is reduced, high EMI noise is restricted, and the huge capacitor bank is eliminated. High efficiency, high power density and high temperature switched-capacitor dc-dc converters could be made for the TEG interface in vehicle applications. Several prototypes have been made to validate the proposed circuit and confirm the circuit operation. In order to apply PV panel for grid-connected application, a low cost dc-ac inverter interface is required. From the use of transformer and safety concern, two different solutions can be implemented, non-isolated or isolated PV inverter. For the non-isolated transformer-less solution, a semi-Z-source inverter for single phase photovoltaic systems has been proposed. The proposed semi-Z-source inverter utilizes only two switching devices with doubly grounded feature. The total cost have been reduced, the safety and EMI issues caused by the high frequency ground current are solved. For the transformer isolated solution, a boost half-bridge dc-ac micro-inverter has been proposed. The proposed boost half-bridge dc-dc converter utilizes only two switching devices with zero voltage switching features which is able to reduce the total system cost and power loss.

Novel design of high voltage pulse source for efficient dielectric barrier discharge generation by using silicon diodes for alternating current.

PubMed

Truong, Hoa Thi; Hayashi, Misaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Ishijima, Tatsuo

2017-06-01

This work focuses on design, construction, and optimization of configuration of a novel high voltage pulse power source for large-scale dielectric barrier discharge (DBD) generation. The pulses were generated by using the high-speed switching characteristic of an inexpensive device called silicon diodes for alternating current and the self-terminated characteristic of DBD. The operation started to be powered by a primary DC low voltage power supply flexibly equipped with a commercial DC power supply, or a battery, or DC output of an independent photovoltaic system without transformer employment. This flexible connection to different types of primary power supply could provide a promising solution for the application of DBD, especially in the area without power grid connection. The simple modular structure, non-control requirement, transformer elimination, and a minimum number of levels in voltage conversion could lead to a reduction in size, weight, simple maintenance, low cost of installation, and high scalability of a DBD generator. The performance of this pulse source has been validated by a load of resistor. A good agreement between theoretically estimated and experimentally measured responses has been achieved. The pulse source has also been successfully applied for an efficient DBD plasma generation.

Novel design of high voltage pulse source for efficient dielectric barrier discharge generation by using silicon diodes for alternating current

NASA Astrophysics Data System (ADS)

Truong, Hoa Thi; Hayashi, Misaki; Uesugi, Yoshihiko; Tanaka, Yasunori; Ishijima, Tatsuo

2017-06-01

This work focuses on design, construction, and optimization of configuration of a novel high voltage pulse power source for large-scale dielectric barrier discharge (DBD) generation. The pulses were generated by using the high-speed switching characteristic of an inexpensive device called silicon diodes for alternating current and the self-terminated characteristic of DBD. The operation started to be powered by a primary DC low voltage power supply flexibly equipped with a commercial DC power supply, or a battery, or DC output of an independent photovoltaic system without transformer employment. This flexible connection to different types of primary power supply could provide a promising solution for the application of DBD, especially in the area without power grid connection. The simple modular structure, non-control requirement, transformer elimination, and a minimum number of levels in voltage conversion could lead to a reduction in size, weight, simple maintenance, low cost of installation, and high scalability of a DBD generator. The performance of this pulse source has been validated by a load of resistor. A good agreement between theoretically estimated and experimentally measured responses has been achieved. The pulse source has also been successfully applied for an efficient DBD plasma generation.

Advanced control of neutral beam injected power in DIII-D

DOE PAGES

Pawley, Carl J.; Crowley, Brendan J.; Pace, David C.; ...

2017-03-23

In the DIII-D tokamak, one of the most powerful techniques to control the density, temperature and plasma rotation is by eight independently modulated neutral beam sources with a total power of 20 MW. The rapid modulation requires a high degree of reproducibility and precise control of the ion source plasma and beam acceleration voltage. Recent changes have been made to the controls to provide a new capability to smoothly vary the beam current and beam voltage during a discharge, while maintaining the modulation capability. The ion source plasma inside the arc chamber is controlled through feedback from the Langmuir probesmore » measuring plasma density near the extraction end. To provide the new capability, the plasma control system (PCS) has been enabled to change the Langmuir probe set point and the beam voltage set point in real time. When the PCS varies the Langmuir set point, the plasma density is directly controlled in the arc chamber, thus changing the beam current (perveance) and power going into the tokamak. Alternately, the PCS can sweep the beam voltage set point by 20 kV or more and adjust the Langmuir probe setting to match, keeping the perveance constant and beam divergence at a minimum. This changes the beam power and average neutral particle energy, which changes deposition in the tokamak plasma. The ion separating magnetic field must accurately match the beam voltage to protect the beam line. To do this, the magnet current control accurately tracks the beam voltage set point. In conclusion, these new capabilities allow continuous in-shot variation of neutral beam ion energy to complement« less

High-voltage subnanosecond dielectric breakdown

NASA Astrophysics Data System (ADS)

Mankowski, John Jerome

Current interests in ultrawideband radar sources are in the microwave regime, which correspond to voltage pulse risetimes less than a nanosecond. Some new sources, including the Phillips Laboratory Hindenberg series of hydrogen gas switched pulsers use hydrogen at hundreds of atmospheres of pressure in the switch. Unfortunately, the published data of electrical breakdown of gas and liquid media at these time lengths are relatively scarce. A study was conducted on the electrical breakdown properties of liquid and gas dielectrics at subnanosecond and nanoseconds. Two separate voltage sources with pulse risetimes less than 400 ps were developed. Diagnostic probes were designed and tested for their capability of detecting high voltage pulses at these fast risetimes. A thorough investigation into E-field strengths of liquid and gas dielectrics at breakdown times ranging from 0.4 to 5 ns was performed. The voltage polarity dependence on breakdown strength is observed. Streak camera images of streamer formation were taken. The effect of ultraviolet radiation, incident upon the gap, on statistical lag time was determined.

Regenerative switching CMOS system

DOEpatents

Welch, James D.

1998-01-01

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a seriesed combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided.

Regenerative switching CMOS system

DOEpatents

Welch, J.D.

1998-06-02

Complementary Metal Oxide Semiconductor (CMOS) Schottky barrier Field Effect Transistor systems, which are a series combination of N and P-Channel MOSFETS, in which Source Schottky barrier junctions of the N and P-Channel Schottky barrier MOSFETS are electrically interconnected, (rather than the Drains as in conventional diffused junction CMOS), which Schottky barrier MOSFET system demonstrates Regenerative Inverting Switching Characteristics in use are disclosed. Both the N and P-Channel Schottky barrier MOSFET devices are unique in that they provide operational Drain Current vs. Drain to Source voltage as a function of Gate voltage only where the polarities of the Drain voltage and Gate voltage are opposite, referenced to the Source as a common terminal, and where the polarity of the voltage applied to the Gate is appropriate to cause Channel inversion. Experimentally derived results which demonstrate and verify the operation of N and P-Channel Schottky barrier MOSFETS actually fabricated on P and N-type Silicon respectively, by a common procedure using vacuum deposited Chromium as a Schottky barrier forming metal, are also provided. 14 figs.

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

Electrical Power Quality - What's Behind the Outlet?

NASA Astrophysics Data System (ADS)

Baird, William H.; Secrest, Jeffery; Padgett, Clifford

2017-09-01

Although we may consider the power outlets in our homes to be nearly ideal voltage sources, a variety of influences in and around the home can cause departures from the nominal 60 Hz, 110-120 V root-mean-square (rms) of the North American grid. Even without instrumentation, we can see that a large motor starting from rest can be sufficient to cause lights to dim momentarily (voltage sag). This dimming is due to the inrush current drawn by a stationary motor, which may be several times the current drawn at operating speed. We prepared a voltage monitoring system using a voltage divider, the construction details of which we omit in the interest of safety.

Modelling of piezoelectric actuator dynamics for active structural control

NASA Technical Reports Server (NTRS)

Hagood, Nesbitt W.; Chung, Walter H.; Von Flotow, Andreas

1990-01-01

The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelectric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.

Intelligent energy harvesting scheme for microbial fuel cells: Maximum power point tracking and voltage overshoot avoidance

NASA Astrophysics Data System (ADS)

Alaraj, Muhannad; Radenkovic, Miloje; Park, Jae-Do

2017-02-01

Microbial fuel cells (MFCs) are renewable and sustainable energy sources that can be used for various applications. The MFC output power depends on its biochemical conditions as well as the terminal operating points in terms of output voltage and current. There exists one operating point that gives the maximum possible power from the MFC, maximum power point (MPP), for a given operating condition. However, this MPP may vary and needs to be tracked in order to maintain the maximum power extraction from the MFC. Furthermore, MFC reactors often develop voltage overshoots that cause drastic drops in the terminal voltage, current, and the output power. When the voltage overshoot happens, an additional control measure is necessary as conventional MPPT algorithms will fail because of the change in the voltage-current relationship. In this paper, the extremum seeking (ES) algorithm was used to track the varying MPP and a voltage overshoot avoidance (VOA) algorithm is developed to manage the voltage overshoot conditions. The proposed ES-MPPT with VOA algorithm was able to extract 197.2 mJ during 10-min operation avoiding voltage overshoot, while the ES MPPT-only scheme stopped harvesting after only 18.75 mJ because of the voltage overshoot happened at 0.4 min.

Load flows and faults considering dc current injections

NASA Technical Reports Server (NTRS)

Kusic, G. L.; Beach, R. F.

1991-01-01

The authors present novel methods for incorporating current injection sources into dc power flow computations and determining network fault currents when electronic devices limit fault currents. Combinations of current and voltage sources into a single network are considered in a general formulation. An example of relay coordination is presented. The present study is pertinent to the development of the Space Station Freedom electrical generation, transmission, and distribution system.

Improvements of the versatile multiaperture negative ion source NIO1

NASA Astrophysics Data System (ADS)

Cavenago, M.; Serianni, G.; De Muri, M.; Veltri, P.; Antoni, V.; Baltador, C.; Barbisan, M.; Brombin, M.; Galatá, A.; Ippolito, N.; Kulevoy, T.; Pasqualotto, R.; Petrenko, S.; Pimazzoni, A.; Recchia, M.; Sartori, E.; Taccogna, F.; Variale, V.; Zaniol, B.; Barbato, P.; Baseggio, L.; Cervaro, V.; Fasolo, D.; Franchin, L.; Ghiraldelli, R.; Laterza, B.; Maniero, M.; Martini, D.; Migliorato, L.; Minarello, A.; Molon, F.; Moro, G.; Patton, T.; Ravarotto, D.; Rizzieri, R.; Rizzolo, A.; Sattin, M.; Stivanello, F.; Zucchetti, S.

2017-08-01

The ion source NIO1 (Negative Ion Optimization 1) was developed and installed as a reduced-size model of multi-aperture sources used in neutral beam injectors. NIO1 beam optics is optimized for a 135 mA H- current (subdivided in 9 beamlets) at a Vs = 60 kV extraction voltage, with an electron-to-ion current ratio Rj up to 2. Depending on gas pressure used, NIO1 was up to now operated with Vs < 25 kV for beam extraction and Vs = 60 kV for insulation tests. The distinction between capacitively coupled plasma (E-mode, consistent with a low electron density plasma ne) and inductively coupled plasma (H-mode, requiring larger ne) was clearly related to several experimental signatures, and was confirmed for several gases, when applied radiofrequency power exceeds a given threshold Pt (with hysteresis). For hydrogen Pt was reduced below 1 kW, with a clean rf window and molybdenum liners on other walls; for oxygen Pt ≤ 400 W. Beams of H- and O- were separately extracted; since no caesium is yet introduced into the source, the expected ion currents are lower than 5 mA; this requires a lower acceleration voltage Vs (to keep the same perveance). NIO1 caesium oven was separately tested and Cs dispensers are in development. Increasing the current in the magnetic filter circuit, modifying its shape, and increasing the bias voltage were helpful to reduce Rj (still very large up to now, about 150 for oxygen, and 40 for hydrogen), in qualitative agreement with theoretical and numerical models. A second bias voltage was tested for hydrogen. Beam footprints and a spectral emission sample are shown.

HIGH VOLTAGE ION SOURCE

DOEpatents

Luce, J.S.

1960-04-19

A device is described for providing a source of molecular ions having a large output current and with an accelerated energy of the order of 600 kv. Ions are produced in an ion source which is provided with a water-cooled source grid of metal to effect maximum recombination of atomic ions to molecular ions. A very high accelerating voltage is applied to withdraw and accelerate the molecular ions from the source, and means are provided for dumping the excess electrons at the lowest possible potentials. An accelerating grid is placed adjacent to the source grid and a slotted, grounded accelerating electrode is placed adjacent to the accelerating grid. A potential of about 35 kv is maintained between the source grid and accelerating grid, and a potential of about 600 kv is maintained between the accelerating grid and accelerating electrode. In order to keep at a minimum the large number of oscillating electrons which are created when such high voltages are employed in the vicinity of a strong magnetic field, a plurality of high voltage cascaded shields are employed with a conventional electron dumping system being employed between each shield so as to dump the electrons at the lowest possible potential rather than at 600 kv.

Analysis of a Van de Graaff Generator for EMP Direct Current Survivability Testing

DTIC Science & Technology

2013-03-01

voltage source, VS , equals the voltage load, VL, as shown in the schematic of Figure 12. When impedance is matched, maximum power is transferred...maximum power is 42 transmitted, and VS =VL. The voltage drops shown in Table 7 are from the skin effect at frequencies above 1 MHz, as well... voltage . 46 3.1.6 Response to CVR Location The purpose of these experiments was to find the best cable and connector attachment that would

Enhancement of SPES source performances.

PubMed

Fagotti, E; Palmieri, A; Ren, X

2008-02-01

Installation of SPES source at LNL was finished in July 2006 and the first beam was extracted in September 2006. Commissioning results confirmed very good performance of the extracted current density. Conversely, source reliability was very poor due to glow-discharge phenomena, which were caused by the ion source axial magnetic field protruding in the high-voltage column. This problem was fixed by changing the stainless steel plasma electrode support with a ferromagnetic one. This new configuration required us to recalculate ion source solenoids positions and fields in order to recover the correct resonance pattern. Details on magnetic simulations and experimental results of high voltage column shielding are presented.

Optimal Dynamic Sub-Threshold Technique for Extreme Low Power Consumption for VLSI

NASA Technical Reports Server (NTRS)

Duong, Tuan A.

2012-01-01

For miniaturization of electronics systems, power consumption plays a key role in the realm of constraints. Considering the very large scale integration (VLSI) design aspect, as transistor feature size is decreased to 50 nm and below, there is sizable increase in the number of transistors as more functional building blocks are embedded in the same chip. However, the consequent increase in power consumption (dynamic and leakage) will serve as a key constraint to inhibit the advantages of transistor feature size reduction. Power consumption can be reduced by minimizing the voltage supply (for dynamic power consumption) and/or increasing threshold voltage (V(sub th), for reducing leakage power). When the feature size of the transistor is reduced, supply voltage (V(sub dd)) and threshold voltage (V(sub th)) are also reduced accordingly; then, the leakage current becomes a bigger factor of the total power consumption. To maintain low power consumption, operation of electronics at sub-threshold levels can be a potentially strong contender; however, there are two obstacles to be faced: more leakage current per transistor will cause more leakage power consumption, and slow response time when the transistor is operated in weak inversion region. To enable low power consumption and yet obtain high performance, the CMOS (complementary metal oxide semiconductor) transistor as a basic element is viewed and controlled as a four-terminal device: source, drain, gate, and body, as differentiated from the traditional approach with three terminals: i.e., source and body, drain, and gate. This technique features multiple voltage sources to supply the dynamic control, and uses dynamic control to enable low-threshold voltage when the channel (N or P) is active, for speed response enhancement and high threshold voltage, and when the transistor channel (N or P) is inactive, to reduce the leakage current for low-leakage power consumption.

Performance of Four-Leg VSC based DSTATCOM using Single Phase P-Q Theory

NASA Astrophysics Data System (ADS)

Jampana, Bangarraju; Veramalla, Rajagopal; Askani, Jayalaxmi

2017-02-01

This paper presents single-phase P-Q theory for four-leg VSC based distributed static compensator (DSTATCOM) in the distribution system. The proposed DSTATCOM maintains unity power factor at source, zero voltage regulation, eliminates current harmonics, load balancing and neutral current compensation. The advantage of using four-leg VSC based DSTATCOM is to eliminate isolated/non-isolated transformer connection at point of common coupling (PCC) for neutral current compensation. The elimination of transformer connection at PCC with proposed topology will reduce cost of DSTATCOM. The single-phase P-Q theory control algorithm is used to extract fundamental component of active and reactive currents for generation of reference source currents which is based on indirect current control method. The proposed DSTATCOM is modelled and the results are validated with various consumer loads under unity power factor and zero voltage regulation modes in the MATLAB R2013a environment using simpower system toolbox.

Solar bus regulator and battery charger for IMP's H, I, and J

NASA Technical Reports Server (NTRS)

Paulkovich, J.

1972-01-01

Interplanetary Monitoring Probe (IMP) spacecrafts H, I, and J utilize a direct energy transfer (DET) type of power system operating from a solar array source. A shunt type of regulator prevents the bus voltage from exceeding a preset voltage level. The power system utilizes a single differential amplifier with dual outputs to control the battery charge/shunt regulator and the discharge regulator. A two-voltage level, current limited, series charger and a current sensor control battery state of charge of the silver-cadmium battery pack. Premature termination of the battery charge is prevented by a power available gate that also initiates charge current to the battery upon availability of excess power.

Self-calibrating multiplexer circuit

DOEpatents

Wahl, Chris P.

1997-01-01

A time domain multiplexer system with automatic determination of acceptable multiplexer output limits, error determination, or correction is comprised of a time domain multiplexer, a computer, a constant current source capable of at least three distinct current levels, and two series resistances employed for calibration and testing. A two point linear calibration curve defining acceptable multiplexer voltage limits may be defined by the computer by determining the voltage output of the multiplexer to very accurately known input signals developed from predetermined current levels across the series resistances. Drift in the multiplexer may be detected by the computer when the output voltage limits, expected during normal operation, are exceeded, or the relationship defined by the calibration curve is invalidated.

Scalable Low-Power Deep Machine Learning with Analog Computation

DTIC Science & Technology

2013-07-19

transimpedance amplifier (TIA) that measures the output current 7 V Cf Vbias MP1 MN1 Vdd = 3 V 2.5 V 2.6 V + − Vox = 4.4 V 0.1 V + − 7 V Cf Vbias MP1 MN1 Vddt... amplifier . The amplifier has Cf as its feedback capacitor and the FG voltage Vfg as its input. The two MUXs at the sources of MP1 and MP2 control the...as a simple operational transconductor amplifier (OTA), converts voltage Vout to output current Iout. Vref determines the nominal voltage of Vout

Alternating current long range alpha particle detector

DOEpatents

MacArthur, Duncan W.; McAtee, James L.

1993-01-01

An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Alternating current long range alpha particle detector

DOEpatents

MacArthur, D.W.; McAtee, J.L.

1993-02-16

An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

Heterojunction fully depleted SOI-TFET with oxide/source overlap

NASA Astrophysics Data System (ADS)

Chander, Sweta; Bhowmick, B.; Baishya, S.

2015-10-01

In this work, a hetero-junction fully depleted (FD) Silicon-on-Insulator (SOI) Tunnel Field Effect Transistor (TFET) nanostructure with oxide overlap on the Germanium-source region is proposed. Investigations using Synopsys Technology Computer Aided Design (TCAD) simulation tools reveal that the simple oxide overlap on the Germanium-source region increases the tunneling area as well as the tunneling current without degrading the band-to-band tunneling (BTBT) and improves the device performance. More importantly, the improvement is independent of gate overlap. Simulation study shows improvement in ON current, subthreshold swing (SS), OFF current, ION/IOFF ration, threshold voltage and transconductance. The proposed device with hafnium oxide (HfO2)/Aluminium Nitride (AlN) stack dielectric material offers an average subthreshold swing of 22 mV/decade and high ION/IOFF ratio (∼1010) at VDS = 0.4 V. Compared to conventional TFET, the Miller capacitance of the device shows the enhanced performance. The impact of the drain voltage variation on different parameters such as threshold voltage, subthreshold swing, transconductance, and ION/IOFF ration are also found to be satisfactory. From fabrication point of view also it is easy to utilize the existing CMOS process flows to fabricate the proposed device.

Five Bit, Five Gigasample TED Analog-to-Digital Converter Development.

DTIC Science & Technology

1981-06-01

pliers. TRW uses two sources at present: materials grown by Horizontal I Bridgman technique from Crystal Specialties, and Czochralski from MRI. The...the circuit modelling and circuit design tasks. A number of design iterations were required to arrive at a satisfactory design. In or-der to riake...made by modeling the TELD as a voltage-controlled current generator with a built-in time delay between impressed voltage and output current. Based on

Pixelated Geiger-Mode Avalanche Photo-Diode Characterization Through Dark Current Measurement

NASA Astrophysics Data System (ADS)

Amaudruz, Pierre-Andre; Bishop, Daryl; Gilhully, Colleen; Goertzen, Andrew; James, Lloyd; Kozlowski, Piotr; Retiere, Fabrice; Shams, Ehsan; Sossi, Vesna; Stortz, Greg; Thiessen, Jonathan D.; Thompson, Christopher J.

2014-06-01

PIXELATED geiger-mode avalanche photodiodes (PPDs), often called silicon photomultipliers (SiPMs) are emerging as an excellent replacement for traditional photomultiplier tubes (PMTs) in a variety of detectors, especially those for subatomic physics experiments, which requires extensive test and operation procedures in order to achieve uniform responses from all the devices. In this paper, we show for two PPD brands, Hamamatsu MPPC and SensL SPM, that at room temperature, the dark noise rate, breakdown voltage and rate of correlated avalanches can be inferred from the sole measure of dark current as a function of operating voltage, hence greatly simplifying the characterization procedure. We introduce a custom electronics system that allows measurement for many devices concurrently, hence allowing rapid testing and monitoring of many devices at low cost. Finally, we show that the dark current of Hamamastu Multi-Pixel Photon Counter (MPPC) is rather independent of temperature at constant operating voltage, hence the current measure cannot be used to probe temperature variations. On the other hand, the MPPC current can be used to monitor light source conditions in DC mode without requiring strong temperature stability, as long as the integrated source brightness is comparable to the dark noise rate.

Programmable, very low noise current source.

PubMed

Scandurra, G; Cannatà, G; Giusi, G; Ciofi, C

2014-12-01

We propose a new approach for the realization of very low noise programmable current sources mainly intended for application in the field of low frequency noise measurements. The design is based on a low noise Junction Field Effect Transistor (JFET) acting as a high impedance current source and programmability is obtained by resorting to a low noise, programmable floating voltage source that allows to set the sourced current at the desired value. The floating voltage source is obtained by exploiting the properties of a standard photovoltaic MOSFET driver. Proper filtering and a control network employing super-capacitors allow to reduce the low frequency output noise to that due to the low noise JFET down to frequencies as low as 100 mHz while allowing, at the same time, to set the desired current by means of a standard DA converter with an accuracy better than 1%. A prototype of the system capable of supplying currents from a few hundreds of μA up to a few mA demonstrates the effectiveness of the approach we propose. When delivering a DC current of about 2 mA, the power spectral density of the current fluctuations at the output is found to be less than 25 pA/√Hz at 100 mHz and less than 6 pA/√Hz for f > 1 Hz, resulting in an RMS noise in the bandwidth from 0.1 to 10 Hz of less than 14 pA.

Programmable, very low noise current source

NASA Astrophysics Data System (ADS)

Scandurra, G.; Cannatà, G.; Giusi, G.; Ciofi, C.

2014-12-01

We propose a new approach for the realization of very low noise programmable current sources mainly intended for application in the field of low frequency noise measurements. The design is based on a low noise Junction Field Effect Transistor (JFET) acting as a high impedance current source and programmability is obtained by resorting to a low noise, programmable floating voltage source that allows to set the sourced current at the desired value. The floating voltage source is obtained by exploiting the properties of a standard photovoltaic MOSFET driver. Proper filtering and a control network employing super-capacitors allow to reduce the low frequency output noise to that due to the low noise JFET down to frequencies as low as 100 mHz while allowing, at the same time, to set the desired current by means of a standard DA converter with an accuracy better than 1%. A prototype of the system capable of supplying currents from a few hundreds of μA up to a few mA demonstrates the effectiveness of the approach we propose. When delivering a DC current of about 2 mA, the power spectral density of the current fluctuations at the output is found to be less than 25 pA/√Hz at 100 mHz and less than 6 pA/√Hz for f > 1 Hz, resulting in an RMS noise in the bandwidth from 0.1 to 10 Hz of less than 14 pA.

CIRCUITS FOR CURRENT MEASUREMENTS

DOEpatents

Cox, R.J.

1958-11-01

Circuits are presented for measurement of a logarithmic scale of current flowing in a high impedance. In one form of the invention the disclosed circuit is in combination with an ionization chamber to measure lonization current. The particular circuit arrangement lncludes a vacuum tube having at least one grid, an ionization chamber connected in series with a high voltage source and the grid of the vacuum tube, and a d-c amplifier feedback circuit. As the ionization chamber current passes between the grid and cathode of the tube, the feedback circuit acts to stabilize the anode current, and the feedback voltage is a measure of the logaritbm of the ionization current.

Device, system and method for a sensing electrical circuit

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

2009-01-01

The invention relates to a driven ground electrical circuit. A driven ground is a current-measuring ground termination to an electrical circuit with the current measured as a vector with amplification. The driven ground module may include an electric potential source V.sub.S driving an electric current through an impedance (load Z) to a driven ground. Voltage from the source V.sub.S excites the minus terminal of an operational amplifier inside the driven ground which, in turn, may react by generating an equal and opposite voltage to drive the net potential to approximately zero (effectively ground). A driven ground may also be a means of passing information via the current passing through one grounded circuit to another electronic circuit as input. It may ground one circuit, amplify the information carried in its current and pass this information on as input to the next circuit.

Power Generation from a Radiative Thermal Source Using a Large-Area Infrared Rectenna

NASA Astrophysics Data System (ADS)

Shank, Joshua; Kadlec, Emil A.; Jarecki, Robert L.; Starbuck, Andrew; Howell, Stephen; Peters, David W.; Davids, Paul S.

2018-05-01

Electrical power generation from a moderate-temperature thermal source by means of direct conversion of infrared radiation is important and highly desirable for energy harvesting from waste heat and micropower applications. Here, we demonstrate direct rectified power generation from an unbiased large-area nanoantenna-coupled tunnel diode rectifier called a rectenna. Using a vacuum radiometric measurement technique with irradiation from a temperature-stabilized thermal source, a generated power density of 8 nW /cm2 is observed at a source temperature of 450 °C for the unbiased rectenna across an optimized load resistance. The optimized load resistance for the peak power generation for each temperature coincides with the tunnel diode resistance at zero bias and corresponds to the impedance matching condition for a rectifying antenna. Current-voltage measurements of a thermally illuminated large-area rectenna show current zero crossing shifts into the second quadrant indicating rectification. Photon-assisted tunneling in the unbiased rectenna is modeled as the mechanism for the large short-circuit photocurrents observed where the photon energy serves as an effective bias across the tunnel junction. The measured current and voltage across the load resistor as a function of the thermal source temperature represents direct current electrical power generation.

Multilevel-Dc-Bus Inverter For Providing Sinusoidal And Pwm Electrical Machine Voltages

DOEpatents

Su, Gui-Jia [Knoxville, TN

2005-11-29

A circuit for controlling an ac machine comprises a full bridge network of commutation switches which are connected to supply current for a corresponding voltage phase to the stator windings, a plurality of diodes, each in parallel connection to a respective one of the commutation switches, a plurality of dc source connections providing a multi-level dc bus for the full bridge network of commutation switches to produce sinusoidal voltages or PWM signals, and a controller connected for control of said dc source connections and said full bridge network of commutation switches to output substantially sinusoidal voltages to the stator windings. With the invention, the number of semiconductor switches is reduced to m+3 for a multi-level dc bus having m levels. A method of machine control is also disclosed.

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

PubMed Central

Neculaes, V. Bogdan; Caiafa, Antonio; Cao, Yang; De Man, Bruno; Edic, Peter M.; Frutschy, Kristopher; Gunturi, Satish; Inzinna, Lou; Reynolds, Joseph; Vermilyea, Mark; Wagner, David; Zhang, Xi; Zou, Yun; Pelc, Norbert J.; Lounsberry, Brian

2016-01-01

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode block per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations. PMID:27487878

Multisource inverse-geometry CT. Part II. X-ray source design and prototype

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

Neculaes, V. Bogdan, E-mail: neculaes@ge.com; Caia

2016-08-15

Purpose: This paper summarizes the development of a high-power distributed x-ray source, or “multisource,” designed for inverse-geometry computed tomography (CT) applications [see B. De Man et al., “Multisource inverse-geometry CT. Part I. System concept and development,” Med. Phys. 43, 4607–4616 (2016)]. The paper presents the evolution of the source architecture, component design (anode, emitter, beam optics, control electronics, high voltage insulator), and experimental validation. Methods: Dispenser cathode emitters were chosen as electron sources. A modular design was adopted, with eight electron emitters (two rows of four emitters) per module, wherein tungsten targets were brazed onto copper anode blocks—one anode blockmore » per module. A specialized ceramic connector provided high voltage standoff capability and cooling oil flow to the anode. A matrix topology and low-noise electronic controls provided switching of the emitters. Results: Four modules (32 x-ray sources in two rows of 16) have been successfully integrated into a single vacuum vessel and operated on an inverse-geometry computed tomography system. Dispenser cathodes provided high beam current (>1000 mA) in pulse mode, and the electrostatic lenses focused the current beam to a small optical focal spot size (0.5 × 1.4 mm). Controlled emitter grid voltage allowed the beam current to be varied for each source, providing the ability to modulate beam current across the fan of the x-ray beam, denoted as a virtual bowtie filter. The custom designed controls achieved x-ray source switching in <1 μs. The cathode-grounded source was operated successfully up to 120 kV. Conclusions: A high-power, distributed x-ray source for inverse-geometry CT applications was successfully designed, fabricated, and operated. Future embodiments may increase the number of spots and utilize fast read out detectors to increase the x-ray flux magnitude further, while still staying within the stationary target inherent thermal limitations.« less

Optically Tuned MM-Wave IMPATT Source.

DTIC Science & Technology

1987-07-01

phase of the work has been extended and generalised. Accuracy of the theory in predicting tuning at the higher oscillator voltage swings has been greatly...Accuracy of the theory in predicting tuning at the higher oscillator voltage swings has been greatly improved by reformulating the Bessel function...voltage modulation and a peak optically injected locking current of 100 pA the predicted ftl locking range would be 540MHz, a practicaUy useful value. 4

Laboratory instrumentation and techniques for characterizing multi-junction solar cells for space applications

NASA Technical Reports Server (NTRS)

Woodyard, James R.

1995-01-01

Multi-junction solar cells are attractive for space applications because they can be designed to convert a larger fraction of AMO into electrical power at a lower cost than single-junction cells. The performance of multi-junction cells is much more sensitive to the spectral irradiance of the illuminating source than single-junction cells. The design of high efficiency multi-junction cells for space applications requires matching the optoelectronic properties of the junctions to AMO spectral irradiance. Unlike single-junction cells, it is not possible to carry out quantum efficiency measurements using only a monochromatic probe beam and determining the cell short-circuit current assuming linearity of the quantum efficiency. Additionally, current-voltage characteristics can not be calculated from measurements under non-AMO light sources using spectral-correction methods. There are reports in the literature on characterizing the performance of multi junction cells by measuring and convoluting the quantum efficiency of each junction with the spectral irradiance; the technique is of limited value for the characterization of cell performance under AMO power-generating conditions. We report the results of research to develop instrumentation and techniques for characterizing multi junction solar cells for space . An integrated system is described which consists of a standard lamp, spectral radiometer, dual-source solar simulator, and personal computer based current-voltage and quantum efficiency equipment. The spectral radiometer is calibrated regularly using the tungsten-halogen standard lamp which has a calibration based on NIST scales. The solar simulator produces the light bias beam for current-voltage and cell quantum efficiency measurements. The calibrated spectral radiometer is used to 'fit' the spectral irradiance of the dual-source solar simulator to WRL AMO data. The quantum efficiency apparatus includes a monochromatic probe beam for measuring the absolute cell quantum efficiency at various voltage biases, including the voltage bias corresponding to the maximum-power point under AMO light bias. The details of the procedures to 'fit' the spectral irradiance to AMO will be discussed. An assessment of the role of the accuracy of the 'fit' of the spectral irradiance and probe beam intensity on measured cell characteristics will be presented. quantum efficiencies were measured with both spectral light bias and AMO light bias; the measurements show striking differences. Spectral irradiances were convoluted with cell quantum efficiencies to calculate cell currents as function of voltage. The calculated currents compare with measured currents at the 1% level. Measurements on a variety of multi-junction cells will be presented. The dependence of defects in junctions on cell quantum efficiencies measured under light and voltage bias conditions will be presented. Comments will be made on issues related to standards for calibration, and limitations of the instrumentation and techniques. Expeditious development of multi-junction solar cell technology for space presents challenges for cell characterization in the laboratory.

Energy breakdown in capacitive deionization.

PubMed

Hemmatifar, Ali; Palko, James W; Stadermann, Michael; Santiago, Juan G

2016-11-01

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Energy breakdown in capacitive deionization

DOE PAGES

Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; ...

2016-08-12

We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages.more » We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.« less

Distributed control system for parallel-connected DC boost converters

DOEpatents

Goldsmith, Steven

2017-08-15

The disclosed invention is a distributed control system for operating a DC bus fed by disparate DC power sources that service a known or unknown load. The voltage sources vary in v-i characteristics and have time-varying, maximum supply capacities. Each source is connected to the bus via a boost converter, which may have different dynamic characteristics and power transfer capacities, but are controlled through PWM. The invention tracks the time-varying power sources and apportions their power contribution while maintaining the DC bus voltage within the specifications. A central digital controller solves the steady-state system for the optimal duty cycle settings that achieve a desired power supply apportionment scheme for a known or predictable DC load. A distributed networked control system is derived from the central system that utilizes communications among controllers to compute a shared estimate of the unknown time-varying load through shared bus current measurements and bus voltage measurements.

Voltage source ac-to-dc converters for high-power transmitters

NASA Technical Reports Server (NTRS)

Cormier, R.

1990-01-01

This work was done to optimize the design of the components used for the beam power supply, which is a component of the transmitters in the Deep Space Network (DSN). The major findings are: (1) the difference in regulation between a six-pulse and a twelve-pulse converter is at most 7 percent worse for the twelve-pulse converter; (2) the commutation overlap angle of a current source converter equals that of a voltage source converter with continuous line currents; (3) the sources of uncharacteristic harmonics are identified with SPICE simulation; (4) the use of an imperfect phase-shifting transformer for the twelve-pulse converter generates a harmonic at six times the line frequency; and (5) the assumptions usually made in analyzing converters can be relaxed with SPICE simulation. The results demonstrate the suitability of using SPICE simulation to obtain detailed performance predictions of ac-to-dc converters.

Fabrication and Characteristics of Pentacene/Vanadium Pentoxide Field-Effect Transistors

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

Minagawa, M.; Nakai, K.; Baba, A.

2011-12-23

Organic field-effect transistors (OFETs) were fabricated using pentacene thin layer, and the effects of inserted Lewis-acid thin layers on electrical properties were investigated. The OFETs have active layers of pentacene and vanadium pentoxide (V{sub 2}O{sub 5}) as a Lewis-acid layer. Typical source-drain current (I{sub DS}) vs. source-drain voltage (V{sub DS}) curves were observed under negative gate voltages (V{sub G}S) application, and the shift of the threshold voltage for FET driving (V{sub t}) to positive side was also observed by V{sub 2}O{sub 5} layer insertion, that is, -2.5 V for device with V{sub 2}O{sub 5} layer and -5.7 V for devicemore » without V{sub 2}O{sub 5} layer. It was thought that charge transfer (CT) complexes which were formed at the interface between pentacene and V{sub 2}O{sub 5} layer were dissociated by the applied gate voltage, and the generated holes seem to contribute to drain current and the apparent V{sub t} improvement.« less

Switches from pi- to sigma-bonding complexes controlled by gate voltages.

PubMed

Matsui, Eriko; Harnack, Oliver; Matsuzawa, Nobuyuki N; Yasuda, Akio

2005-10-01

A conjugated polymer/metal ion/liquid-crystal molecular system was set between source and drain electrodes with a 100 nm gap. When gate voltage (Vg) increases, the current between source and drain electrodes increases. Infrared spectra show this system to be composed of pi and sigma complexes. At Vg = 0, the pi complex dominates the sigma complex, whereas the sigma complex becomes dominant when Vg is switched on. Calculations found that the pi complex has lower conductivity than the sigma complex.

Large dynamic range radiation detector and methods thereof

DOEpatents

Marrs, Roscoe E [Livermore, CA; Madden, Norman W [Sparks, NV

2012-02-14

According to one embodiment, a radiation detector comprises a scintillator and a photodiode optically coupled to the scintillator. The radiation detector also includes a bias voltage source electrically coupled to the photodiode, a first detector operatively electrically coupled to the photodiode for generating a signal indicative of a level of a charge at an output of the photodiode, and a second detector operatively electrically coupled to the bias voltage source for generating a signal indicative of an amount of current flowing through the photodiode.

Studies on the Extraction Region of the Type VI RF Driven H- Ion Source

NASA Astrophysics Data System (ADS)

McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.

2002-11-01

IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the vicinity of the peak of the external magnetic filter field) and changes to source parameters as a function of power, and argon addition are reported. The behaviour of the electron density is different when the plasma is argon seeded showing a strong increase with RF power. The plasma potential is decreased by 2 V when argon is added to the plasma. The effect of the presence of unwanted silver sputtered from the Faraday screen by Ar+ ions on both the source performance and the plasma parameters is also presented. The silver dramatically downgraded source performance in terms of current density and produced an early saturation of current with applied RF power. Recently, collaboration was begun with the Technical University of Augsburg to perform spectroscopic measurements on the Type VI ion source. The final results of this analysis are not yet ready but some interesting initial observations on the gas temperature, disassociation degree and impurity ions will be presented.

Transistor-based interface circuitry

DOEpatents

Taubman, Matthew S [Richland, WA

2007-02-13

Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.

Modelling and simulation of current fed dc to dc converter for PHEV applications using renewable source

NASA Astrophysics Data System (ADS)

Milind Metha, Manish; Tutki, Sanjay; Rajan, Aju; Elangovan, D.; Arunkumar, G.

2017-11-01

With the current rate of depletion of the fossil fuel the need to switch on to the renewable energy sources is the need of the hour. Thus the need for new and efficient converters arises so as to replace the existing less efficient diesel and petroleum IC engines with renewable energy sources. The PHEVs, which have been launched in the market, and Upcoming PHEVs have converters around 380V to 400V generated with a power range between 2KW to 2.8KW. The fundamental target of this paper is to plan a productive converter keeping in mind cost and size restriction. In this paper, a two-stage dc-dc converter is proposed. The proposed converter is utilized to venture up a voltage from 24V (photovoltaic source) to a yield voltage of 400V to take care of a power demand of 2.4kW for a plug-in hybrid electric vehicle (PHEV) application considering the real time scenario of PHEV. This paper talks about in detail why the current fed converter is utilized alongside a voltage doubler thus minimizing the transformer turns thereby reducing the overall size of the final product. Simulation results along with calculation for the duty cycle of the firing sequence for different value of transformer turns are presented for a prototype unit.

Revisiting the role of trap-assisted-tunneling process on current-voltage characteristics in tunnel field-effect transistors

NASA Astrophysics Data System (ADS)

Omura, Yasuhisa; Mori, Yoshiaki; Sato, Shingo; Mallik, Abhijit

2018-04-01

This paper discusses the role of trap-assisted-tunneling process in controlling the ON- and OFF-state current levels and its impacts on the current-voltage characteristics of a tunnel field-effect transistor. Significant impacts of high-density traps in the source region are observed that are discussed in detail. With regard to recent studies on isoelectronic traps, it has been discovered that deep level density must be minimized to suppress the OFF-state leakage current, as is well known, whereas shallow levels can be utilized to control the ON-state current level. A possible mechanism is discussed based on simulation results.

Simulation of RF power and multi-cusp magnetic field requirement for H- ion sources

NASA Astrophysics Data System (ADS)

Pathak, Manish; Senecha, V. K.; Kumar, Rajnish; Ghodke, Dharmraj. V.

2016-12-01

A computer simulation study for multi-cusp RF based H- ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H- Linac project for SNS applications. The average reaction rates for different reactions responsible for H- ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H- ion source for a maximum possible H- ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H- ion source like excited hydrogen molecular density, H- ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H- ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H- ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

Physics of Intense Electron Current Sources for Helicity Injection

NASA Astrophysics Data System (ADS)

Hinson, E. T.; Barr, J. L.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Lewicki, B. T.; Perry, J. M.; Redd, A. J.; Winz, G. R.

2014-10-01

DC helicity injection (HI) for non-solenoidal ST startup requires sources of current at the tokamak edge. Since the rate of HI scales with injection voltage, understanding of the physics setting injector impedance is necessary for a predictive model of the HI rate and subsequent growth of Ip. In Pegasus, arc plasma sources are used for current injection. They operate immersed in tokamak edge plasma, and are biased at ~1-2 kV with respect to the vessel to draw current densities J ~ 1 kA/cm2 from an arc plasma cathode. Prior to tokamak formation, impedance data manifests two regimes, one at low current (< 1 kA) with I ~V 3 / 2 , and a higher current mode where I ~V 1 / 2 holds. The impedance in the I ~V 3 / 2 regime is consistent with an electrostatic double layer. Current in the I ~V 1 / 2 regime is linear in arc gas fueling rate, suggesting a space-charge limit set by nedge. In the presence of tokamak plasmas, voltage oscillations of the order 100s of volts are measured during MHD relaxation activity. These fluctuations occur at the characteristic frequencies of the n = 1 and n = 0 MHD activity observed on magnetic probes, and are suggestive of dynamic activity found in LHI simulations in NIMROD. Advanced injector design techniques have allowed higher voltage operation. These include staged shielding to prevent external arcing, and shaped cathodes, which minimize the onset and material damage due to cathode spot formation. Work supported by US DOE Grant DE-FG02-96ER54375.

A 155-dB Dynamic Range Current Measurement Front End for Electrochemical Biosensing.

PubMed

Dai, Shanshan; Perera, Rukshan T; Yang, Zi; Rosenstein, Jacob K

2016-10-01

An integrated current measurement system with ultra wide dynamic range is presented and fabricated in a 180-nm CMOS technology. Its dual-mode design provides concurrent voltage and frequency outputs, without requiring an external clock source. An integrator-differentiator core provides a voltage output with a noise floor of 11.6 fA/ [Formula: see text] and a -3 dB cutoff frequency of 1.4 MHz. It is merged with an asynchronous current-to-frequency converter, which generates an output frequency linearly proportional to the input current. Together, the voltage and frequency outputs yield a current measurement range of 155 dB, spanning from 204 fA (100 Hz) or 1.25 pA (10 kHz) to 11.6 μA. The proposed architecture's low noise, wide bandwidth, and wide dynamic range make it ideal for measurements of highly nonlinear electrochemical and electrophysiological systems.

Electrical model of dielectric barrier discharge homogenous and filamentary modes

NASA Astrophysics Data System (ADS)

López-Fernandez, J. A.; Peña-Eguiluz, R.; López-Callejas, R.; Mercado-Cabrera, A.; Valencia-Alvarado, R.; Muñoz-Castro, A.; Rodríguez-Méndez, B. G.

2017-01-01

This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results.

La conception, la modelisation et la simulation du systeme VSC-HVDC offshore

NASA Astrophysics Data System (ADS)

Benhalima, Seghir

Wind energy is recognized worldwide as a proven technology to meet the growing demands of green sustainable energy. To exploit this stochastic energy source and put together with the conventional energy sources without affecting the performance of existing electrical grids, several research projects have been achieved. In addition, at ocean level, wind energy has a great potential. It means that the production of this energy will increase in the world. The optimal extraction of this energy source needs to be connected to the grid via a voltage source converter which plays the role of interface. To minimise losses due to the transport of energy at very long distances, the technology called High Voltage Direct Current based on Voltage Source Converter (VSC-HVDC) is used. To achieve this goal, a new topology is designed with a new control algorithm based on control of power generated by the wind farm, the DC voltage regulation and the synchronization between wind farm and VSC-HVDC (based on NPC). The proposed topology and its control technique are validated using the "MATLAB/Simulink program". The results are promising, because the THD is less than 5% and the power factor is close to one.

Submicrosecond linear pulse transformer for 800 kV voltage with modular low-inductance primary power supply

NASA Astrophysics Data System (ADS)

Bykov, Yu. A.; Krastelev, E. G.; Popov, G. V.; Sedin, A. A.; Feduschak, V. F.

2016-12-01

A pulsed power source with voltage amplitude up to 800 kV for fast charging (350-400 ns) of the forming line of a high-current nanosecond accelerator is developed. The source includes capacitive energy storage and a linear pulse transformer. The linear transformer consists of a set of 20 inductors with circular ferromagnetic cores surrounded by primary windings inside of which a common stock adder of voltage with film-glycerol insulation is placed. The primary energy storage consists of ten modules, each of which is a low-inductance assembly of two capacitors with a capacitance of 0.35 μF and one gas switch mounted in the same frame. The total energy stored in capacitors is 5.5 kJ at the operating voltage of 40 kV. According to test results, the parameters of the equivalent circuit of the source are the following: shock capacitance = 17.5 nF, inductance = 2 μH, resistance = 3.2 Ω.

Submicrosecond linear pulse transformer for 800 kV voltage with modular low-inductance primary power supply

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

Bykov, Yu. A.; Krastelev, E. G., E-mail: ekrastelev@yandex.ru; Popov, G. V.

A pulsed power source with voltage amplitude up to 800 kV for fast charging (350–400 ns) of the forming line of a high-current nanosecond accelerator is developed. The source includes capacitive energy storage and a linear pulse transformer. The linear transformer consists of a set of 20 inductors with circular ferromagnetic cores surrounded by primary windings inside of which a common stock adder of voltage with film-glycerol insulation is placed. The primary energy storage consists of ten modules, each of which is a low-inductance assembly of two capacitors with a capacitance of 0.35 μF and one gas switch mounted inmore » the same frame. The total energy stored in capacitors is 5.5 kJ at the operating voltage of 40 kV. According to test results, the parameters of the equivalent circuit of the source are the following: shock capacitance = 17.5 nF, inductance = 2 μH, resistance = 3.2 Ω.« less

Membrane Pump for Synthetic Muscle Actuation

DTIC Science & Technology

2009-09-28

FIG. 3 is a schematic representation of an embodiment of a muscle equipped to use electroosmotic flow in accordance with the present invention...water through the membrane to the cathode. This movement of water across the membrane during the application of current is called electroosmotic ...current and a 120 V AC source, again with an appropriate electronics package to control voltage and current. Preferably, the power source 316 can be

Studies and optimization of Pohang Light Source-II superconducting radio frequency system at stable top-up operation with beam current of 400 mA

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

Joo, Youngdo, E-mail: Ydjoo77@postech.ac.kr; Yu, Inha; Park, Insoo

After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. Although available beam current is enhanced by setting a higher RF accelerating voltage, it is bettermore » to keep the RF accelerating voltage as low as possible in the long time top-up operation. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. In our simulation, an equivalent physical modeling was developed using a finite-difference time-domain code. The simulation revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window, which comes with the rapid increase of window vacuum pressure. The RF accelerating voltage of PLS-II RF system was set to 4.95 MV, which was estimated using the maximum available beam current that works as a function of RF voltage, and the top-up operation test with the beam current of 400 mA was successfully carried out.« less

A high-efficiency low-voltage CMOS rectifier for harvesting energy in implantable devices.

PubMed

Hashemi, S Saeid; Sawan, Mohamad; Savaria, Yvon

2012-08-01

We present, in this paper, a new full-wave CMOS rectifier dedicated for wirelessly-powered low-voltage biomedical implants. It uses bootstrapped capacitors to reduce the effective threshold voltage of selected MOS switches. It achieves a significant increase in its overall power efficiency and low voltage-drop. Therefore, the rectifier is good for applications with low-voltage power supplies and large load current. The rectifier topology does not require complex circuit design. The highest voltages available in the circuit are used to drive the gates of selected transistors in order to reduce leakage current and to lower their channel on-resistance, while having high transconductance. The proposed rectifier was fabricated using the standard TSMC 0.18 μm CMOS process. When connected to a sinusoidal source of 3.3 V peak amplitude, it allows improving the overall power efficiency by 11% compared to the best recently published results given by a gate cross-coupled-based structure.

Ohm's Law and Electrical Sources, a Programmed Text.

ERIC Educational Resources Information Center

Balabanian, Norman

This programed textbook was developed under contract with the United States Office of Education as Number 2 of a series of materials for use in an electrical engineering sequence. It is divided into five parts--(1) Ohm's Law, (2) resistance, (3) conductance, (4) voltage sources, and (5) current sources. (DH)

Current conduction in junction gate field effect transistors. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Kim, C.

1970-01-01

The internal physical mechanism that governs the current conduction in junction-gate field effect transistors is studied. A numerical method of analyzing the devices with different length-to-width ratios and doping profiles is developed. This method takes into account the two dimensional character of the electric field and the field dependent mobility. Application of the method to various device models shows that the channel width and the carrier concentration in the conductive channel decrease with increasing drain-to-source voltage for conventional devices. It also shows larger differential drain conductances for shorter devices when the drift velocity is not saturated. The interaction of the source and the drain gives the carrier accumulation in the channel which leads to the space-charge-limited current flow. The important parameters for the space-charge-limited current flow are found to be the L/L sub DE ratio and the crossover voltage.

Compact microwave ion source for industrial applications.

PubMed

Cho, Yong-Sub; Kim, Dae-Il; Kim, Han-Sung; Seol, Kyung-Tae; Kwon, Hyeok-Jung; Hong, In-Seok

2012-02-01

A 2.45 GHz microwave ion source for ion implanters has many good properties for industrial application, such as easy maintenance and long lifetime, and it should be compact for budget and space. But, it has a dc current supply for the solenoid and a rf generator for plasma generation. Usually, they are located on high voltage platform because they are electrically connected with beam extraction power supply. Using permanent magnet solenoid and multi-layer dc break, high voltage deck and high voltage isolation transformer can be eliminated, and the dose rate on targets can be controlled by pulse duty control with semiconductor high voltage switch. Because the beam optics does not change, beam transfer components, such as focusing elements and beam shutter, can be eliminated. It has shown the good performances in budget and space for industrial applications of ion beams.

Real-Time Microscopic Monitoring of Flow, Voltage and Current in the Proton Exchange Membrane Water Electrolyzer.

PubMed

Lee, Chi-Yuan; Li, Shih-Chun; Chen, Chia-Hung; Huang, Yen-Ting; Wang, Yu-Syuan

2018-03-15

Looking for alternative energy sources has been an inevitable trend since the oil crisis, and close attentioned has been paid to hydrogen energy. The proton exchange membrane (PEM) water electrolyzer is characterized by high energy efficiency, high yield, simple system and low operating temperature. The electrolyzer generates hydrogen from water free of any carbon sources (provided the electrons come from renewable sources such as solar and wind), so it is very clean and completely satisfies the environmental requirement. However, in long-term operation of the PEM water electrolyzer, the membrane material durability, catalyst corrosion and nonuniformity of local flow, voltage and current in the electrolyzer can influence the overall performance. It is difficult to measure the internal physical parameters of the PEM water electrolyzer, and the physical parameters are interrelated. Therefore, this study uses micro-electro-mechanical systems (MEMS) technology to develop a flexible integrated microsensor; internal multiple physical information is extracted to determine the optimal working parameters for the PEM water electrolyzer. The real operational data of local flow, voltage and current in the PEM water electrolyzer are measured simultaneously by the flexible integrated microsensor, so as to enhance the performance of the PEM water electrolyzer and to prolong the service life.

Real-Time Microscopic Monitoring of Flow, Voltage and Current in the Proton Exchange Membrane Water Electrolyzer

PubMed Central

Lee, Chi-Yuan; Li, Shih-Chun; Chen, Chia-Hung; Huang, Yen-Ting; Wang, Yu-Syuan

2018-01-01

Looking for alternative energy sources has been an inevitable trend since the oil crisis, and close attentioned has been paid to hydrogen energy. The proton exchange membrane (PEM) water electrolyzer is characterized by high energy efficiency, high yield, simple system and low operating temperature. The electrolyzer generates hydrogen from water free of any carbon sources (provided the electrons come from renewable sources such as solar and wind), so it is very clean and completely satisfies the environmental requirement. However, in long-term operation of the PEM water electrolyzer, the membrane material durability, catalyst corrosion and nonuniformity of local flow, voltage and current in the electrolyzer can influence the overall performance. It is difficult to measure the internal physical parameters of the PEM water electrolyzer, and the physical parameters are interrelated. Therefore, this study uses micro-electro-mechanical systems (MEMS) technology to develop a flexible integrated microsensor; internal multiple physical information is extracted to determine the optimal working parameters for the PEM water electrolyzer. The real operational data of local flow, voltage and current in the PEM water electrolyzer are measured simultaneously by the flexible integrated microsensor, so as to enhance the performance of the PEM water electrolyzer and to prolong the service life. PMID:29543734

Study of mechanism of stress-induced threshold voltage shift and recovery in top-gate amorphous-InGaZnO4 thin-film transistors with source- and drain-offsets

NASA Astrophysics Data System (ADS)

Mativenga, Mallory; Kang, Dong Han; Lee, Ung Gi; Jang, Jin

2012-09-01

Bias instability of top-gate amorphous-indium-gallium-zinc-oxide thin-film transistors with source- and drain-offsets is reported. Positive and negative gate bias-stress (VG_STRESS) respectively induce reversible negative threshold-voltage shift (ΔVTH) and reduction in on-current. Migration of positive charges towards the offsets lowers the local resistance of the offsets, resulting in the abnormal negative ΔVTH under positive VG_STRESS. The reduction in on-current under negative VG_STRESS is due to increase in resistance of the offsets when positive charges migrate away from the offsets. Appropriate drain and source bias-stresses applied simultaneously with VG_STRESS either suppress or enhance the instability, verifying lateral ion migration to be the instability mechanism.

Design and implementation of current fed DC-DC converter for PHEV application using renewable source

NASA Astrophysics Data System (ADS)

Milind Metha, Manish; Tutki, Sanjay; Rajan, Aju; Elangovan, D.; Arunkumar, G.

2017-11-01

As the fossil fuels are depleting day by day, the use of renewable energy sources came into existence and they evolved a lot lately. To increase efficiency and productivity in the hybrid vehicles, the existence less efficient petroleum and diesel IC engines need to be replaced with the new and efficient converters with renewable energy sources. This has to be done in such a way that impacts three factors mainly: cost, efficiency and reliability. The PHEVs that have been launched and the upcoming PHEVs using converters with voltage range around 380V to 400V generated with power ranges between 2.4KW to 2.8KW. The basic motto of this paper is to design a prolific converter while considering the factor such as cost and size. In this paper, a two stage DC-DC converter is proposed and the proposed DC-DC converter is utilized to endeavour voltage from 24V (photovoltaic source) to a yield voltage of 400V and to meet the power demand of 250W, since only one panel is being used for this proposed paper. This paper discuss in detail about why and how the current fed DC-DC converter is utilized along with a voltage doubler, thus reducing transformer turns and thereby reducing overall size of the product. Simulation and hardware results have been presented along with calculations for duty cycle required for firing sequence for different values of transformer turns.

Vertical architecture for enhancement mode power transistors based on GaN nanowires

NASA Astrophysics Data System (ADS)

Yu, F.; Rümmler, D.; Hartmann, J.; Caccamo, L.; Schimpke, T.; Strassburg, M.; Gad, A. E.; Bakin, A.; Wehmann, H.-H.; Witzigmann, B.; Wasisto, H. S.; Waag, A.

2016-05-01

The demonstration of vertical GaN wrap-around gated field-effect transistors using GaN nanowires is reported. The nanowires with smooth a-plane sidewalls have hexagonal geometry made by top-down etching. A 7-nanowire transistor exhibits enhancement mode operation with threshold voltage of 1.2 V, on/off current ratio as high as 108, and subthreshold slope as small as 68 mV/dec. Although there is space charge limited current behavior at small source-drain voltages (Vds), the drain current (Id) and transconductance (gm) reach up to 314 mA/mm and 125 mS/mm, respectively, when normalized with hexagonal nanowire circumference. The measured breakdown voltage is around 140 V. This vertical approach provides a way to next-generation GaN-based power devices.

Epitaxial thinning process

NASA Technical Reports Server (NTRS)

Siegel, C. M. (Inventor)

1984-01-01

A method is described for thinning an epitaxial layer of a wafer that is to be used in producing diodes having a specified breakdown voltage and which also facilitates the thinning process. Current is passed through the epitaxial layer, by connecting a current source between the substrate of the wafer and an electrolyte in which the wafer is immersed. When the wafer is initially immersed, the voltage across the wafer initially drops and then rises at a steep rate. When light is applied to the wafer the voltage drops, and when the light is interrupted the voltage rises again. These changes in voltage, each indicate the breakdown voltage of a Schottky diode that could be prepared from the wafer at that time. The epitaxial layer is thinned by continuing to apply current through the wafer while it is immersed and light is applied, to form an oxide film and when the oxide film is thick the wafer can then be cleaned of oxide and the testing and thinning continued. Uninterrupted thinning can be achieved by first forming an oxide film, and then using an electrolyte that dissolves the oxide about as fast as it is being formed, to limit the thickness of the oxide layer.

Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors

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

Liu, Kuan-Hsien; Chou, Wu-Ching, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw; Chang, Ting-Chang, E-mail: tcchang3708@gmail.com, E-mail: wuchingchou@mail.nctu.edu.tw

2014-10-21

This paper investigates abnormal dimension-dependent thermal instability in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Device dimension should theoretically have no effects on threshold voltage, except for in short channel devices. Unlike short channel drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, for devices with either a relatively large channel width or a short channel length, the output drain current decreases instead of saturating with an increase in drain voltage. Moreover, the wider the channel and the shorter the channel length, the larger the threshold voltage and output on-state current degradation that is observed. Because of themore » surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider/shorter channel length devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast I{sub D}-V{sub G} and modulated peak/base pulse time I{sub D}-V{sub D} measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.« less

Online Assessment of Voltage Stability in Power Systems with PMUs

NASA Astrophysics Data System (ADS)

Chitare, Prasad Bhagwat; Murthy Balijepalli, V. S. K.; Khaparde, S. A.

2013-05-01

Abstract: For the assessment of voltage instability which comprises the detection of voltage instability and identification of critical buses, two indices namely, system wide Qtax, and bus-specific qtax, are proposed. The Qtax, based on the sensitivity of the reactive power injections to the loading in the system provides early detection of impending voltage instability. The computed qtax indices identify the critcal buses among the load buses in the system. The identified critical buses provided optimal lacations for the corrective control actions for averting voltage instability. Additionally, for voltage stability monitoring, determining the poing of exhaustion of the reactive reserves in system is also crucial. This is addressed by proposed Q-Monitoring Index (QMI), which is the ratio of the reactive component of the source current to the sink current that flows through the adjacent transmission line. These proposed indices together can provide early indication to impending voltage instability. This has been illustrated on IEEE-39 bus system. The reactive support on identified critical buses results in maximum increase in the loadability of the system.

[Automatic adjustment control system for DC glow discharge plasma source].

PubMed

Wan, Zhen-zhen; Wang, Yong-qing; Li, Xiao-jia; Wang, Hai-zhou; Shi, Ning

2011-03-01

There are three important parameters in the DC glow discharge process, the discharge current, discharge voltage and argon pressure in discharge source. These parameters influence each other during glow discharge process. This paper presents an automatic control system for DC glow discharge plasma source. This system collects and controls discharge voltage automatically by adjusting discharge source pressure while the discharge current is constant in the glow discharge process. The design concept, circuit principle and control program of this automatic control system are described. The accuracy is improved by this automatic control system with the method of reducing the complex operations and manual control errors. This system enhances the control accuracy of glow discharge voltage, and reduces the time to reach discharge voltage stability. The glow discharge voltage stability test results with automatic control system are provided as well, the accuracy with automatic control system is better than 1% FS which is improved from 4% FS by manual control. Time to reach discharge voltage stability has been shortened to within 30 s by automatic control from more than 90 s by manual control. Standard samples like middle-low alloy steel and tin bronze have been tested by this automatic control system. The concentration analysis precision has been significantly improved. The RSDs of all the test result are better than 3.5%. In middle-low alloy steel standard sample, the RSD range of concentration test result of Ti, Co and Mn elements is reduced from 3.0%-4.3% by manual control to 1.7%-2.4% by automatic control, and that for S and Mo is also reduced from 5.2%-5.9% to 3.3%-3.5%. In tin bronze standard sample, the RSD range of Sn, Zn and Al elements is reduced from 2.6%-4.4% to 1.0%-2.4%, and that for Si, Ni and Fe is reduced from 6.6%-13.9% to 2.6%-3.5%. The test data is also shown in this paper.

Comment on ‘The most energy efficient way to charge the capacitor in a RC circuit’

NASA Astrophysics Data System (ADS)

Oven, R.

2018-07-01

In a recent paper, Wang (2017 Phys. Educ. 52 065019), a comparison was made between the efficiency in charging a capacitor (C) in series with a resistor (R) using either a voltage source or a constant current source. The paper concluded that using a current source was more efficient. We show that this is not correct when the energy loss within the current source is considered. It is also shown that the energy loss is not dependent on the charging rate. A formal proof using calculus and simpler graphical arguments are presented.

A compact high-resolution X-ray ion mobility spectrometer

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

Reinecke, T.; Kirk, A. T.; Heptner, A.

For the ionization of gaseous samples, most ion mobility spectrometers employ radioactive ionization sources, e.g., containing {sup 63}Ni or {sup 3}H. Besides legal restrictions, radioactive materials have the disadvantage of a constant radiation with predetermined intensity. In this work, we replaced the {sup 3}H source of our previously described high-resolution ion mobility spectrometer with 75 mm drift tube length with a commercially available X-ray source. It is shown that the current configuration maintains the resolving power of R = 100 which was reported for the original setup containing a {sup 3}H source. The main advantage of an X-ray source ismore » that the intensity of the radiation can be adjusted by varying its operating parameters, i.e., filament current and acceleration voltage. At the expense of reduced resolving power, the sensitivity of the setup can be increased by increasing the activity of the source. Therefore, the performance of the setup can be adjusted to the specific requirements of any application. To investigate the relation between operating parameters of the X-Ray source and the performance of the ion mobility spectrometer, parametric studies of filament current and acceleration voltage are performed and the influence on resolving power, peak height, and noise is analyzed.« less

Design issue analysis for InAs nanowire tunnel FETs

NASA Astrophysics Data System (ADS)

Sylvia, Somaia S.; Khayer, M. Abul; Alam, Khairul; Lake, Roger K.

2011-10-01

InAs nanowire-tunnel eld eect transistors (NW-TFETs) are being considered for future, beyond-Si electronics. They oer the possibility of beating the ideal thermal limit to the inverse subthreshold slope of 60 mV/dec and thus promise reduced power operation. However, whether the tunneling can provide sucient on-current for high-speed operation is an open question. In this work, for a p-i-n device, we investigate the source doping level necessary to achieve a target on-current (1 A) while maintaining a high ION=IOFF ratio (1106) for a range of NW diameters (2 -8 nm). With a xed drain bias voltage and a maximum gate overdrive, we compare the performance in terms of the inverse subthreshold slope (SS) and ION=IOFF ratio as a function of NW- diameter and source doping. As expected, increasing the source doping level increases the current as a result of the reduced screening length and increased electric eld at source which narrows the tunnel barrier. However, since the degeneracy is also increasing, it moves the eective energy window for tunneling away from the barrier where it is the narrowest. This, in turn, tends to decrease the current for a given voltage which, along with the consideration of inverse SS and ION=IOFF ratio leads to an optimum choice of source doping.

Remnant field detector

DOEpatents

Visser, Age T.

1988-05-03

A method apparatus for qualitatively detecting remnant magnetic fields in matched pairs of magnet cores. Equal magnitude and oppositely oriented magnetic flux is induced in the magnet cores by oppositely wound primary windings and current source. Identically wound secondary windings generate output voltages in response to the induced flux. The output voltages generated should be of equal magnitude and opposite polarity if there is no remnant field in the cores. The output voltages will be unequal which is detected if either core has a remnant field.

Remnant field detector

DOEpatents

Visser, Age T.

1988-01-01

A method apparatus for qualitatively detecting remnant magnetic fields in matched pairs of magnet cores. Equal magnitude and oppositely oriented magnetic flux is induced in the magnet cores by oppositely wound primary windings and current source. Identically wound secondary windings generate output voltages in response to the induced flux. The output voltages generated should be of equal magnitude and opposite polarity if there is no remnant field in the cores. The output voltages will be unequal which is detected if either core has a remnant field.

Methods, systems and apparatus for adjusting duty cycle of pulse width modulated (PWM) waveforms

DOEpatents

Gallegos-Lopez, Gabriel; Kinoshita, Michael H; Ransom, Ray M; Perisic, Milun

2013-05-21

Embodiments of the present invention relate to methods, systems and apparatus for controlling operation of a multi-phase machine in a vector controlled motor drive system when the multi-phase machine operates in an overmodulation region. The disclosed embodiments provide a mechanism for adjusting a duty cycle of PWM waveforms so that the correct phase voltage command signals are applied at the angle transitions. This can reduce variations/errors in the phase voltage command signals applied to the multi-phase machine so that phase current may be properly regulated thus reducing current/torque oscillation, which can in turn improve machine efficiency and performance, as well as utilization of the DC voltage source.

High voltage photovoltaic power converter

DOEpatents

Haigh, Ronald E.; Wojtczuk, Steve; Jacobson, Gerard F.; Hagans, Karla G.

2001-01-01

An array of independently connected photovoltaic cells on a semi-insulating substrate contains reflective coatings between the cells to enhance efficiency. A uniform, flat top laser beam profile is illuminated upon the array to produce electrical current having high voltage. An essentially wireless system includes a laser energy source being fed through optic fiber and cast upon the photovoltaic cell array to prevent stray electrical signals prior to use of the current from the array. Direct bandgap, single crystal semiconductor materials, such as GaAs, are commonly used in the array. Useful applications of the system include locations where high voltages are provided to confined spaces such as in explosive detonation, accelerators, photo cathodes and medical appliances.

Gas Composition Sensing Using Carbon Nanotube Arrays

NASA Technical Reports Server (NTRS)

Li, Jing; Meyyappan, Meyya

2012-01-01

This innovation is a lightweight, small sensor for inert gases that consumes a relatively small amount of power and provides measurements that are as accurate as conventional approaches. The sensing approach is based on generating an electrical discharge and measuring the specific gas breakdown voltage associated with each gas present in a sample. An array of carbon nanotubes (CNTs) in a substrate is connected to a variable-pulse voltage source. The CNT tips are spaced appropriately from the second electrode maintained at a constant voltage. A sequence of voltage pulses is applied and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of the current-voltage characteristics. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas. The CNTs in the gas sensor have a sharp (low radius of curvature) tip; they are preferably multi-wall carbon nanotubes (MWCNTs) or carbon nanofibers (CNFs), to generate high-strength electrical fields adjacent to the tips for breakdown of the gas components with lower voltage application and generation of high current. The sensor system can provide a high-sensitivity, low-power-consumption tool that is very specific for identification of one or more gas components. The sensor can be multiplexed to measure current from multiple CNT arrays for simultaneous detection of several gas components.

Electric power distribution and load transfer system

NASA Technical Reports Server (NTRS)

Bradford, Michael P. (Inventor); Parkinson, Gerald W. (Inventor); Grant, Ross M. (Inventor)

1987-01-01

A power distribution system includes a plurality of power sources and load transfer units including transistors and diodes connected in series and leading to a common power output, each of the transistors being controller switchable subject to voltage levels of the respective input and output sides of said transistors, and the voltage and current level of said common power output. The system is part of an interconnection scheme in which all but one of the power sources is connected to a single load transfer unit, enabling the survival of at least a single power source with the failure of one of the load transfer units.

Electric power distribution and load transfer system

NASA Technical Reports Server (NTRS)

Bradford, Michael P. (Inventor); Parkinson, Gerald W. (Inventor); Grant, Ross M. (Inventor)

1989-01-01

A power distribution system includes a plurality of power sources and load transfer units including transistors and diodes connected in series and leading to a common power output, each of the transistors being controller switchable subject to voltage levels of the respective input and output sides of said transistors, and the voltage and current level of said common power output. The system is part of an interconnection scheme in which all but one of the power sources is connected to a single load transfer unit, enabling the survival of at least a single power source with the failure of one of the load transfer units.

Proceedings of the Particle Beam Research Workshop, Held at US Air Force Academy, Colorado, Springs, CO on 10-11 January 1980

DTIC Science & Technology

1980-05-01

Components 25 2.7.1 Transformers 25 2.7.2 Solid Dielectric 26 2.7.3 Cables and Connectors 27 III. SOURCES 29 3.1 Preface 29 3.2 Electron Sources 30 3.3 High...be developed which can withstand high voltages , high current densities, and pass large energies per pulse with high repetition rates, high reliability...Ceramics - high voltage hold-off 2) Dielectrics - hold-off recovery after breakdown 3) Metals - low erosion rates, higher j and esaturation 4) Degradation

Investigation of interface property in Al/SiO2/ n-SiC structure with thin gate oxide by illumination

NASA Astrophysics Data System (ADS)

Chang, P. K.; Hwu, J. G.

2017-04-01

The reverse tunneling current of Al/SiO2/ n-SiC structure employing thin gate oxide is introduced to examine the interface property by illumination. The gate current at negative bias decreases under blue LED illumination, yet increases under UV lamp illumination. Light-induced electrons captured by interface states may be emitted after the light sources are off, leading to the recovery of gate currents. Based on transient characteristics of gate current, the extracted trap level is close to the light energy for blue LED, indicating that electron capture induced by lighting may result in the reduction of gate current. Furthermore, bidirectional C- V measurements exhibit a positive voltage shift caused by electron trapping under blue LED illumination, while a negative voltage shift is observed under UV lamp illumination. Distinct trapping and detrapping behaviors can be observed from variations in I- V and C- V curves utilizing different light sources for 4H-SiC MOS capacitors with thin insulators.

PI and fuzzy logic controllers for shunt Active Power Filter--a report.

PubMed

P, Karuppanan; Mahapatra, Kamala Kanta

2012-01-01

This paper presents a shunt Active Power Filter (APF) for power quality improvements in terms of harmonics and reactive power compensation in the distribution network. The compensation process is based only on source current extraction that reduces the number of sensors as well as its complexity. A Proportional Integral (PI) or Fuzzy Logic Controller (FLC) is used to extract the required reference current from the distorted line-current, and this controls the DC-side capacitor voltage of the inverter. The shunt APF is implemented with PWM-current controlled Voltage Source Inverter (VSI) and the switching patterns are generated through a novel Adaptive-Fuzzy Hysteresis Current Controller (A-F-HCC). The proposed adaptive-fuzzy-HCC is compared with fixed-HCC and adaptive-HCC techniques and the superior features of this novel approach are established. The FLC based shunt APF system is validated through extensive simulation for diode-rectifier/R-L loads. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Testing Single Phase IGBT H-Bridge Switch Plates for the High Voltage Converter Modulator at the Spallation Neutron Source

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

Peplov, Vladimir V; Anderson, David E; Solley, Dennis J

2014-01-01

Three IGBT H-bridge switching networks are used in each High Voltage Converter Modulator (HVCM) system at the Spallation Neutron Source (SNS) to generate drive currents to three boost transformer primaries switching between positive and negative bus voltages at 20 kHz. Every switch plate assembly is tested before installing it into an operational HVCM. A Single Phase Test Stand has been built for this purpose, and it is used for adjustment, measurement and testing of different configurations of switch plates. This paper will present a description of the Test Stand configuration and discuss the results of testing switch plates with twomore » different types of IGBT gate drivers currently in use on the HVCM systems. Comparison of timing characteristics of the original and new drivers and the resulting performance reinforces the necessity to replace the original H-bridge network drivers with the upgraded units.« less

The Noise Level Optimization for Induction Magnetometer of SEP System

NASA Astrophysics Data System (ADS)

Zhu, W.; Fang, G.

2011-12-01

The Surface Electromagnetic Penetration (SEP) System, subsidized by the SinoProbe Plan in China, is designed for 3D conductivity imaging in geophysical mineral exploration, underground water distribution exploration, oil and gas reservoir exploration. Both the Controlled Source Audio Magnetotellurics (CSAMT) method and Magnetotellurics (MT) method can be surveyed by SEP system. In this article, an optimization design is introduced, which can minimize the noise level of the induction magnetometer for SEP system magnetic field's acquisition. The induction magnetometer transfers the rate of the magnetic field's change to voltage signal by induction coil, and amplified it by Low Noise Amplifier The noise parts contributed to the magnetometer are: the coil's thermal noise, the equivalent input voltage and current noise of the pre-amplifier. The coil's thermal noise is decided by coil's DC resistance. The equivalent input voltage and current noise of the pre-amplifier depend on the amplifier's type and DC operation condition. The design here optimized the DC operation point of pre-amplifier, adjusted the DC current source, and realized the minimum of total noise level of magnetometer. The calculation and test results show that: the total noise is about 1pT/√Hz, the thermal noise of coils is 1.7nV/√Hz, the preamplifier equivalent input voltage and current noise is 3nV/ √Hz and 0.1pA/√Hz, the weight of the magnetometer is 4.5kg and meet the requirement of SEP system.

A liquid hydrocarbon deuteron source for neutron generators

NASA Astrophysics Data System (ADS)

Schwoebel, P. R.

2017-06-01

Experimental studies of a deuteron spark source for neutron generators using hydrogen isotope fusion reactions are reported. The ion source uses a spark discharge between electrodes coated with a deuterated hydrocarbon liquid, here Santovac 5, to inhibit permanent electrode erosion and extend the lifetime of high-output neutron generator spark ion sources. Thompson parabola mass spectra show that principally hydrogen and deuterium ions are extracted from the ion source. Hydrogen is the chief residual gas phase species produced due to source operation in a stainless-steel vacuum chamber. The prominent features of the optical emission spectra of the discharge are C+ lines, the hydrogen Balmer Hα-line, and the C2 Swan bands. Operation of the ion source was studied in a conventional laboratory neutron generator. The source delivered an average deuteron current of ˜0.5 A nominal to the target in a 5 μs duration pulse at 1 Hz with target voltages of -80 to -100 kV. The thickness of the hydrocarbon liquid in the spark gap and the consistency thereof from spark to spark influences the deuteron yield and plays a role in determining the beam-focusing characteristics through the applied voltage necessary to break down the spark gap. Higher breakdown voltages result in larger ion beam spots on the target and vice-versa. Because the liquid self-heals and thereby inhibits permanent electrode erosion, the liquid-based source provides long life, with 104 pulses to date, and without clear evidence that, in principle, the lifetime could not be much longer. Initial experiments suggest that an alternative cylindrical target-type generator design can extract approximately 10 times the deuteron current from the source. Preliminary data using the deuterated source liquid as a neutron-producing target are also presented.

Properties and Applications of Varistor-Transistor Hybrid Devices

NASA Astrophysics Data System (ADS)

Pandey, R. K.; Stapleton, William A.; Sutanto, Ivan; Scantlin, Amanda A.; Lin, Sidney

2014-05-01

The nonlinear current-voltage characteristics of a varistor device are modified with the help of external agents, resulting in tuned varistor-transistor hybrid devices with multiple applications. The substrate used to produce these hybrid devices belongs to the modified iron titanate family with chemical formula 0.55FeTiO3·0.45Fe2O3 (IHC45), which is a prominent member of the ilmenite-hematite solid-solution series. It is a wide-bandgap magnetic oxide semiconductor. Electrical resistivity and Seebeck coefficient measurements from room temperature to about 700°C confirm that it retains its p-type nature for the entire temperature range. The direct-current (DC) and alternating-current (AC) properties of these hybrid devices are discussed and their applications identified. It is shown here that such varistor embedded ceramic transistors with many interesting properties and applications can be mass produced using incredibly simple structures. The tuned varistors by themselves can be used for current amplification and band-pass filters. The transistors on the other hand could be used to produce sensors, voltage-controlled current sources, current-controlled voltage sources, signal amplifiers, and low-band-pass filters. We believe that these devices could be suitable for a number of applications in consumer and defense electronics, high-temperature and space electronics, bioelectronics, and possibly also for electronics specific to handheld devices.

Current control circuitry

DOEpatents

Taubman, Matthew S [Richland, WA

2005-03-15

Among the embodiments of the present invention is an apparatus that includes a transistor (30), a servo device (40), and a current source (50). The servo device (40) is operable to provide a common base mode of operation of the transistor (30) by maintaining an approximately constant voltage level at the transistor base (32b). The current source (150) is operable to provide a bias current to the transistor (30). A first device (24) provides an input signal to an electrical node (70) positioned between the emitter (32e) of the transistor (30) and the current source (50). A second device (26) receives an output signal from the collector (32c) of the transistor (30).

Dynamic Performance of a Back-to-Back HVDC Station Based on Voltage Source Converters

NASA Astrophysics Data System (ADS)

Khatir, Mohamed; Zidi, Sid-Ahmed; Hadjeri, Samir; Fellah, Mohammed-Karim

2010-01-01

The recent developments in semiconductors and control equipment have made the voltage source converter based high voltage direct current (VSC-HVDC) feasible. This new DC transmission is known as "HVDC Light or "HVDC Plus by leading vendors. Due to the use of VSC technology and pulse width modulation (PWM) the VSC-HVDC has a number of potential advantages as compared with classic HVDC. In this paper, the scenario of back-to-back VSC-HVDC link connecting two adjacent asynchronous AC networks is studied. Control strategy is implemented and its dynamic performances during disturbances are investigated in MATLAB/Simulink program. The simulation results have shown good performance of the proposed system under balanced and unbalanced fault conditions.

Four-gate transistor analog multiplier circuit

NASA Technical Reports Server (NTRS)

Mojarradi, Mohammad M. (Inventor); Blalock, Benjamin (Inventor); Cristoloveanu, Sorin (Inventor); Chen, Suheng (Inventor); Akarvardar, Kerem (Inventor)

2011-01-01

A differential output analog multiplier circuit utilizing four G.sup.4-FETs, each source connected to a current source. The four G.sup.4-FETs may be grouped into two pairs of two G.sup.4-FETs each, where one pair has its drains connected to a load, and the other par has its drains connected to another load. The differential output voltage is taken at the two loads. In one embodiment, for each G.sup.4-FET, the first and second junction gates are each connected together, where a first input voltage is applied to the front gates of each pair, and a second input voltage is applied to the first junction gates of each pair. Other embodiments are described and claimed.

A novel technique to measure interface trap density in a GaAs MOS capacitor using time-varying magnetic fields

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

Choudhury, Aditya N. Roy, E-mail: aditya@physics.iisc.ernet.in; Venkataraman, V.

Interface trap density (D{sub it}) in a GaAs metal-oxide-semiconductor (MOS) capacitor can be measured electrically by measuring its impedance, i.e. by exciting it with a small signal voltage source and measuring the resulting current through the circuit. We propose a new method of measuring D{sub it} where the MOS capacitor is subjected to a (time-varying) magnetic field instead, which produces an effect equivalent to a (time-varying) voltage drop across the sample. This happens because the electron chemical potential of GaAs changes with a change in an externally applied magnetic field (unlike that of the gate metal); this is not themore » voltage induced by Faraday’s law of electromagnetic induction. So, by measuring the current through the MOS, D{sub it} can be found similarly. Energy band diagrams and equivalent circuits of a MOS capacitor are drawn in the presence of a magnetic field, and analyzed. The way in which a magnetic field affects a MOS structure is shown to be fundamentally different compared to an electrical voltage source.« less

Temperature dependence of DC transport characteristics for a two-dimensional electron gas in an undoped Si/SiGe heterostructure

NASA Astrophysics Data System (ADS)

Chou, Kuan-Yu; Hsu, Nai-Wen; Su, Yi-Hsin; Chou, Chung-Tao; Chiu, Po-Yuan; Chuang, Yen; Li, Jiun-Yun

2018-02-01

We investigate DC characteristics of a two-dimensional electron gas (2DEG) in an undoped Si/SiGe heterostructure and its temperature dependence. An insulated-gate field-effect transistor was fabricated, and transfer characteristics were measured at 4 K-300 K. At low temperatures (T < 45 K), source electrons are injected into the buried 2DEG channel first and drain current increases with the gate voltage. By increasing the gate voltage further, the current saturates followed by a negative transconductance observed, which can be attributed to electron tunneling from the buried channel to the surface channel. Finally, the drain current is saturated again at large gate biases due to parallel conduction of buried and surface channels. By increasing the temperature, an abrupt increase in threshold voltage is observed at T ˜ 45 K and it is speculated that negatively charged impurities at the Al2O3/Si interface are responsible for the threshold voltage shift. At T > 45 K, the current saturation and negative transconductance disappear and the device acts as a normal transistor.

Raman imaging of carrier distribution in the channel of an ionic liquid-gated transistor fabricated with regioregular poly(3-hexylthiophene)

NASA Astrophysics Data System (ADS)

Wada, Y.; Enokida, I.; Yamamoto, J.; Furukawa, Y.

2018-05-01

Raman images of carriers (positive polarons) at the channel of an ionic liquid-gated transistor (ILGT) fabricated with regioregular poly(3-hexylthiophene) (P3HT) have been measured with excitation at 785 nm. The observed spectra indicate that carriers generated are positive polarons. The intensities of the 1415 cm-1 band attributed to polarons in the P3HT channel were plotted as Raman images; they showed the carrier density distribution. When the source-drain voltage VD is lower than the source-gate voltage VG (linear region), the carrier density was uniform. When VD is nearly equal to VG (saturation region), a negative carrier density gradient from the source electrode towards the drain electrode was observed. This carrier density distribution is associated with the observed current-voltage characteristics, which is not consistent with the "pinch-off" theory of inorganic semiconductor transistors.

An innovative high-power constant-current pulsed-arc power-supply for a high-density pulsed-arc-plasma ion-source using a LaB6-filament.

PubMed

Ueno, A; Oguri, H; Ikegami, K; Namekawa, Y; Ohkoshi, K; Tokuchi, A

2010-02-01

An innovative high-power constant-current (CC) pulsed-arc (PA) power-supply (PS) indispensable for a high-density PA plasma ion-source using a lanthanum hexaboride (LaB(6)) filament was devised by combining a constant-voltage (CV) PA-PS, which is composed of an insulated gate bipolar transistor (IGBT) switch, a CV direct-current (dc) PS and a 270 mF capacitor with a CC-PA-PS, which is composed of an IGBT-switch, a CC-dc-PS and a 400 microH inductor, through the inductor. The hybrid-CC-PA-PS succeeded in producing a flat arc-pulse with a peak power of 56 kW (400 A x 140 V) and a duty factor of more than 1.5% (600 micros x 25 Hz) for Japan Proton Accelerator Research Complex (J-PARC) H(-) ion-source stably. It also succeeded in shortening the 99% rising-time of the arc-pulse-current to about 20 micros and tilting up or down the arc-pulse-current arbitrarily and almost linearly by changing the setting voltage of its CV-dc-PS.

Gummel Symmetry Test on charge based drain current expression using modified first-order hyperbolic velocity-field expression

NASA Astrophysics Data System (ADS)

Singh, Kirmender; Bhattacharyya, A. B.

2017-03-01

Gummel Symmetry Test (GST) has been a benchmark industry standard for MOSFET models and is considered as one of important tests by the modeling community. BSIM4 MOSFET model fails to pass GST as the drain current equation is not symmetrical because drain and source potentials are not referenced to bulk. BSIM6 MOSFET model overcomes this limitation by taking all terminal biases with reference to bulk and using proper velocity saturation (v -E) model. The drain current equation in BSIM6 is charge based and continuous in all regions of operation. It, however, adopts a complicated method to compute source and drain charges. In this work we propose to use conventional charge based method formulated by Enz for obtaining simpler analytical drain current expression that passes GST. For this purpose we adopt two steps: (i) In the first step we use a modified first-order hyperbolic v -E model with adjustable coefficients which is integrable, simple and accurate, and (ii) In the second we use a multiplying factor in the modified first-order hyperbolic v -E expression to obtain correct monotonic asymptotic behavior around the origin of lateral electric field. This factor is of empirical form, which is a function of drain voltage (vd) and source voltage (vs) . After considering both the above steps we obtain drain current expression whose accuracy is similar to that obtained from second-order hyperbolic v -E model. In modified first-order hyperbolic v -E expression if vd and vs is replaced by smoothing functions for the effective drain voltage (vdeff) and effective source voltage (vseff), it will as well take care of discontinuity between linear to saturation regions of operation. The condition of symmetry is shown to be satisfied by drain current and its higher order derivatives, as both of them are odd functions and their even order derivatives smoothly pass through the origin. In strong inversion region and technology node of 22 nm the GST is shown to pass till sixth-order derivative and for weak inversion it is shown till fifth-order derivative. In the expression of drain current major short channel phenomena like vertical field mobility reduction, velocity saturation and velocity overshoot have been taken into consideration.

Energy & mass-charge distribution peculiarities of ion emitted from penning source

NASA Astrophysics Data System (ADS)

Mamedov, N. V.; Kolodko, D. V.; Sorokin, I. A.; Kanshin, I. A.; Sinelnikov, D. N.

2017-05-01

The optimization of hydrogen Penning sources used, in particular, in plasma chemical processing of materials and DLC deposition, is still very important. Investigations of mass-charge composition of these ion source emitted beams are particular relevant for miniature linear accelerators (neutron flux generators) nowadays. The Penning ion source energy and mass-charge ion distributions are presented. The relation between the discharge current abrupt jumps with increasing plasma density in the discharge center and increasing potential whipping (up to 50% of the anode voltage) is shown. Also the energy spectra in the discharge different modes as the pressure and anode potential functions are presented. It has been revealed that the atomic hydrogen ion concentration is about 5-10%, and it weakly depends on the pressure and the discharge current (in the investigated range from 1 to 10 mTorr and from 50 to 1000 μA) and increases with the anode voltage (up 1 to 3,5 kV).

High precision triangular waveform generator

DOEpatents

Mueller, Theodore R.

1983-01-01

An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

High-precision triangular-waveform generator

DOEpatents

Mueller, T.R.

1981-11-14

An ultra-linear ramp generator having separately programmable ascending and decending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Study of a control strategy for grid side converter in doubly- fed wind power system

NASA Astrophysics Data System (ADS)

Zhu, D. J.; Tan, Z. L.; Yuan, F.; Wang, Q. Y.; Ding, M.

2016-08-01

The grid side converter is an important part of the excitation system of doubly-fed asynchronous generator used in wind power system. As a three-phase voltage source PWM converter, it can not only transfer slip power in the form of active power, but also adjust the reactive power of the grid. This paper proposed a control approach for improving its performance. In this control approach, the dc voltage is regulated by a sliding mode variable structure control scheme and current by a variable structure controller based on the input output linearization. The theoretical bases of the sliding mode variable structure control were introduced, and the stability proof was presented. Switching function of the system has been deduced, sliding mode voltage controller model has been established, and the output of the outer voltage loop is the instruction of the inner current loop. Affine nonlinear model of two input two output equations on d-q axis for current has been established its meeting conditions of exact linearization were proved. In order to improve the anti-jamming capability of the system, a variable structure control was added in the current controller, the control law was deduced. The dual-loop control with sliding mode control in outer voltage loop and linearization variable structure control in inner current loop was proposed. Simulation results demonstrate the effectiveness of the proposed control strategy even during the dc reference voltage and system load variation.

Current-voltage characteristics and increase in the quantum efficiency of three-terminal gate and avalanche-based silicon LEDs.

PubMed

Xu, Kaikai

2013-09-20

In this paper, the emission of visible light by a monolithically integrated silicon p-n junction under reverse-bias is discussed. The modulation of light intensity is achieved using an insulated-gate terminal on the surface of the p-n junction. By varying the gate voltage, the breakdown voltage of the p-n junction will be adjustable so that the reverse current I(sub) flowing through the p-n junction at a fixed reverse-bias voltage is changed. It is observed that the light, which is emitted from the defects located at the p-n junction, depends closely on the reverse current I(sub). In regard to the phenomenon of electroluminescence, the relationship between the optical emission power and the reverse current I(sub) is linear. On the other hand, it is observed that both the quantum efficiency and the power conversion efficiency are able to have obvious enhancement, although the reverse-bias of the p-n junction is reduced and the corresponding reverse-current is much lower. Moreover, the successful fabrication on monolithic silicon light source on the bulk silicon by means of standard silicon complementary metal-oxide-semiconductor process technology is presented.

Efficient Low-Voltage Operation of a CW Gyrotron Oscillator at 233 GHz.

PubMed

Hornstein, Melissa K; Bajaj, Vikram S; Griffin, Robert G; Temkin, Richard J

2007-02-01

The gyrotron oscillator is a source of high average power millimeter-wave through terahertz radiation. In this paper, we report low beam power and high-efficiency operation of a tunable gyrotron oscillator at 233 GHz. The low-voltage operating mode provides a path to further miniaturization of the gyrotron through reduction in the size of the electron gun, power supply, collector, and cooling system, which will benefit industrial and scientific applications requiring portability. Detailed studies of low-voltage operation in the TE(2) (,) (3) (,) (1) mode reveal that the mode can be excited with less than 7 W of beam power at 3.5 kV. During CW operation with 3.5-kV beam voltage and 50-mA beam current, the gyrotron generates 12 W of RF power at 233.2 GHz. The EGUN electron optics code describes the low-voltage operation of the electron gun. Using gun-operating parameters derived from EGUN simulations, we show that a linear theory adequately predicts the low experimental starting currents.

Efficient Low-Voltage Operation of a CW Gyrotron Oscillator at 233 GHz

PubMed Central

Hornstein, Melissa K.; Bajaj, Vikram S.; Griffin, Robert G.; Temkin, Richard J.

2007-01-01

The gyrotron oscillator is a source of high average power millimeter-wave through terahertz radiation. In this paper, we report low beam power and high-efficiency operation of a tunable gyrotron oscillator at 233 GHz. The low-voltage operating mode provides a path to further miniaturization of the gyrotron through reduction in the size of the electron gun, power supply, collector, and cooling system, which will benefit industrial and scientific applications requiring portability. Detailed studies of low-voltage operation in the TE2,3,1 mode reveal that the mode can be excited with less than 7 W of beam power at 3.5 kV. During CW operation with 3.5-kV beam voltage and 50-mA beam current, the gyrotron generates 12 W of RF power at 233.2 GHz. The EGUN electron optics code describes the low-voltage operation of the electron gun. Using gun-operating parameters derived from EGUN simulations, we show that a linear theory adequately predicts the low experimental starting currents. PMID:17687412

Applying PWM to control overcurrents at unbalanced faults of force-commutated VSCs used as static var compensators

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

Jiang, Y.; Ekstroem, A.

1997-01-01

This study is devoted to investigating the possibility of controlling the overcurrent of a forced-commutated voltage source converter (VSC) by PWM when the ac system is undergoing large unbalanced disturbance. The converter is supposed to be used as a static var compensator at a high power level. A novel control strategy is proposed for controlling the reactive current and the dc side voltage independently. Digital simulation results are presented and compared with the results by using just the reactive current control with fundamental switching frequency.

Application of Microsecond Voltage Pulses for Water Disinfection by Diaphragm Electric Discharge

NASA Astrophysics Data System (ADS)

Kakaurov, S. V.; Suvorov, I. F.; Yudin, A. S.; Solovyova, T. L.; Kuznetsova, N. S.

2015-11-01

The paper presents the dependence of copper and silver ions formation on the duration of voltage pulses of diaphragm electric discharge and on the pH of treated liquid medium. Knowing it allows one to create an automatic control system to control bactericidal agent's parameters obtained in diaphragm electric discharge reactor. The current-voltage characteristic of the reactor with a horizontal to the diaphragm membrane water flow powered from the author's custom pulse voltage source is also presented. The results of studies of the power consumption of diaphragm electric discharge depending on temperature of the treated liquid medium are given.

Characteristics of camel-gate structures with active doping channel profiles

NASA Astrophysics Data System (ADS)

Tsai, Jung-Hui; Lour, Wen-Shiung; Laih, Lih-Wen; Liu, Rong-Chau; Liu, Wen-Chau

1996-03-01

In this paper, we demonstrate the influence of channel doping profile on the performances of camel-gate field effect transistors (CAMFETs). For comparison, single and tri-step doping channel structures with identical doping thickness products are employed, while other parameters are kept unchanged. The results of a theoretical analysis show that the single doping channel FET with lightly doping active layer has higher barrier height and drain-source saturation current. However, the transconductance is decreased. For a tri-step doping channel structure, it is found that the output drain-source saturation current and the barrier height are enhanced. Furthermore, the relatively voltage independent performances are improved. Two CAMFETs with single and tri-step doping channel structures have been fabricated and discussed. The devices exhibit nearly voltage independent transconductances of 144 mS mm -1 and 222 mS mm -1 for single and tri-step doping channel CAMFETs, respectively. The operation gate voltage may extend to ± 1.5 V for a tri-step doping channel CAMFET. In addition, the drain current densities of > 750 and 405 mA mm -1 are obtained for the tri-step and single doping CAMFETs. These experimental results are inconsistent with theoretical analysis.

Transistor biased amplifier minimizes diode discriminator threshold attenuation

NASA Technical Reports Server (NTRS)

Larsen, R. N.

1967-01-01

Transistor biased amplifier has a biased diode discriminator driven by a high impedance /several megohms/ current source, rather than a voltage source with several hundred ohms output impedance. This high impedance input arrangement makes the incremental impedance of the threshold diode negligible relative to the input impedance.

[Studies on the general properties of a novel microwave plasma enhanced glow discharge source].

PubMed

Li, Y; Du, Z; Duan, Y; Zhang, H; Jin, Q; Liu, H

1998-04-01

This paper introduced a novel microwave plasma enhanced glow descharge source, the structure design and operation were decribed, and the mutual effects of the main characters, such as pressure, current, voltage, microwave power and sputtering rates were also investigated in details.

Applicability of Generalized Peek's Law to Scaling of Corona Onset Voltages in Electropositive Gases

NASA Astrophysics Data System (ADS)

Li, Yan-Ming

2008-10-01

We have developed the steady state positive corona model with the ionization zone physics in the point-plane configuration. The geometry is axisymmetric, consisting of a pointed anode of small tip radius and a planar cathode. The model solves the Poisson equation, drift dominated electron and the positive ion transport equations with the nonlinear Townsend ionization source terms, to give the complete electric field, electron and positive ion density distributions. The corona plasma properties can be determined as function of discharge current, ranging from the pico-ampere up to a milli-ampere. The calculated voltage-current characteristics obeyed the Townsend equation, agreeing with the general experimental observations. The model is applied to different electropositive gases, argon, xenon, nitrogen and mercury. Corona onset potentials are determined based on the discharge voltages at very low currents. Extensive parametric study for argon positive corona with varying anode tip radius, gap distance and gas pressure has been completed. All the simulated corona onset voltages are very well described by the generalized Peek's Law [1]. At sufficiently high current in the range of 0.1 mA, discharge filament is formed near the anode tip. [1] Peek F. W., Dielectric Phenomena in High Voltage Engineering, McGraw Hill, New York (1929).

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.

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

Han, Dong-Suk; Kang, Yu-Jin; Park, Jae-Hyung

Highlights: • We developed and investigated source/drain electrodes in oxide TFTs. • The Mo S/D electrodes showed good output characteristics. • Intrinsic TFT parameters were calculated by the transmission line method. - Abstract: This paper investigates the feasibility of a low-resistivity electrode material (Mo) for source/drain (S/D) electrodes in thin film transistors (TFTs). The effective resistances between Mo source/drain electrodes and amorphous zinc–tin-oxide (a-ZTO) thin film transistors were studied. Intrinsic TFT parameters were calculated by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low source/drain voltage. The TFTs fabricated with Momore » source/drain electrodes showed good transfer characteristics with a field-effect mobility of 10.23 cm{sup 2}/V s. In spite of slight current crowding effects, the Mo source/drain electrodes showed good output characteristics with a steep rise in the low drain-to-source voltage (V{sub DS}) region.« less

Method for measuring the alternating current half-wave voltage of a Mach-Zehnder modulator based on opto-electronic oscillation.

PubMed

Hong, Jun; Chen, Dongchu; Peng, Zhiqiang; Li, Zulin; Liu, Haibo; Guo, Jian

2018-05-01

A new method for measuring the alternating current (AC) half-wave voltage of a Mach-Zehnder modulator is proposed and verified by experiment in this paper. Based on the opto-electronic self-oscillation technology, the physical relationship between the saturation output power of the oscillating signal and the AC half-wave voltage is revealed, and the value of the AC half-wave voltage is solved by measuring the saturation output power of the oscillating signal. The experimental results show that the measured data of this new method involved are in agreement with a traditional method, and not only an external microwave signal source but also the calibration for different frequency measurements is not needed in our new method. The measuring process is simplified with this new method on the premise of ensuring the accuracy of measurement, and it owns good practical value.

Investigation of the novel attributes in double recessed gate SiC MESFETs at drain side

NASA Astrophysics Data System (ADS)

Orouji, Ali A.; Razavi, S. M.; Ebrahim Hosseini, Seyed; Amini Moghadam, Hamid

2011-11-01

In this paper, the potential impact of drain side-double recessed gate (DS-DRG) on silicon carbide (SiC)-based metal semiconductor field effect transistors (MESFETs) is studied. We investigate the device performance focusing on breakdown voltage, threshold voltage, drain current and dc output conductance with two-dimensional and two-carrier device simulation. Our simulation results demonstrate that the channel thickness under the gate in the drain side is an important factor in the breakdown voltage. Also, the positive shift in the threshold voltage for the DS-DRG structure is larger in comparison with that for the source side-double recessed gate (SS-DRG) SiC MESFET. The saturated drain current for the DS-DRG structure is larger compared to that for the SS-DRG structure. The maximum dc output conductance in the DS-DRG structure is smaller than that in the SS-DRG structure.

Energy storage connection system

DOEpatents

Benedict, Eric L.; Borland, Nicholas P.; Dale, Magdelena; Freeman, Belvin; Kite, Kim A.; Petter, Jeffrey K.; Taylor, Brendan F.

2012-07-03

A power system for connecting a variable voltage power source, such as a power controller, with a plurality of energy storage devices, at least two of which have a different initial voltage than the output voltage of the variable voltage power source. The power system includes a controller that increases the output voltage of the variable voltage power source. When such output voltage is substantially equal to the initial voltage of a first one of the energy storage devices, the controller sends a signal that causes a switch to connect the variable voltage power source with the first one of the energy storage devices. The controller then causes the output voltage of the variable voltage power source to continue increasing. When the output voltage is substantially equal to the initial voltage of a second one of the energy storage devices, the controller sends a signal that causes a switch to connect the variable voltage power source with the second one of the energy storage devices.

An Optimal Control Strategy for DC Bus Voltage Regulation in Photovoltaic System with Battery Energy Storage

PubMed Central

Daud, Muhamad Zalani; Mohamed, Azah; Hannan, M. A.

2014-01-01

This paper presents an evaluation of an optimal DC bus voltage regulation strategy for grid-connected photovoltaic (PV) system with battery energy storage (BES). The BES is connected to the PV system DC bus using a DC/DC buck-boost converter. The converter facilitates the BES power charge/discharge to compensate for the DC bus voltage deviation during severe disturbance conditions. In this way, the regulation of DC bus voltage of the PV/BES system can be enhanced as compared to the conventional regulation that is solely based on the voltage-sourced converter (VSC). For the grid side VSC (G-VSC), two control methods, namely, the voltage-mode and current-mode controls, are applied. For control parameter optimization, the simplex optimization technique is applied for the G-VSC voltage- and current-mode controls, including the BES DC/DC buck-boost converter controllers. A new set of optimized parameters are obtained for each of the power converters for comparison purposes. The PSCAD/EMTDC-based simulation case studies are presented to evaluate the performance of the proposed optimized control scheme in comparison to the conventional methods. PMID:24883374

An optimal control strategy for DC bus voltage regulation in photovoltaic system with battery energy storage.

PubMed

Daud, Muhamad Zalani; Mohamed, Azah; Hannan, M A

2014-01-01

This paper presents an evaluation of an optimal DC bus voltage regulation strategy for grid-connected photovoltaic (PV) system with battery energy storage (BES). The BES is connected to the PV system DC bus using a DC/DC buck-boost converter. The converter facilitates the BES power charge/discharge to compensate for the DC bus voltage deviation during severe disturbance conditions. In this way, the regulation of DC bus voltage of the PV/BES system can be enhanced as compared to the conventional regulation that is solely based on the voltage-sourced converter (VSC). For the grid side VSC (G-VSC), two control methods, namely, the voltage-mode and current-mode controls, are applied. For control parameter optimization, the simplex optimization technique is applied for the G-VSC voltage- and current-mode controls, including the BES DC/DC buck-boost converter controllers. A new set of optimized parameters are obtained for each of the power converters for comparison purposes. The PSCAD/EMTDC-based simulation case studies are presented to evaluate the performance of the proposed optimized control scheme in comparison to the conventional methods.

High breakdown voltage and high driving current in a novel silicon-on-insulator MESFET with high- and low-resistance boxes in the drift region

NASA Astrophysics Data System (ADS)

Naderi, Ali; Mohammadi, Hamed

2018-06-01

In this paper a novel silicon-on-insulator metal oxide field effect transistor (SOI-MESFET) with high- and low-resistance boxes (HLRB) is proposed. This structure increases the current and breakdown voltage, simultaneously. The semiconductor at the source side of the channel is doped with higher impurity than the other parts to reduce its resistance and increase the driving current as low-resistance box. An oxide box is implemented at the upper part of the channel from the drain region toward the middle of the channel as the high-resistance box. Inserting a high-resistance box increases the breakdown voltage and improves the RF performance of the device because of its higher tolerable electric field and modification in gate-drain capacitance, respectively. The high-resistance region reduces the current density of the device which is completely compensated by low-resistance box. A 92% increase in breakdown voltage and an 11% improvement in the device current have been obtained. Also, maximum oscillation frequency, unilateral power gain, maximum available gain, maximum stable gain, and maximum output power density are improved by 7%, 35%, 23%, 26%, and 150%, respectively. These results show that the HLRB-SOI-MESFET can be considered as a candidate to replace Conventional SOI-MESFET (C-SOI-MESFET) for high-voltage and high-frequency applications.

High current polarized electron source

NASA Astrophysics Data System (ADS)

Suleiman, R.; Adderley, P.; Grames, J.; Hansknecht, J.; Poelker, M.; Stutzman, M.

2018-05-01

Jefferson Lab operates two DC high voltage GaAs photoguns with compact inverted insulators. One photogun provides the polarized electron beam at the Continuous Electron Beam Accelerator Facility (CEBAF) up to 200 µA. The other gun is used for high average current photocathode lifetime studies at a dedicated test facility up to 4 mA of polarized beam and 10 mA of un-polarized beam. GaAs-based photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed facilities that must operate in excess of tens of mA of polarized average current. This contribution describes techniques to maintain good vacuum while delivering high beam currents, and techniques that minimize damage due to ion bombardment, the dominant mechanism that reduces photocathode yield. Advantages of higher DC voltage include reduced space-charge emittance growth and the potential for better photocathode lifetime. Highlights of R&D to improve the performance of polarized electron sources and prolong the lifetime of strained-superlattice GaAs are presented.

Some Notes on Sparks and Ignition of Fuels

NASA Technical Reports Server (NTRS)

Fisher, Franklin A.

2000-01-01

This report compliments a concurrent analysis of the electromagnetic field threat to the fuel system of a transport aircraft. The accompanying effort assessed currents, voltages and power levels that may be induced upon fuel tank wiring from radio transmitters (inside and outside the aircraft). In addition to this, it was also essential to determine how much voltage, current, or power is required to create a fuel-vapor ignition hazard. The widely accepted minimum guideline for aircraft fuel-vapor ignition is the application of a 0.2 millijoule energy level. However, when considering radio frequency (RF) sources, this guideline is seriously inadequate. This report endeavors to bridge the gap between a traditional understanding of electrical breakdown, heating and combustion; and supplement the knowledge with available information regarding aircraft fuel-vapor ignition by RF sources

Ferroelectric Emission Cathodes for Low-Power Electric Propulsion

NASA Technical Reports Server (NTRS)

Kovaleski, Scott D.; Burke, Tom (Technical Monitor)

2002-01-01

Low- or no-flow electron emitters are required for low-power electric thrusters, spacecraft plasma contactors, and electrodynamic tether systems to reduce or eliminate the need for propellant/expellant. Expellant-less neutralizers can improve the viability of very low-power colloid thrusters, field emission electric propulsion devices, ion engines, Hall thrusters, and gridded vacuum arc thrusters. The NASA Glenn Research Center (GRC) is evaluating ferroelectric emission (FEE) cathodes as zero expellant flow rate cathode sources for the applications listed above. At GRC, low voltage (100s to approx. 1500 V) operation of FEE cathodes is examined. Initial experiments, with unipolar, bipolar, and RF burst applied voltage, have produced current pulses 250 to 1000 ns in duration with peak currents of up to 2 A at voltages at or below 1500 V. In particular, FEE cathodes driven by RF burst voltages from 1400 to 2000 V peak to peak, at burst frequencies from 70 to 400 kHz, emitted average current densities from 0.1 to 0.7 A/sq cm. Pulse repeatability as a function of input voltage has been initially established. Reliable emission has been achieved in air background at pressures as high as 10(exp -6) Torr.

Study of the generator/motor operation of induction machines in a high frequency link space power system

NASA Technical Reports Server (NTRS)

Lipo, Thomas A.; Sood, Pradeep K.

1987-01-01

Static power conversion systems have traditionally utilized dc current or voltage source links for converting power from one ac or dc form to another since it readily achieves the temporary energy storage required to decouple the input from the output. Such links, however, result in bulky dc capacitors and/or inductors and lead to relatively high losses in the converters due to stresses on the semiconductor switches. The feasibility of utilizing a high frequency sinusoidal voltage link to accomplish the energy storage and decoupling function is examined. In particular, a type of resonant six pulse bridge interface converter is proposed which utilizes zero voltage switching principles to minimize switching losses and uses an easy to implement technique for pulse density modulation to control the amplitude, frequency, and the waveshape of the synthesized low frequency voltage or current. Adaptation of the proposed topology for power conversion to single-phase ac and dc voltage or current outputs is shown to be straight forward. The feasibility of the proposed power circuit and control technique for both active and passive loads are verified by means of simulation and experiment.

A high open-circuit voltage gallium nitride betavoltaic microbattery

NASA Astrophysics Data System (ADS)

Cheng, Zaijun; Chen, Xuyuan; San, Haisheng; Feng, Zhihong; Liu, Bo

2012-07-01

A high open-circuit voltage betavoltaic microbattery based on a gallium nitride (GaN) p-i-n homojunction is demonstrated. As a beta-absorbing layer, the low electron concentration of the n-type GaN layer is achieved by the process of Fe compensation doping. Under the irradiation of a planar solid 63Ni source with activity of 0.5 mCi, the open-circuit voltage of the fabricated microbattery with 2 × 2 mm2 area reaches as much as 1.64 V, which is the record value reported for betavoltaic batteries with 63Ni source, the short-circuit current was measured as 568 pA and the conversion effective of 0.98% was obtained. The experimental results suggest that GaN is a high-potential candidate for developing the betavoltaic microbattery.

First results from negative ion beam extraction in ROBIN in surface mode

NASA Astrophysics Data System (ADS)

Pandya, Kaushal; Gahlaut, Agrajit; Yadav, Ratnakar K.; Bhuyan, Manas; Bandyopadhyay, Mainak; Das, B. K.; Bharathi, P.; Vupugalla, Mahesh; Parmar, K. G.; Tyagi, Himanshu; Patel, Kartik; Bhagora, Jignesh; Mistri, Hiren; Prajapati, Bhavesh; Pandey, Ravi; Chakraborty, Arun. K.

2017-08-01

ROBIN, the first step in the Indian R&D program on negative ion beams has reached an important milestone, with the production of negative ions in the surface conversion mode through Cesium (Cs) vapor injection into the source. In the present set-up, negative hydrogen ion beam extraction is effected through an extraction area of ˜73.38 cm2 (146 apertures of 8mm diameter). The three grid electrostatic accelerator system of ROBIN is fed by high voltage DC power supplies (Extraction Power Supply System: 11kV, 35A and Acceleration Power Supply System: 35kV, 15A). Though, a considerable reduction of co-extracted electron current is usually observed during surface mode operation, in order to increase the negative ion current, various other parameters such as plasma grid temperature, plasma grid bias, extraction to acceleration voltage ratio, impurity control and Cs recycling need to be optimized. In the present experiments, to control and to understand the impurity behavior, a Cryopump (14,000 l/s for Hydrogen) is installed along with a Residual Gas Analyzer (RGA). To characterize the source plasma, two sets of Langmuir probes are inserted through the diagnostic flange ports available at the extraction plane. To characterize the beam properties, thermal differential calorimeter, Doppler Shift Spectroscopy and electrical current measurements are implemented in ROBIN. In the present set up, all the negative ion beam extraction experiments have been performed by varying different experimental parameters e.g. RF power (30-70 kW), source operational pressure (0.3 - 0.6Pa), plasma grid bias voltage, extraction & acceleration voltage combination etc. The experiments in surface mode operation is resulted a reduction of co-extracted electron current having electron to ion ratio (e/i) ˜2 whereas the extracted negative ion current density was increased. However, further increase in negative ion current density is expected to be improved after a systematic optimization of the operational parameters and Cs conditioning of the source. It was also found out that a better performance of ROBIN is achieved in the pressure range: 0.5-0.6 Pa. In this paper, the preliminary results on parametric study of ROBIN operation and beam optimization in surface mode are discussed.

Coaxial-type water load for measuring high voltage, high current and short pulse of a compact Marx system for a high power microwave source

NASA Astrophysics Data System (ADS)

Han, Jaeeun; Kim, Jung-ho; Park, Sang-duck; Yoon, Moohyun; Park, Soo Yong; Choi, Do Won; Shin, Jin Woo; So, Joon Ho

2009-11-01

A coaxial-type water load was used to measure the voltage output from a Marx generator for a high power microwave source. This output had a rise time of 20 ns, a pulse duration of a few hundred ns, and an amplitude up to 500 kV. The design of the coaxial water load showed that it is an ideal resistive divider and can also accurately measure a short pulse. Experiments were performed to test the performance of the Marx generator with the calibrated coaxial water load.

Development of Three-Phase Source Inverter for Research and Laboratories

DTIC Science & Technology

2011-03-01

Budget, Paperwork Reduction Project (0704-0188) Washington DC 20503. 1 . AGENCY USE ONLY (Leave blank) 2 . REPORT DATE March 2011 3. REPORT TYPE AND...THEORY OF OPERATION ................................5 1 . Overview ......................................5 2 . Voltage Source Inverter...29 1 . Low Pass Filter MATLAB Code ..................31 2 . Current Sensor ...............................33 3. Optocouplers

Power conditioning using dynamic voltage restorers under different voltage sag types.

PubMed

Saeed, Ahmed M; Abdel Aleem, Shady H E; Ibrahim, Ahmed M; Balci, Murat E; El-Zahab, Essam E A

2016-01-01

Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

Power conditioning using dynamic voltage restorers under different voltage sag types

PubMed Central

Saeed, Ahmed M.; Abdel Aleem, Shady H.E.; Ibrahim, Ahmed M.; Balci, Murat E.; El-Zahab, Essam E.A.

2015-01-01

Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type. PMID:26843975

A new curvature compensation technique for CMOS voltage reference using |VGS| and ΔVBE

NASA Astrophysics Data System (ADS)

Xuemin, Li; Mao, Ye; Gongyuan, Zhao; Yun, Zhang; Yiqiang, Zhao

2016-05-01

A new mixed curvature compensation technique for CMOS voltage reference is presented, which resorts to two sub-references with complementary temperature characteristics. The first sub-reference is the source-gate voltage |VGS|p of a PMOS transistor working in the saturated region. The second sub-reference is the weighted sum of gate-source voltages |VGS|n of NMOS transistors in the subthreshold region and the difference between two base-emitter voltages ΔVBE of bipolar junction transistors (BJTs). The voltage reference implemented utilizing the proposed curvature compensation technique exhibits a low temperature coefficient and occupies a small silicon area. The proposed technique was verified in 0.18 μm standard CMOS process technology. The performance of the circuit has been measured. The measured results show a temperature coefficient as low as 12.7 ppm/°C without trimming, over a temperature range from -40 to 120 °C, and the current consumption is 50 μA at room temperature. The measured power-supply rejection ratio (PSRR) is -31.2 dB @ 100 kHz. The circuit occupies an area of 0.045 mm2. Project supported by the National Natural Science Foundation of China (No. 61376032).

Research on uncertainty evaluation measure and method of voltage sag severity

NASA Astrophysics Data System (ADS)

Liu, X. N.; Wei, J.; Ye, S. Y.; Chen, B.; Long, C.

2018-01-01

Voltage sag is an inevitable serious problem of power quality in power system. This paper focuses on a general summarization and reviews on the concepts, indices and evaluation methods about voltage sag severity. Considering the complexity and uncertainty of influencing factors, damage degree, the characteristics and requirements of voltage sag severity in the power source-network-load sides, the measure concepts and their existing conditions, evaluation indices and methods of voltage sag severity have been analyzed. Current evaluation techniques, such as stochastic theory, fuzzy logic, as well as their fusion, are reviewed in detail. An index system about voltage sag severity is provided for comprehensive study. The main aim of this paper is to propose thought and method of severity research based on advanced uncertainty theory and uncertainty measure. This study may be considered as a valuable guide for researchers who are interested in the domain of voltage sag severity.

Pulsed electromagnetic gas acceleration. [magnetohydrodynamics, plasma power sources and plasma propulsion

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1975-01-01

Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.

Improving off-state leakage characteristics for high voltage AlGaN/GaN-HFETs on Si substrates

NASA Astrophysics Data System (ADS)

Moon, Sung-Woon; Twynam, John; Lee, Jongsub; Seo, Deokwon; Jung, Sungdal; Choi, Hong Goo; Shim, Heejae; Yim, Jeong Soon; Roh, Sungwon D.

2014-06-01

We present a reliable process and design technique for realizing high voltage AlGaN/GaN hetero-junction field effect transistors (HFETs) on Si substrates with very low and stable off-state leakage current characteristics. In this work, we have investigated the effects of the surface passivation layer, prepared by low pressure chemical vapor deposition (LPCVD) of silicon nitride (SiNx), and gate bus isolation design on the off-state leakage characteristics of metal-oxide-semiconductor (MOS) gate structure-based GaN HFETs. The surface passivated devices with gate bus isolation fully surrounding the source and drain regions showed extremely low off-state leakage currents of less than 20 nA/mm at 600 V, with very small variation. These techniques were successfully applied to high-current devices with 80-mm gate width, yielding excellent off-state leakage characteristics within a drain voltage range 0-700 V.

Modular chemiresistive sensor

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

Alam, Maksudul M.; Sampathkumaran, Uma

The present invention relates to a modular chemiresistive sensor. In particular, a modular chemiresistive sensor for hypergolic fuel and oxidizer leak detection, carbon dioxide monitoring and detection of disease biomarkers. The sensor preferably has two gold or platinum electrodes mounted on a silicon substrate where the electrodes are connected to a power source and are separated by a gap of 0.5 to 4.0 .mu.M. A polymer nanowire or carbon nanotube spans the gap between the electrodes and connects the electrodes electrically. The electrodes are further connected to a circuit board having a processor and data storage, where the processor canmore » measure current and voltage values between the electrodes and compare the current and voltage values with current and voltage values stored in the data storage and assigned to particular concentrations of a pre-determined substance such as those listed above or a variety of other substances.« less

Non-linear control of the output stage of a solar microinverter

NASA Astrophysics Data System (ADS)

Lopez-Santos, Oswaldo; Garcia, Germain; Martinez-Salamero, Luis; Avila-Martinez, Juan C.; Seguier, Lionel

2017-01-01

This paper presents a proposal to control the output stage of a two-stage solar microinverter to inject real power into the grid. The input stage of the microinverter is used to extract the maximum available power of a photovoltaic module enforcing a power source behavior in the DC-link to feed the output stage. The work here reported is devoted to control a grid-connected power source inverter with a high power quality level at the grid side ensuring the power balance of the microinverter regulating the voltage of the DC-link. The proposed control is composed of a sinusoidal current reference generator and a cascade type controller composed by a current tracking loop and a voltage regulation loop. The current reference is obtained using a synchronized generator based on phase locked loop (PLL) which gives the shape, the frequency and phase of the current signal. The amplitude of the reference is obtained from a simple controller regulating the DC-link voltage. The tracking of the current reference is accomplished by means of a first-order sliding mode control law. The solution takes advantage of the rapidity and inherent robustness of the sliding mode current controller allowing a robust behavior in the regulation of the DC-link using a simple linear controller. The analytical expression to determine the power quality indicators of the micro-inverter's output is theoretically solved giving expressions relating the converter parameters. The theoretical approach is validated using simulation and experimental results.

Controlling Electron Backstreaming Phenomena Through the Use of a Transverse Magnetic Field

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.

2002-01-01

DEEP-SPACE mission propulsion requirements can be satisfied by the use of high specific impulse systems such as ion thrusters. For such missions. however. the ion thruster will be required to provide thrust for long periods of time. To meet the long operation time and high-propellant throughput requirements, thruster lifetime must be increased. In general, potential ion thruster failure mechanisms associated with long-duration thrusting can be grouped into four areas: (1) ion optics failure; (2) discharge cathode failure; (3) neutralizer failure; and (4) electron backstreaming caused by accelerator grid aperture enlargement brought on by accelerator grid erosion. The work presented here focuses on electron backstreaming. which occurs when the potential at the center of an accelerator grid aperture is insufficient to prevent the backflow of electrons into the ion thruster. The likelihood of this occurring depends on ion source operation time. plasma density, and grid voltages, as accelerator grid apertures enlarge as a result of erosion. Electrons that enter the gap between the high-voltage screen and accelerator grids are accelerated to the energies approximately equal to the beam voltage. This energetic electron beam (typically higher than 1 kV) can damage not only the ion source discharge cathode assembly. but also any of the discharge surfaces upstream of the ion acceleration optics that the electrons happen to impact. Indeed. past backstreaming studies have shown that near the backstreaming limit, which corresponds to the absolute value of the accelerator grid voltage below which electrons can backflow into the thruster, there is a rather sharp rise in temperature at structures such as the cathode keeper electrode. In this respect operation at accelerator grid voltages near the backstreaming limit is avoided. Generally speaking, electron backstreaming is prevented by operating the accelerator grid at a sufficiently negative voltage to ensure a sufficiently negative aperture center potential. This approach can provide the necessary margin assuming an expected aperture enlargement. Operation at very negative accelerator grid voltages, however, enhances ion charge-exchange and direct impingement erosion of the accelerator grid. The focus of the work presented here is the mitigation of electron backstreaming by the use of a magnetic field. The presence of a magnetic field oriented perpendicular to the thruster axis can significantly decrease the magnitude of the backflowing electron current by significantly reducing the electron diffusion coefficient. Negative ion sources utilize this principle to reduce the fraction of electrons in the negative ion beam. The focus of these efforts has been on the attenuation of electron current diffusing from the discharge plasma into the negative ion extraction optics by placing the transverse magnetic field upstream of the extraction electrodes. In contrast. in the case of positive ion sources such as ion thrusters, the approach taken in the work presented here is to apply the transverse field downstream of the ion extraction system so as to prevent electrons from flowing back into the source. It was found in the work presented here that the magnetic field also reduces the absolute value of the electron backstreaming limit voltage. In this respect. the applied transverse magnetic field provides two mechanisms for electron backstreaming mitigation: (1) electron current attenuation and (2) backstreaming limit voltage shift. Such a shift to less negative voltages can lead to reduced accelerator grid erosion rates.

Carbon nanotube vacuum gauges with wide-dynamic range and processes thereof

NASA Technical Reports Server (NTRS)

Manohara, Harish (Inventor); Kaul, Anupama B. (Inventor)

2013-01-01

A miniature thermal conductivity gauge employs a carbon single-walled-nanotube. The gauge operates on the principle of thermal exchange between the voltage-biased nanotube and the surrounding gas at low levels of power and low temperatures to measure vacuum across a wide dynamic range. The gauge includes two terminals, a source of constant voltage to the terminals, a single-walled carbon nanotube between the terminals, a calibration of measured conductance of the nanotube to magnitudes of surrounding vacuum and a current meter in electrical communication with the source of constant voltage. Employment of the nanotube for measuring vacuum includes calibrating the electrical conductance of the nanotube to magnitudes of vacuum, exposing the nanotube to a vacuum, applying a constant voltage across the nanotube, measuring the electrical conductance of the nanotube in the vacuum with the constant voltage applied and converting the measured electrical conductance to the corresponding calibrated magnitude of vacuum using the calibration. The nanotube may be suspended to minimize heat dissipation through the substrate, increasing sensitivity at even tower pressures.

Two-electrode non-differential biopotential amplifier.

PubMed

Dobrev, D

2002-09-01

A circuit is proposed for a non-differential two-electrode biopotential amplifier, with a current source and a transimpedance amplifier as a potential equaliser for its inputs, fully emulating a differential amplifier. The principle of operation is that the current in the input of the transimpedance amplifier is sensed and made to flow with the same value in the other input. The circuit has a simple structure and uses a small number of components. The current source maintains balanced common-mode interference currents, thus ensuring high signal input impedance. In addition, these currents can be tolerated up to more than 10 microA per input, at a supply voltage of +/- 5 V. A two-electrode differential amplifier with 2 x 10 Mohm input resistances to the reference point allows less than 0.5 microA per input. The circuit can be useful in cases of biosignal acquisition by portable instruments, using low supply voltages, from subjects in areas of high electromagnetic fields. Examples include biosignal recordings in electric power stations and electrically powered locomotives, where traditionally designed input amplifier stages can be saturated.

Non-invasive probe diagnostic method for electron temperature and ion current density in atmospheric pressure plasma jet source

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

Kim, Young-Cheol; Kim, Yu-Sin; Lee, Hyo-Chang

2015-08-15

The electrical probe diagnostics are very hard to be applied to atmospheric plasmas due to severe perturbation by the electrical probes. To overcome this, the probe for measuring electron temperature and ion current density is indirectly contacted with an atmospheric jet source. The plasma parameters are obtained by using floating harmonic analysis. The probe is mounted on the quartz tube that surrounds plasma. When a sinusoidal voltage is applied to a probe contacting on a quartz tube, the electrons near the sheath at dielectric tube are collected and the probe current has harmonic components due to probe sheath nonlinearity. Frommore » the relation of the harmonic currents and amplitude of the sheath voltage, the electron temperature near the wall can be obtained with collisional sheath model. The electron temperatures and ion current densities measured at the discharge region are in the ranges of 2.7–3.4 eV and 1.7–5.2 mA/cm{sup 2} at various flow rates and input powers.« less

Development of neutral beam injection system by use of washer gun plasma source

NASA Astrophysics Data System (ADS)

Imanaka, Heizo; Kajiya, Hirotaka; Nemoto, Yuichi; Azuma, Akiyoshi; Asai, Tomoaki; Yamada, Takuma; Inomoto, Michiaki; Ono, Yasushi

2008-11-01

For the past ten years, we have been investigating high-beta Spherical Tokamaks (ST) formation using reconnection heating of their axial merging in the TS-4 experiment, University of Tokyo. The produced ST was observed to have the maximum beta of 50-60% right after the merging of two STs. A key issue after the formation is to maintain the produced high-beta ST over 100 Alfven times for its stability check. A new low-cost pulsed neutral beam injection (NBI) system has been arranged for its sustainment experiment. Its advantages are 1) low voltage (15kV for low-field side of ST) and high current (20A), 2) maintenance-free, 3) low-cost. The conventional filament plasma source was replaced by the washer gun to realize air-cooled and maintenance free NBI system. In its startup experiment, we already extracted the maximum beam current of 3.7A for then acceleration voltage of 10kV successfully. This result suggests that the increase in the acceleration voltage and several conditioning work will realize its designed beam parameters of 15kV, 20A.

Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation

NASA Astrophysics Data System (ADS)

Singh, B.; Shahani, D. T.; Verma, A. K.

2015-03-01

This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.

Input-current shaped ac to dc converters

NASA Technical Reports Server (NTRS)

1986-01-01

The problem of achieving near unity power factor while supplying power to a dc load from a single phase ac source of power is examined. Power processors for this application must perform three functions: input current shaping, energy storage, and output voltage regulation. The methods available for performing each of these three functions are reviewed. Input current shaping methods are either active or passive, with the active methods divided into buck-like and boost-like techniques. In addition to large reactances, energy storage methods include resonant filters, active filters, and active storage schemes. Fast voltage regulation can be achieved by post regulation or by supplementing the current shaping topology with an extra switch. Some indications of which methods are best suited for particular applications concludes the discussion.

A 3.2-GHz fully integrated low-phase noise CMOS VCO with self-biasing current source for the IEEE 802.11a/hiperLAN WLAN standard

NASA Astrophysics Data System (ADS)

Quemada, C.; Adin, I.; Bistue, G.; Berenguer, R.; Mendizabal, J.

2005-06-01

A 3.3V, fully integrated 3.2-GHz voltage-controlled oscillator (VCO) is designed in a 0.18μm CMOS technology for the IEE 802.11a/HiperLAN WLAN standard for the UNII band from 5.15 to 5.35 GHz. The VCO is tunable between 2.85 GHz and 3.31 GHz. NMOS architecture with self-biasing current of the tank source is chosen. A startup circuit has been employed to avoid zero initial current. Current variation is lower than 1% for voltage supply variations of 10%. The use of a self-biasing current source in the tank provides a greater safety in the transconductance value and allows running along more extreme point operation The designed VCO displays a phase noise and output power of -98dBc/Hz (at 100 KHz offset frequency) and 0dBm respectively. This phase noise has been obtained with inductors of 2.2nH and quality factor of 12 at 3.2 GHz, and P-N junction varactors whose quality factor is estimated to exceed 40 at 3.2 GHz. These passive components have been fabricated, measured and modeled previously. The core of the VCO consumes 33mW DC power.

40 CFR 61.126 - Monitoring of operations.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) The owner or operator of any source subject to this subpart using an electrostatic precipitator... measurement and recording of the primary and secondary current and the voltage in each electric field. These...

40 CFR 61.126 - Monitoring of operations.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) The owner or operator of any source subject to this subpart using an electrostatic precipitator... measurement and recording of the primary and secondary current and the voltage in each electric field. These...

Monitoring apparatus and method for battery power supply

DOEpatents

Martin, Harry L.; Goodson, Raymond E.

1983-01-01

A monitoring apparatus and method are disclosed for monitoring and/or indicating energy that a battery power source has then remaining and/or can deliver for utilization purposes as, for example, to an electric vehicle. A battery mathematical model forms the basis for monitoring with a capacity prediction determined from measurement of the discharge current rate and stored battery parameters. The predicted capacity is used to provide a state-of-charge indication. Self-calibration over the life of the battery power supply is enacted through use of a feedback voltage based upon the difference between predicted and measured voltages to correct the battery mathematical model. Through use of a microprocessor with central information storage of temperature, current and voltage, system behavior is monitored, and system flexibility is enhanced.

Increasing the dynamic range of CMOS photodiode imagers

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor); Cunningham, Thomas J. (Inventor); Hancock, Bruce R. (Inventor)

2007-01-01

A multiple-step reset process and circuit for resetting a voltage stored on a photodiode of an imaging device. A first stage of the reset occurs while a source and a drain of a pixel source-follower transistor are held at ground potential and the photodiode and a gate of the pixel source-follower transistor are charged to an initial reset voltage having potential less that of a supply voltage. A second stage of the reset occurs after the initial reset voltage is stored on the photodiode and the gate of the pixel source-follower transistor and the source and drain voltages of the pixel source-follower transistor are released from ground potential thereby allowing the source and drain voltages of the pixel source-follower transistor to assume ordinary values above ground potential and resulting in a capacitive feed-through effect that increases the voltage on the photodiode to a value greater than the initial reset voltage.

High linearity current communicating passive mixer employing a simple resistor bias

NASA Astrophysics Data System (ADS)

Rongjiang, Liu; Guiliang, Guo; Yuepeng, Yan

2013-03-01

A high linearity current communicating passive mixer including the mixing cell and transimpedance amplifier (TIA) is introduced. It employs the resistor in the TIA to reduce the source voltage and the gate voltage of the mixing cell. The optimum linearity and the maximum symmetric switching operation are obtained at the same time. The mixer is implemented in a 0.25 μm CMOS process. The test shows that it achieves an input third-order intercept point of 13.32 dBm, conversion gain of 5.52 dB, and a single sideband noise figure of 20 dB.

Current-voltage characteristics in macroporous silicon/SiOx/SnO2:F heterojunctions.

PubMed

Garcés, Felipe A; Urteaga, Raul; Acquaroli, Leandro N; Koropecki, Roberto R; Arce, Roberto D

2012-07-25

We study the electrical characteristics of macroporous silicon/transparent conductor oxide junctions obtained by the deposition of fluorine doped-SnO2 onto macroporous silicon thin films using the spray pyrolysis technique. Macroporous silicon was prepared by the electrochemical anodization of a silicon wafer to produce pore sizes ranging between 0.9 to 1.2 μm in diameter. Scanning electronic microscopy was performed to confirm the pore filling and surface coverage. The transport of charge carriers through the interface was studied by measuring the current-voltage curves in the dark and under illumination. In the best configuration, we obtain a modest open-circuit voltage of about 70 mV and a short-circuit current of 3.5 mA/cm2 at an illumination of 110 mW/cm2. In order to analyze the effects of the illumination on the electrical properties of the junction, we proposed a model of two opposing diodes, each one associated with an independent current source. We obtain a good accordance between the experimental data and the model. The current-voltage curves in illuminated conditions are well fitted with the same parameters obtained in the dark where only the photocurrent intensities in the diodes are free parameters.

Low voltage arc formation in railguns

DOEpatents

Hawke, R.S.

1985-08-05

A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

Low voltage arc formation in railguns

DOEpatents

Hawke, Ronald S.

1987-01-01

A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

Low voltage arc formation in railguns

DOEpatents

Hawke, R.S.

1987-11-17

A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile. 2 figs.

Modelling and Simulation of Single-Phase Series Active Compensator for Power Quality Improvement

NASA Astrophysics Data System (ADS)

Verma, Arun Kumar; Mathuria, Kirti; Singh, Bhim; Bhuvaneshwari, G.

2017-10-01

A single-phase active series compensator is proposed in this work to reduce harmonic currents at the ac mains and to regulate the dc link voltage of a diode bridge rectifier (DBR) that acts as the front end converter for a voltage source inverter feeding an ac motor. This ac motor drive is used in any of the domestic, commercial or industrial appliances. Under fluctuating ac mains voltages, the dc link voltage of the DBR depicts wide variations and hence the ac motor is used at reduced rating as compared to its name-plate rating. The active series compensator proposed here provides dual functions of improving the power quality at the ac mains and regulating the dc link voltage thus averting the need for derating of the ac motor.

Direct DC 10 V comparison between two programmable Josephson voltage standards made of niobium nitride (NbN)-based and niobium (Nb)-based Josephson junctions

NASA Astrophysics Data System (ADS)

Solve, S.; Chayramy, R.; Maruyama, M.; Urano, C.; Kaneko, N.-H.; Rüfenacht, A.

2018-04-01

BIPM’s new transportable programmable Josephson voltage standard (PJVS) has been used for an on-site comparison at the National Metrology Institute of Japan (NMIJ) and the National Institute of Advanced Industrial Science and Technology (AIST) (NMIJ/AIST, hereafter called just NMIJ unless otherwise noted). This is the first time that an array of niobium-based Josephson junctions with amorphous niobium silicon Nb x Si1-x barriers, developed by the National Institute of Standards and Technology4 (NIST), has been directly compared to an array of niobium nitride (NbN)-based junctions (developed by the NMIJ in collaboration with the Nanoelectronics Research Institute (NeRI), AIST). Nominally identical voltages produced by both systems agreed within 5 parts in 1012 (0.05 nV at 10 V) with a combined relative uncertainty of 7.9  ×  10-11 (0.79 nV). The low side of the NMIJ apparatus is, by design, referred to the ground potential. An analysis of the systematic errors due to the leakage current to ground was conducted for this ground configuration. The influence of a multi-stage low-pass filter installed at the output measurement leads of the NMIJ primary standard was also investigated. The number of capacitances in parallel in the filter and their insulation resistance have a direct impact on the amplitude of the systematic voltage error introduced by the leakage current, even if the current does not necessarily return to ground. The filtering of the output of the PJVS voltage leads has the positive consequence of protecting the array from external sources of noise. Current noise, when coupled to the array, reduces the width or current range of the quantized voltage steps. The voltage error induced by the leakage current in the filter is an order of magnitude larger than the voltage error in the absence of all filtering, even though the current range of steps is significantly decreased without filtering.

Control strategy based on SPWM switching patterns for grid connected photovoltaic inverter

NASA Astrophysics Data System (ADS)

Hassaine, L.; Mraoui, A.

2017-02-01

Generally, for lower installation of photovoltaic systems connected to the grid, pulse width modulation (PWM) is a widely used technique for controlling the voltage source inverters injects currents into the grid. The current injected must be sinusoidal with reduced harmonic distortion. In this paper, a digital implementation of a control strategy based on PWM switching patterns for an inverter for photovoltaic system connected to the grid is presented. This strategy synchronize a sinusoidal inverter output current with a grid voltage The digital implementation of the proposed PWM switching pattern when is compared with the conventional one exhibit the advantage: Simplicity, reduction of the memory requirements and power calculation for the control

An adaptable multiple power source for mass spectrometry and other scientific instruments.

PubMed

Lin, T-Y; Anderson, G A; Norheim, R V; Prost, S A; LaMarche, B L; Leach, F E; Auberry, K J; Smith, R D; Koppenaal, D W; Robinson, E W; Paša-Tolić, L

2015-09-01

An Adaptable Multiple Power Source (AMPS) system has been designed and constructed. The AMPS system can provide up to 16 direct current (DC) (±400 V; 5 mA), 4 radio frequency (RF) (two 500 VPP sinusoidal signals each, 0.5-5 MHz) channels, 2 high voltage sources (±6 kV), and one ∼40 W, 250 °C temperature-regulated heater. The system is controlled by a microcontroller, capable of communicating with its front panel or a computer. It can assign not only pre-saved fixed DC and RF signals but also profiled DC voltages. The AMPS system is capable of driving many mass spectrometry components and ancillary devices and can be adapted to other instrumentation/engineering projects.

Analysis and application of two-current-source circuit as a signal conditioner for resistive sensors

NASA Astrophysics Data System (ADS)

Idzkowski, Adam; Gołębiowski, Jerzy; Walendziuk, Wojciech

2017-05-01

The article presents the analysis of metrological properties of a two-current-source supplied circuit. It includes such data as precise and simplified equations for two circuit output voltages in the function of relative resistance increments of sensors. Moreover, graphs showing nonlinearity coefficients of both output voltages for two resistance increments varying widely are presented. Graphs of transfer resistances, depending on relative increments of sensors resistance were also created. The article also contains a description of bridge-based circuit realization with the use of a computer and a data acquisition (DAQ) card. Laboratory measurement of the difference and sum of relative resistance increments of two resistance decade boxes were carried out indirectly with the use of the created measurement system. Measurement errors were calculated and included in the article, as well.

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses.

PubMed

Wang, Dapeng; Zhao, Wenjing; Li, Hua; Furuta, Mamoru

2018-04-05

In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses ( T IGZO ) are investigated. As the T IGZO increased, the turn-on voltage ( V on ) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm²·V −1 ·s −1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the T IGZO . The PBS results exhibit that the V on shift is aggravated as the T IGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various T IGZO values is revealed using current–voltage and capacitance–voltage ( C – V ) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source ( C gs ) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the T IGZO value increased, the hump in the off state of the C gs curve was gradually weakened.

A vacuum spark ion source: High charge state metal ion beams

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

Yushkov, G. Yu., E-mail: gyushkov@mail.ru; Nikolaev, A. G.; Frolova, V. P.

2016-02-15

High ion charge state is often important in ion beam physics, among other reasons for the very practical purpose that it leads to proportionately higher ion beam energy for fixed accelerating voltage. The ion charge state of metal ion beams can be increased by replacing a vacuum arc ion source by a vacuum spark ion source. Since the voltage between anode and cathode remains high in a spark discharge compared to the vacuum arc, higher metal ion charge states are generated which can then be extracted as an ion beam. The use of a spark of pulse duration less thanmore » 10 μs and with current up to 10 kA allows the production of ion beams with current of several amperes at a pulse repetition rate of up to 5 pps. We have demonstrated the formation of high charge state heavy ions (bismuth) of up to 15 + and a mean ion charge state of more than 10 +. The physics and techniques of our vacuum spark ion source are described.« less

Photocurrent microscopy of contact resistance and charge carrier traps in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Liewald, C.; Reiser, D.; Westermeier, C.; Nickel, B.

2016-08-01

We use a pentacene transistor with asymmetric source drain contacts to test the sensitivity of scanning photocurrent microscopy (SPCM) for contact resistance and charge traps. The drain current of the device strongly depends on the choice of the drain electrode. In one case, more than 94% of the source drain voltage is lost due to contact resistance. Here, SPCM maps show an enhanced photocurrent signal at the hole-injecting contact. For the other bias condition, i.e., for ohmic contacts, the SPCM signal peaks heterogeneously along the channel. We argue from basic transport models that bright areas in SPCM maps indicate areas of large voltage gradients or high electric field strength caused by injection barriers or traps. Thus, SPCM allows us to identify and image the dominant voltage loss mechanism in organic field-effect transistors.

On an efficient multilevel inverter assembly: structural savings and design optimisations

NASA Astrophysics Data System (ADS)

Choupan, Reza; Nazarpour, Daryoush; Golshannavaz, Sajjad

2018-01-01

This study puts forward an efficient unit cell to be taken in use in multilevel inverter assemblies. The proposed structure is in line with reductions in number of direct current (dc) voltage sources, insulated-gate bipolar transistors (IGBTs), gate driver circuits, installation area, and hence the implementation costs. Such structural savings do not sacrifice the technical performance of the proposed design wherein an increased number of output voltage levels is attained, interestingly. Targeting a techno-economic characteristic, the contemplated structure is included as the key unit of cascaded multilevel inverters. Such extensions require development of applicable design procedures. To this end, two efficient strategies are elaborated to determine the magnitudes of input dc voltage sources. As well, an optimisation process is developed to explore the optimal allocation of different parameters in overall performance of the proposed inverter. These parameters are investigated as the number of IGBTs, dc sources, diodes, and overall blocked voltage on switches. In the lights of these characteristics, a comprehensive analysis is established to compare the proposed design with the conventional and recently developed structures. Detailed simulation and experimental studies are conducted to assess the performance of the proposed design. The obtained results are discussed in depth.

Double-gated Si NW FET sensors: Low-frequency noise and photoelectric properties

NASA Astrophysics Data System (ADS)

Gasparyan, F.; Khondkaryan, H.; Arakelyan, A.; Zadorozhnyi, I.; Pud, S.; Vitusevich, S.

2016-08-01

The transport, noise, and photosensitivity properties of an array of silicon nanowire (NW) p+-p-p+ field-effect transistors (FETs) are investigated. The peculiarities of photosensitivity and detectivity are analyzed over a wide spectrum range. The absorbance of p-Si NW shifts to the short wavelength region compared with bulk Si. The photocurrent and photosensitivity reach increased values in the UV range of the spectrum at 300 K. It is shown that sensitivity values can be tuned by the drain-source voltage and may reach record values of up to 2-4 A/W at a wavelength of 300 nm at room temperature. Low-frequency noise studies allow calculating the photodetectivity values, which increase with decreasing wavelength down to 300 nm. We show that the drain current of Si NW biochemical sensors substantially depends on pH value and the signal-to-noise ratio reaches the high value of 105. Increasing pH sensitivity with gate voltage is revealed for certain source-drain currents of pH-sensors based on Si NW FETs. The noise characteristic index decreases from 1.1 to 0.7 with the growth of the liquid gate voltage. Noise behavior is successfully explained in the framework of the correlated number-mobility unified fluctuation model. pH sensitivity increases as a result of the increase in liquid gate voltage, thus giving the opportunity to measure very low proton concentrations in the electrolyte medium at certain values of the liquid gate voltage.

Low Wind Speed Turbine Project Phase II: The Application of Medium-Voltage Electrical Apparatus to the Class of Variable Speed Multi-Megawatt Low Wind Speed Turbines; 15 June 2004--30 April 2005

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

Erdman, W.; Behnke, M.

2005-11-01

Kilowatt ratings of modern wind turbines have progressed rapidly from 50 kW to 1,800 kW over the past 25 years, with 3.0- to 7.5-MW turbines expected in the next 5 years. The premise of this study is simple: The rapid growth of wind turbine power ratings and the corresponding growth in turbine electrical generation systems and associated controls are quickly making low-voltage (LV) electrical design approaches cost-ineffective. This report provides design detail and compares the cost of energy (COE) between commercial LV-class wind power machines and emerging medium-voltage (MV)-class multi-megawatt wind technology. The key finding is that a 2.5% reductionmore » in the COE can be achieved by moving from LV to MV systems. This is a conservative estimate, with a 3% to 3.5% reduction believed to be attainable once purchase orders to support a 250-turbine/year production level are placed. This evaluation considers capital costs as well as installation, maintenance, and training requirements for wind turbine maintenance personnel. Subsystems investigated include the generator, pendant cables, variable-speed converter, and padmount transformer with switchgear. Both current-source and voltage-source converter/inverter MV topologies are compared against their low-voltage, voltage-source counterparts at the 3.0-, 5.0-, and 7.5-MW levels.« less

Study of switching transients in high frequency converters

NASA Technical Reports Server (NTRS)

Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

1993-01-01

As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is evaluated.

Tunneling effects in the current-voltage characteristics of high-efficiency GaAs solar cells

NASA Technical Reports Server (NTRS)

Kachare, R.; Anspaugh, B. E.; Garlick, G. F. J.

1988-01-01

Evidence is that tunneling via states in the forbidden gap is the dominant source of excess current in the dark current-voltage (I-V) characteristics of high-efficiency DMCVD grown Al(x)Ga(1-x)As/GaAs(x is equal to or greater than 0.85) solar cells. The dark forward and reverse I-V measurements were made on several solar cells, for the first time, at temperatures between 193 and 301 K. Low-voltage reverse-bias I-V data of a number of cells give a thermal activation energy for excess current of 0.026 + or - 0.005 eV, which corresponds to the carbon impurity in GaAs. However, other energy levels between 0.02 eV and 0.04 eV were observed in some cells which may correspond to impurity levels introduced by Cu, Si, Ge, or Cd. The forward-bias excess current is mainly due to carrier tunneling between localized levels created in the space-charge layer by impurities such as carbon, which are incorporated during the solar cell growth process. A model is suggested to explain the results.

Removal of Direct Current Link Harmonic Ripple in Single Phase Voltage Source Inverter Systems Using Supercapacitors

DTIC Science & Technology

2016-09-01

micro-sources can include sources such as micro- turbines and battery banks. Among the many benefits provided by an EMS is the ability to allow...efficient and reliable sharing of grid loads by several disparate power sources, which allows alternative energy sources such as solar and wind energy to...positions associated with the applicable configuration, with wires and components greyed out when they are not being used. a. SC Bank Disconnected

Photoconducting positions monitor and imaging detector

DOEpatents

Shu, Deming; Kuzay, Tuncer M.

2000-01-01

A photoconductive, high energy photon beam detector/monitor for detecting x-rays and gamma radiation, having a thin, disk-shaped diamond substrate with a first and second surface, and electrically conductive coatings, or electrodes, of a predetermined configuration or pattern, disposed on the surfaces of the substrate. A voltage source and a current amplifier is connected to the electrodes to provide a voltage bias to the electrodes and to amplify signals from the detector.

Investigation of a High Voltage, High Frequency Power Conditioning System for Use with Flux Compression Generators

DTIC Science & Technology

2007-06-01

missouri.edu Abstract The University of Missouri-Columbia is developing a compact pulsed power system to condition the high current signal from a...flux compression generator (FCG) to the high voltage, high frequency signal required for many pulsed power applications. The system consists of a...non-magnetic core, spiral-wound transformer, series exploding wire fuse, and an oscillating mesoband source. The flux compression generator is being

250 kV 6 mA compact Cockcroft-Walton high-voltage power supply.

PubMed

Ma, Zhan-Wen; Su, Xiao-Dong; Lu, Xiao-Long; Wei, Zhen; Wang, Jun-Run; Huang, Zhi-Wu; Miao, Tian-You; Su, Tong-Ling; Yao, Ze-En

2016-08-01

A compact power supply system for a compact neutron generator has been developed. A 4-stage symmetrical Cockcroft-Walton circuit is adopted to produce 250 kV direct current high-voltage. A 2-stage 280 kV isolation transformer system is used to drive the ion source power supply. For a compact structure, safety, and reliability during the operation, the Cockcroft-Walton circuit and the isolation transformer system are enclosed in an epoxy vessel containing the transformer oil whose size is about ∅350 mm × 766 mm. Test results indicate that the maximum output voltage of the power supply is 282 kV, and the stability of the output voltage is better than 0.63% when the high voltage power supply is operated at 250 kV, 6.9 mA with the input voltage varying ±10%.

250 kV 6 mA compact Cockcroft-Walton high-voltage power supply

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

Ma, Zhan-Wen; Su, Xiao-Dong; Wei, Zhen

A compact power supply system for a compact neutron generator has been developed. A 4-stage symmetrical Cockcroft-Walton circuit is adopted to produce 250 kV direct current high-voltage. A 2-stage 280 kV isolation transformer system is used to drive the ion source power supply. For a compact structure, safety, and reliability during the operation, the Cockcroft-Walton circuit and the isolation transformer system are enclosed in an epoxy vessel containing the transformer oil whose size is about ∅350 mm × 766 mm. Test results indicate that the maximum output voltage of the power supply is 282 kV, and the stability of themore » output voltage is better than 0.63% when the high voltage power supply is operated at 250 kV, 6.9 mA with the input voltage varying ±10%.« less

Two-electrode low supply voltage electrocardiogram signal amplifier.

PubMed

Dobrev, D

2004-03-01

Portable biomedical instrumentation has become an important part of diagnostic and treatment instrumentation, including telemedicine applications. Low-voltage and low-power design tendencies prevail. Modern battery cell voltages in the range of 3-3.6 V require appropriate circuit solutions. A two-electrode biopotential amplifier design is presented, with a high common-mode rejection ratio (CMRR), high input voltage tolerance and standard first-order high-pass characteristic. Most of these features are due to a high-gain first stage design. The circuit makes use of passive components of popular values and tolerances. Powered by a single 3 V source, the amplifier tolerates +/- 1 V common mode voltage, +/- 50 microA common mode current and 2 V input DC voltage, and its worst-case CMRR is 60 dB. The amplifier is intended for use in various applications, such as Holter-type monitors, defibrillators, ECG monitors, biotelemetry devices etc.

Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons.

PubMed

Lazcano-Pérez, Fernando; Castro, Héctor; Arenas, Isabel; García, David E; González-Muñoz, Ricardo; Arreguín-Espinosa, Roberto

2016-05-05

The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7), voltage-gated calcium channel (CaV2.2), the A-type transient outward (IA) and delayed rectifier (IDR) currents of KV channels of the superior cervical ganglion (SCG) neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels.

Activity of Palythoa caribaeorum Venom on Voltage-Gated Ion Channels in Mammalian Superior Cervical Ganglion Neurons

PubMed Central

Lazcano-Pérez, Fernando; Castro, Héctor; Arenas, Isabel; García, David E.; González-Muñoz, Ricardo; Arreguín-Espinosa, Roberto

2016-01-01

The Zoanthids are an order of cnidarians whose venoms and toxins have been poorly studied. Palythoa caribaeorum is a zoanthid commonly found around the Mexican coastline. In this study, we tested the activity of P. caribaeorum venom on voltage-gated sodium channel (NaV1.7), voltage-gated calcium channel (CaV2.2), the A-type transient outward (IA) and delayed rectifier (IDR) currents of KV channels of the superior cervical ganglion (SCG) neurons of the rat. These results showed that the venom reversibly delays the inactivation process of voltage-gated sodium channels and inhibits voltage-gated calcium and potassium channels in this mammalian model. The compounds responsible for these effects seem to be low molecular weight peptides. Together, these results provide evidence for the potential use of zoanthids as a novel source of cnidarian toxins active on voltage-gated ion channels. PMID:27164140

A 13.56 MHz CMOS Active Rectifier With Switched-Offset and Compensated Biasing for Biomedical Wireless Power Transfer Systems.

PubMed

Yan Lu; Wing-Hung Ki

2014-06-01

A full-wave active rectifier switching at 13.56 MHz with compensated bias current for a wide input range for wirelessly powered high-current biomedical implants is presented. The four diodes of a conventional passive rectifier are replaced by two cross-coupled PMOS transistors and two comparator- controlled NMOS switches to eliminate diode voltage drops such that high voltage conversion ratio and power conversion efficiency could be achieved even at low AC input amplitude |VAC|. The comparators are implemented with switched-offset biasing to compensate for the delays of active diodes and to eliminate multiple pulsing and reverse current. The proposed rectifier uses a modified CMOS peaking current source with bias current that is quasi-inversely proportional to the supply voltage to better control the reverse current over a wide AC input range (1.5 to 4 V). The rectifier was fabricated in a standard 0.35 μm CMOS N-well process with active area of 0.0651 mm(2). For the proposed rectifier measured at |VAC| = 3.0 V, the voltage conversion ratios are 0.89 and 0.93 for RL=500 Ω and 5 kΩ, respectively, and the measured power conversion efficiencies are 82.2% to 90.1% with |VAC| ranges from 1.5 to 4 V for RL=500 Ω.

The Design of Operational Amplifier for Low Voltage and Low Current Sound Energy Harvesting System

NASA Astrophysics Data System (ADS)

Fang, Liew Hui; Rahim, Rosemizi Bin Abd; Isa, Muzamir; Idris Syed Hassan, Syed; Ismail, Baharuddin Bin

2018-03-01

The objective of this paper is to design a combination of an operational amplifier (op-amp) with a rectifier used in an alternate current (ac) to direct current (dc) power conversion. The op-amp was designed to specifically work at low voltage and low current for a sound energy harvesting system. The goal of the op-amp design with adjustable gain was to control output voltage based on the objectives of the experiment conducted. The op-amp was designed for minimum power dissipation performance, with the means of increasing the output current when receiving a large amount of load. The harvesting circuits which designed further improved the power output efficiency by shortening the fully charged time needed by a supercapacitor bank. It can fulfil the long-time power demands for low power device. Typically, a small amount of energy sources were converted to electricity and stored in the supercapacitor bank, which was built by 10 pieces of capacitors with 0.22 F each, arranged in parallel connection. The highest capacitance was chosen based on the characteristic that have the longest discharging time to support the applications of a supercapacitor bank. Testing results show that the op-amp can boost the low input ac voltage (∼3.89 V) to high output dc voltage (5.0 V) with output current of 30 mA and stored the electrical energy in a big supercapacitor bank having a total of 2.2 F, effectively. The measured results agree well with the calculated results.

Physics of the current injection process during localized helicity injection

NASA Astrophysics Data System (ADS)

Hinson, Edward Thomas

An impedance model has been developed for the arc-plasma cathode electron current source used in localized helicity injection tokamak startup. According to this model, a potential double layer (DL) is established between the high-density arc plasma (narc ˜ 1021 m-3) in the electron source, and the less-dense external tokamak edge plasma (nedge ˜ 10 18 m-3) into which current is injected. The DL launches an electron beam at the applied voltage with cross-sectional area close to that of the source aperture: Ainj ≈ 2 cm 2. The injected current, Iinj, increases with applied voltage, Vinj, according to the standard DL scaling, Iinj ˜ V(3/2/ inj), until the more restrictive of two limits to beam density nb arises, producing Iinj ˜ V(1/2/inj), a scaling with beam drift velocity. For low external tokamak edge density nedge, space-charge neutralization of the intense electron beam restricts the injected beam density to nb ˜ nedge. At high Jinj and sufficient edge density, the injected current is limited by expansion of the DL sheath, which leads to nb ˜ narc. Measurements of narc, Iinj , nedge, Vinj, support these predicted scalings, and suggest narc as a viable control actuator for the source impedance. Magnetic probe signals ≈ 300 degrees toroidally from the injection location are consistent with expectations for a gyrating, coherent electron beam with a compact areal cross-section. Technological development of the source has allowed an extension of the favorable Iinj ˜ V(1/2/inj) to higher power without electrical breakdown.

An Energy Saving Green Plug Device for Nonlinear Loads

NASA Astrophysics Data System (ADS)

Bloul, Albe; Sharaf, Adel; El-Hawary, Mohamed

2018-03-01

The paper presents a low cost a FACTS Based flexible fuzzy logic based modulated/switched tuned arm filter and Green Plug compensation (SFC-GP) scheme for single-phase nonlinear loads ensuring both voltage stabilization and efficient energy utilization. The new Green Plug-Switched filter compensator SFC modulated LC-Filter PWM Switched Capacitive Compensation Devices is controlled using a fuzzy logic regulator to enhance power quality, improve power factor at the source and reduce switching transients and inrush current conditions as well harmonic contents in source current. The FACTS based SFC-GP Device is a member of family of Green Plug/Filters/Compensation Schemes used for efficient energy utilization, power quality enhancement and voltage/inrush current/soft starting control using a dynamic error driven fuzzy logic controller (FLC). The device with fuzzy logic controller is validated using the Matlab / Simulink Software Environment for enhanced power quality (PQ), improved power factor and reduced inrush currents. This is achieved using modulated PWM Switching of the Filter-Capacitive compensation scheme to cope with dynamic type nonlinear and inrush cyclical loads..

Method for sputtering with low frequency alternating current

DOEpatents

Timberlake, John R.

1996-01-01

Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking.

Method for sputtering with low frequency alternating current

DOEpatents

Timberlake, J.R.

1996-04-30

Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking. 6 figs.

Technical Note: Procedure for the calibration and validation of kilo-voltage cone-beam CT models

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

Vilches-Freixas, Gloria; Létang, Jean Michel; Rit,

2016-09-15

Purpose: The aim of this work is to propose a general and simple procedure for the calibration and validation of kilo-voltage cone-beam CT (kV CBCT) models against experimental data. Methods: The calibration and validation of the CT model is a two-step procedure: the source model then the detector model. The source is described by the direction dependent photon energy spectrum at each voltage while the detector is described by the pixel intensity value as a function of the direction and the energy of incident photons. The measurements for the source consist of a series of dose measurements in air performedmore » at each voltage with varying filter thicknesses and materials in front of the x-ray tube. The measurements for the detector are acquisitions of projection images using the same filters and several tube voltages. The proposed procedure has been applied to calibrate and assess the accuracy of simple models of the source and the detector of three commercial kV CBCT units. If the CBCT system models had been calibrated differently, the current procedure would have been exclusively used to validate the models. Several high-purity attenuation filters of aluminum, copper, and silver combined with a dosimeter which is sensitive to the range of voltages of interest were used. A sensitivity analysis of the model has also been conducted for each parameter of the source and the detector models. Results: Average deviations between experimental and theoretical dose values are below 1.5% after calibration for the three x-ray sources. The predicted energy deposited in the detector agrees with experimental data within 4% for all imaging systems. Conclusions: The authors developed and applied an experimental procedure to calibrate and validate any model of the source and the detector of a CBCT unit. The present protocol has been successfully applied to three x-ray imaging systems. The minimum requirements in terms of material and equipment would make its implementation suitable in most clinical environments.« less

Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments

ERIC Educational Resources Information Center

Jin, Hao; Qin, Yiheng; Pan, Si; Alam, Arif U.; Dong, Shurong; Ghosh, Raja; Deen, M. Jamal

2018-01-01

pH determination is an essential experiment in many chemistry laboratories. It requires a potentiometric instrument with extremely low input bias current to accurately measure the voltage between a pH sensing electrode and a reference electrode. In this technology report, we propose an open-source potentiometric instrument for pH determination…

Neutron Yield With a Pulsed Surface Flashover Deuterium Source

NASA Astrophysics Data System (ADS)

Guethlein, G.; Falabella, S.; Sampayan, S. E.; Meyer, G.; Tang, V.; Kerr, P.

2009-03-01

As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact, low average power ion source is needed. Towards that end, we are testing a high current, pulsed surface flashover ion source, with deuterated titanium as the spark contacts. Neutron yield and source lifetime data will be presented using a low voltage (<100 kV) deuterated target. With 20 ns spark drive pulses we have shown >106 neutrons/s with 1 kHz PRF

The R&D progress of 4 MW EAST-NBI high current ion source.

PubMed

Xie, Yahong; Hu, Chundong; Liu, Sheng; Xu, Yongjian; Liang, Lizhen; Xie, Yuanlai; Sheng, Peng; Jiang, Caichao; Liu, Zhimin

2014-02-01

A high current ion source, which consists of the multi-cusp bucket plasma generator and tetrode accelerator with multi-slot apertures, is developed and tested for the Experimental Advanced Superconducting Tokamak neutral beam injector. Three ion sources are tested on the test bed with arc power of 80 kW, beam voltage of 80 keV, and beam power of 4 MW. The arc regulation technology with Langmuir probes is employed for the long pulse operation of ion source, and the long pulse beam of 50 keV @ 15.5 A @ 100 s and 80 keV @ 52A @ 1s are extracted, respectively.

Comparative study of 0° X-cut and Y + 36°-cut lithium niobate high-voltage sensing

NASA Astrophysics Data System (ADS)

Patel, N.; Branch, D. W.; Schamiloglu, E.; Cular, S.

2015-08-01

A comparison study between Y + 36° and 0° X-cut lithium niobate (LiNbO3) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y + 36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5 μs voltage pulses to both crystals, the voltage-induced shift scaled linearly with voltage. For the Y + 36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz-100 kHz. Using the same conditions as the Y + 36° cut, the 0° X-cut crystal sensed a shift of 10-273 ps for DC voltages and 189-813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250-2 ns and the Y + 36°-cut crystal sensed a time shift of 0.115-1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. When the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.

Comparative study of 0° X-cut and Y + 36°-cut lithium niobate high-voltage sensing

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

Patel, N.; Department of Electrical and Computer Engineering, MSC01 1100, University of New Mexico, Albuquerque, New Mexico 87131-0001; Branch, D. W.

2015-08-15

A comparison study between Y + 36° and 0° X-cut lithium niobate (LiNbO{sub 3}) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y + 36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5more » μs voltage pulses to both crystals, the voltage-induced shift scaled linearly with voltage. For the Y + 36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz–100 kHz. Using the same conditions as the Y + 36° cut, the 0° X-cut crystal sensed a shift of 10–273 ps for DC voltages and 189–813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250–2 ns and the Y + 36°-cut crystal sensed a time shift of 0.115–1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. When the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.« less

Comparative study of 0° X-cut and Y+36°-cut lithium niobate high-voltage sensing

DOE PAGES

Patel, N.; Branch, D. W.; Schamiloglu, E.; ...

2015-08-11

A comparison study between Y+36° and 0° X-cut lithium niobate (LiNbO 3) was performed to evaluate the influence of crystal cut on the acoustic propagation to realize a piezoelectric high-voltage sensor. The acoustic time-of-flight for each crystal cut was measured when applying direct current (DC), alternating current (AC), and pulsed voltages. Results show that the voltage-induced shift in the acoustic wave propagation time scaled quadratically with voltage for DC and AC voltages applied to X-cut crystals. For the Y+36° crystal, the voltage-induced shift scales linearly with DC voltages and quadratically with AC voltages. When applying 5 μs voltage pulses tomore » both crystals, the voltage-induced shift scaled linearly with voltage. For the Y+36° cut, the voltage-induced shift from applying DC voltages ranged from 10 to 54 ps and 35 to 778 ps for AC voltages at 640 V over the frequency range of 100 Hz–100 kHz. Using the same conditions as the Y+36° cut, the 0° X-cut crystal sensed a shift of 10–273 ps for DC voltages and 189–813 ps for AC voltage application. For 5 μs voltage pulses, the 0° X-cut crystal sensed a voltage induced shift of 0.250–2 ns and the Y+36°-cut crystal sensed a time shift of 0.115–1.6 ns. This suggests a frequency sensitive response to voltage where the influence of the crystal cut was not a significant contributor under DC, AC, or pulsed voltage conditions. The measured DC data were compared to a 1-D impedance matrix model where the predicted incremental length changed as a function of voltage. Furthermore, when the voltage source error was eliminated through physical modeling from the uncertainty budget, the combined uncertainty of the sensor (within a 95% confidence interval) decreased to 0.0033% using a Y + 36°-cut crystal and 0.0032% using an X-cut crystal for all the voltage conditions used in this experiment.« less

Systematic analysis of the contributions of stochastic voltage gated channels to neuronal noise

PubMed Central

O'Donnell, Cian; van Rossum, Mark C. W.

2014-01-01

Electrical signaling in neurons is mediated by the opening and closing of large numbers of individual ion channels. The ion channels' state transitions are stochastic and introduce fluctuations in the macroscopic current through ion channel populations. This creates an unavoidable source of intrinsic electrical noise for the neuron, leading to fluctuations in the membrane potential and spontaneous spikes. While this effect is well known, the impact of channel noise on single neuron dynamics remains poorly understood. Most results are based on numerical simulations. There is no agreement, even in theoretical studies, on which ion channel type is the dominant noise source, nor how inclusion of additional ion channel types affects voltage noise. Here we describe a framework to calculate voltage noise directly from an arbitrary set of ion channel models, and discuss how this can be use to estimate spontaneous spike rates. PMID:25360105

Voltage Based Detection Method for High Impedance Fault in a Distribution System

NASA Astrophysics Data System (ADS)

Thomas, Mini Shaji; Bhaskar, Namrata; Prakash, Anupama

2016-09-01

High-impedance faults (HIFs) on distribution feeders cannot be detected by conventional protection schemes, as HIFs are characterized by their low fault current level and waveform distortion due to the nonlinearity of the ground return path. This paper proposes a method to identify the HIFs in distribution system and isolate the faulty section, to reduce downtime. This method is based on voltage measurements along the distribution feeder and utilizes the sequence components of the voltages. Three models of high impedance faults have been considered and source side and load side breaking of the conductor have been studied in this work to capture a wide range of scenarios. The effect of neutral grounding of the source side transformer is also accounted in this study. The results show that the algorithm detects the HIFs accurately and rapidly. Thus, the faulty section can be isolated and service can be restored to the rest of the consumers.

p-MOSFET total dose dosimeter

NASA Technical Reports Server (NTRS)

Buehler, Martin G. (Inventor); Blaes, Brent R. (Inventor)

1994-01-01

A p-MOSFET total dose dosimeter where the gate voltage is proportional to the incident radiation dose. It is configured in an n-WELL of a p-BODY substrate. It is operated in the saturation region which is ensured by connecting the gate to the drain. The n-well is connected to zero bias. Current flow from source to drain, rather than from peripheral leakage, is ensured by configuring the device as an edgeless MOSFET where the source completely surrounds the drain. The drain junction is the only junction not connected to zero bias. The MOSFET is connected as part of the feedback loop of an operational amplifier. The operational amplifier holds the drain current fixed at a level which minimizes temperature dependence and also fixes the drain voltage. The sensitivity to radiation is made maximum by operating the MOSFET in the OFF state during radiation soak.

METHOD AND APPARATUS FOR DETERMINING AMALGAM DECOMPOSITION RATE

DOEpatents

Johnson, R.W.; Wright, C.C.

1962-04-24

A method and apparatus for measuring the rate at which an amalgam decomposes in contact with aqueous solutions are described. The amalgam and an aqueous hydroxide solution are disposed in an electrolytic cell. The amalgam is used as the cathode of the cell, and an electrode and anode are disposed in the aqueous solution. A variable source of plating potential is connected across the cell. The difference in voltage between the amalgam cathode and a calibrated source of reference potential is used to control the variable source to null the difference in voltage and at the same time to maintain the concentration of the amalgam at some predetermined constant value. The value of the current required to maintain this concentration constant is indicative of the decomposition rate of the amalgam. (AEC)

Series Connected Converter for Control of Multi-Bus Spacecraft Power Utility

NASA Technical Reports Server (NTRS)

Beach, Raymond F. (Inventor); Brush, Andy (Inventor)

1997-01-01

The invention provides a power system using series connected regulators. Power from a source, such as a solar array, is processed through the regulators and provided to corresponding buses used to charge a battery and supply loads. The regulators employ a bypass loop around a DC-DC converter. The bypass loop connects a hot input of the converter to a return output, preferably though an inductor. Part of the current from the source passes through the bypass loop to the power bus. The converter bucks or boosts the voltage from the source to maintain the desired voltage at the bus. Thus, only part of the power is processed through the converter. The converter can also be used without the bypass loop to provide isolation. All of the converters can be substantially identical.

The discovery of the electric current

NASA Astrophysics Data System (ADS)

Cotti, Piero

1995-02-01

The first battery, the so called voltaic pile, turns out to be the only and hidden entrance to the world of electrodynamics. It was not until 20 years after Alessandro Volta's discovery that the realisation came that the sensational novelty of the voltaic pile was not the permanent voltage source but the current source. This was not to be expected, and had, therefore, not been searched for specifically, but, rather had been found through a great deal of luck and coincidence in experimentation.

Pb/InAs nanowire josephson junction with high critical current and magnetic flux focusing.

PubMed

Paajaste, J; Amado, M; Roddaro, S; Bergeret, F S; Ercolani, D; Sorba, L; Giazotto, F

2015-03-11

We have studied mesoscopic Josephson junctions formed by highly n-doped InAs nanowires and superconducting Ti/Pb source and drain leads. The current-voltage properties of the system are investigated by varying temperature and external out-of-plane magnetic field. Superconductivity in the Pb electrodes persists up to ∼7 K and with magnetic field values up to 0.4 T. Josephson coupling at zero backgate voltage is observed up to 4.5 K and the critical current is measured to be as high as 615 nA. The supercurrent suppression as a function of the magnetic field reveals a diffraction pattern that is explained by a strong magnetic flux focusing provided by the superconducting electrodes forming the junction.

Multilevel non-volatile data storage utilizing common current hysteresis of networked single walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Hwang, Ihn; Wang, Wei; Hwang, Sun Kak; Cho, Sung Hwan; Kim, Kang Lib; Jeong, Beomjin; Huh, June; Park, Cheolmin

2016-05-01

The characteristic source-drain current hysteresis frequently observed in field-effect transistors with networked single walled carbon-nanotube (NSWNT) channels is problematic for the reliable switching and sensing performance of devices. But the two distinct current states of the hysteresis curve at a zero gate voltage can be useful for memory applications. In this work, we demonstrate a novel non-volatile transistor memory with solution-processed NSWNTs which are suitable for multilevel data programming and reading. A polymer passivation layer with a small amount of water employed on the top of the NSWNT channel serves as an efficient gate voltage dependent charge trapping and de-trapping site. A systematic investigation evidences that the water mixed in a polymer passivation solution is critical for reliable non-volatile memory operation. The optimized device is air-stable and temperature-resistive up to 80 °C and exhibits excellent non-volatile memory performance with an on/off current ratio greater than 104, a switching time less than 100 ms, data retention longer than 4000 s, and write/read endurance over 100 cycles. Furthermore, the gate voltage dependent charge injection mediated by water in the passivation layer allowed for multilevel operation of our memory in which 4 distinct current states were programmed repetitively and preserved over a long time period.The characteristic source-drain current hysteresis frequently observed in field-effect transistors with networked single walled carbon-nanotube (NSWNT) channels is problematic for the reliable switching and sensing performance of devices. But the two distinct current states of the hysteresis curve at a zero gate voltage can be useful for memory applications. In this work, we demonstrate a novel non-volatile transistor memory with solution-processed NSWNTs which are suitable for multilevel data programming and reading. A polymer passivation layer with a small amount of water employed on the top of the NSWNT channel serves as an efficient gate voltage dependent charge trapping and de-trapping site. A systematic investigation evidences that the water mixed in a polymer passivation solution is critical for reliable non-volatile memory operation. The optimized device is air-stable and temperature-resistive up to 80 °C and exhibits excellent non-volatile memory performance with an on/off current ratio greater than 104, a switching time less than 100 ms, data retention longer than 4000 s, and write/read endurance over 100 cycles. Furthermore, the gate voltage dependent charge injection mediated by water in the passivation layer allowed for multilevel operation of our memory in which 4 distinct current states were programmed repetitively and preserved over a long time period. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00505e

Properties of the surface generation-recombination noise in 1.94 μm GaSb-based laser diodes

NASA Astrophysics Data System (ADS)

Glemža, Justinas; Palenskis, Vilius; Pralgauskaitė, Sandra; Vyšniauskas, Juozas; Matukas, Jonas

2018-06-01

A detail investigation of generation-recombination (g-r) noise in 1.94 μm GaSb-based type-I ridge waveguide laser diodes (LDs) has been performed in a temperature range (230-295) K. Lorentzian-type noise spectra have been observed in the current range below the threshold at the forward and reverse biases of the LDs with the same characteristic time (3.7 μs) and activation energy (≈0.37 eV) of charge carriers transitions associated with the g-r processes. An equivalent electrical circuit possessing the voltage noise source is presented, which allows the description of both the current-voltage characteristic and the voltage fluctuation spectral density of the laser diode. Results indicate that the origin of the g-r noise in the investigated samples is the surface recombination caused by the surface leakage current channel between n+GaSb and p+GaSb contacts, which is practically independent from the applied bias polarity.

Nanopatterned textile-based wearable triboelectric nanogenerator.

PubMed

Seung, Wanchul; Gupta, Manoj Kumar; Lee, Keun Young; Shin, Kyung-Sik; Lee, Ju-Hyuck; Kim, Tae Yun; Kim, Sanghyun; Lin, Jianjian; Kim, Jung Ho; Kim, Sang-Woo

2015-01-01

Here we report a fully flexible, foldable nanopatterned wearable triboelectric nanogenerator (WTNG) with high power-generating performance and mechanical robustness. Both a silver (Ag)-coated textile and polydimethylsiloxane (PDMS) nanopatterns based on ZnO nanorod arrays on a Ag-coated textile template were used as active triboelectric materials. A high output voltage and current of about 120 V and 65 μA, respectively, were observed from a nanopatterned PDMS-based WTNG, while an output voltage and current of 30 V and 20 μA were obtained by the non-nanopatterned flat PDMS-based WTNG under the same compressive force of 10 kgf. Furthermore, very high voltage and current outputs with an average value of 170 V and 120 μA, respectively, were obtained from a four-layer-stacked WTNG under the same compressive force. Notably it was found there are no significant differences in the output voltages measured from the multilayer-stacked WTNG over 12 000 cycles, confirming the excellent mechanical durability of WTNGs. Finally, we successfully demonstrated the self-powered operation of light-emitting diodes, a liquid crystal display, and a keyless vehicle entry system only with the output power of our WTNG without any help of external power sources.

Public magnetic field exposure based on internal current density for electric low voltage systems.

PubMed

Keikko, Tommi; Seesvuori, Reino; Hyvönen, Martti; Valkealahti, Seppo

2009-04-01

A measurement concept utilizing a new magnetic field exposure metering system has been developed for indoor substations where voltage is transformed from a medium voltage of 10 or 20 kV to a low voltage of 400 V. The new metering system follows the guidelines published by the International Commission on Non-Ionizing Radiation Protection. It can be used to measure magnetic field values, total harmonic distortion of the magnetic field, magnetic field exposure ratios for public and workers, load current values, and total harmonic distortion of the load current. This paper demonstrates how exposure to non-sinusoidal magnetic fields and magnetic flux density exposure values can be compared directly with limit values for internal current densities in a human body. Further, we present how the magnetic field and magnetic field exposure behaves in the vicinity of magnetic field sources within the indoor substation and in the neighborhood. Measured magnetic fields around the substation components have been used to develop a measurement concept by which long-term measurements in the substations were performed. Long-term measurements revealed interesting and partly unexpected dependencies between the measured quantities, which have been further analyzed. The principle of this paper is to substitute a demanding exposure measurement with measurements of the basic quantities like the 50 Hz fundamental magnetic field component, which can be estimated based on the load currents for certain classes of substation lay-out.

Hydrogen-induced reversible changes in drain current in Sc2O3/AlGaN/GaN high electron mobility transistors

NASA Astrophysics Data System (ADS)

Kang, B. S.; Mehandru, R.; Kim, S.; Ren, F.; Fitch, R. C.; Gillespie, J. K.; Moser, N.; Jessen, G.; Jenkins, T.; Dettmer, R.; Via, D.; Crespo, A.; Gila, B. P.; Abernathy, C. R.; Pearton, S. J.

2004-06-01

Pt contacted AlGaN/GaN high electron mobility transistors with Sc2O3 gate dielectrics show reversible changes in drain-source current upon exposure to H2-containing ambients, even at room temperature. The changes in current (as high as 3 mA for relatively low gate voltage and drain-source voltage) are approximately an order of magnitude larger than for Pt/GaN Schottky diodes and a factor of 5 larger than Sc2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) diodes exposed under the same conditions. This shows the advantage of using a transistor structure in which the gain produces larger current changes upon exposure to hydrogen-containing ambients. The increase in current is the result of a decrease in effective barrier height of the MOS gate of 30-50 mV at 25 °C for 10% H2/90% N2 ambients relative to pure N2 and is due to catalytic dissociation of the H2 on the Pt contact, followed by diffusion to the Sc2O3/AlGaN interface.

Lithium-cupric sulfide cell

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

Cuesta, A.J.; Bump, D.D.

1980-01-01

Lithium cells have become the primary power source for cardiac pacemakers due to their reliability and longevity at low current drain rates. A lithium-cupric sulfide cell was developed which makes maximum use of the shape of a pacemaker's battery compartment. The cell has a stable voltage throughout 90% of its lifetime. It then drops to a second stable voltage before depletion. The voltage drop creates a small decrease in pacemaker rate, which alerts the physician to replace the pacemaker. No loss of capacity due to self-discharge as been seen to date, and cells have proven to be safe under extrememore » conditions. 2 refs.« less

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

Thiemann, H.; Bogus, K.P.

The behavior of solar cell modules at high voltages in a surrounding simulated LEO plasma has been characterized over an applied voltage range from -700 to +500 V. Measurements were obtained in a large chamber under high vacuum using argon ions from a Kaufman source to generate a high-density plasma of up to 10 to the 6th/cu cm. The results suggest that secondary electrons contribute to the anomalous current increase noted at positive module voltages above 300 V. The surface potential on the coverglasses of the solar cells was shown to increase to high values only in the vicinity ofmore » the interconnectors. 27 references.« less

Variable frequency inverter for ac induction motors with torque, speed and braking control

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1975-01-01

A variable frequency inverter was designed for driving an ac induction motor which varies the frequency and voltage to the motor windings in response to varying torque requirements for the motor so that the applied voltage amplitude and frequency are of optimal value for any motor load and speed requirement. The slip frequency of the motor is caused to vary proportionally to the torque and feedback is provided so that the most efficient operating voltage is applied to the motor. Winding current surge is limited and a controlled negative slip causes motor braking and return of load energy to a dc power source.

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

PubMed Central

Zhao, Wenjing; Li, Hua; Furuta, Mamoru

2018-01-01

In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses (TIGZO) are investigated. As the TIGZO increased, the turn-on voltage (Von) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm2·V−1·s−1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the TIGZO. The PBS results exhibit that the Von shift is aggravated as the TIGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various TIGZO values is revealed using current–voltage and capacitance–voltage (C–V) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source (Cgs) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the TIGZO value increased, the hump in the off state of the Cgs curve was gradually weakened. PMID:29621154

Improved Signal Chains for Readout of CMOS Imagers

NASA Technical Reports Server (NTRS)

Pain, Bedabrata; Hancock, Bruce; Cunningham, Thomas

2009-01-01

An improved generic design has been devised for implementing signal chains involved in readout from complementary metal oxide/semiconductor (CMOS) image sensors and for other readout integrated circuits (ICs) that perform equivalent functions. The design applies to any such IC in which output signal charges from the pixels in a given row are transferred simultaneously into sampling capacitors at the bottoms of the columns, then voltages representing individual pixel charges are read out in sequence by sequentially turning on column-selecting field-effect transistors (FETs) in synchronism with source-follower- or operational-amplifier-based amplifier circuits. The improved design affords the best features of prior source-follower-and operational- amplifier-based designs while overcoming the major limitations of those designs. The limitations can be summarized as follows: a) For a source-follower-based signal chain, the ohmic voltage drop associated with DC bias current flowing through the column-selection FET causes unacceptable voltage offset, nonlinearity, and reduced small-signal gain. b) For an operational-amplifier-based signal chain, the required bias current and the output noise increase superlinearly with size of the pixel array because of a corresponding increase in the effective capacitance of the row bus used to couple the sampled column charges to the operational amplifier. The effect of the bus capacitance is to simultaneously slow down the readout circuit and increase noise through the Miller effect.

Double-gated Si NW FET sensors: Low-frequency noise and photoelectric properties

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

Gasparyan, F.; Forschungszentrum Jülich, Peter Grünberg Institute; Khondkaryan, H.

2016-08-14

The transport, noise, and photosensitivity properties of an array of silicon nanowire (NW) p{sup +}-p-p{sup +} field-effect transistors (FETs) are investigated. The peculiarities of photosensitivity and detectivity are analyzed over a wide spectrum range. The absorbance of p-Si NW shifts to the short wavelength region compared with bulk Si. The photocurrent and photosensitivity reach increased values in the UV range of the spectrum at 300 K. It is shown that sensitivity values can be tuned by the drain-source voltage and may reach record values of up to 2–4 A/W at a wavelength of 300 nm at room temperature. Low-frequency noise studies allow calculatingmore » the photodetectivity values, which increase with decreasing wavelength down to 300 nm. We show that the drain current of Si NW biochemical sensors substantially depends on pH value and the signal-to-noise ratio reaches the high value of 10{sup 5}. Increasing pH sensitivity with gate voltage is revealed for certain source-drain currents of pH-sensors based on Si NW FETs. The noise characteristic index decreases from 1.1 to 0.7 with the growth of the liquid gate voltage. Noise behavior is successfully explained in the framework of the correlated number-mobility unified fluctuation model. pH sensitivity increases as a result of the increase in liquid gate voltage, thus giving the opportunity to measure very low proton concentrations in the electrolyte medium at certain values of the liquid gate voltage.« less

Abrupt current switching in graphene bilayer tunnel transistors enabled by van Hove singularities.

PubMed

Alymov, Georgy; Vyurkov, Vladimir; Ryzhii, Victor; Svintsov, Dmitry

2016-04-21

In a continuous search for the energy-efficient electronic switches, a great attention is focused on tunnel field-effect transistors (TFETs) demonstrating an abrupt dependence of the source-drain current on the gate voltage. Among all TFETs, those based on one-dimensional (1D) semiconductors exhibit the steepest current switching due to the singular density of states near the band edges, though the current in 1D structures is pretty low. In this paper, we propose a TFET based on 2D graphene bilayer which demonstrates a record steep subthreshold slope enabled by van Hove singularities in the density of states near the edges of conduction and valence bands. Our simulations show the accessibility of 3.5 × 10(4) ON/OFF current ratio with 150 mV gate voltage swing, and a maximum subthreshold slope of (20 μV/dec)(-1) just above the threshold. The high ON-state current of 0.8 mA/μm is enabled by a narrow (~0.3 eV) extrinsic band gap, while the smallness of the leakage current is due to an all-electrical doping of the source and drain contacts which suppresses the band tailing and trap-assisted tunneling.

Abrupt current switching in graphene bilayer tunnel transistors enabled by van Hove singularities

PubMed Central

Alymov, Georgy; Vyurkov, Vladimir; Ryzhii, Victor; Svintsov, Dmitry

2016-01-01

In a continuous search for the energy-efficient electronic switches, a great attention is focused on tunnel field-effect transistors (TFETs) demonstrating an abrupt dependence of the source-drain current on the gate voltage. Among all TFETs, those based on one-dimensional (1D) semiconductors exhibit the steepest current switching due to the singular density of states near the band edges, though the current in 1D structures is pretty low. In this paper, we propose a TFET based on 2D graphene bilayer which demonstrates a record steep subthreshold slope enabled by van Hove singularities in the density of states near the edges of conduction and valence bands. Our simulations show the accessibility of 3.5 × 104 ON/OFF current ratio with 150 mV gate voltage swing, and a maximum subthreshold slope of (20 μV/dec)−1 just above the threshold. The high ON-state current of 0.8 mA/μm is enabled by a narrow (~0.3 eV) extrinsic band gap, while the smallness of the leakage current is due to an all-electrical doping of the source and drain contacts which suppresses the band tailing and trap-assisted tunneling. PMID:27098051

DETECTORS AND EXPERIMENTAL METHODS: Equivalent properties of single event burnout induced by different sources

NASA Astrophysics Data System (ADS)

Yang, Shi-Yu; Cao, Zhou; Da, Dao-An; Xue, Yu-Xiong

2009-05-01

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the “turn-off" state is more susceptible to single event burnout than it is in the “turn-on" state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and 252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.

Solid state light source driver establishing buck or boost operation

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

Palmer, Fred

A solid state light source driver circuit that operates in either a buck convertor or a boost convertor configuration is provided. The driver circuit includes a controller, a boost switch circuit and a buck switch circuit, each coupled to the controller, and a feedback circuit, coupled to the light source. The feedback circuit provides feedback to the controller, representing a DC output of the driver circuit. The controller controls the boost switch circuit and the buck switch circuit in response to the feedback signal, to regulate current to the light source. The controller places the driver circuit in its boostmore » converter configuration when the DC output is less than a rectified AC voltage coupled to the driver circuit at an input node. The controller places the driver circuit in its buck converter configuration when the DC output is greater than the rectified AC voltage at the input node.« less

Monitoring and remediation of on-farm and off-farm ground current measured as step potential on a Wisconsin dairy farm: A case study.

PubMed

Stetzer, Dave; Leavitt, Adam M; Goeke, Charles L; Havas, Magda

2016-01-01

Ground current commonly referred to as "stray voltage" has been an issue on dairy farms since electricity was first brought to rural America. Equipment that generates high-frequency voltage transients on electrical wires combined with a multigrounded (electrical distribution) system and inadequate neutral returns all contribute to ground current. Despite decades of problems, we are no closer to resolving this issue, in part, due to three misconceptions that are addressed in this study. Misconception 1. The current standard of 1 V at cow contact is adequate to protect dairy cows; Misconception 2. Frequencies higher than 60 Hz do not need to be considered; and Misconception 3. All sources of ground current originate on the farm that has a ground current problem. This case study of a Wisconsin dairy farm documents, 1. how to establish permanent monitoring of ground current (step potential) on a dairy farm; 2. how to determine and remediate both on-farm and off-farm sources contributing to step potential; 3. which step-potential metrics relate to cow comfort and milk production; and 4. how these metrics relate to established standards. On-farm sources include lighting, variable speed frequency drives on motors, radio frequency identification system and off-farm sources are due to a poor primary neutral return on the utility side of the distribution system. A step-potential threshold of 1 V root mean square (RMS) at 60 Hz is inadequate to protect dairy cows as decreases of a few mV peak-peak at higher frequencies increases milk production, reduces milking time and improves cow comfort.

Triple voltage dc-to-dc converter and method

DOEpatents

Su, Gui-Jia

2008-08-05

A circuit and method of providing three dc voltage buses and transforming power between a low voltage dc converter and a high voltage dc converter, by coupling a primary dc power circuit and a secondary dc power circuit through an isolation transformer; providing the gating signals to power semiconductor switches in the primary and secondary circuits to control power flow between the primary and secondary circuits and by controlling a phase shift between the primary voltage and the secondary voltage. The primary dc power circuit and the secondary dc power circuit each further comprising at least two tank capacitances arranged in series as a tank leg, at least two resonant switching devices arranged in series with each other and arranged in parallel with the tank leg, and at least one voltage source arranged in parallel with the tank leg and the resonant switching devices, said resonant switching devices including power semiconductor switches that are operated by gating signals. Additional embodiments having a center-tapped battery on the low voltage side and a plurality of modules on both the low voltage side and the high voltage side are also disclosed for the purpose of reducing ripple current and for reducing the size of the components.

Characteristics of MAO coating obtained on ZK60 Mg alloy under two and three steps voltage-increasing modes in dual electrolyte

NASA Astrophysics Data System (ADS)

Yang, Jun; Wang, Ze-Xin; Lu, Sheng; Lv, Wei-gang; Jiang, Xi-zhi; Sun, Lei

2017-03-01

The micro-arc oxidation process was conducted on ZK60 Mg alloy under two and three steps voltage-increasing modes by DC pulse electrical source. The effect of each mode on current-time responses during MAO process and the coating characteristic were analysed and discussed systematically. The microstructure, thickness and corrosion resistance of MAO coatings were evaluated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), microscope with super-depth of field and electrochemical impedance spectroscopy (EIS). The results indicate that two and three steps voltage-increasing modes can improve weak spark discharges with insufficient breakdown strength in later period during the MAO process. Due to higher value of voltage and voltage increment, the coating with maximum thickness of about 20.20μm formed under two steps voltage-increasing mode shows the best corrosion resistance. In addition, the coating fabricated under three steps voltage-increasing mode shows a smoother coating with better corrosion resistance due to the lower amplitude of voltage-increasing.

Electro-Thermo-Mechanical Transient Modeling of Stress Development in AlGaN/GaN High Electron Mobility Transistors (HEMTs) (Postprint)

DTIC Science & Technology

2014-02-01

Applied Drain Voltage Ids Drain-to-Source current MPa Megapascals σxx x-Component of Stress INTRODUCTION Gallium nitride (GaN) based high electron...the thermodynamic model to obtain the current densities within a semiconductor device. In doing so, it is possible to determine the electric

Calculated and measured brachytherapy dosimetry parameters in water for the Xoft Axxent X-Ray Source: an electronic brachytherapy source.

PubMed

Rivard, Mark J; Davis, Stephen D; DeWerd, Larry A; Rusch, Thomas W; Axelrod, Steve

2006-11-01

A new x-ray source, the model S700 Axxent X-Ray Source (Source), has been developed by Xoft Inc. for electronic brachytherapy. Unlike brachytherapy sources containing radionuclides, this Source may be turned on and off at will and may be operated at variable currents and voltages to change the dose rate and penetration properties. The in-water dosimetry parameters for this electronic brachytherapy source have been determined from measurements and calculations at 40, 45, and 50 kV settings. Monte Carlo simulations of radiation transport utilized the MCNP5 code and the EPDL97-based mcplib04 cross-section library. Inter-tube consistency was assessed for 20 different Sources, measured with a PTW 34013 ionization chamber. As the Source is intended to be used for a maximum of ten treatment fractions, tube stability was also assessed. Photon spectra were measured using a high-purity germanium (HPGe) detector, and calculated using MCNP. Parameters used in the two-dimensional (2D) brachytherapy dosimetry formalism were determined. While the Source was characterized as a point due to the small anode size, < 1 mm, use of the one-dimensional (1D) brachytherapy dosimetry formalism is not recommended due to polar anisotropy. Consequently, 1D brachytherapy dosimetry parameters were not sought. Calculated point-source model radial dose functions at gP(5) were 0.20, 0.24, and 0.29 for the 40, 45, and 50 kV voltage settings, respectively. For 1

Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

NASA Astrophysics Data System (ADS)

Lim, Sungkeun

Gordon Moore famously predicted the exponential increase in transistor integration and computing power that has been witnessed in recent decades [1]. In the near future, it is expected that more than one billion transistors will be integrated per chip, and advanced microprocessors will require clock speeds in excess of several GHz. The increasing number of transistors and high clock speeds will necessitate the consumption of more power. By 2014, it is expected that the maximum power consumption of the microprocessor will reach approximately 150W, and the maximum load current will be around 150A. Today's trend in power and thermal management is to reduce supply voltage as low as possible to reduce delivered power. It is anticipated that the Intel cores will operate on 0.8V of supply voltage by 2014 [2]. A significant challenge in Voltage Regulator Module (VRM) development for next generation microprocessors is to regulate the supply voltage within a certain tolerance band during high slew rate load transitions, since the required supply voltage tolerance band will be much narrower than the current requirement. If VR output impedance is maintained at a constant value from DC to high frequency, large output voltage spikes can be avoided during load cur- rent transients. Based on this, the Adaptive Voltage Position (AVP) concept was developed to achieve constant VR output impedance to improve transient response performance [3]. However, the VR output impedance can not be made constant over the entire frequency range with AVP design, because the AVP design makes the VR output impedance constant only at low frequencies. To make the output impedance constant at high frequencies, many bulk capacitors and ceramic capacitors are required. The tight supply voltage tolerance for the next generation of microprocessors during high slew rate load transitions requires fast transient response power supplies. A VRM can not follow the high slew rate load current transients, because of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is designed to improve the performance of an LDO regulator during output current transients. A TPIC for a LDO regulator is proposed to reduce the over voltage spike settling time. During a load current step down transient, the only current discharging path is a light load current. However, it takes a long time to discharge the current charged in the output capacitors with the light load current. The proposed TPIC will make an additional current discharging path to reduce the long settling time. By reducing the settling time, the load current transient frequency of the LDO regulator can be increased. A Ripple Cancellation Circuit (RCC) is proposed to reduce the output voltage ripple. The RCC has a very similar concept with the TPIC which is sinking or injecting additional current to the power stage to compensate the inductor ripple current. The proposed TPICs and RCC have been implemented with a 0.6m CMOS process. A single-phase VR, a 4SBB converter, and a LDO regulator have been utilized with the proposed TPIC to evaluate its performance. The theoretical analysis will be confirmed by Cadence simulation results and experimental results.

Survivability of Autonomous Microgrid during Overload Events

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

Du, Wei; Lasseter, Robert H.; Khalsa, Amrit S.

Grid-forming sources are voltage sources that draw necessary currents to meet any load changes. A load step can cause part or all of these sources to become overloaded in a microgrid. This paper presents an overload mitigation controller that addresses the two overload issues in a microgrid by actively controlling the sources’ frequency. When part of the sources in a microgrid is overloaded, the controller autonomously transfers the extra load to other sources by rapidly reducing its frequency. The frequency difference between sources during transient results in a change of phase angle, which redistributes the power flow. When all sourcesmore » in a microgrid are overloaded, each source keeps dropping the frequency. Therefore, under frequency load shedding can be used to trip the non-critical loads resulting in the survival of microgrid. The advantages of these concepts are that communications between sources are not needed during transient, and the robust voltage control is maintained. Lastly, simulation and field tests from CERTS/AEP microgrid test site verify that the control strategy is effective in both purely inverter-based microgrids and inverter & generator mixed microgrids.« less

Survivability of Autonomous Microgrid during Overload Events

DOE PAGES

Du, Wei; Lasseter, Robert H.; Khalsa, Amrit S.

2018-04-23

Grid-forming sources are voltage sources that draw necessary currents to meet any load changes. A load step can cause part or all of these sources to become overloaded in a microgrid. This paper presents an overload mitigation controller that addresses the two overload issues in a microgrid by actively controlling the sources’ frequency. When part of the sources in a microgrid is overloaded, the controller autonomously transfers the extra load to other sources by rapidly reducing its frequency. The frequency difference between sources during transient results in a change of phase angle, which redistributes the power flow. When all sourcesmore » in a microgrid are overloaded, each source keeps dropping the frequency. Therefore, under frequency load shedding can be used to trip the non-critical loads resulting in the survival of microgrid. The advantages of these concepts are that communications between sources are not needed during transient, and the robust voltage control is maintained. Lastly, simulation and field tests from CERTS/AEP microgrid test site verify that the control strategy is effective in both purely inverter-based microgrids and inverter & generator mixed microgrids.« less

Development of Real Time Implementation of 5/5 Rule based Fuzzy Logic Controller Shunt Active Power Filter for Power Quality Improvement

NASA Astrophysics Data System (ADS)

Puhan, Pratap Sekhar; Ray, Pravat Kumar; Panda, Gayadhar

2016-12-01

This paper presents the effectiveness of 5/5 Fuzzy rule implementation in Fuzzy Logic Controller conjunction with indirect control technique to enhance the power quality in single phase system, An indirect current controller in conjunction with Fuzzy Logic Controller is applied to the proposed shunt active power filter to estimate the peak reference current and capacitor voltage. Current Controller based pulse width modulation (CCPWM) is used to generate the switching signals of voltage source inverter. Various simulation results are presented to verify the good behaviour of the Shunt active Power Filter (SAPF) with proposed two levels Hysteresis Current Controller (HCC). For verification of Shunt Active Power Filter in real time, the proposed control algorithm has been implemented in laboratory developed setup in dSPACE platform.

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed Central

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc. PMID:26039589

The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

PubMed

Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

2015-01-01

Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

Capaciflector-guided mechanisms

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

1996-01-01

A plurality of capaciflector proximity sensors, one or more of which may be overlaid on each other, and at least one shield are mounted on a device guided by a robot so as to see a designated surface, hole or raised portion of an object, for example, in three dimensions. Individual current-measuring voltage follower circuits interface the sensors and shield to a common AC signal source. As the device approaches the object, the sensors respond by a change in the currents therethrough. The currents are detected by the respective current-measuring voltage follower circuits with the outputs thereof being fed to a robot controller. The device is caused to move under robot control in a predetermined pattern over the object while directly referencing each other without any offsets, whereupon by a process of minimization of the sensed currents, the device is dithered or wiggled into position for a soft touchdown or contact without any prior contact with the object.

An easy way to measure accurately the direct magnetoelectric voltage coefficient of thin film devices

NASA Astrophysics Data System (ADS)

Poullain, Gilles; More-Chevalier, Joris; Cibert, Christophe; Bouregba, Rachid

2017-01-01

TbxDy1-xFe2/Pt/Pb(Zrx, Ti1-x)O3 thin films were grown on Pt/TiO2/SiO2/Si substrate by multi-target sputtering. The magnetoelectric voltage coefficient αΗΜΕ was determined at room temperature using a lock-in amplifier. By adding, in series in the circuit, a capacitor of the same value as that of the device under test, we were able to demonstrate that the magnetoelectric device behaves as a voltage source. Furthermore, a simple way to subtract the stray voltage arising from the flow of eddy currents in the measurement set-up, is proposed. This allows the easy and accurate determination of the true magnetoelectric voltage coefficient. A large αΗΜΕ of 8.3 V/cm. Oe was thus obtained for a Terfenol-D/Pt/PZT thin film device, without DC magnetic field nor mechanical resonance.

Systems and methods for initializing a charging system

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

Perisic, Milun; Ransonm, Ray M.; Kojouke, Lateef A.

2017-09-26

Systems and methods are provided for charging a battery. The system, for example, includes, but is not limited to a first interface configured to receive a voltage from an AC voltage source, a matrix conversion module comprising a plurality of switches electrically connected to the first interface and configured to provide a charging voltage to the battery, and a controller communicatively connected to the matrix conversion module, wherein the controller is configured to: determine a voltage of the battery, determine an angle of the AC voltage source to initiate charging of the battery based upon the voltage of the battery,more » and control the plurality of switches to provide the charging voltage to the battery between the determined angle of the AC voltage source and a subsequent zero-crossing of the AC voltage source.« less

High-frequency graphene voltage amplifier.

PubMed

Han, Shu-Jen; Jenkins, Keith A; Valdes Garcia, Alberto; Franklin, Aaron D; Bol, Ageeth A; Haensch, Wilfried

2011-09-14

While graphene transistors have proven capable of delivering gigahertz-range cutoff frequencies, applying the devices to RF circuits has been largely hindered by the lack of current saturation in the zero band gap graphene. Herein, the first high-frequency voltage amplifier is demonstrated using large-area chemical vapor deposition grown graphene. The graphene field-effect transistor (GFET) has a 6-finger gate design with gate length of 500 nm. The graphene common-source amplifier exhibits ∼5 dB low frequency gain with the 3 dB bandwidth greater than 6 GHz. This first AC voltage gain demonstration of a GFET is attributed to the clear current saturation in the device, which is enabled by an ultrathin gate dielectric (4 nm HfO(2)) of the embedded gate structures. The device also shows extrinsic transconductance of 1.2 mS/μm at 1 V drain bias, the highest for graphene FETs using large-scale graphene reported to date.

Analysis of a flux-coupling type superconductor fault current limiter with pancake coils

NASA Astrophysics Data System (ADS)

Liu, Shizhuo; Xia, Dong; Zhang, Zhifeng; Qiu, Qingquan; Zhang, Guomin

2017-10-01

The characteristics of a flux-coupling type superconductor fault current limiter (SFCL) with pancake coils are investigated in this paper. The conventional double-wound non-inductive pancake coil used in AC power systems has an inevitable defect in Voltage Sourced Converter Based High Voltage DC (VSC-HVDC) power systems. Due to its special structure, flashover would occur easily during the fault in high voltage environment. Considering the shortcomings of conventional resistive SFCLs with non-inductive coils, a novel flux-coupling type SFCL with pancake coils is carried out. The module connections of pancake coils are performed. The electromagnetic field and force analysis of the module are contrasted under different parameters. To ensure proper operation of the module, the impedance of the module under representative operating conditions is calculated. Finally, the feasibility of the flux-coupling type SFCL in VSC-HVDC power systems is discussed.

Method and apparatus for in-situ characterization of energy storage and energy conversion devices

DOEpatents

Christophersen, Jon P [Idaho Falls, ID; Motloch, Chester G [Idaho Falls, ID; Morrison, John L [Butte, MT; Albrecht, Weston [Layton, UT

2010-03-09

Disclosed are methods and apparatuses for determining an impedance of an energy-output device using a random noise stimulus applied to the energy-output device. A random noise signal is generated and converted to a random noise stimulus as a current source correlated to the random noise signal. A bias-reduced response of the energy-output device to the random noise stimulus is generated by comparing a voltage at the energy-output device terminal to an average voltage signal. The random noise stimulus and bias-reduced response may be periodically sampled to generate a time-varying current stimulus and a time-varying voltage response, which may be correlated to generate an autocorrelated stimulus, an autocorrelated response, and a cross-correlated response. Finally, the autocorrelated stimulus, the autocorrelated response, and the cross-correlated response may be combined to determine at least one of impedance amplitude, impedance phase, and complex impedance.

Foundations of DC plasma sources

NASA Astrophysics Data System (ADS)

Tomas Gudmundsson, Jon; Hecimovic, Ante

2017-12-01

A typical dc discharge is configured with the negative cathode at one end and a positive anode at the other end, separated by a gas filled gap, placed inside a long glass cylinder. A few hundred volts between the cathode and anode is required to maintain the discharge. The type of discharge that is formed between the two electrodes depends upon the pressure of the working gas, the nature of the working gas, the applied voltage and the geometry of the discharge. We discuss the current-voltage characteristics of the discharge as well as the distinct structure that develops in the glow discharge region. The dc glow discharge appears in the discharge current range from μA to mA at 0.5-300 Pa pressure. We discuss the various phenomena observed in the dc glow discharge, including the cathode region, the positive column, and striations. The dc glow discharge is maintained by the emission of secondary electrons from the cathode target due to the bombardment of ions. For decades, the dc glow discharge has been used as a sputter source. Then it is often operated as an obstructed abnormal glow discharge and the required applied voltage is in the range 2-5 kV. Typically, the cathode target (the material to be deposited) is connected to a negative voltage supply (dc or rf) and the substrate holder faces the target. The relatively high operating pressure, in the range from 2 to 4 Pa, high applied voltages, and the necessity to have a conductive target limit the application of dc glow discharge as a sputter source. In order to lower the discharge voltage and expand the operation pressure range, the lifetime of the electrons in target vicinity is increased through applying magnetic field, by adding permanent magnets behind the cathode target. This arrangement is coined the magnetron sputtering discharge. The various configurations of the magnetron sputtering discharge and its applications are described. Furthermore, the use of dc discharges for chemical analysis, the Penning discharge and the hollow cathode discharges and some of its applications are briefly discussed.

Power conditioning system for energy sources

DOEpatents

Mazumder, Sudip K [Chicago, IL; Burra, Rajni K [Chicago, IL; Acharya, Kaustuva [Chicago, IL

2008-05-13

Apparatus for conditioning power generated by an energy source includes an inverter for converting a DC input voltage from the energy source to a square wave AC output voltage, and a converter for converting the AC output voltage from the inverter to a sine wave AC output voltage.

Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media

DOEpatents

McLellan, Edward J.

1983-01-01

Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode (1) and cathode (2) to below breakdown voltage using a dc voltage source (3). An array of resistors (4) or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit (5) producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO.sub.2 laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

Four-Quadrant Analog Multipliers Using G4-FETs

NASA Technical Reports Server (NTRS)

Mojarradi, Mohammad; Blalock, Benjamin; Christoloveanu, Sorin; Chen, Suheng; Akarvardar, Kerem

2006-01-01

Theoretical analysis and some experiments have shown that the silicon-on-insulator (SOI) 4-gate transistors known as G4-FETs can be used as building blocks of four-quadrant analog voltage multiplier circuits. Whereas a typical prior analog voltage multiplier contains between six and 10 transistors, it is possible to construct a superior voltage multiplier using only four G4-FETs. A G4-FET is a combination of a junction field-effect transistor (JFET) and a metal oxide/semiconductor field-effect transistor (MOSFET). It can be regarded as a single transistor having four gates, which are parts of a structure that affords high functionality by enabling the utilization of independently biased multiple inputs. The structure of a G4-FET of the type of interest here (see Figure 1) is that of a partially-depleted SOI MOSFET with two independent body contacts, one on each side of the channel. The drain current comprises of majority charge carriers flowing from one body contact to the other that is, what would otherwise be the side body contacts of the SOI MOSFET are used here as the end contacts [the drain (D) and the source (S)] of the G4-FET. What would otherwise be the source and drain of the SOI MOSFET serve, in the G4-FET, as two junction-based extra gates (JG1 and JG2), which are used to squeeze the channel via reverse-biased junctions as in a JFET. The G4-FET also includes a polysilicon top gate (G1), which plays the same role as does the gate in an accumulation-mode MOSFET. The substrate emulates a fourth MOS gate (G2). By making proper choices of G4-FET device parameters in conjunction with bias voltages and currents, one can design a circuit in which two input gate voltages (Vin1,Vin2) control the conduction characteristics of G4-FETs such that the output voltage (Vout) closely approximates a value proportional to the product of the input voltages. Figure 2 depicts two such analog multiplier circuits. In each circuit, there is the following: The input and output voltages are differential, The multiplier core consists of four G4- FETs (M1 through M4) biased by a constant current sink (Ibias), and The G4-FETs in two pairs are loaded by two identical resistors (RL), which convert a differential output current to a differential output voltage. The difference between the two circuits stems from their input and bias configurations. In each case, provided that the input voltages remain within their design ranges as determined by considerations of bias, saturation, and cutoff, then the output voltage is nominally given by Vout = kVin1Vin2, where k is a constant gain factor that depends on the design parameters and is different for the two circuits. In experimental versions of these circuits constructed using discrete G4- FETs and resistors, multiplication of voltages in all four quadrants (that is, in all four combinations of input polarities) was demonstrated, and deviations of the output voltages from linear dependence on the input voltages were found to amount to no more than a few percent. It is anticipated that in fully integrated versions of these circuits, the deviations from linearity will be made considerably smaller through better matching of devices.

High voltage holding in the negative ion sources with cesium deposition

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

Belchenko, Yu.; Abdrashitov, G.; Ivanov, A.

High voltage holding of the large surface-plasma negative ion source with cesium deposition was studied. It was found that heating of ion-optical system electrodes to temperature >100 °C facilitates the source conditioning by high voltage pulses in vacuum and by beam shots. The procedure of electrode conditioning and the data on high-voltage holding in the negative ion source with small cesium seed are described. The mechanism of high voltage holding improvement by depletion of cesium coverage is discussed.

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements.

PubMed

Scandurra, Graziella; Giusi, Gino; Ciofi, Carmine

2014-04-01

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level.

A very low noise, high accuracy, programmable voltage source for low frequency noise measurements

NASA Astrophysics Data System (ADS)

Scandurra, Graziella; Giusi, Gino; Ciofi, Carmine

2014-04-01

In this paper an approach for designing a programmable, very low noise, high accuracy voltage source for biasing devices under test in low frequency noise measurements is proposed. The core of the system is a supercapacitor based two pole low pass filter used for filtering out the noise produced by a standard DA converter down to 100 mHz with an attenuation in excess of 40 dB. The high leakage current of the supercapacitors, however, introduces large DC errors that need to be compensated in order to obtain high accuracy as well as very low output noise. To this end, a proper circuit topology has been developed that allows to considerably reduce the effect of the supercapacitor leakage current on the DC response of the system while maintaining a very low level of output noise. With a proper design an output noise as low as the equivalent input voltage noise of the OP27 operational amplifier, used as the output buffer of the system, can be obtained with DC accuracies better that 0.05% up to the maximum output of 8 V. The expected performances of the proposed voltage source have been confirmed both by means of SPICE simulations and by means of measurements on actual prototypes. Turn on and stabilization times for the system are of the order of a few hundred seconds. These times are fully compatible with noise measurements down to 100 mHz, since measurement times of the order of several tens of minutes are required in any case in order to reduce the statistical error in the measured spectra down to an acceptable level.

Source-drain burnout mechanism of GaAs power MESFETS: Three terminal effects

NASA Astrophysics Data System (ADS)

Takamiya, Saburo; Sonoda, Takuji; Yamanouchi, Masahide; Fujioka, Takashi; Kohno, Masaki

1997-03-01

Theoretical expressions for thermal and electrical feedback effects are derived. These limit the power capability of a power FET and lead a device to catastrophic breakdown (source-drain burnout) when the loop gain of the former reaches unity. Field emission of thermally excited electrons at the Schottky gate plays the key role in thermal feedback, while holes being impact ionized by the drain current play a similar role in the electrical feedback. Thermal feedback is dominant in a high temperature and low drain voltage area. Electrical feedback is dominant in a high drain voltage and low temperature area. In the first area, a high junction temperature is the main factor causing the thermal runaway of the device. In the second area, the electrcal feedback increases the drain current and the temperature and gives a trigger to the thermal feedback so that it reaches unity more easily. Both effects become significant in proportion to transconductance and gate bias resistance, and cause simultaneous runaway of the gate and drain currents. The expressions of the loop gains clearly indicate the safe operating conditions for a power FET. C-band 4 W (1 chip) and 16 W (4 chip) GaAs MESFETs were used as the experimental samples. With these devices the simultaneous runaway of the gate and the drain currents, apparent dependence of the three teminal breakdown voltage on the gate bias resistance in the region dominated by electrical feedback, the rapid increase of the field emitted current at the critical temperature and clear coincidence between the measured and calculated three terminal gate currents both in the thermal feedback dominant region, etc. are demonstrated. The theory explains the experimental results well.

MHD-EMP protection guidelines

NASA Astrophysics Data System (ADS)

Barnes, P. R.; Vance, E. F.

A nuclear detonation at altitudes several hundred kilometers above the earth will severely distort the earth's magnetic field and result in a strong magnetohydrodynamic electromagnetic pulse (MHD-EMP). The geomagnetic disturbance interacts with the soil to induce current and horizontal electric gradients. MHD-EMP, also called E3 since it is the third component of the high-altitude EMP (HEMP), lasts over 100 s after an exoatmospheric burst. MHD-EMP is similar to solar geomagnetic storms in it's global and low frequency (less than 1 Hz) nature except that E3 can be much more intense with a far shorter duration. When the MHD-EMP gradients are integrated over great distances by power lines, communication cables, or other long conductors, the induced voltages are significant. (The horizontal gradients in the soil are too small to induce major responses by local interactions with facilities.) The long pulse waveform for MHD-EMP-induced currents on long lines has a peak current of 200 A and a time-to-half-peak of 100 s. If this current flows through transformer windings, it can saturate the magnetic circuit and cause 60 Hz harmonic production. To mitigate the effects of MHD-EMP on a facility, long conductors must be isolated from the building and the commercial power harmonics and voltage swings must be addressed. The transfer switch would be expected to respond to the voltage fluctuations as long as the harmonics have not interfered with the switch control circuitry. The major sources of MHD-EMP induced currents are the commercial power lines and neutral; neutral current indirect coupling to the facility power or ground system via the metal fence, powered gate, parking lights, etc; metal water pipes; phone lines; and other long conductors that enter or come near the facility. The major source of harmonics is the commercial power system.

A compact 45 kV curve tracer with picoampere current measurement capability.

PubMed

Sullivan, W W; Mauch, D; Bullick, A; Hettler, C; Neuber, A; Dickens, J

2013-03-01

This paper discusses a compact high voltage curve tracer for high voltage semiconductor device characterization. The system sources up to 3 mA at up to 45 kV in dc conditions. It measures from 328 V to 60 kV with 15 V resolution and from 9.4 pA to 4 mA with 100 fA minimum resolution. Control software for the system is written in Microsoft Visual C# and features real-time measurement control and IV plotting, arc-protection and detection, an electrically isolated universal serial bus interface, and easy data exporting capabilities. The system has survived numerous catastrophic high voltage device-under-test arcing failures with no loss of measurement capability or system damage. Overall sweep times are typically under 2 min, and the curve tracer system was used to characterize the blocking performance of high voltage ceramic capacitors, high voltage silicon carbide photoconductive semiconductor switches, and high voltage coaxial cable.

THE USE OF ATOMIC BEAMS AS A PROBE FOR STUDYING LOW DENSITY PLASMAS. Quarterly Report for July 1, 1962-October 1, 1962

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

None

1963-10-31

A charge transfer cell was designed with the intention of minimizing space charge effects, since space charge represents a particularly serious handicap in the low energy (1 to 100 ev) region. Some cesium triode characteristice of the cell are presented in the form of curves of plate current versus plate voltage for several different voltages of grid (G1) to cathode. The potassium beamnoble gas attenuatlon studies were continued. The characteristics of a plasma source are described. The source consists of two water cooled copper spindles around which very thin tantalum, tungsten, or rhenium sheet may be wound. The cesium willmore » enter the source through a hole drilled in the face of one of the spindles. (N.W.R.)« less

Pencil-like mm-size electron beams produced with linear inductive voltage adders

NASA Astrophysics Data System (ADS)

Mazarakis, M. G.; Poukey, J. W.; Rovang, D. C.; Maenchen, J. E.; Cordova, S. R.; Menge, P. R.; Pepping, R.; Bennett, L.; Mikkelson, K.; Smith, D. L.; Halbleib, J.; Stygar, W. A.; Welch, D. R.

1997-02-01

We present the design, analysis, and results of the high brightness electron beam experiments currently under investigation at Sandia National Laboratories. The anticipated beam parameters are the following: energy 12 MeV, current 35-40 kA, rms radius 0.5 mm, and pulse duration 40 ns full width at half-maximum. The accelerator is SABRE, a pulsed linear inductive voltage adder modified to higher impedance, and the electron source is a magnetically immersed foilless electron diode. 20-30 T solenoidal magnets are required to insulate the diode and contain the beam to its extremely small-sized (1 mm) envelope. These experiments are designed to push the technology to produce the highest possible electron current in a submillimeter radius beam. Design, numerical simulations, and experimental results are presented.

Power Quality Improvement by Unified Power Quality Conditioner Based on CSC Topology Using Synchronous Reference Frame Theory

PubMed Central

Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

2014-01-01

This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems. PMID:25013854

Power quality improvement by unified power quality conditioner based on CSC topology using synchronous reference frame theory.

PubMed

Dharmalingam, Rajasekaran; Dash, Subhransu Sekhar; Senthilnathan, Karthikrajan; Mayilvaganan, Arun Bhaskar; Chinnamuthu, Subramani

2014-01-01

This paper deals with the performance of unified power quality conditioner (UPQC) based on current source converter (CSC) topology. UPQC is used to mitigate the power quality problems like harmonics and sag. The shunt and series active filter performs the simultaneous elimination of current and voltage problems. The power fed is linked through common DC link and maintains constant real power exchange. The DC link is connected through the reactor. The real power supply is given by the photovoltaic system for the compensation of power quality problems. The reference current and voltage generation for shunt and series converter is based on phase locked loop and synchronous reference frame theory. The proposed UPQC-CSC design has superior performance for mitigating the power quality problems.

Low-power transcutaneous current stimulator for wearable applications.

PubMed

Karpul, David; Cohen, Gregory K; Gargiulo, Gaetano D; van Schaik, André; McIntyre, Sarah; Breen, Paul P

2017-10-03

Peripheral neuropathic desensitization associated with aging, diabetes, alcoholism and HIV/AIDS, affects tens of millions of people worldwide, and there is little or no treatment available to improve sensory function. Recent studies that apply imperceptible continuous vibration or electrical stimulation have shown promise in improving sensitivity in both diseased and healthy participants. This class of interventions only has an effect during application, necessitating the design of a wearable device for everyday use. We present a circuit that allows for a low-power, low-cost and small form factor implementation of a current stimulator for the continuous application of subthreshold currents. This circuit acts as a voltage-to-current converter and has been tested to drive + 1 to - 1 mA into a 60 k[Formula: see text] load from DC to 1 kHz. Driving a 60 k[Formula: see text] load with a 2 mA peak-to-peak 1 kHz sinusoid, the circuit draws less than 21 mA from a 9 V source. The minimum operating current of the circuit is less than 12 mA. Voltage compliance is ± 60 V with just 1.02 mA drawn by the high voltage current drive circuitry. The circuit was implemented as a compact 46 mm × 21 mm two-layer PCB highlighting its potential for use in a body-worn device. No design to the best of our knowledge presents comparably low quiescent power with such high voltage compliance. This makes the design uniquely appropriate for low-power transcutaneous current stimulation in wearable applications. Further development of driving and instrumentation circuitry is recommended.

Thermally-induced voltage alteration for integrated circuit analysis

DOEpatents

Cole, Jr., Edward I.

2000-01-01

A thermally-induced voltage alteration (TIVA) apparatus and method are disclosed for analyzing an integrated circuit (IC) either from a device side of the IC or through the IC substrate to locate any open-circuit or short-circuit defects therein. The TIVA apparatus uses constant-current biasing of the IC while scanning a focused laser beam over electrical conductors (i.e. a patterned metallization) in the IC to produce localized heating of the conductors. This localized heating produces a thermoelectric potential due to the Seebeck effect in any conductors with open-circuit defects and a resistance change in any conductors with short-circuit defects, both of which alter the power demand by the IC and thereby change the voltage of a source or power supply providing the constant-current biasing. By measuring the change in the supply voltage and the position of the focused and scanned laser beam over time, any open-circuit or short-circuit defects in the IC can be located and imaged. The TIVA apparatus can be formed in part from a scanning optical microscope, and has applications for qualification testing or failure analysis of ICs.

Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters

NASA Astrophysics Data System (ADS)

Žumer, Marko; Zajec, Bojan; Rozman, Robert; Nemanič, Vincenc

2012-04-01

Gas-discharge tube (GDT) surge protectors are known for many decades as passive units used in low-voltage telecom networks for protection of electrical components from transient over-voltages (discharging) such as lightning. Unreliability of the mean turn-on DC breakdown voltage and the run-to-run variability has been overcome successfully in the past by adding, for example, a radioactive source inside the tube. Radioisotopes provide a constant low level of free electrons, which trigger the breakdown. In the last decades, any concept using environmentally harmful compounds is not acceptable anymore and new solutions were searched. In our application, a cold field electron emitter source is used as the trigger for the gas discharge but with no activating compound on the two main electrodes. The patent literature describes in details the implementation of the so-called trigger wires (auxiliary electrodes) made of graphite, placed in between the two main electrodes, but no physical explanation has been given yet. We present experimental results, which show that stable cold field electron emission current in the high vacuum range originating from the nano-structured edge of the graphite layer is well correlated to the stable breakdown voltage of the GDT surge protector filled with a mixture of clean gases.

Studies of extraction and transport system for highly charged ion beam of 18 GHz superconducting electron cyclotron resonance ion source at Research Center for Nuclear Physics.

PubMed

Yorita, T; Hatanaka, K; Fukuda, M; Ueda, H; Yasuda, Y; Morinobu, S; Tamii, A; Kamakura, K

2014-02-01

An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] and the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure

NASA Astrophysics Data System (ADS)

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R.

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. [Figure not available: see fulltext.

Numerical Simulation of Ion Transport in a Nano-Electrospray Ion Source at Atmospheric Pressure.

PubMed

Wang, Wei; Bajic, Steve; John, Benzi; Emerson, David R

2018-03-01

Understanding ion transport properties from the ion source to the mass spectrometer (MS) is essential for optimizing device performance. Numerical simulation helps in understanding of ion transport properties and, furthermore, facilitates instrument design. In contrast to previously reported numerical studies, ion transport simulations in a continuous injection mode whilst considering realistic space-charge effects have been carried out. The flow field was solved using Reynolds-averaged Navier-Stokes (RANS) equations, and a particle-in-cell (PIC) method was applied to solve a time-dependent electric field with local charge density. A series of ion transport simulations were carried out at different cone gas flow rates, ion source currents, and capillary voltages. A force evaluation analysis reveals that the electric force, the drag force, and the Brownian force are the three dominant forces acting on the ions. Both the experimental and simulation results indicate that cone gas flow rates of ≤250 slph (standard liter per hour) are important for high ion transmission efficiency, as higher cone gas flow rates reduce the ion signal significantly. The simulation results also show that the ion transmission efficiency reduces exponentially with an increased ion source current. Additionally, the ion loss due to space-charge effects has been found to be predominant at a higher ion source current, a lower capillary voltage, and a stronger cone gas counterflow. The interaction of the ion driving force, ion opposing force, and ion dispersion is discussed to illustrate ion transport mechanism in the ion source at atmospheric pressure. Graphical Abstract.

Electrical characteristics of silicon percolating nanonet-based field effect transistors in the presence of dispersion

NASA Astrophysics Data System (ADS)

Cazimajou, T.; Legallais, M.; Mouis, M.; Ternon, C.; Salem, B.; Ghibaudo, G.

2018-05-01

We studied the current-voltage characteristics of percolating networks of silicon nanowires (nanonets), operated in back-gated transistor mode, for future use as gas or biosensors. These devices featured P-type field-effect characteristics. It was found that a Lambert W function-based compact model could be used for parameter extraction of electrical parameters such as apparent low field mobility, threshold voltage and subthreshold slope ideality factor. Their variation with channel length and nanowire density was related to the change of conduction regime from direct source/drain connection by parallel nanowires to percolating channels. Experimental results could be related in part to an influence of the threshold voltage dispersion of individual nanowires.

Direct electronic probing of biological complexes formation

NASA Astrophysics Data System (ADS)

Macchia, Eleonora; Magliulo, Maria; Manoli, Kyriaki; Giordano, Francesco; Palazzo, Gerardo; Torsi, Luisa

2014-10-01

Functional bio-interlayer organic field - effect transistors (FBI-OFET), embedding streptavidin, avidin and neutravidin as bio-recognition element, have been studied to probe the electronic properties of protein complexes. The threshold voltage control has been achieved modifying the SiO2 gate diaelectric surface by means of the deposition of an interlayer of bio-recognition elements. A threshold voltage shift with respect to the unmodified dielectric surface toward more negative potential values has been found for the three different proteins, in agreement with their isoelectric points. The relative responses in terms of source - drain current, mobility and threshold voltage upon exposure to biotin of the FBI-OFET devices have been compared for the three bio-recognition elements.

Power Strategy in DC/DC Converters to Increase Efficiency of Electrical Stimulators.

PubMed

Aqueveque, Pablo; Acuña, Vicente; Saavedra, Francisco; Debelle, Adrien; Lonys, Laurent; Julémont, Nicolas; Huberland, François; Godfraind, Carmen; Nonclercq, Antoine

2016-06-13

Power efficiency is critical for electrical stimulators. Battery life of wearable stimulators and wireless power transmission in implanted systems are common limiting factors. Boost DC/DC converters are typically needed to increase the supply voltage of the output stage. Traditionally, boost DC/DC converters are used with fast control to regulate the supply voltage of the output. However, since stimulators are acting as current sources, such voltage regulation is not needed. Banking on this, this paper presents a DC/DC conversion strategy aiming to increase power efficiency. It compares, in terms of efficiency, the traditional use of boost converters to two alternatives that could be implemented in future hardware designs.

An electrostatic Si e-gun and a high temperature elemental B source for Si heteroepitaxial growth

NASA Astrophysics Data System (ADS)

Scarinci, F.; Casella, A.; Lagomarsino, S.; Fiordelisi, M.; Strappaveccia, P.; Gambacorti, N.; Grimaldi, M. G.; Xue, LiYing

1996-08-01

In this paper we present two kind of sources used in Si MBE growth: a Si source where an electron beam is electrostatically deflected onto a Si rod and a high temperature B source to be used for p-doping. Both sources have been designed and constructed at IESS. The Si source is constituted of a Si rod mounted on a 3/4″ flange with high-voltage connector. A W filament held at high voltage (up to 2000 V) is heated by direct current. Electrons from the filament are electrostatically focused onto the Si rod which is grounded. This mounting allows a minimum heating dispersion and no contamination, because the only hot objects are the Si rod and the W filament which is mounted in such a way that it cannot see the substrate. Growth rates of 10 Å/min on a substrate at 20 cm from the source have been measured. Auger and LEED have shown no contamination. The B source is constituted of a graphite block heated by direct current. A pyrolitic graphite crucible put in the graphite heater contains the elemental B. The cell is water cooled and contains Ta screens to avoid heat dispersion. It has been tested up to a temperature of 1700°C. P-doped Si 1- xGe x layers have been grown and B concentration has been measured by SIMS. A good control and reproducibility has been attained.

Line transients with corona

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

Saied, M.M.; Safar, Y.A.; Salama, M.H.

1987-01-01

This paper investigates the effect of corona on the electromagnetic transients along high voltage overhead lines. A method is presented to simulate the line by dividing it into a number of sections connected in cascade. For {ital n} line sections, the number of the unknown variables is 2{ital n} + 1. The method allows any waveform of the exciting voltage function, as well as any impedance loading condition. The corona is represented by voltage-dependent shunt current sources. A systematic way for writing a sufficient number of differential equations is shown. For their solution, a digital computer subroutine based on themore » Runge--Kutta--Verner method was used. An artificial frequency-dependent damping by means of linear resistors was used to suppress the Gibb's oscillations in the solution. The proposed method is applied to study the transients on a 40 km high voltage line with 30-ft flat phase spacing and a single 1.4 inch ACSR conductor per phase. The exciting voltage has a double-exponential impulse waveform. Solutions are given for three values of resistive loads Z{sub {ital c}}2Z{sub {ital c}} and Z{sub {ital c}}/2, where Z{sub {ital c}} is the line surge impedance. The results of two interesting cases of inductive and capacitive loads are also given. Physical interpretations for the different solutions are given. Also, the current-voltage duality between inductive and capacitive loads is recognized. The corona was found to attenuate and distort the travelling waves. For example, during one wave excursion, the reduction of the current wave peaks can reach values as high as 8.5%. The effect is more noticeable in the current than in the voltage waves. As expected, it increases also with the line corona losses. The effect of the increase of the line effective capacitance due to the corona discharge is also demonstrated.« less

A Single-Phase Embedded Z-Source DC-AC Inverter

PubMed Central

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively. PMID:25133241

A single-phase embedded Z-source DC-AC inverter.

PubMed

Kim, Se-Jin; Lim, Young-Cheol

2014-01-01

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

Addressing Circuitous Currents MVDC Power Systems Protection

DTIC Science & Technology

2017-12-31

load . The converter modules are current-controlled buck converters. They are being controlled to provide a no - load voltage of 155V at their outputs...PAGE Form Approved 0MB No . 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response...distribution is unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT The work investigates Z-source breakers in multi-zone systems with current to the load through

Effect of substrate thinning on the electronic transport characteristics of AlGaN/GaN HEMTs

NASA Astrophysics Data System (ADS)

Zhu, Hui; Meng, Xiao; Zheng, Xiang; Yang, Ying; Feng, Shiwei; Zhang, Yamin; Guo, Chunsheng

2018-07-01

We studied how substrate thinning affected the electronic transport characteristics of AlGaN/GaN HEMTs. By thinning their sapphire substrate from 460 μm to 80 μm, we varied the residual stress in these HEMTs. The thinned sample showed decreased drain-source current and occurrence of kink effect. Furthermore, shown by current transient measurements and time constant analysis, the detrapping behaviors of trap states shifted toward a larger time constant, and the detrapping behavior under the gate and in the gate-drain access region showed increased amplitude. By using pulsed current-voltage measurements, the thinned sample showed a positive shift of the threshold voltage, a decrease in peak transconductance, and an aggravation in current collapse, as compared with the thick one. The degradation of electrical behavior were associated with the structural degradation, as confirmed by the increase of pit density on the thinned sample surface.

Cross-contact chain

NASA Technical Reports Server (NTRS)

Lieneweg, Udo (Inventor)

1988-01-01

A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on a normal probability chart, enables prediction of the yield of good integrated circuits from the wafer.

Cross-contact chain

NASA Technical Reports Server (NTRS)

Lieneweg, U. (Inventor)

1986-01-01

A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on normal probability chart enables prediction of the yield of good integrated circuits from the wafer.

Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media. [CO/sub 2/ laser oscillator and pulse smoother

DOEpatents

McLellan, E.J.

1980-10-17

Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode and cathode to below breakdown voltage using a dc voltage source. An array of resistors or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO/sub 2/ laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

A Discrete-Time Average Model Based Predictive Control for Quasi-Z-Source Inverter

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

Liu, Yushan; Abu-Rub, Haitham; Xue, Yaosuo

A discrete-time average model-based predictive control (DTA-MPC) is proposed for a quasi-Z-source inverter (qZSI). As a single-stage inverter topology, the qZSI regulates the dc-link voltage and the ac output voltage through the shoot-through (ST) duty cycle and the modulation index. Several feedback strategies have been dedicated to produce these two control variables, among which the most popular are the proportional–integral (PI)-based control and the conventional model-predictive control (MPC). However, in the former, there are tradeoffs between fast response and stability; the latter is robust, but at the cost of high calculation burden and variable switching frequency. Moreover, they require anmore » elaborated design or fine tuning of controller parameters. The proposed DTA-MPC predicts future behaviors of the ST duty cycle and modulation signals, based on the established discrete-time average model of the quasi-Z-source (qZS) inductor current, the qZS capacitor voltage, and load currents. The prediction actions are applied to the qZSI modulator in the next sampling instant, without the need of other controller parameters’ design. A constant switching frequency and significantly reduced computations are achieved with high performance. Transient responses and steady-state accuracy of the qZSI system under the proposed DTA-MPC are investigated and compared with the PI-based control and the conventional MPC. Simulation and experimental results verify the effectiveness of the proposed approach for the qZSI.« less

A Discrete-Time Average Model Based Predictive Control for Quasi-Z-Source Inverter

DOE PAGES

Liu, Yushan; Abu-Rub, Haitham; Xue, Yaosuo; ...

2017-12-25

A discrete-time average model-based predictive control (DTA-MPC) is proposed for a quasi-Z-source inverter (qZSI). As a single-stage inverter topology, the qZSI regulates the dc-link voltage and the ac output voltage through the shoot-through (ST) duty cycle and the modulation index. Several feedback strategies have been dedicated to produce these two control variables, among which the most popular are the proportional–integral (PI)-based control and the conventional model-predictive control (MPC). However, in the former, there are tradeoffs between fast response and stability; the latter is robust, but at the cost of high calculation burden and variable switching frequency. Moreover, they require anmore » elaborated design or fine tuning of controller parameters. The proposed DTA-MPC predicts future behaviors of the ST duty cycle and modulation signals, based on the established discrete-time average model of the quasi-Z-source (qZS) inductor current, the qZS capacitor voltage, and load currents. The prediction actions are applied to the qZSI modulator in the next sampling instant, without the need of other controller parameters’ design. A constant switching frequency and significantly reduced computations are achieved with high performance. Transient responses and steady-state accuracy of the qZSI system under the proposed DTA-MPC are investigated and compared with the PI-based control and the conventional MPC. Simulation and experimental results verify the effectiveness of the proposed approach for the qZSI.« less

Experimental study of the processes accompanying argon breakdown in a long discharge tube at a reduced pressure

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

Meshchanov, A. V.; Ionikh, Yu. Z., E-mail: y.ionikh@spbu.ru; Shishpanov, A. I.

Results are presented from experimental studies of the breakdown stage of a low-pressure discharge (1 and 5 Torr) in a glass tube the length of which (75 cm) is much larger than its diameter (2.8 cm). Breakdowns occurred under the action of positive voltage pulses with an amplitude of up to 9.4 kV and a characteristic rise time of 2–50 μs. The discharge current in the steady-state mode was 10–120 mA. The electrode voltage, discharge current, and radiation from the discharge gap were detected simultaneously. The dynamic breakdown voltage was measured, the prebreakdown ionization wave was recorded, and its velocitymore » was determined. The dependence of the discharge parameters on the time interval between voltage pulses (the socalled “memory effect”) was analyzed. The memory effect manifests itself in a decrease or an increase in the breakdown voltage and a substantial decrease in its statistical scatter. The time interval between pulses in this case can reach 0.5 s. The effect of illumination of the discharge tube with a light source on the breakdown was studied. It is found that the irradiation of the anode region of the tube by radiation with wavelengths of ≤500 nm substantially reduces the dynamic breakdown voltage. Qualitative explanations of the obtained results are offered.« less

Modeling of Dual Gate Material Hetero-dielectric Strained PNPN TFET for Improved ON Current

NASA Astrophysics Data System (ADS)

Kumari, Tripty; Saha, Priyanka; Dash, Dinesh Kumar; Sarkar, Subir Kumar

2018-01-01

The tunnel field effect transistor (TFET) is considered to be a promising alternative device for future low-power VLSI circuits due to its steep subthreshold slope, low leakage current and its efficient performance at low supply voltage. However, the main challenging issue associated with realizing TFET for wide scale applications is its low ON current. To overcome this, a dual gate material with the concept of dielectric engineering has been incorporated into conventional TFET structure to tune the tunneling width at source-channel interface allowing significant flow of carriers. In addition to this, N+ pocket is implanted at source-channel junction of the proposed structure and the effect of strain is added for exploring the performance of the model in nanoscale regime. All these added features upgrade the device characteristics leading to higher ON current, low leakage and low threshold voltage. The present work derives the surface potential, electric field expression and drain current by solving 2D Poisson's equation at different boundary conditions. A comparative analysis of proposed model with conventional TFET has been done to establish the superiority of the proposed structure. All analytical results have been compared with the results obtained in SILVACO ATLAS device simulator to establish the accuracy of the derived analytical model.

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.

Asymmetrical Capacitors for Propulsion

NASA Technical Reports Server (NTRS)

Canning, Francis X.; Melcher, Cory; Winet, Edwin

2004-01-01

Asymmetrical Capacitor Thrusters have been proposed as a source of propulsion. For over eighty years, it has been known that a thrust results when a high voltage is placed across an asymmetrical capacitor, when that voltage causes a leakage current to flow. However, there is surprisingly little experimental or theoretical data explaining this effect. This paper reports on the results of tests of several Asymmetrical Capacitor Thrusters (ACTs). The thrust they produce has been measured for various voltages, polarities, and ground configurations and their radiation in the VHF range has been recorded. These tests were performed at atmospheric pressure and at various reduced pressures. A simple model for the thrust was developed. The model assumed the thrust was due to electrostatic forces on the leakage current flowing across the capacitor. It was further assumed that this current involves charged ions which undergo multiple collisions with air. These collisions transfer momentum. All of the measured data was consistent with this model. Many configurations were tested, and the results suggest general design principles for ACTs to be used for a variety of purposes.

Study of current-mode active pixel sensor circuits using amorphous InSnZnO thin-film transistor for 50-μm pixel-pitch indirect X-ray imagers

NASA Astrophysics Data System (ADS)

Cheng, Mao-Hsun; Zhao, Chumin; Kanicki, Jerzy

2017-05-01

Current-mode active pixel sensor (C-APS) circuits based on amorphous indium-tin-zinc-oxide thin-film transistors (a-ITZO TFTs) are proposed for indirect X-ray imagers. The proposed C-APS circuits include a combination of a hydrogenated amorphous silicon (a-Si:H) p+-i-n+ photodiode (PD) and a-ITZO TFTs. Source-output (SO) and drain-output (DO) C-APS are investigated and compared. Acceptable signal linearity and high gains are realized for SO C-APS. APS circuit characteristics including voltage gain, charge gain, signal linearity, charge-to-current conversion gain, electron-to-voltage conversion gain are evaluated. The impact of the a-ITZO TFT threshold voltage shifts on C-APS is also considered. A layout for a pixel pitch of 50 μm and an associated fabrication process are suggested. Data line loadings for 4k-resolution X-ray imagers are computed and their impact on circuit performances is taken into consideration. Noise analysis is performed, showing a total input-referred noise of 239 e-.

GTA weld penetration and the effects of deviations in machine variables

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

Giedt, W.H.

1987-07-01

Analytical models for predicting the temperature distribution during GTA welding are reviewed with the purpose of developing a procedure for investigating the effects of deviations in machine parameters. The objective was to determine the accuracy required in machine settings to obtain reproducible results. This review revealed a wide range of published values (21 to 90%) for the arc heating efficiency. Low values (21 to 65%) were associated with evaluation of efficiency using constant property conduction models. Values from 75 to 90% were determined from calorimetric type measurements and are applicable for more accurate numerical solution procedures. Although numerical solutions canmore » yield better overall weld zone predictions, calculations are lengthy and complex. In view of this and the indication that acceptable agreement with experimental measurements can be achieved with the moving-point-source solution, it was utilized to investigate the effects of deviations or errors in voltage, current, and travel speed on GTA weld penetration. Variations resulting from welding within current goals for voltage (+-0.1 V), current (+-3.0 A), and travel speed (+-2.0%) were found to be +-2 to 4%, with voltage and current being more influential than travel speed.« less

Ion Current Rectification, Limiting and Overlimiting Conductances in Nanopores

PubMed Central

van Oeffelen, Liesbeth; Van Roy, Willem; Idrissi, Hosni; Charlier, Daniel; Lagae, Liesbet; Borghs, Gustaaf

2015-01-01

Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dependent and steady state PNP simulations under less restrictive boundary conditions, including Neumann boundary conditions applied throughout the membrane relatively far away from the nanopore. We simulated ion currents through cylindrical and conical nanopores with several surface charge configurations, studying the spatial and temporal dependence of the currents contributed by each ion species. This revealed that, due to slow co-diffusion of oppositely charged ions, steady state is generally not reached in simulations or in practice. Furthermore, it is shown that ion concentration polarization is responsible for the observed limiting conductances and ion current rectification in nanopores with asymmetric surface charges or shapes. Hence, after more than a decade of collective research attempting to understand the nature of ion current rectification in solid-state nanopores, a relatively intuitive model is retrieved. Moreover, we measured and simulated current-voltage characteristics of rectifying silicon nitride nanopores presenting overlimiting conductances. The similarity between measurement and simulation shows that overlimiting conductances can result from the increased conductance of the electric double-layer at the membrane surface at the depletion side due to voltage-induced polarization charges. The MATLAB source code of the simulation software is available via the website http://micr.vub.ac.be. PMID:25978328

Variable current speed controller for eddy current motors

DOEpatents

Gerth, H.L.; Bailey, J.M.; Casstevens, J.M.; Dixon, J.H.; Griffith, B.O.; Igou, R.E.

1982-03-12

A speed control system for eddy current motors is provided in which the current to the motor from a constant frequency power source is varied by comparing the actual motor speed signal with a setpoint speed signal to control the motor speed according to the selected setpoint speed. A three-phase variable voltage autotransformer is provided for controlling the voltage from a three-phase power supply. A corresponding plurality of current control resistors is provided in series with each phase of the autotransformer output connected to inputs of a three-phase motor. Each resistor is connected in parallel with a set of normally closed contacts of plurality of relays which are operated by control logic. A logic circuit compares the selected speed with the actual motor speed obtained from a digital tachometer monitoring the motor spindle speed and operated the relays to add or substract resistance equally in each phase of the motor input to vary the motor current to control the motor at the selected speed.

Effect of Ion Escape Velocity and Conversion Surface Material on H- Production

NASA Astrophysics Data System (ADS)

Tarvainen, O.; Kalvas, T.; Komppula, J.; Koivisto, H.; Geros, E.; Stelzer, J.; Rouleau, G.; Johnson, K. F.; Carmichael, J.

2011-09-01

According to generally accepted models surface production of negative ions depends on ion escape velocity and work function of the surface. We have conducted an experimental study addressing the role of the ion escape velocity on H- production. A converter-type ion source at Los Alamos Neutron Science Center was employed for the experiment. The ion escape velocity was affected by varying the bias voltage of the converter electrode. It was observed that due to enhanced stripping of H- no direct gain of extracted beam current can be achieved by increasing the converter voltage. The conversion efficiency of H- was observed to vary with converter voltage and follow the existing theories in qualitative manner. We present calculations predicting relative H- yields from different cesiated surfaces with comparison to experimental observations from different types of H- ion sources. Utilizing materials exhibiting negative electron affinity and exposed to UV-light is considered for Cesium-free H-/D- production.

Precision absolute-value amplifier for a precision voltmeter

DOEpatents

Hearn, W.E.; Rondeau, D.J.

1982-10-19

Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resistor is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resistor. The output current through the load resistor is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resistor. A second gain determining resistor is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

Precision absolute value amplifier for a precision voltmeter

DOEpatents

Hearn, William E.; Rondeau, Donald J.

1985-01-01

Bipolar inputs are afforded by the plus inputs of first and second differential input amplifiers. A first gain determining resister is connected between the minus inputs of the differential amplifiers. First and second diodes are connected between the respective minus inputs and the respective outputs of the differential amplifiers. First and second FETs have their gates connected to the outputs of the amplifiers, while their respective source and drain circuits are connected between the respective minus inputs and an output lead extending to a load resister. The output current through the load resister is proportional to the absolute value of the input voltage difference between the bipolar input terminals. A third differential amplifier has its plus input terminal connected to the load resister. A second gain determining resister is connected between the minus input of the third differential amplifier and a voltage source. A third FET has its gate connected to the output of the third amplifier. The source and drain circuit of the third transistor is connected between the minus input of the third amplifier and a voltage-frequency converter, constituting an output device. A polarity detector is also provided, comprising a pair of transistors having their inputs connected to the outputs of the first and second differential amplifiers. The outputs of the polarity detector are connected to gates which switch the output of the voltage-frequency converter between up and down counting outputs.

Inflation Fighters.

ERIC Educational Resources Information Center

Cohen, Sheldon H., Ed.

1983-01-01

Describes a low-cost, high-voltage, two-terminal, constant-current source for student use in electrophoresis experiments (includes circuit diagram) and a simple device for the continuous registering of gas flows. Also lists seven cost-saving tips for chemical reagent, including use decorative stones (purchased from nursery stores) in place of…

Starting Circuit For Erasable Programmable Logic Device

NASA Technical Reports Server (NTRS)

Cole, Steven W.

1990-01-01

Voltage regulator bypassed to supply starting current. Starting or "pullup" circuit supplies large inrush of current required by erasable programmable logic device (EPLD) while being turned on. Operates only during such intervals of high demand for current and has little effect any other time. Performs needed bypass, acting as current-dependent shunt connecting battery or other source of power more nearly directly to EPLD. Input capacitor of regulator removed when starting circuit installed, reducing probability of damage to transistor in event of short circuit in or across load.

A Solid-State Fault Current Limiting Device for VSC-HVDC Systems

NASA Astrophysics Data System (ADS)

Larruskain, D. Marene; Zamora, Inmaculada; Abarrategui, , Oihane; Iturregi, Araitz

2013-08-01

Faults in the DC circuit constitute one of the main limitations of voltage source converter VSC-HVDC systems, as the high fault currents can damage seriously the converters. In this article, a new design for a fault current limiter (FCL) is proposed, which is capable of limiting the fault current as well as interrupting it, isolating the DC grid. The operation of the proposed FCL is analysed and verified with the most usual faults that can occur in overhead lines.

Organic Light-Emitting Diode-on-Silicon Pixel Circuit Using the Source Follower Structure with Active Load for Microdisplays

NASA Astrophysics Data System (ADS)

Kwak, Bong-Choon; Lim, Han-Sin; Kwon, Oh-Kyong

2011-03-01

In this paper, we propose a pixel circuit immune to the electrical characteristic variation of organic light-emitting diodes (OLEDs) for organic light-emitting diode-on-silicon (OLEDoS) microdisplays with a 0.4 inch video graphics array (VGA) resolution and a 6-bit gray scale. The proposed pixel circuit is implemented using five p-channel metal oxide semiconductor field-effect transistors (MOSFETs) and one storage capacitor. The proposed pixel circuit has a source follower with a diode-connected transistor as an active load for improving the immunity against the electrical characteristic variation of OLEDs. The deviation in the measured emission current ranges from -0.165 to 0.212 least significant bit (LSB) among 11 samples while the anode voltage of OLED is 0 V. Also, the deviation in the measured emission current ranges from -0.262 to 0.272 LSB in pixel samples, while the anode voltage of OLED varies from 0 to 2.5 V owing to the electrical characteristic variation of OLEDs.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air.

PubMed

Jain, Vishal; Visani, Anand; Srinivasan, R; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (∼0.28 W/cm 2 ) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (∼50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Design and development of a low cost, high current density power supply for streamer free atmospheric pressure DBD plasma generation in air

NASA Astrophysics Data System (ADS)

Jain, Vishal; Visani, Anand; Srinivasan, R.; Agarwal, Vivek

2018-03-01

This paper presents a new power supply architecture for generating a uniform dielectric barrier discharge (DBD) plasma in air medium at atmospheric pressure. It is quite a challenge to generate atmospheric pressure uniform glow discharge plasma, especially in air. This is because air plasma needs very high voltage for initiation of discharge. If the high voltage is used along with high current density, it leads to the formation of streamers, which is undesirable for most applications like textile treatment, etc. Researchers have tried to generate high-density plasma using a RF source, nanosecond pulsed DC source, and medium frequency AC source. However, these solutions suffer from low current discharge and low efficiency due to the addition of an external resistor to control the discharge current. Moreover, they are relatively costly and bulky. This paper presents a new power supply configuration which is very compact and generates high average density (˜0.28 W/cm2) uniform glow DBD plasma in air at atmospheric pressure. The efficiency is also higher as no external resistor is required to control the discharge current. An inherent feature of this topology is that it can drive higher current oscillations (˜50 A peak and 2-3 MHz frequency) into the plasma that damp out due to the plasma dissipation only. A newly proposed model has been used with experimental validation in this paper. Simulations and experimental validation of the proposed topology are included. Also, the application of the generated plasma for polymer film treatment is demonstrated.

Plasma-anode electron gun

NASA Astrophysics Data System (ADS)

Santoru, Joseph; Schumacher, Robert W.; Gregoire, Daniel J.

1994-11-01

The plasma-anode electron gun (PAG) is an electron source in which the thermionic cathode is replaced with a cold, secondary-electron-emitting electrode. Electron emission is stimulated by bombarding the cathode with high-energy ions. Ions are injected into the high-voltage gap through a gridded structure from a plasma source (gas pressure less than or equal to 50 mTorr) that is embedded in the anode electrode. The gridded structure serves as both a cathode for the plasma discharge and as an anode for the PAG. The beam current is modulated at near ground potential by modulating the plasma source, eliminating the need for a high-voltage modulator system. During laboratory tests, the PAG has demonstrated square-wave, 17-microsecond-long beam pulses at 100 kV and 10 A, and it has operated stably at 70 kV and 2.5 A for 210 microsecond pulse lengths without gap closure.

Synthesis of polymer nanostructures with conductance switching properties

DOEpatents

Su, Kai; Nuraje, Nurxat; Zhang, Lingzhi; Matsui, Hiroshi; Yang, Nan Loh

2015-03-03

The present invention is directed to crystalline organic polymer nanoparticles comprising a conductive organic polymer; wherein the crystalline organic polymer nanoparticles have a size of from 10 nm to 200 nm and exhibits two current-voltage states: (1) a high resistance current-voltage state, and (2) a low resistance current-voltage state, wherein when a first positive threshold voltage (V.sub.th1) or higher positive voltage, or a second negative threshold voltage (V.sub.th2) or higher negative voltage is applied to the nanoparticle, the nanoparticle exhibits the low-resistance current-voltage state, and when a voltage less positive than the first positive threshold voltage or a voltage less negative than the second negative threshold voltage is applied to the nanoparticle, the nanoparticle exhibits the high-resistance current-voltage state. The present invention is also directed methods of manufacturing the nanoparticles using novel interfacial oxidative polymerization techniques.

E-beam high voltage switching power supply

DOEpatents

Shimer, Daniel W.; Lange, Arnold C.

1997-01-01

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360.degree./n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load.

E-beam high voltage switching power supply

DOEpatents

Shimer, D.W.; Lange, A.C.

1997-03-11

A high power, solid state power supply is described for producing a controllable, constant high voltage output under varying and arcing loads suitable for powering an electron beam gun or other ion source. The present power supply is most useful for outputs in a range of about 100-400 kW or more. The power supply is comprised of a plurality of discrete switching type dc-dc converter modules, each comprising a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, and an output rectifier for producing a dc voltage at the output of each module. The inputs to the converter modules are fed from a common dc rectifier/filter and are linked together in parallel through decoupling networks to suppress high frequency input interactions. The outputs of the converter modules are linked together in series and connected to the input of the transmission line to the load through a decoupling and line matching network. The dc-dc converter modules are phase activated such that for n modules, each module is activated equally 360{degree}/n out of phase with respect to a successive module. The phased activation of the converter modules, combined with the square current waveforms out of the step up transformers, allows the power supply to operate with greatly reduced output capacitance values which minimizes the stored energy available for discharge into an electron beam gun or the like during arcing. The present power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle using simulated voltage feedback signals and voltage feedback loops. Circuitry is also provided for sensing incipient arc currents reflected at the output of the power supply and for simultaneously decoupling the power supply circuitry from the arcing load. 7 figs.

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.

Device for monitoring cell voltage

DOEpatents

Doepke, Matthias [Garbsen, DE; Eisermann, Henning [Edermissen, DE

2012-08-21

A device for monitoring a rechargeable battery having a number of electrically connected cells includes at least one current interruption switch for interrupting current flowing through at least one associated cell and a plurality of monitoring units for detecting cell voltage. Each monitoring unit is associated with a single cell and includes a reference voltage unit for producing a defined reference threshold voltage and a voltage comparison unit for comparing the reference threshold voltage with a partial cell voltage of the associated cell. The reference voltage unit is electrically supplied from the cell voltage of the associated cell. The voltage comparison unit is coupled to the at least one current interruption switch for interrupting the current of at least the current flowing through the associated cell, with a defined minimum difference between the reference threshold voltage and the partial cell voltage.

Status of high polarization DC high voltage Gallium Arsenide photoelectron guns

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

M. Poelker, P. Adderley, J. Brittian, J. Clark, J. Grames, J. Hansknecht, J. McCarter, M. Stutzman, R. Suleiman, K. Surles-Law

2008-01-01

Users receive very high beam polarization from reliable GaAs photoelectron guns at facilities worldwide. Satisfaction with beam quality (and a number of lab closures) has reduced the level of polarized source R&D from the heyday of 1990s. However, new experiments and new accelerators proposals including high current unpolarized machines, require GaAs photoguns with capabilities that exceed today's state of the art. This submission describes the capabilities of today's high- polarization DC high voltage GaAs photoguns and discusses issues that must be addressed to meet new demands.

Research on Novel High-Power Microwave/Millimeter Wave Sources and Applications

DTIC Science & Technology

2010-08-28

density with acceptable operating temperature and lifetime. The MIG is optimized with the EGUN code for a cath- ode voltage Vb of 100 kV and a beam...emission suppression. Figure 2 is an EGUN drawing of the MIG configuration/ dimensions and electron trajectories. The design is flexible TABLE I. Predicted...and measured MIG parameters. EGUN prediction smooth cathode Measurement Voltage kV 100.0 100.0 Current A 8.0 8.0 0 1.40 1.40 vz /vz0 3.5% 4.6

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2010-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2011-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Aoki, Ichiro (Inventor); Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor)

2013-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2008-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Frequency analysis of DC tolerant current transformers

NASA Astrophysics Data System (ADS)

Mlejnek, P.; Kaspar, P.

2013-09-01

This article deals with wide frequency range behaviour of DC tolerant current transformers that are usually used in modern static energy meters. In this application current transformers must comply with European and International Standards in their accuracy and DC tolerance. Therefore, the linear DC tolerant current transformers and double core current transformers are used in this field. More details about the problems of these particular types of transformers can be found in our previous works. Although these transformers are designed mainly for power distribution network frequency (50/60 Hz), it can be interesting to understand their behaviour in wider frequency range. Based on this knowledge the new generations of energy meters with measuring quality of electric energy will be produced. This solution brings better measurement of consumption of nonlinear loads or measurement of non-sinusoidal voltage and current sources such as solar cells or fuel cells. The determination of actual power consumption in such energy meters is done using particular harmonics component of current and voltage. We measured the phase and ratio errors that are the most important parameters of current transformers, to characterize several samples of current transformers of both types.

80 A/cm2 electron beams from metal targets irradiated by KrCl and XeCl excimer lasers

NASA Astrophysics Data System (ADS)

Beloglazov, A.; Martino, M.; Nassisi, V.

1996-05-01

Due to the growing demand for high-current and long-duration electron-beam devices, laser electron sources were investigated in our laboratory. Experiments on electron-beam generation and propagation from aluminium and copper targets illuminated by XeCl (308 nm) and KrCl (222 nm) excimer lasers, were carried out under plasma ignition due to laser irradiation. This plasma supplied a spontaneous accelerating electric field of about 370 kV/m without an external accelerating voltage. By applying the modified one-dimensional Poisson equation, we computed the expected current and we also estimated the plasma concentration during the accelerating process. At 40 kV of accelerating voltage, an output current pulse of about 80 A/cm2 was detected from an Al target irradiated by the shorter wavelength laser.

A future, intense source of negative hydrogen ions

NASA Technical Reports Server (NTRS)

Siefken, Hugh; Stein, Charles

1994-01-01

By directly heating lithium hydride in a vacuum, up to 18 micro-A/sq cm of negative hydrogen has been obtained from the crystal lattice. The amount of ion current extracted and analyzed is closely related to the temperature of the sample and to the rate at which the temperature is changed. The ion current appears to be emission limited and saturates with extraction voltage. For a fixed extraction voltage, the ion current could be maximized by placing a grid between the sample surface and the extraction electrode. Electrons accompanying the negative ions were removed by a magnetic trap. A Wein velocity filter was designed and built to provide definitive mass analysis of the extracted ion species. This technique when applied to other alkali hydrides may produce even higher intensity beams possessing low values of emittance.

Fabrication and characterization of a pd nanowire-based glucose biofuel cell

NASA Astrophysics Data System (ADS)

Amoah, Kweku Obeng

The use of glucose as a source in biofuel cell technology has received a lot of attention in part due to the potential applications of such systems. In addition to the being a clean energy alternative, it provides a pathway for implantable microelectronic devices, such as pacemakers, to be powered by interstitial fluid and eliminate the need for batteries. Furthermore, using interstitial fluid as fuel sources will drastically reduce necessary invasive surgeries to replace batteries. Additionally, cost to such patients will be reduced while quality of life enhanced. The research presents a unique platform for harvesting energy from glucose. Using semiconductor cleanroom techniques, electrically conductive palladium nanowires are grown on anodized aluminum oxide templates using silicon and glass as supporting substrates. Photolithography is used to create two non-continuous gold windows and contact pads on the substrates. AAO templates are attached to the two gold windows and palladium nanowires are electrochemically grown on the AAO templates. Glucose oxidase and catalase are immobilized on the anode and laccase on the cathode. In the presence of glucose, electrons are released that result in the generation of voltage and current. The current-voltage behavior of the fuel cell, as well as electrochemical properties, is characterized using standard performance metrics. In 5 mM glucose solution with a neutral pH of 7.3, the open circuit voltage obtained was 335 mV and the short circuit current of 6 microA to yield a maximum power output of 1.38 microW.

"DIANA" - A New, Deep-Underground Accelerator Facility for Astrophysics Experiments

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

Leitner, M.; Leitner, D.; Lemut, A.

2009-05-28

The DIANA project (Dakota Ion Accelerators for Nuclear Astrophysics) is a collaboration between the University of Notre Dame, University of North Carolina, Western Michigan University, and Lawrence Berkeley National Laboratory to build a nuclear astrophysics accelerator facility 1.4 km below ground. DIANA is part of the US proposal DUSEL (Deep Underground Science and Engineering Laboratory) to establish a cross-disciplinary underground laboratory in the former gold mine of Homestake in South Dakota, USA. DIANA would consist of two high-current accelerators, a 30 to 400 kV variable, high-voltage platform, and a second, dynamitron accelerator with a voltage range of 350 kV tomore » 3 MV. As a unique feature, both accelerators are planned to be equipped with either high-current microwave ion sources or multi-charged ECR ion sources producing ions from protons to oxygen. Electrostatic quadrupole transport elements will be incorporated in the dynamitron high voltage column. Compared to current astrophysics facilities, DIANA could increase the available beam densities on target by magnitudes: up to 100 mA on the low energy accelerator and several mA on the high energy accelerator. An integral part of the DIANA project is the development of a high-density super-sonic gas-jet target which can handle these anticipated beam powers. The paper will explain the main components of the DIANA accelerators and their beam transport lines and will discuss related technical challenges.« less

First experiments with the negative ion source NIO1.

PubMed

Cavenago, M; Serianni, G; De Muri, M; Agostinetti, P; Antoni, V; Baltador, C; Barbisan, M; Baseggio, L; Bigi, M; Cervaro, V; Degli Agostini, F; Fagotti, E; Kulevoy, T; Ippolito, N; Laterza, B; Minarello, A; Maniero, M; Pasqualotto, R; Petrenko, S; Poggi, M; Ravarotto, D; Recchia, M; Sartori, E; Sattin, M; Sonato, P; Taccogna, F; Variale, V; Veltri, P; Zaniol, B; Zanotto, L; Zucchetti, S

2016-02-01

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW).

Plasma monitoring of the RLVIP-process with a Langmuir probe

NASA Astrophysics Data System (ADS)

Huber, D.; Hallbauer, A.; Pulker, H. K.

2005-09-01

The aim of this investigation was to study the characteristics of a reactive-low-voltage-high-current-ion-plating plasma and to correlate the observed plasma data with the properties of films deposited under such conditions. A Langmuir probe system (Smart Probe - Scientific Systems) was inserted into a Balzers BAP 800 ion plating plant above the e-gun evaporation source close to the insulated substrate holder. In this position during RLVIP deposition, plasma potential, floating potential, self-bias voltage, electron temperature, ion current density, and particle number density were measured and calculated, respectively. All measurements were performed in dependence of arc current (20-80A) and oxygen partial pressure (1 - 36 x 10-4mbar). With rising arc current the number of charged particles, the self-bias voltage between plasma and substrates as well as the energy of the condensing and bombarding species were increased. These data explain the increase of density, refractive index and mechanical stress of RLVIP-metal-oxide-layers, like Ta2O5 and Nb2O5, deposited with higher arc currents. An increase of gas pressure decreased the energy of the particles and therefore reduced slightly film density and refractive index. However, it improved chemistry and eliminated unwanted residual optical absorption and also decreased compressive mechanical film stress.

Current-voltage characteristics of a cathodic plasma contactor with discharge chamber for application in electrodynamic tether propulsion

NASA Astrophysics Data System (ADS)

Xie, Kan; Martinez, Rafael A.; Williams, John D.

2014-04-01

This paper focuses on the net electron-emission current as a function of bias voltage of a plasma source that is being used as the cathodic element in a bare electrodynamic tether system. An analysis is made that enables an understanding of the basic issues determining the current-voltage (C-V) behaviour. This is important for the efficiency of the electrodynamic tether and for low impedance performance without relying on the properties of space plasma for varying orbital altitudes, inclinations, day-night cycles or the position of the plasma contactor relative to the wake of the spacecraft. The cathodic plasma contactor considered has a cylindrical discharge chamber (10 cm in diameter and ˜11 cm in length) and is driven by a hollow cathode. Experiments and a 1D spherical model are both used to study the contactor's C-V curves. The experiments demonstrate how the cathodic contactor would emit electrons into space for anode voltages in the range of 25-40 V, discharge currents in the range of 1-2.5 A, and low xenon gas flows of 2-4 sccm. Plasma properties are measured and compared with (3 A) and without net electron emission. A study of the dependence of relevant parameters found that the C-V behaviour strongly depends on electron temperature, initial ion energy and ion emission current at the contactor exit. However, it depended only weakly on ambient plasma density. The error in the developed model compared with the experimental C-V curves is within 5% at low electron-emission currents (0-2 A). The external ionization processes and high ion production rate caused by the discharge chamber, which dominate the C-V behaviour at electron-emission currents over 2 A, are further highlighted and discussed.

Performance characterization of a solenoid-type gas valve for the H- magnetron source at FNAL

NASA Astrophysics Data System (ADS)

Sosa, A.; Bollinger, D. S.; Karns, P. R.

2017-08-01

The magnetron-style H- ion sources currently in operation at Fermilab use piezoelectric gas valves to function. This kind of gas valve is sensitive to small changes in ambient temperature, which affect the stability and performance of the ion source. This motivates the need to find an alternative way of feeding H2 gas into the source. A solenoid-type gas valve has been characterized in a dedicated off-line test stand to assess the feasibility of its use in the operational ion sources. H- ion beams have been extracted at 35 keV using this valve. In this study, the performance of the solenoid gas valve has been characterized measuring the beam current output of the magnetron source with respect to the voltage and pulse width of the signal applied to the gas valve.

Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology

NASA Astrophysics Data System (ADS)

Razzak, M. Abdur; Takamura, Shuichi; Uesugi, Yoshihiko; Ohno, Noriyasu

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

Multivariable polynomial fitting of controlled single-phase nonlinear load of input current total harmonic distortion

NASA Astrophysics Data System (ADS)

Sikora, Roman; Markiewicz, Przemysław; Pabjańczyk, Wiesława

2018-04-01

The power systems usually include a number of nonlinear receivers. Nonlinear receivers are the source of disturbances generated to the power system in the form of higher harmonics. The level of these disturbances describes the total harmonic distortion coefficient THD. Its value depends on many factors. One of them are the deformation and change in RMS value of supply voltage. A modern LED luminaire is a nonlinear receiver as well. The paper presents the results of the analysis of the influence of change in RMS value of supply voltage and the level of dimming of the tested luminaire on the value of the current THD. The analysis was made using a mathematical model based on multivariable polynomial fitting.

Gas composition sensing using carbon nanotube arrays

NASA Technical Reports Server (NTRS)

Li, Jing (Inventor); Meyyappan, Meyya (Inventor)

2008-01-01

A method and system for estimating one, two or more unknown components in a gas. A first array of spaced apart carbon nanotubes (''CNTs'') is connected to a variable pulse voltage source at a first end of at least one of the CNTs. A second end of the at least one CNT is provided with a relatively sharp tip and is located at a distance within a selected range of a constant voltage plate. A sequence of voltage pulses {V(t.sub.n)}.sub.n at times t=t.sub.n (n=1, . . . , N1; N1.gtoreq.3) is applied to the at least one CNT, and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of a curve I(t.sub.n) for current or a curve e(t.sub.n) for electric charge transported from the at least one CNT to the constant voltage plate. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas.

Analyzing Single-Event Gate Ruptures In Power MOSFET's

NASA Technical Reports Server (NTRS)

Zoutendyk, John A.

1993-01-01

Susceptibilities of power metal-oxide/semiconductor field-effect transistors (MOSFET's) to single-event gate ruptures analyzed by exposing devices to beams of energetic bromine ions while applying appropriate bias voltages to source, gate, and drain terminals and measuring current flowing into or out of each terminal.

A grid-connected single-phase photovoltaic micro inverter

NASA Astrophysics Data System (ADS)

Wen, X. Y.; Lin, P. J.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.

2017-11-01

In this paper, the topology of a single-phase grid-connected photovoltaic (PV) micro-inverter is proposed. The PV micro-inverter consists of DC-DC stage with high voltage gain boost and DC-AC conversion stage. In the first stage, we apply the active clamp circuit and two voltage multipliers to achieve soft switching technology and high voltage gain. In addition, the flower pollination algorithm (FPA) is employed for the maximum power point tracking (MPPT) in the PV module in this stage. The second stage cascades a H-bridge inverter and LCL filter. To feed high quality sinusoidal power into the grid, the software phase lock, outer voltage loop and inner current loop control method are adopted as the control strategy. The performance of the proposed topology is tested by Matlab/Simulink. A PV module with maximum power 300W and maximum power point voltage 40V is applied as the input source. The simulation results indicate that the proposed topology and the control strategy are feasible.

Adjustable, High Voltage Pulse Generator with Isolated Output for Plasma Processing

NASA Astrophysics Data System (ADS)

Ziemba, Timothy; Miller, Kenneth E.; Prager, James; Slobodov, Ilia

2015-09-01

Eagle Harbor Technologies (EHT), Inc. has developed a high voltage pulse generator with isolated output for etch, sputtering, and ion implantation applications within the materials science and semiconductor processing communities. The output parameters are independently user adjustable: output voltage (0 - 2.5 kV), pulse repetition frequency (0 - 100 kHz), and duty cycle (0 - 100%). The pulser can drive loads down to 200 Ω. Higher voltage pulsers have also been tested. The isolated output allows the pulse generator to be connected to loads that need to be biased. These pulser generators take advantage modern silicon carbide (SiC) MOSFETs. These new solid-state switches decrease the switching and conduction losses while allowing for higher switching frequency capabilities. This pulse generator has applications for RF plasma heating; inductive and arc plasma sources; magnetron driving; and generation of arbitrary pulses at high voltage, high current, and high pulse repetition frequency. This work was supported in part by a DOE SBIR.

Power-Quality Improvement in PFC Bridgeless SEPIC-Fed BLDC Motor Drive

NASA Astrophysics Data System (ADS)

Singh, Bhim; Bist, Vashist

2013-06-01

This article presents a design of a power factor correction (PFC)-based brushless DC (BLDC) motor drive. The speed control of BLDC motor is achieved by controlling the DC link voltage of the voltage source inverter (VSI) feeding BLDC motor using a single voltage sensor. A front-end bridgeless single-ended primary inductance converter (SEPIC) is used for DC link voltage control and PFC operation. A bridgeless SEPIC is designed to operate in discontinuous inductor current mode (DICM) thus utilizing a simple control scheme of voltage follower. An electronic commutation of BLDC motor is used for VSI to operate in a low-frequency operation for reduced switching losses in the VSI. Moreover, a bridgeless topology offers less conduction losses due to absence of diode bridge rectifier for further increasing the efficiency. The proposed BLDC motor drive is designed to operate over a wide range of speed control with an improved power-quality at the AC mains under the recommended international power-quality standards such as IEC 61000-3-2.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

1997-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2002-01-01

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with seperate DC sources

DOEpatents

Peng, Fang Zheng; Lai, Jih-Sheng

2001-04-03

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Multilevel cascade voltage source inverter with separate DC sources

DOEpatents

Peng, F.Z.; Lai, J.S.

1997-06-24

A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations. 15 figs.

Real power regulation design for multi-terminal VSC-HVDC systems

NASA Astrophysics Data System (ADS)

Li, Guo-Jie; Ruan, Si-Ye; Lie, Tek Tjing

2013-06-01

A multi-terminal voltage-source-converter (VSC) based high voltage direct current (HVDC) system is concerned for its flexibility and reliability. In this study, a control strategy for multiple VSCs is proposed to auto-share the real power variation without changing control mode, which is based on "dc voltage droop" power regulation functions. With the proposed power regulation design, the multiple VSCs automatically share the real power change and the VSC-HVDC system is stable even under loss of any one converter while there is no overloading for any individual converter. Simulation results show that it is effective to balance real power for power disturbance and thus improves operation reliability for the multi-terminal VSC-HVDC system by the proposed control strategy.

Demonstration of a High Open-Circuit Voltage GaN Betavoltaic Microbattery

NASA Astrophysics Data System (ADS)

Cheng, Zai-Jun; San, Hai-Sheng; Chen, Xu-Yuan; Liu, Bo; Feng, Zhi-Hong

2011-07-01

A high open-circuit voltage betavoltaic microbattery based on a GaN p-i-n diode is demonstrated. Under the irradiation of a 4×4 mm2 planar solid 63Ni source with an activity of 2 mCi, the open-circuit voltage Voc of the fabricated single 2×2mm2 cell reaches as high as 1.62 V, the short-circuit current density Jsc is measured to be 16nA/cm2. The microbattery has a fill factor of 55%, and the energy conversion efficiency of beta radiation into electricity reaches to 1.13%. The results suggest that GaN is a highly promising potential candidate for long-life betavoltaic microbatteries used as power supplies for microelectromechanical system devices.

LOW VOLTAGE 14 Mev NEUTRON SOURCE

DOEpatents

Little, R.N. Jr.; Graves, E.R.

1959-09-29

An apparatus yielding high-energy neutrons at the rate of 10/sup 8/ or more per second by the D,T or D,D reactions is described. The deuterium gas filling is ionized by electrons emitted from a filament, and the resulting ions are focused into a beam and accelerated against a fixed target. The apparatus is built in accordance with the relationship V/sub s/ = A--B log pd, where V/sub s/ is the sparking voltage, p the gas pressure, and d the gap length between the high voltage electrodes. Typical parameters to obtain the high neutron yields are 55 to 80 kv, 0.5 to 7.0 ma beam current, 5 to 12 microns D/sub 2/, and a gap length of 1 centimeter.

Research on resistance characteristics of YBCO tape under short-time DC large current impact

NASA Astrophysics Data System (ADS)

Zhang, Zhifeng; Yang, Jiabin; Qiu, Qingquan; Zhang, Guomin; Lin, Liangzhen

2017-06-01

Research of the resistance characteristics of YBCO tape under short-time DC large current impact is the foundation of the developing DC superconducting fault current limiter (SFCL) for voltage source converter-based high voltage direct current system (VSC-HVDC), which is one of the valid approaches to solve the problems of renewable energy integration. SFCL can limit DC short-circuit and enhance the interrupting capabilities of DC circuit breakers. In this paper, under short-time DC large current impacts, the resistance features of naked tape of YBCO tape are studied to find the resistance - temperature change rule and the maximum impact current. The influence of insulation for the resistance - temperature characteristics of YBCO tape is studied by comparison tests with naked tape and insulating tape in 77 K. The influence of operating temperature on the tape is also studied under subcooled liquid nitrogen condition. For the current impact security of YBCO tape, the critical current degradation and top temperature are analyzed and worked as judgment standards. The testing results is helpful for in developing SFCL in VSC-HVDC.

Electron stripping processes of H⁻ ion beam in the 80 kV high voltage extraction column and low energy beam transport line at LANSCE.

PubMed

Draganic, I N

2016-02-01

Basic vacuum calculations were performed for various operating conditions of the Los Alamos National Neutron Science H(-) Cockcroft-Walton (CW) injector and the Ion Source Test Stand (ISTS). The vacuum pressure was estimated for both the CW and ISTS at five different points: (1) inside the H(-) ion source, (2) in front of the Pierce electrode, (3) at the extraction electrode, (4) at the column electrode, and (5) at the ground electrode. A static vacuum analysis of residual gases and the working hydrogen gas was completed for the normal ion source working regime. Gas density and partial pressure were estimated for the injected hydrogen gas. The attenuation of H(-) beam current and generation of electron current in the high voltage acceleration columns and low energy beam transport lines were calculated. The interaction of H(-) ions on molecular hydrogen (H2) is discussed as a dominant collision process in describing electron stripping rates. These results are used to estimate the observed increase in the ratio of electrons to H(-) ion beam in the ISTS beam transport line.

Single Crystal Diamond Needle as Point Electron Source.

PubMed

Kleshch, Victor I; Purcell, Stephen T; Obraztsov, Alexander N

2016-10-12

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Single Crystal Diamond Needle as Point Electron Source

NASA Astrophysics Data System (ADS)

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-10-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

MOSFET-based high voltage short pulse generator for ultrasonic transducer excitation

NASA Astrophysics Data System (ADS)

Hidayat, Darmawan; Setianto, Syafei, Nendi Suhendi; Wibawa, Bambang Mukti

2018-02-01

This paper presents the generation of a high-voltage short pulse for the excitation of high frequency ultrasonic transducers. This is highly required in the purpose of various ultrasonic-based evaluations, particularly when high resolution measurement is necessary. A high voltage (+760 V) DC voltage source was pulsated by an ultrafast switching MOSFET which was driven by a pulse generator circuit consisting of an astable multivibrator, a one-shot multivibrator with Schmitt trigger input and a high current MOSFET driver. The generated pulses excited a 200-kHz and a 1-MHz ultrasonic transducers and tested in the transmission mode propagation to evaluate the performances of the generated pulse. The test results showed the generator were able to produce negative spike pulses up to -760 V voltage with the shortest time-width of 107.1 nanosecond. The transmission-received ultrasonic waves show frequency oscillation at 200 and 961 kHz and their amplitudes varied with the voltage of excitation pulse. These results conclude that the developed pulse generator is applicable to excite transducer for the generation of high frequency ultrasonic waves.

Precision Voltage Referencing Techniques in MOS Technology.

NASA Astrophysics Data System (ADS)

Song, Bang-Sup

With the increasing complexity of functions on a single MOS chip, precision analog cicuits implemented in the same technology are in great demand so as to be integrated together with digital circuits. The future development of MOS data acquisition systems will require precision on-chip MOS voltage references. This dissertation will probe two most promising configurations of on-chip voltage references both in NMOS and CMOS technologies. In NMOS, an ion-implantation effect on the temperature behavior of MOS devices is investigated to identify the fundamental limiting factors of a threshold voltage difference as an NMOS voltage source. For this kind of voltage reference, the temperature stability on the order of 20ppm/(DEGREES)C is achievable with a shallow single-threshold implant and a low-current, high-body bias operation. In CMOS, a monolithic prototype bandgap reference is designed, fabricated and tested which embodies a curvature compensation and exhibits a minimized sensitivity to the process parameter variation. Experimental results imply that an average temperature stability on the order of 10ppm/(DEGREES)C with a production spread of less than 10ppm/(DEGREES)C feasible over the commercial temperature range.

Source of Sustained Voltage Difference between the Xylem of a Potted Ficus benjamina Tree and Its Soil

PubMed Central

Love, Christopher J.; Zhang, Shuguang; Mershin, Andreas

2008-01-01

It has long been known that there is a sustained electrical potential (voltage) difference between the xylem of many plants and their surrounding soil, but the mechanism behind this voltage has remained controversial. After eliminating any extraneous capacitive or inductive couplings and ground-mediated electric current flows, we have measured sustained differences of 50–200 mV between the xylem region of a Faraday-caged, intact, potted Ficus benjamina tree and its soil, as well as between its cut branches and soils and ionic solutions standardized to various pH values. Using identical platinum electrodes, no correlation between the voltage and time of day, illumination, sap flow, electrode elevation, or ionic composition of soil was found, suggesting no direct connection to simple dissimilar-metal redox reactions or transpirational activity. Instead, a clear relationship between the voltage polarity and magnitude and the pH difference between xylem and soil was observed. We attribute these sustained voltages to a biological concentration cell likely set up by the homeostatic mechanisms of the tree. Potential applications of this finding are briefly explored. PMID:18698415

A microwave field-driven transistor-like skyrmionic device with the microwave current-assisted skyrmion creation

NASA Astrophysics Data System (ADS)

Xia, Jing; Huang, Yangqi; Zhang, Xichao; Kang, Wang; Zheng, Chentian; Liu, Xiaoxi; Zhao, Weisheng; Zhou, Yan

2017-10-01

Magnetic skyrmion is a topologically protected domain-wall structure at nanoscale, which could serve as a basic building block for advanced spintronic devices. Here, we propose a microwave field-driven skyrmionic device with the transistor-like function, where the motion of a skyrmion in a voltage-gated ferromagnetic nanotrack is studied by micromagnetic simulations. It is demonstrated that the microwave field can drive the motion of a skyrmion by exciting the propagating spin waves, and the skyrmion motion can be governed by a gate voltage. We also investigate the microwave current-assisted creation of a skyrmion to facilitate the operation of the transistor-like skyrmionic device on the source terminal. It is found that the microwave current with an appropriate frequency can reduce the threshold current density required for the creation of a skyrmion from the ferromagnetic background. The proposed transistor-like skyrmionic device operated with the microwave field and current could be useful for building future skyrmion-based circuits.

Development of a helicon ion source: Simulations and preliminary experiments.

PubMed

Afsharmanesh, M; Habibi, M

2018-03-01

In the present context, the extraction system of a helicon ion source has been simulated and constructed. Results of the ion source commissioning at up to 20 kV are presented as well as simulations of an ion beam extraction system. Argon current of more than 200 μA at up to 20 kV is extracted and is characterized with a Faraday cup and beam profile monitoring grid. By changing different ion source parameters such as RF power, extraction voltage, and working pressure, an ion beam with current distribution exhibiting a central core has been detected. Jump transition of ion beam current emerges at the RF power near to 700 W, which reveals that the helicon mode excitation has reached this power. Furthermore, measuring the emission line intensity of Ar ii at 434.8 nm is the other way we have used for demonstrating the mode transition from inductively coupled plasma to helicon. Due to asymmetrical longitudinal power absorption of a half-helix helicon antenna, it is used for the ion source development. The modeling of the plasma part of the ion source has been carried out using a code, HELIC. Simulations are carried out by taking into account a Gaussian radial plasma density profile and for plasma densities in range of 10 18 -10 19 m -3 . Power absorption spectrum and the excited helicon mode number are obtained. Longitudinal RF power absorption for two different antenna positions is compared. Our results indicate that positioning the antenna near to the plasma electrode is desirable for the ion beam extraction. The simulation of the extraction system was performed with the ion optical code IBSimu, making it the first helicon ion source extraction designed with the code. Ion beam emittance and Twiss parameters of the ellipse emittance are calculated at different iterations and mesh sizes, and the best values of the mesh size and iteration number have been obtained for the calculations. The simulated ion beam extraction system has been evaluated using optimized parameters such as the gap distance between electrodes, electrodes aperture, and extraction voltage. The gap distance, ground electrode aperture, and extraction voltage have been changed between 3 and 9 mm, 2-6.5 mm, and 10-35 kV in the simulations, respectively.

Development of a helicon ion source: Simulations and preliminary experiments

NASA Astrophysics Data System (ADS)

Afsharmanesh, M.; Habibi, M.

2018-03-01

In the present context, the extraction system of a helicon ion source has been simulated and constructed. Results of the ion source commissioning at up to 20 kV are presented as well as simulations of an ion beam extraction system. Argon current of more than 200 μA at up to 20 kV is extracted and is characterized with a Faraday cup and beam profile monitoring grid. By changing different ion source parameters such as RF power, extraction voltage, and working pressure, an ion beam with current distribution exhibiting a central core has been detected. Jump transition of ion beam current emerges at the RF power near to 700 W, which reveals that the helicon mode excitation has reached this power. Furthermore, measuring the emission line intensity of Ar ii at 434.8 nm is the other way we have used for demonstrating the mode transition from inductively coupled plasma to helicon. Due to asymmetrical longitudinal power absorption of a half-helix helicon antenna, it is used for the ion source development. The modeling of the plasma part of the ion source has been carried out using a code, HELIC. Simulations are carried out by taking into account a Gaussian radial plasma density profile and for plasma densities in range of 1018-1019 m-3. Power absorption spectrum and the excited helicon mode number are obtained. Longitudinal RF power absorption for two different antenna positions is compared. Our results indicate that positioning the antenna near to the plasma electrode is desirable for the ion beam extraction. The simulation of the extraction system was performed with the ion optical code IBSimu, making it the first helicon ion source extraction designed with the code. Ion beam emittance and Twiss parameters of the ellipse emittance are calculated at different iterations and mesh sizes, and the best values of the mesh size and iteration number have been obtained for the calculations. The simulated ion beam extraction system has been evaluated using optimized parameters such as the gap distance between electrodes, electrodes aperture, and extraction voltage. The gap distance, ground electrode aperture, and extraction voltage have been changed between 3 and 9 mm, 2-6.5 mm, and 10-35 kV in the simulations, respectively.

SU-F-T-554: Dark Current Effect On CyberKnife Beam Dosimetry

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

Kim, H; Chang, A

Purpose: All RF linear accelerators produce dark current to varying degrees when an accelerating voltage and RF input is applied in the absence of electron gun injection. This study is to evaluate how dark current from the linear accelerator of CyberKnife affect the dose in the reference dosimetry. Methods: The G4 CyberKnife system with 6MV photon beam was used in this study. Using the ion chamber and the diode detector, the dose was measured in water with varying time delay between acquiring charges and staring beam-on after applying high-voltage into the linear accelerator. The dose was measured after the timemore » delay with over the range of 0 to 120 seconds in the accelerating high-voltage mode without beam-on, applying 0, 10, 50, 100, and 200 MUs. For the measurements, the collimator of 60 mm was used and the detectors were placed at the depths of 10 cm with the source-to-surface distance of 80 cm. Results: The dark current was constant over time regardless of MU. The dose due to the dark current increased over time linearly with the R-squared value of 0.9983 up to 4.4 cGy for the time 120 seconds. In the dose rate setting of 720 MU/min, the relative dose when applying the accelerating voltage without beam-on was increased over time up to 0.6% but it was less than the leakage radiation resulted from the accelerated head. As the reference dosimetry condition, when 100 MU was delivered after 10 seconds time delay, the relative dose increased by 0.7% but 6.7% for the low MU (10 MU). Conclusion: In the dosimetry using CyberKnife system, the constant dark current affected to the dose. Although the time delay in the accelerating high-voltage mode without beam-on is within 10 seconds, the dose less than 100 cGy can be overestimated more than 1%.« less

A wireless wearable surface functional electrical stimulator

NASA Astrophysics Data System (ADS)

Wang, Hai-Peng; Guo, Ai-Wen; Zhou, Yu-Xuan; Xia, Yang; Huang, Jia; Xu, Chong-Yao; Huang, Zong-Hao; Lü, Xiao-Ying; Wang, Zhi-Gong

2017-09-01

In this paper, a wireless wearable functional electrical stimulator controlled by Android phone with real-time-varying stimulation parameters for multichannel surface functional electrical stimulation application has been developed. It can help post-stroke patients using more conveniently. This study focuses on the prototype design, including the specific wristband concept, circuits and stimulation pulse-generation algorithm. A novel stimulator circuit with a driving stage using a complementary current source technique is proposed to achieve a high-voltage compliance, a large output impedance and an accurate linear voltage-to-current conversion. The size of the prototype has been significantly decreased to 17 × 7.5 × 1 cm3. The performance of the prototype has been tested with a loaded resistor and wrist extension/flexion movement of three hemiplegic patients. According to the experiments, the stimulator can generate four-channel charge-balanced biphasic stimulation with a voltage amplitude up to 60 V, and the pulse frequency and width can be adjusted in real time with a range of 100-600 μs and 20-80 Hz, respectively.

Adaptive Harmonic Detection Control of Grid Interfaced Solar Photovoltaic Energy System with Power Quality Improvement

NASA Astrophysics Data System (ADS)

Singh, B.; Goel, S.

2015-03-01

This paper presents a grid interfaced solar photovoltaic (SPV) energy system with a novel adaptive harmonic detection control for power quality improvement at ac mains under balanced as well as unbalanced and distorted supply conditions. The SPV energy system is capable of compensation of linear and nonlinear loads with the objectives of load balancing, harmonics elimination, power factor correction and terminal voltage regulation. The proposed control increases the utilization of PV infrastructure and brings down its effective cost due to its other benefits. The adaptive harmonic detection control algorithm is used to detect the fundamental active power component of load currents which are subsequently used for reference source currents estimation. An instantaneous symmetrical component theory is used to obtain instantaneous positive sequence point of common coupling (PCC) voltages which are used to derive inphase and quadrature phase voltage templates. The proposed grid interfaced PV energy system is modelled and simulated in MATLAB Simulink and its performance is verified under various operating conditions.

Modelling a single phase voltage controlled rectifier using Laplace transforms

NASA Technical Reports Server (NTRS)

Kraft, L. Alan; Kankam, M. David

1992-01-01

The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

Frequency pulling in a low-voltage medium-power gyrotron

NASA Astrophysics Data System (ADS)

Luo, Li; Du, Chao-Hai; Huang, Ming-Guang; Liu, Pu-Kun

2018-04-01

Many recent biomedical applications use medium-power frequency-tunable terahertz (THz) sources, such as sensitivity-enhanced nuclear magnetic resonance, THz imaging, and biomedical treatment. As a promising candidate, a low-voltage gyrotron can generate watt-level, continuous THz-wave radiation. In particular, the frequency-pulling effect in a gyrotron, namely, the effect of the electron beam parameters on the oscillation frequency, can be used to tune the operating frequency. Most previous investigations used complicated and time-consuming gyrotron nonlinear theory to study the influence of many beam parameters on the interaction performance. While gyrotron linear theory investigation demonstrates the advantages of rapidly and clearly revealing the physical influence of individual key beam parameters on the overall system performance, this paper demonstrates systematically the use of gyrotron linear theory to study the frequency-pulling effect in a low-voltage gyrotron with either a Gaussian or a sinusoidal axial-field profile. Furthermore, simulations of a gyrotron operating in the first axial mode are carried out in the framework of nonlinear theory as a contrast. Close agreement is achieved between the two theories. Besides, some interesting results are obtained. In a low-current sinusoidal-profile cavity, the ranges of frequency variation for different axial modes are isolated from each other, and the frequency tuning bandwidth for each axial mode increases by increasing either the beam voltage or pitch factor. Lowering the voltage, the total tuning ranges are squeezed and become concentrated. However, the isolated frequency regions of each axial mode cannot be linked up unless the beam current is increased, meaning that higher current operation is the key to achieving a wider and continuous tuning frequency range. The results presented in this paper can provide a reference for designing a broadband low-voltage gyrotron.

Transformer coupling for transmitting direct current through a barrier

DOEpatents

Brown, Ralph L.; Guilford, Richard P.; Stichman, John H.

1988-01-01

The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level.

Transformer coupling for transmitting direct current through a barrier

DOEpatents

Brown, R.L.; Guilford, R.P.; Stichman, J.H.

1987-06-29

The transmission system for transmitting direct current from an energy source on one side of an electrical and mechanical barrier to a load on the other side of the barrier utilizes a transformer comprising a primary core on one side of the transformer and a secondary core on the other side of the transformer. The cores are magnetically coupled selectively by moving a magnetic ferrite coupler in and out of alignment with the poles of the cores. The direct current from the energy source is converted to a time varying current by an oscillating circuit, which oscillating circuit is optically coupled to a secondary winding on the secondary core to interrupt oscillations upon the voltage in the secondary winding exceeding a preselected level. 4 figs.

Ciguatoxins: Cyclic Polyether Modulators of Voltage-gated Iion Channel Function

PubMed Central

Nicholson, Graham M.; Lewis, Richard J.

2006-01-01

Ciguatoxins are cyclic polyether toxins, derived from marine dinoflagellates, which are responsible for the symptoms of ciguatera poisoning. Ingestion of tropical and subtropical fin fish contaminated by ciguatoxins results in an illness characterised by neurological, cardiovascular and gastrointestinal disorders. The pharmacology of ciguatoxins is characterised by their ability to cause persistent activation of voltage-gated sodium channels, to increase neuronal excitability and neurotransmitter release, to impair synaptic vesicle recycling, and to cause cell swelling. It is these effects, in combination with an action to block voltage-gated potassium channels at high doses, which are believed to underlie the complex of symptoms associated with ciguatera. This review examines the sources, structures and pharmacology of ciguatoxins. In particular, attention is placed on their cellular modes of actions to modulate voltage-gated ion channels and other Na+-dependent mechanisms in numerous cell types and to current approaches for detection and treatment of ciguatera.

TiO2 dye sensitized solar cell (DSSC): linear relationship of maximum power point and anthocyanin concentration

NASA Astrophysics Data System (ADS)

Ahmadian, Radin

2010-09-01

This study investigated the relationship of anthocyanin concentration from different organic fruit species and output voltage and current in a TiO2 dye-sensitized solar cell (DSSC) and hypothesized that fruits with greater anthocyanin concentration produce higher maximum power point (MPP) which would lead to higher current and voltage. Anthocyanin dye solution was made with crushing of a group of fresh fruits with different anthocyanin content in 2 mL of de-ionized water and filtration. Using these test fruit dyes, multiple DSSCs were assembled such that light enters through the TiO2 side of the cell. The full current-voltage (I-V) co-variations were measured using a 500 Ω potentiometer as a variable load. Point-by point current and voltage data pairs were measured at various incremental resistance values. The maximum power point (MPP) generated by the solar cell was defined as a dependent variable and the anthocyanin concentration in the fruit used in the DSSC as the independent variable. A regression model was used to investigate the linear relationship between study variables. Regression analysis showed a significant linear relationship between MPP and anthocyanin concentration with a p-value of 0.007. Fruits like blueberry and black raspberry with the highest anthocyanin content generated higher MPP. In a DSSC, a linear model may predict MPP based on the anthocyanin concentration. This model is the first step to find organic anthocyanin sources in the nature with the highest dye concentration to generate energy.

Improved Control of Charging Voltage for Li-Ion Battery

NASA Technical Reports Server (NTRS)

Timmerman, Paul; Bugga, Ratnakumar

2006-01-01

The protocol for charging a lithium-ion battery would be modified, according to a proposal, to compensate for the internal voltage drop (charging current internal resistance of the battery). The essence of the modification is to provide for measurement of the internal voltage drop and to increase the terminal-voltage setting by the amount of the internal voltage drop. Ordinarily, a lithium-ion battery is charged at constant current until its terminal voltage attains a set value equal to the nominal full-charge potential. The set value is chosen carefully so as not to exceed the lithium-plating potential, because plated lithium in metallic form constitutes a hazard. When the battery is charged at low temperature, the internal voltage drop is considerable because the electrical conductivity of the battery electrolyte is low at low temperature. Charging the battery at high current at any temperature also gives rise to a high internal voltage drop. In some cases, the internal voltage drop can be as high as 1 volt per cell. Because the voltage available for charging is less than the terminal voltage by the amount of the internal voltage drop, the battery is not fully charged (see figure), even when the terminal voltage reaches the set value. In the modified protocol, the charging current would be periodically interrupted so that the zero-current battery-terminal voltage indicative of the state of charge could be measured. The terminal voltage would also be measured at full charging current. The difference between the full-current and zero-current voltages would equal the internal voltage drop. The set value of terminal voltage would then be increased beyond the nominal full-charge potential by the amount of the internal voltage drop. This adjustment would be performed repeatedly, in real time, so that the voltage setting would track variations in the internal voltage drop to afford full charge without risk of lithium plating. If the charging current and voltage settings were controlled by a computer, then this method of charge control could readily be implemented in software.

Prospectively ECG-triggered high-pitch coronary angiography with third-generation dual-source CT at 70 kVp tube voltage: feasibility, image quality, radiation dose, and effect of iterative reconstruction.

PubMed

Hell, Michaela M; Bittner, Daniel; Schuhbaeck, Annika; Muschiol, Gerd; Brand, Michael; Lell, Michael; Uder, Michael; Achenbach, Stephan; Marwan, Mohamed

2014-01-01

Low tube voltage reduces radiation exposure in coronary CT angiography (CTA). Using 70 kVp tube potential has so far not been possible because CT systems were unable to provide sufficiently high tube current with low voltage. We evaluated feasibility, image quality (IQ), and radiation dose of coronary CTA using a third-generation dual-source CT system capable of producing 450 mAs tube current at 70 kVp tube voltage. Coronary CTA was performed in 26 consecutive patients with suspected coronary artery disease, selected for body weight <100 kg and heart rate <60 beats/min. High-pitch spiral acquisition was used. Filtered back projection (FBP) and iterative reconstruction (IR) algorithms were applied. IQ was assessed using a 4-point rating scale (1 = excellent, 4 = nondiagnostic) and objective parameters. Mean age was 62 ± 9 years (46% males; mean body mass index, 27.7 ± 3.8 kg/m(2); mean heart rate, 54 ± 5 beats/min). Mean dose-length product was 20.6 ± 1.9 mGy × cm; mean estimated effective radiation dose was 0.3 ± 0.03 mSv. Diagnostic IQ was found in 365 of 367 (FBP) and 366 of 367 (IR) segments (P nonsignificant). IQ was rated "excellent" in 53% (FBP) and 86% (IR) segments (P = .001) and "nondiagnostic" in 2 (FBP) and 1 segment (IR) (P nonsignificant). Mean IQ score was lesser in FBP vs IR (1.5 ± 0.4 vs 1.1 ± 0.2; P < .001). Image noise was lower in IR vs FBP (60 ± 10 HU vs 74 ± 8 HU; P < .001). In patients <100 kg and with a regular heart rate <60 beats/min, third-generation dual-source CT using high-pitch spiral acquisition and 70 kVp tube voltage is feasible and provides both robust IQ and very low radiation exposure. Copyright © 2014 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

High sensitivity field asymmetric ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

2017-03-01

A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

Comment on 'Power loss in open cavity diodes and a modified Child-Langmuir law' [Phys. Plasmas 12, 093102 (2005)

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

Swanekamp, S. B.; Ottinger, P. F.

In this Comment, it is shown that no modification of the Child-Langmuir law [Phys. Rev.32, 492 (1911); Phys. Rev. 2, 450 (1913)] is necessary to treat the space-charge-limited flow from a diode with an open boundary as reported in Phys. Plasmas 12, 093102 (2005). The open boundary condition in their simulations can be represented by a voltage source and a resistor whose value is the vacuum-wave impedance of the opening. The diode can be represented as a variable resistor whose value depends on the voltage drop across the diode (as measured by the line integral of E across the diodemore » gap). This is a simple voltage-divider circuit whose analysis shows that the real diode voltage drops as the vacuum-wave impedance increases. Furthermore, it is shown that in equilibrium, the voltage drop between the anode and cathode is independent of the path chosen for the line integral of the electric field so that E=-{nabla}{phi} is valid. In this case, the equations of electrostatics are applicable. This clearly demonstrates that the electric field is electrostatic and static fields DO NOT RADIATE. It is shown that the diode voltage drops as the vacuum wave impedance increases and the current drops according to the Child-Langmuir law. Therefore, the observed drop in circuit current can be explained by a real drop in voltage across the diode and not an effective drop as claimed by the authors.« less

Manifestation of counteracting photovoltaic effect on IV characteristics in multi-junction solar cells

NASA Astrophysics Data System (ADS)

Mintairov, M. A.; Evstropov, V. V.; Mintairov, S. A.; Shvarts, M. Z.; Kozhukhovskaia, S. A.; Kalyuzhnyy, N. A.

2017-11-01

The existence within monolithic double- and triple-junction solar cells of a photoelectric source, which counteracts the basic photovoltaic p-n junctions, is proved. The paper presents a detailed analysis of the shape of the light IV-characteristics, as well as the dependence Voc-Jsc (open circuit voltage - short-circuit current). It is established that the counteracting source is tunnel p+-n+ junction. The photoelectric characteristics of samples with different tunnel diode peak current values were investigated, including the case of a zero value. When the tunnel p+-n+ junction is photoactive, the Voc-Jsc dependence has a dropping part, including a sharp jump. This undesirable effect decreases with increasing peak current.

Theory of the Bloch oscillating transistor

NASA Astrophysics Data System (ADS)

Hassel, J.; Seppä, H.

2005-01-01

The Bloch oscillating transistor (BOT) is a device in which single electron current through a normal tunnel junction enhances Cooper pair current in a mesoscopic Josephson junction, leading to signal amplification. In this article we develop a theory in which the BOT dynamics is described as a two-level system. The theory is used to predict current-voltage characteristics and small-signal response. The transition from stable operation into the hysteretic regime is studied. By identifying the two-level switching noise as the main source of fluctuations, the expressions for equivalent noise sources and the noise temperature are derived. The validity of the model is tested by comparing the results with simulations and experiments.

Studies of extraction and transport system for highly charged ion beam of 18 GHz superconducting electron cyclotron resonance ion source at Research Center for Nuclear Physics

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

Yorita, T., E-mail: yorita@rcnp.osaka-u.ac.jp; Hatanaka, K.; Fukuda, M.

2014-02-15

An 18 GHz superconducting electron cyclotron resonance ion source is installed to increase beam currents and to extend the variety of ions especially for highly charged heavy ions which can be accelerated by cyclotrons of Research Center for Nuclear Physics (RCNP), Osaka University. The beam production developments of several ions from B to Xe have been already done [T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 79, 02A311 (2008) and T. Yorita, K. Hatanaka, M. Fukuda, M. Kibayashi, S. Morinobu, H.Okamura, and A. Tamii, Rev. Sci. Instrum. 81, 02A332 (2010)] andmore » the further studies for those beam extraction and its transport have been done in order to increase the beam current more. The plasma electrode, extraction electrode, and einzel lens are modified. Especially extraction electrode can be applied minus voltage for the beam extraction and it works well to improve the extracted beam current. The extraction voltage dependences of transmission and emittance also have been studied for beam current improvement which is injected into azimuthally varying field cyclotron at RCNP.« less

Improvement in the performance of graphene nanoribbon p-i-n tunneling field effect transistors by applying lightly doped profile on drain region

NASA Astrophysics Data System (ADS)

Naderi, Ali

2017-12-01

In this paper, an efficient structure with lightly doped drain region is proposed for p-i-n graphene nanoribbon field effect transistors (LD-PIN-GNRFET). Self-consistent solution of Poisson and Schrödinger equation within Nonequilibrium Green’s function (NEGF) formalism has been employed to simulate the quantum transport of the devices. In proposed structure, source region is doped by constant doping density, channel is an intrinsic GNR, and drain region contains two parts with lightly and heavily doped doping distributions. The important challenge in tunneling devices is obtaining higher current ratio. Our simulations demonstrate that LD-PIN-GNRFET is a steep slope device which not only reduces the leakage current and current ratio but also enhances delay, power delay product, and cutoff frequency in comparison with conventional PIN GNRFETs with uniform distribution of impurity and with linear doping profile in drain region. Also, the device is able to operate in higher drain-source voltages due to the effectively reduced electric field at drain side. Briefly, the proposed structure can be considered as a more reliable device for low standby-power logic applications operating at higher voltages and upper cutoff frequencies.

Power inversion design for ocean wave energy harvesting

NASA Astrophysics Data System (ADS)

Talebani, Anwar N.

The needs for energy sources are increasing day by day because of several factors, such as oil depletion, and global climate change due to the higher level of CO2, so the exploration of various renewable energy sources is very promising area of study. The available ocean waves can be utilized as free source of energy as the water covers 70% of the earth surface. This thesis presents the ocean wave energy as a source of renewable energy. By addressing the problem of designing efficient power electronics system to deliver 5 KW from the induction generator to the grid with less possible losses and harmonics as possible and to control current fed to the grid to successfully harvest ocean wave energy. We design an AC-DC full bridge rectifier converter, and a DC-DC boost converter to harvest wave energy from AC to regulated DC. In order to increase the design efficiency, we need to increase the power factor from (0.5-0.6) to 1. This is accomplished by designing the boost converter with power factor correction in continues mode with RC circuit as an input to the boost converter power factor correction. This design results in a phase shift between the input current and voltage of the full bridge rectifier to generate a small reactive power. The reactive power is injected to the induction generator to maintain its functionality by generating a magnetic field in its stator. Next, we design a single-phase pulse width modulator full bridge voltage source DC-AC grid-tied mode inverter to harvest regulated DC wave energy to AC. The designed inverter is modulated by inner current loop, to control current injected to the grid with minimal filter component to maintain power quality at the grid. The simulation results show that our design successfully control the current level fed to the grid. It is noteworthy that the simulated efficiency is higher than the calculated one since we used an ideal switch in the simulated circuit.

Miniature x-ray source

DOEpatents

Trebes, James E.; Bell, Perry M.; Robinson, Ronald B.

2000-01-01

A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode, a getter for maintaining high vacuum, a connector for initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is fabricated from highly x-ray transparent materials, such as sapphire, diamond, or boron nitride.

Paramagnetic defects and charge trapping behavior of ZrO2 films deposited on germanium by plasma-enhanced CVD

NASA Astrophysics Data System (ADS)

Mahata, C.; Bera, M. K.; Bose, P. K.; Maiti, C. K.

2009-02-01

Internal photoemission and magnetic resonance studies have been performed to investigate the charge trapping behavior and chemical nature of defects in ultrathin (~14 nm) high-k ZrO2 dielectric films deposited on p-Ge (1 0 0) substrates at low temperature (<200 °C) by plasma-enhanced chemical vapor deposition (PECVD) in a microwave (700 W, 2.45 GHz) plasma at a pressure of ~65 Pa. Both the band and defect-related electron states have been characterized using electron paramagnetic resonance, internal photoemission, capacitance-voltage and current-voltage measurements under UV illumination. Capacitance-voltage and photocurrent-voltage measurements were used to determine the centroid of oxide charge within the high-k gate stack. The observed shifts in photocurrent response of the Al/ZrO2/GeO2/p-Ge metal-insulator-semiconductor (MIS) capacitors indicate the location of the centroids to be within the ZrO2 dielectric near to the gate electrode. Moreover, the measured flat band voltage and photocurrent shifts also indicate a large density of traps in the dielectric. The impact of plasma nitridation on the interfacial quality of the oxides has been investigated. Different N sources, such as NO and NH3, have been used for nitrogen engineering. Oxynitride samples show a lower defect density and trapping over the non-nitrided samples. The charge trapping and detrapping properties of MIS capacitors under stressing in constant current and voltage modes have been investigated in detail.

High temperature charge amplifier for geothermal applications

DOEpatents

Lindblom, Scott C.; Maldonado, Frank J.; Henfling, Joseph A.

2015-12-08

An amplifier circuit in a multi-chip module includes a charge to voltage converter circuit, a voltage amplifier a low pass filter and a voltage to current converter. The charge to voltage converter receives a signal representing an electrical charge and generates a voltage signal proportional to the input signal. The voltage amplifier receives the voltage signal from the charge to voltage converter, then amplifies the voltage signal by the gain factor to output an amplified voltage signal. The lowpass filter passes low frequency components of the amplified voltage signal and attenuates frequency components greater than a cutoff frequency. The voltage to current converter receives the output signal of the lowpass filter and converts the output signal to a current output signal; wherein an amplifier circuit output is selectable between the output signal of the lowpass filter and the current output signal.

Ion funnel device

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

Ibrahim, Yehia M.; Chen, Tsung-Chi; Harrer, Marques B.

2017-11-21

An ion funnel device is disclosed. A first pair of electrodes is positioned in a first direction. A second pair of electrodes is positioned in a second direction. The device includes an RF voltage source and a DC voltage source. A RF voltage with a superimposed DC voltage gradient is applied to the first pair of electrodes, and a DC voltage gradient is applied to the second pair of electrodes.

High concentration effects of neutral-potential-well interface traps on recombination dc current-voltage lineshape in metal-oxide-silicon transistors

NASA Astrophysics Data System (ADS)

Chen, Zuhui; Jie, Bin B.; Sah, Chih-Tang

2008-11-01

Steady-state Shockley-Read-Hall kinetics is employed to explore the high concentration effect of neutral-potential-well interface traps on the electron-hole recombination direct-current current-voltage (R-DCIV) properties in metal-oxide-silicon field-effect transistors. Extensive calculations include device parameter variations in neutral-trapping-potential-well electron interface-trap density NET (charge states 0 and -1), dopant impurity concentration PIM, oxide thickness Xox, forward source/drain junction bias VPN, and transistor temperature T. It shows significant distortion of the R-DCIV lineshape by the high concentrations of the interface traps. The result suggests that the lineshape distortion observed in past experiments, previously attributed to spatial variation in surface impurity concentration and energy distribution of interface traps in the silicon energy gap, can also arise from interface-trap concentration along surface channel region.

System and method for charging electrochemical cells in series

DOEpatents

DeLuca, William H.; Hornstra, Jr, Fred; Gelb, George H.; Berman, Baruch; Moede, Larry W.

1980-01-01

A battery charging system capable of equalizing the charge of each individual cell at a selected full charge voltage includes means for regulating charger current to first increase current at a constant rate until a bulk charging level is achieved or until any cell reaches a safe reference voltage. A system controller then begins to decrease the charging rate as long as any cell exceeds the reference voltage until an equalization current level is reached. At this point, the system controller activates a plurality of shunt modules to permit shunting of current around any cell having a voltage exceeding the reference voltage. Leads extending between the battery of cells and shunt modules are time shared to permit alternate shunting of current and voltage monitoring without the voltage drop caused by the shunt current. After each cell has at one time exceeded the reference voltage, the charging current is terminated.

Performance Characterization of a Solenoid-type Gas Valve for the H- Magnetron Source at FNAL

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

Sosa, A.; Bollinger, D. S.; Karns, P. R.

2016-09-06

The magnetron-style H- ion sources currently in operation at Fermilab use piezoelectric gas valves to function. This kind of gas valve is sensitive to small changes in ambient temperature, which affect the stability and performance of the ion source. This motivates the need to find an alternative way of feeding H2 gas into the source. A solenoid-type gas valve has been characterized in a dedicated off-line test stand to assess the feasibility of its use in the operational ion sources. H- ion beams have been extracted at 35 keV using this valve. In this study, the performance of the solenoidmore » gas valve has been characterized measuring the beam current output of the magnetron source with respect to the voltage and pulse width of the signal applied to the gas valve.« less

Conditioning of BPM pickup signals for operations of the Duke storage ring with a wide range of single-bunch current

NASA Astrophysics Data System (ADS)

Xu, Wei; Li, Jing-Yi; Huang, Sen-Lin; Z. Wu, W.; Hao, H.; P., Wang; K. Wu, Y.

2014-10-01

The Duke storage ring is a dedicated driver for the storage ring based oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source (HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA per bunch for various operations and accelerator physics studies. High performance operations of the FEL and γ-ray source require a stable electron beam orbit, which has been realized by the global orbit feedback system. As a critical part of the orbit feedback system, the electron beam position monitors (BPMs) are required to be able to precisely measure the electron beam orbit in a wide range of the single-bunch current. However, the high peak voltage of the BPM pickups associated with high single-bunch current degrades the performance of the BPM electronics, and can potentially damage the BPM electronics. A signal conditioning method using low pass filters is developed to reduce the peak voltage to protect the BPM electronics, and to make the BPMs capable of working with a wide range of single-bunch current. Simulations and electron beam based tests are performed. The results show that the Duke storage ring BPM system is capable of providing precise orbit measurements to ensure highly stable FEL and HIGS operations.

An ultra-stable voltage source for precision Penning-trap experiments

NASA Astrophysics Data System (ADS)

Böhm, Ch.; Sturm, S.; Rischka, A.; Dörr, A.; Eliseev, S.; Goncharov, M.; Höcker, M.; Ketter, J.; Köhler, F.; Marschall, D.; Martin, J.; Obieglo, D.; Repp, J.; Roux, C.; Schüssler, R. X.; Steigleder, M.; Streubel, S.; Wagner, Th.; Westermann, J.; Wieder, V.; Zirpel, R.; Melcher, J.; Blaum, K.

2016-08-01

An ultra-stable and low-noise 25-channel voltage source providing 0 to -100 V has been developed. It will supply stable bias potentials for Penning-trap electrodes used in high-precision experiments. The voltage source generates all its supply voltages via a specially designed transformer. Each channel can be operated either in a precision mode or can be dynamically ramped. A reference module provides reference voltages for all the channels, each of which includes a low-noise amplifier to gain a factor of 10 in the output stage. A relative voltage stability of δV / V ≈ 2 ×10-8 has been demonstrated at -89 V within about 10 min.

Plasma Interactions with High Voltage Solar Arrays for a Direct Drive Hall Effect Thruster System

NASA Technical Reports Server (NTRS)

Schneider, T.; Horvater, M. A.; Vaughn, J.; Carruth, M. R.; Jongeward, G. A.; Mikellides, I. G.

2003-01-01

The Environmental Effects Group of NASA s Marshall Space Flight Center (MSFC) is conducting research into the effects of plasma interaction with high voltage solar arrays. These high voltage solar arrays are being developed for a direct drive Hall Effect Thruster propulsion system. A direct drive system configuration will reduce power system mass by eliminating a conventional power-processing unit. The Environmental Effects Group has configured two large vacuum chambers to test different high-voltage array concepts in a plasma environment. Three types of solar arrays have so far been tested, an International Space Station (ISS) planar array, a Tecstar planar array, and a Tecstar solar concentrator array. The plasma environment was generated using a hollow cathode plasma source, which yielded densities between 10(exp 6) - 10(exp 7) per cubic centimeter and electron temperatures of 0.5-1 eV. Each array was positioned in this plasma and biased in the -500 to + 500 volt range. The current collection was monitored continuously. In addition, the characteristics of arcing, snap over, and other features, were recorded. Analysis of the array performance indicates a time dependence associated with the current collection as well as a tendency for "conditioning" over a large number of runs. Mitigation strategies, to reduce parasitic current collection, as well as arcing, include changing cover-glass geometry and layout as well as shielding the solar cell edges. High voltage performance data for each of the solar array types tested will be presented. In addition, data will be provided to indicate the effectiveness of the mitigation techniques.

Methods for solid electrolyte interphase formation and anode pre-lithiation of lithium ion capacitors

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

Raman, Santhanam; Xi, Xiaomei; Ye, Xiang-Rong

A method of pre-doping an anode of an energy storage device can include immersing the anode and a dopant source in an electrolyte, and coupling a substantially constant current between the anode and the dopant source. A method of pre-doping an anode of an energy storage device can include immersing the anode and a dopant source in an electrolyte, and coupling a substantially constant voltage across the anode and the dopant source. An energy storage device can include an anode having a lithium ion pre-doping level of about 60% to about 90%.

46 CFR 111.05-29 - Dual voltage direct current systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Dual voltage direct current systems. Each dual voltage direct current system must have a suitably sensitive ground detection system which indicates current in the ground connection, has a range of at least... 46 Shipping 4 2010-10-01 2010-10-01 false Dual voltage direct current systems. 111.05-29 Section...

46 CFR 111.05-29 - Dual voltage direct current systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Dual voltage direct current systems. Each dual voltage direct current system must have a suitably sensitive ground detection system which indicates current in the ground connection, has a range of at least... 46 Shipping 4 2011-10-01 2011-10-01 false Dual voltage direct current systems. 111.05-29 Section...

Voltage-Dependent Gating of hERG Potassium Channels

PubMed Central

Cheng, Yen May; Claydon, Tom W.

2012-01-01

The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

Battery Cell By-Pass Circuit

NASA Technical Reports Server (NTRS)

Mumaw, Susan J. (Inventor); Evers, Jeffrey (Inventor); Craig, Calvin L., Jr. (Inventor); Walker, Stuart D. (Inventor)

2001-01-01

The invention is a circuit and method of limiting the charging current voltage from a power supply net work applied to an individual cell of a plurality of cells making up a battery being charged in series. It is particularly designed for use with batteries that can be damaged by overcharging, such as Lithium-ion type batteries. In detail. the method includes the following steps: 1) sensing the actual voltage level of the individual cell; 2) comparing the actual voltage level of the individual cell with a reference value and providing an error signal representative thereof; and 3) by-passing the charging current around individual cell necessary to keep the individual cell voltage level generally equal a specific voltage level while continuing to charge the remaining cells. Preferably this is accomplished by by-passing the charging current around the individual cell if said actual voltage level is above the specific voltage level and allowing the charging current to the individual cell if the actual voltage level is equal or less than the specific voltage level. In the step of bypassing the charging current, the by-passed current is transferred at a proper voltage level to the power supply. The by-pass circuit a voltage comparison circuit is used to compare the actual voltage level of the individual cell with a reference value and to provide an error signal representative thereof. A third circuit, designed to be responsive to the error signal, is provided for maintaining the individual cell voltage level generally equal to the specific voltage level. Circuitry is provided in the third circuit for bypassing charging current around the individual cell if the actual voltage level is above the specific voltage level and transfers the excess charging current to the power supply net work. The circuitry also allows charging of the individual cell if the actual voltage level is equal or less than the specific voltage level.

Joule-Thief Circuit Performance for Electricity Energy Saving of Emergency Lamps

NASA Astrophysics Data System (ADS)

Nuryanto Budisusila, Eka; Arifin, Bustanul

2017-04-01

The alternative energy such as battery as power source is required as energy source failures. The other need is outdoor lighting. The electrical power source is expected to be a power saving, optimum and has long life operating. The Joule-Thief circuit is one of solution method for energy saving by using raised electromagnetic force on cored coil when there is back-current. This circuit has a transistor operated as a switch to cut voltage and current flowing along the coils. The present of current causing magnetic induction and generates energy. Experimental prototype was designed by using battery 1.5V to activate Light Emitting Diode or LED as load. The LED was connected in parallel or serial circuit configuration. The result show that the joule-thief circuit able to supply LED circuits up to 40 LEDs.

Quantum Mechanical Study of Nanoscale MOSFET

NASA Technical Reports Server (NTRS)

Svizhenko, Alexei; Anantram, M. P.; Govindan, T. R.; Biegel, Bryan

2001-01-01

The steady state characteristics of MOSFETS that are of practical Interest are the drive current, off-current, dope of drain current versus drain voltage, and threshold voltage. In this section, we show that quantum mechanical simulations yield significantly different results from drift-diffusion based methods. These differences arise because of the following quantum mechanical features: (I) polysilicon gate depletion in a manner opposite to the classical case (II) dependence of the resonant levels in the channel on the gate voltage, (III) tunneling of charge across the gate oxide and from source to drain, (IV) quasi-ballistic flow of electrons. Conclusions dI/dV versus V does not increase in a manner commensurate with the increase in number of subbands. - The increase in dI/dV with bias is much smaller then the increase in the number of subbands - a consequence of bragg reflection. Our calculations show an increase in transmission with length of contact, as seen in experiments. It is desirable for molecular electronics applications to have a small contact area, yet large coupling. In this case, the circumferential dependence of the nanotube wave function dictates: - Transmission in armchair tubes saturates around unity - Transmission in zigzag tubes saturates at two.

Gate length variation effect on performance of gate-first self-aligned In₀.₅₃Ga₀.₄₇As MOSFET.

PubMed

Mohd Razip Wee, Mohd F; Dehzangi, Arash; Bollaert, Sylvain; Wichmann, Nicolas; Majlis, Burhanuddin Y

2013-01-01

A multi-gate n-type In₀.₅₃Ga₀.₄₇As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm(2)/Vs are achieved for the gate length and width of 0.2 µm and 30 µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10(-8) A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared.

Gate Length Variation Effect on Performance of Gate-First Self-Aligned In0.53Ga0.47As MOSFET

PubMed Central

Mohd Razip Wee, Mohd F.; Dehzangi, Arash; Bollaert, Sylvain; Wichmann, Nicolas; Majlis, Burhanuddin Y.

2013-01-01

A multi-gate n-type In0.53Ga0.47As MOSFET is fabricated using gate-first self-aligned method and air-bridge technology. The devices with different gate lengths were fabricated with the Al2O3 oxide layer with the thickness of 8 nm. In this letter, impact of gate length variation on device parameter such as threshold voltage, high and low voltage transconductance, subthreshold swing and off current are investigated at room temperature. Scaling the gate length revealed good enhancement in all investigated parameters but the negative shift in threshold voltage was observed for shorter gate lengths. The high drain current of 1.13 A/mm and maximum extrinsic transconductance of 678 mS/mm with the field effect mobility of 364 cm2/Vs are achieved for the gate length and width of 0.2 µm and 30µm, respectively. The source/drain overlap length for the device is approximately extracted about 51 nm with the leakage current in order of 10−8 A. The results of RF measurement for cut-off and maximum oscillation frequency for devices with different gate lengths are compared. PMID:24367548

CALUTRON CONTROL DEVICE

DOEpatents

Baldwin, L.W.

1959-08-25

Several interlock and control circuits for a calutron are described. In one of the arrangements, the ton source cooling water flow is interlocked with the current supply to the heaters assoctated with the charge chamber, arc chamber, and electrode structure. When the ion source coolant flow rate exceeds a predetermined level, the heater associated with the charge chamber is energized. After the charge chamber has reached a predetermined temperature, the arc chamber heater is energized. Thereafter, the electrode structure heater is energized and the ion source is ready to have the operating voltages applied.

Shuttle-promoted nano-mechanical current switch

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

Song, Taegeun, E-mail: tsong@ictp.it; Kiselev, Mikhail N.; Gorelik, Leonid Y.

2015-09-21

We investigate electron shuttling in three-terminal nanoelectromechanical device built on a movable metallic rod oscillating between two drains. The device shows a double-well shaped electromechanical potential tunable by a source-drain bias voltage. Four stationary regimes controllable by the bias are found for this device: (i) single stable fixed point, (ii) two stable fixed points, (iii) two limit cycles, and (iv) single limit cycle. In the presence of perpendicular magnetic field, the Lorentz force makes possible switching from one electromechanical state to another. The mechanism of tunable transitions between various stable regimes based on the interplay between voltage controlled electromechanical instabilitymore » and magnetically controlled switching is suggested. The switching phenomenon is implemented for achieving both a reliable active current switch and sensoring of small variations of magnetic field.« less

Subthreshold Schottky-barrier thin-film transistors with ultralow power and high intrinsic gain

NASA Astrophysics Data System (ADS)

Lee, Sungsik; Nathan, Arokia

2016-10-01

The quest for low power becomes highly compelling in newly emerging application areas related to wearable devices in the Internet of Things. Here, we report on a Schottky-barrier indium-gallium-zinc-oxide thin-film transistor operating in the deep subthreshold regime (i.e., near the OFF state) at low supply voltages (<1 volt) and ultralow power (<1 nanowatt). By using a Schottky-barrier at the source and drain contacts, the current-voltage characteristics of the transistor were virtually channel-length independent with an infinite output resistance. It exhibited high intrinsic gain (>400) that was both bias and geometry independent. The transistor reported here is useful for sensor interface circuits in wearable devices where high current sensitivity and ultralow power are vital for battery-less operation.

System and method for determining stator winding resistance in an AC motor

DOEpatents

Lu, Bin [Kenosha, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Theisen, Peter J [West Bend, WI

2011-05-31

A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

Harvesting dissipated energy with a mesoscopic ratchet

NASA Astrophysics Data System (ADS)

Roche, B.; Roulleau, P.; Jullien, T.; Jompol, Y.; Farrer, I.; Ritchie, D. A.; Glattli, D. C.

2015-04-01

The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced.

Flicker Vision of Selected Light Sources

NASA Astrophysics Data System (ADS)

Otomański, Przemysław; Wiczyński, Grzegorz; Zając, Bartosz

2017-10-01

The results of the laboratory research concerning a dependence of flicker vision on voltage fluctuations are presented in the paper. The research was realized on a designed measuring stand, which included an examined light source, a voltage generator with amplitude modulation supplying the light source and a positioning system of the observer with respect to the observed surface. In this research, the following light sources were used: one incandescent lamp and four LED luminaires by different producers. The research results formulate a conclusion concerning the description of the influence of voltage fluctuations on flicker viewing for selected light sources. The research results indicate that LED luminaires are less susceptible to voltage fluctuations than incandescent bulbs and that flicker vision strongly depends on the type of LED source.

Design of a Programmable Gain, Temperature Compensated Current-Input Current-Output CMOS Logarithmic Amplifier.

PubMed

Ming Gu; Chakrabartty, Shantanu

2014-06-01

This paper presents the design of a programmable gain, temperature compensated, current-mode CMOS logarithmic amplifier that can be used for biomedical signal processing. Unlike conventional logarithmic amplifiers that use a transimpedance technique to generate a voltage signal as a logarithmic function of the input current, the proposed approach directly produces a current output as a logarithmic function of the input current. Also, unlike a conventional transimpedance amplifier the gain of the proposed logarithmic amplifier can be programmed using floating-gate trimming circuits. The synthesis of the proposed circuit is based on the Hart's extended translinear principle which involves embedding a floating-voltage source and a linear resistive element within a translinear loop. Temperature compensation is then achieved using a translinear-based resistive cancelation technique. Measured results from prototypes fabricated in a 0.5 μm CMOS process show that the amplifier has an input dynamic range of 120 dB and a temperature sensitivity of 230 ppm/°C (27 °C- 57°C), while consuming less than 100 nW of power.

A study of Schwarz converters for nuclear powered spacecraft

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.; Schwarze, Gene E.

1987-01-01

High power space systems which use low dc voltage, high current sources such as thermoelectric generators, will most likely require high voltage conversion for transmission purposes. This study considers the use of the Schwarz resonant converter for use as the basic building block to accomplish this low-to-high voltage conversion for either a dc or an ac spacecraft bus. The Schwarz converter has the important assets of both inherent fault tolerance and resonant operation; parallel operation in modular form is possible. A regulated dc spacecraft bus requires only a single stage converter while a constant frequency ac bus requires a cascaded Schwarz converter configuration. If the power system requires constant output power from the dc generator, then a second converter is required to route unneeded power to a ballast load.

Design and Implementation of 13 Levels Multilevel Inverter for Photovoltaic System

NASA Astrophysics Data System (ADS)

Subramani, C.; Dhineshkumar, K.; Palanivel, P.

2018-04-01

This paper approaches the appearing and modernization of S-Type PV based 13- level multilevel inverter with less quantity of switch. The current S-Type Multi level inverter contains more number of switches and voltage sources. Multilevel level inverter is a be understandable among the most gainful power converters for high power application and present day applications with reduced switches. The fundamental good arrangement of the 13-level multilevel inverter is to get ventured voltage from a couple of levels of DC voltages.. The controller gives actual way day and age to switches through driver circuit using PWM methodology. The execution assessment of proposed multilevel inverter is checked using MATLAB/Simulink. This is the outstanding among other techniquem appeared differently in relation to all other existing system

ELECTRONIC TRIGGER CIRCUIT

DOEpatents

Russell, J.A.G.

1958-01-01

An electronic trigger circuit is described of the type where an output pulse is obtained only after an input voltage has cqualed or exceeded a selected reference voltage. In general, the invention comprises a source of direct current reference voltage in series with an impedance and a diode rectifying element. An input pulse of preselected amplitude causes the diode to conduct and develop a signal across the impedance. The signal is delivered to an amplifier where an output pulse is produced and part of the output is fed back in a positive manner to the diode so that the amplifier produces a steep wave front trigger pulsc at the output. The trigger point of the described circuit is not subject to variation due to the aging, etc., of multi-electrode tabes, since the diode circuit essentially determines the trigger point.

Modeling of the Electric Characteristics of Solar Cells

NASA Astrophysics Data System (ADS)

Logan, Benjamin; Tzolov, Marian

The purpose of a solar cell is to covert solar energy, through means of photovoltaic action, into a sustainable electrical current that produces usable electricity. The electrical characteristics of solar cells can be modeled to better understand how they function. As an electrical device, solar cells can be conveniently represented as an equivalent electrical circuit with an ideal diode, ideal current source for the photovoltaic action, a shunt resistor for recombination, a resistor in series to account for contact resistance, and a resistor modeling external power consumption. The values of these elements have been modified to model dark and illumination states. Fitting the model to the experimental current voltage characteristics allows to determine the values of the equivalent circuit elements. Comparing values of open circuit voltage, short circuit current, and shunt resistor can determine factors such as the amount of recombination to diagnose problems in solar cells. The many measurable quantities of a solar cell's characteristics give guidance for the design when they are related with microscopic processes.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

PubMed

Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

2016-04-01

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

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

Giusi, G.; Giordano, O.; Scandurra, G.

Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz{sup 1/2}, while DC performances are limited only bymore » the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.« less

Integral Battery Power Limiting Circuit for Intrinsically Safe Applications

NASA Technical Reports Server (NTRS)

Burns, Bradley M.; Blalock, Norman N.

2010-01-01

A circuit topology has been designed to guarantee the output of intrinsically safe power for the operation of electrical devices in a hazardous environment. This design uses a MOSFET (metal oxide semiconductor field-effect transistor) as a switch to connect and disconnect power to a load. A test current is provided through a separate path to the load for monitoring by a comparator against a preset threshold level. The circuit is configured so that the test current will detect a fault in the load and open the switch before the main current can respond. The main current passes through the switch and then an inductor. When a fault occurs in the load, the current through the inductor cannot change immediately, but the voltage drops immediately to safe levels. The comparator detects this drop and opens the switch before the current in the inductor has a chance to respond. This circuit protects both the current and voltage from exceeding safe levels. Typically, this type of protection is accomplished by a fuse or a circuit breaker, but in order for a fuse or a circuit breaker to blow or trip, the current must exceed the safe levels momentarily, which may be just enough time to ignite anything in a hazardous environment. To prevent this from happening, a fuse is typically current-limited by the addition of the resistor to keep the current within safe levels while the fuse reacts. The use of a resistor is acceptable for non-battery applications where the wasted energy and voltage drop across the resistor can be tolerated. The use of the switch and inductor minimizes the wasted energy. For example, a circuit runs from a 3.6-V battery that must be current-limited to 200 mA. If the circuit normally draws 10 mA, then an 18-ohm resistor would drop 180 mV during normal operation, while a typical switch (0.02 ohm) and inductor (0.97 ohm) would only drop 9.9 mV. From a power standpoint, the current-limiting resistor protection circuit wastes about 18 times more power than the switch and the inductor configuration. In the fault condition, both the resistor and the inductor react immediately. The resistor reacts by allowing more current to flow and dropping the voltage. Initially, the inductor reacts by dropping the voltage, and then by not allowing the current to change. When the comparator detects the drop in voltage, it opens the switch, thus preventing any further current flow. The inductor alone is not sufficient protection, because after the voltage drop has settled, the inductor would then allow the current to change, in this example, the current would be 3.7 A. In the fault condition, the resistor is flowing 200 mA until the fuse blows (anywhere from 1 ms to 100 s), while the switch and inductor combination is flowing about 2 A test current while monitoring for the fault to be corrected. Finally, as an additional safety feature, the circuit can be configured to hold the switch opened until both the load and source are disconnected.

Errors due to measuring voltage on current-carrying electrodes in electric current computed tomography.

PubMed

Cheng, K S; Simske, S J; Isaacson, D; Newell, J C; Gisser, D G

1990-01-01

Electric current computed tomography is a process for determining the distribution of electrical conductivity inside a body based upon measurements of voltage or current made at the body's surface. Most such systems use different electrodes for the application of current and the measurement of voltage. This paper shows that when a multiplicity of electrodes are attached to a body's surface, the voltage data are most sensitive to changes in resistivity in the body's interior when voltages are measured from all electrodes, including those carrying current. This assertion is true despite the presence of significant levels of skin impedance at the electrodes. This conclusion is supported both theoretically and by experiment. Data were first taken using all electrodes for current and voltage. Then current was applied only at a pair of electrodes, with voltages measured on all other electrodes. We then constructed the second data set by calculation from the first. Targets could be detected with better signal-to-noise ratio by using the reconstructed data than by using the directly measured voltages on noncurrent-carrying electrodes. Images made from voltage data using only noncurrent-carrying electrodes had higher noise levels and were less able to accurately locate targets. We conclude that in multiple electrode systems for electric current computed tomography, current should be applied and voltage should be measured from all available electrodes.

Improved Transient and Steady-State Performances of Series Resonant ZCS High-Frequency Inverter-Coupled Voltage Multiplier Converter with Dual Mode PFM Control Scheme

NASA Astrophysics Data System (ADS)

Chu, Enhui; Gamage, Laknath; Ishitobi, Manabu; Hiraki, Eiji; Nakaoka, Mutsuo

The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

Méthode de synthèse de la structure des convertisseurs multi-niveaux

NASA Astrophysics Data System (ADS)

Bartholoméüs, P.; Le Moigne, P.; Rombaut, C.

1997-09-01

In this paper a study of the multilevel converters' structures is presented. Multilevel cells with series connection of voltage sources are considered. The notion of power reversibility of the cell is introduced. It allows for the definition of reversible and non-reversible converter structures. The knowledge of the sign of the current which circulates in the cell permits the definition of the static characteristics of the switches involved in the connection between the different points of the voltage source and the current source. Two configurations of the cells are studied. For each one, the static characteristic of each switch is determined. For the first configuration, called “N_c-switch cell", each point of the voltage source is connected to the current source by one switch only. The second one is constituted of a stacking-up of switching elementary cells. It is called “elementary cell association structure". In this case, several switches are involved in each connection. Thanks to these two configurations, different cells have been developed, and they allow for the definition of new structures of rectifiers. Une méthode d'étude des structures de convertisseurs réalisés à partir de cellules multi-niveaux à association de sources de tension en série est présentée. La notion de non réversibilité en puissance de la cellule de commutation est introduite. Elle permet la définition des structures de conversion réversibles ou non réversibles. À partir du sens de circulation du courant dans les cellules, il est possible de définir la caractéristique statique des interrupteurs réalisant les connexions entre un des différents points de la source de tension et la source de courant. Deux trames d'interrupteurs sont considérées. Pour la première, nommée “cellule à N_c interrupteurs", les connexions sont réalisées par un seul interrupteur à la fois. Pour la seconde, constituée d'un empilage de cellules élémentaires de commutation, et nommée “cellule à association de cellules élémentaires", les connexions nécessitent la mise en série de plusieurs interrupteurs. À partir de ces deux trames d'interrupteurs, plusieurs cellules conduisant à de nouvelles structures de redresseurs non réversibles ont pu être définies.

Negative ion beam development at Cadarache (invited)

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

Simonin, A.; Bucalossi, J.; Desgranges, C.

1996-03-01

Neutral beam injection (NBI) is one of the candidates for plasma heating and current drive in the new generation of large magnetic fusion devices (ITER). In order to produce the required deuterium atom beams with energies of 1 MeV and powers of tens of MW, negative D{sup {minus}} ion beams are required. For this purpose, multiampere D{sup {minus}} beam production and 1 MeV electrostatic acceleration is being studied at Cadarache. The SINGAP experiment, a 1 MeV 0.1 A D{sup {minus}} multisecond beam accelerator facility, has recently started operation. It is equipped with a Pagoda ion source, a multiaperture 60 keVmore » preaccelerator and a 1 MV 120 mA power supply. The particular feature of SINGAP is that the postaccelerator merges the 60 keV beamlets, aiming at accelerating the whole beam to 1 MeV in a single gap. The 1 MV level was obtained in less than 2 weeks, the accumulated voltage on-time of being {approximately}22 min. A second test bed MANTIS, is devoted to the development of multiampere D{sup {minus}} sources. It is capable of driving discharges with current up to 2500 A at arc voltages up to 150 V. A large multicusp source has been tested in pure volume and cesiated operation. With cesium seeding, an accelerated D{sup {minus}} beam current density of up to 5.2 mA/cm{sup 2} (2 A of D{sup {minus}}) was obtained. A modification of the extractor is underway in order to improve this performance. A 3D Monte Carlo code has been developed to simulate the negative ion transport in magnetized plasma sources and optimize magnetic field configuration of the large area D{sup {minus}} sources. {copyright} {ital 1996 American Institute of Physics.}« less

Growth of Pb(Ti,Zr)O 3 thin films by metal-organic molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Avrutin, V.; Liu, H. Y.; Izyumskaya, N.; Xiao, B.; Özgür, Ü.; Morkoç, H.

2009-02-01

Single-crystal Pb(Zr xTi 1-x)O 3 thin films have been grown on (0 0 1) SrTiO 3 and SrTiO 3:Nb substrates by molecular beam epitaxy using metal-organic source of Zr and two different sources of reactive oxygen—RF plasma and hydrogen-peroxide sources. The same growth modes and comparable structural properties were observed for the films grown with both oxygen sources, while the plasma source allowed higher growth rates. The films with x up to 0.4 were single phase, while attempts to increase x beyond gave rise to the ZrO 2 second phase. The effects of growth conditions on growth modes, Zr incorporation, and phase composition of the Pb(Zr xTi 1-x)O 3 films are discussed. Electrical and ferroelectric properties of the Pb(Zr xTi 1-x)O 3 films of ~100 nm in thickness grown on SrTiO 3:Nb were studied using current-voltage, capacitance-voltage, and polarization-field measurements. The single-phase films show low leakage currents and large breakdown fields, while the values of remanent polarization are low (around 5 μC/cm 2). It was found that, at high sweep fields, the contribution of the leakage current to the apparent values of remanent polarization can be large, even for the films with large electrical resistivity (˜10 8-10 9 Ω cm at an electric filed of 1 MV/cm). The measured dielectric constant ranges from 410 to 260 for Pb(Zr 0.33Ti 0.67)O 3 and from 313 to 213 for Pb(Zr 0.2Ti 0.8)O 3 in the frequency range from 100 to 1 MHz.

High current proton beams production at Simple Mirror Ion Source 37.

PubMed

Skalyga, V; Izotov, I; Razin, S; Sidorov, A; Golubev, S; Kalvas, T; Koivisto, H; Tarvainen, O

2014-02-01

This paper presents the latest results of high current proton beam production at Simple Mirror Ion Source (SMIS) 37 facility at the Institute of Applied Physics (IAP RAS). In this experimental setup, the plasma is created and the electrons are heated by 37.5 GHz gyrotron radiation with power up to 100 kW in a simple mirror trap fulfilling the ECR condition. Latest experiments at SMIS 37 were performed using a single-aperture two-electrode extraction system. Proton beams with currents up to 450 mA at high voltages below 45 kV were obtained. The maximum beam current density was measured to be 600 mA/cm(2). A possibility of further improvement through the development of an advanced extraction system is discussed.