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Sample records for langmuir probe system

  1. RF-Compensated Langmuir Probe Measurements in an IPVD System

    NASA Astrophysics Data System (ADS)

    Juliano, Daniel R.; Ruzic, David N.

    1998-10-01

    The experimental apparatus consists of a commercial-scale magnetron with an RF coil between the target and substrate holder. This coil creates a secondary inductive plasma that ionizes a significant portion of the sputter flux en route from target to substrate. In order to understand and predict the ionization of the sputter flux arriving at the substrate, Langmuir probe measurements of this secondary inductive plasma were made under various combinations of powers (magnetron and RF), pressures, and working gas mixtures. The probe apparatus is RF-compensated in order to keep the voltage difference between the probe tip and plasma constant throughout the RF cycle. In order to yield accurate measurements in the dirty depositing environment of the IPVD system, the back of probe tip is recessed in a small ceramic tube, preventing shorting. Further, the potential on the probe tip is kept low except during the data-collecting voltage sweeps in order to continuously clean it and maintain stable electrical characterisitics.

  2. Advanced Langmuir Probe (LP)

    NASA Technical Reports Server (NTRS)

    Voronka, N. R.; Block, B. P.; Carignan, G. R.

    1991-01-01

    The dynamic response of the MK-2 version of the Langmuir probe amplifier was studied. The settling time of the step response is increased by: (1) stray node-to-ground capacitance at series connections between high value feedback resistors; and (2) input capacitance due to the input cable, FET switches, and input source follower. The stray node-to-ground capacitances can be reduced to tolerable levels by elevating the string of feedback resistors above the printing board. A new feedback network was considered, with promising results. The design uses resistances having much lower nominal values, thereby minimizing the effect of stray capacitances. Faster settling times can be achieved by using an operational amplifier having a higher gain-bandwidth product.

  3. A compact and portable PC-based Gundestrup-Langmuir probe diagnostic system

    SciTech Connect

    Sicard, P.; Boucher, C.; Litnovsky, A.; St-Germain, J.-P.

    2005-01-01

    A compact Gundestrup-Langmuir probe diagnostics system capable of data acquisition as well as data analysis was conceived at INRS-EMT, Canada, and used at IPP-FZJ, Germany. Data acquisition and analysis can be done with this system using several types of probes (Langmuir, double-Langmuir, Mach, Gundestrup,...). The versatility as to the different types of probe that one can use and the relative small size of the whole system makes it advantageous. Using a laptop computer makes the system small size and highly portable. The system acquires data at 1000 scans/s at 12 bit resolution on two probe systems simultaneously, using a total of 12 input channels. Bias is done by a DAC-ADC card and is amplified to give a {+-}100 V sweeping range. Measured temperatures ranged from 0.75 eV to 6.0 eV with densities observed as low as 1x10{sup 10} cm{sup -3} up to 5x10{sup 11} cm{sup -3}, which are the range of conditions to be found in our experimental device. This system is also easy to reproduce since the hardware is commercially available and the scripts can be duplicated and modified according to the specifics of the hardware.

  4. Time-Resolved Langmuir Probe Measurements in an Ionized PVD System

    NASA Astrophysics Data System (ADS)

    Juliano, D. R.; Hayden, D. B.; Ruzic, D. N.

    1997-10-01

    The experimental apparatus consists of a commercial-scale magnetron (Donated by Materials Research Corporation) with an RF coil between the target and substrate holder. This coil creates a secondary inductive plasma that ionizes a significant portion of the sputter flux en route from target to substrate. Ionization of the metal atoms that make up the sputter flux is highly sensitive to the high energy tail of the electron energy distribution, which in turn is highly dependent on the background gas mixture. Since there is some capacitive coupling from the coil this high energy population could change through the RF cycle. Time-averaged Langmuir probe measurements would not reveal either the extent of this high energy population or its time dependence. Further, if the probe voltage were held constant for such time-resolved measurements, they would yield incorrect results. At probe voltages above the plasma potential minimum the sheath is disrupted so that at points in the phase for which the probe voltage is below plasma potential the data is invalid. Therefore in order to take valid measurements at all phase points, it is necessary for the probe voltage to follow the RF variation in plasma potential. Using such a system, we have made time-resolved Langmuir probe measurements. Current-voltage traces as a function of phase then reveal plasma parameters as a function of time over the RF cycle for various background gases and operating parameters.

  5. Embedded calibration system for the DIII-D Langmuir probe analog fiber optic links

    SciTech Connect

    Watkins, J. G.; Rajpal, R.; Mandaliya, H.; Watkins, M.; Boivin, R. L.

    2012-10-15

    This paper describes a generally applicable technique for simultaneously measuring offset and gain of 64 analog fiber optic data links used for the DIII-D fixed Langmuir probes by embedding a reference voltage waveform in the optical transmitted signal before every tokamak shot. The calibrated data channels allow calibration of the power supply control fiber optic links as well. The array of fiber optic links and the embedded calibration system described here makes possible the use of superior modern data acquisition electronics in the control room.

  6. Embedded calibration system for the DIII-D Langmuir probe analog fiber optic links.

    PubMed

    Watkins, J G; Rajpal, R; Mandaliya, H; Watkins, M; Boivin, R L

    2012-10-01

    This paper describes a generally applicable technique for simultaneously measuring offset and gain of 64 analog fiber optic data links used for the DIII-D fixed Langmuir probes by embedding a reference voltage waveform in the optical transmitted signal before every tokamak shot. The calibrated data channels allow calibration of the power supply control fiber optic links as well. The array of fiber optic links and the embedded calibration system described here makes possible the use of superior modern data acquisition electronics in the control room.

  7. High-speed dual Langmuir probe.

    PubMed

    Lobbia, Robert B; Gallimore, Alec D

    2010-07-01

    In an effort to temporally resolve the electron density, electron temperature, and plasma potential for turbulent plasma discharges, a unique high-speed dual Langmuir probe (HDLP) has been developed. A traditional single Langmuir probe of cylindrical geometry (exposed to the plasma) is swept simultaneously with a nearby capacitance and noise compensating null probe (fully insulated from the plasma) to enable bias sweep rates on a microsecond timescale. Traditional thin-sheath Langmuir probe theory is applied for interpretation of the collected probe data. Data at a sweep rate of 100 kHz are presented; however the developed system is capable of running at 1 MHz-near the upper limit of the applied electrostatic Langmuir probe theory for the investigated plasma conditions. Large sets (100,000 sweeps at each of 352 spatial locations) of contiguous turbulent plasma properties are collected using simple electronics for probe bias driving and current measurement attaining 80 dB signal-to-noise measurements with dc to 1 MHz bandwidth. Near- and far-field plume measurements with the HDLP system are performed downstream from a modern Hall effect thruster where the time-averaged plasma properties exhibit the approximate ranges: electron density n(e) from (1x10(15))-(5x10(16)) m(-3), electron temperature T(e) from 1 to 3.5 eV, and plasma potential V(p) from 5 to 15 V. The thruster discharge of 200 V (constant anode potential) and 2 A (average discharge current) displays strong, 2.2 A peak-to-peak, current oscillations at 19 kHz, characteristic of the thruster "breathing mode" ionization instability. Large amplitude discharge current fluctuations are typical for most Hall thrusters, yet the HDLP system reveals the presence of the same 19 kHz fluctuations in n(e)(t), T(e)(t), and V(p)(t) throughout the entire plume with peak-to-peak divided by mean plasma properties that average 94%. The propagation delays between the discharge current fluctuations and the corresponding plasma

  8. The Fixed-bias Langmuir Probe on the Communication-navigation Outage Forecast System Satellite: Calibration and Validation

    NASA Technical Reports Server (NTRS)

    Klenzing, Jeffrey H.; Rowland, Douglas E.

    2012-01-01

    A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication Navigation Outage Forecast System (CNOFS) satellite.CNOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H+ and O+. The ion current collected by the probe surface per unit plasmadensity is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the CNOFS satellite. The application of the calibration is discussed with respect to future xed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on CNOFS.

  9. The Fixed-Bias Langmuir Probe on the Communication-Navigation Outage Forecast System Satellite: Calibration and Validation

    NASA Technical Reports Server (NTRS)

    Klenzing, J.; Rowland, D.

    2012-01-01

    A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication Navigation Outage Forecast System (CNOFS) satellite.CNOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H+ and O+. The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the CNOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on CNOFS.

  10. The fixed-bias Langmuir probe on the Communication/Navigation Outage Forecast System satellite: calibration and validation.

    PubMed

    Klenzing, J; Rowland, D

    2012-11-01

    A fixed-bias spherical Langmuir probe is included as part of the Vector Electric Field Instrument (VEFI) suite on the Communication/Navigation Outage Forecast System (C/NOFS) satellite. C/NOFS gathers data in the equatorial ionosphere between 400 and 860 km, where the primary constituent ions are H(+) and O(+). The ion current collected by the probe surface per unit plasma density is found to be a strong function of ion composition. The calibration of the collected current to an absolute density is discussed, and the performance of the spherical probe is compared to other in situ instruments on board the C/NOFS satellite. The application of the calibration is discussed with respect to future fixed-bias probes; in particular, it is demonstrated that some density fluctuations will be suppressed in the collected current if the plasma composition rapidly changes along with density. This is illustrated in the observation of plasma density enhancements on C/NOFS.

  11. A new compact and low cost Langmuir Probe and associated onboard data handling system for CubeSat

    NASA Astrophysics Data System (ADS)

    Muralikrishna, Polinaya; Domingos, Sinval; Paredes, Andres; Abrahão Dos Santos, Walter

    2016-07-01

    A new compact and low cost Langmuir Probe and associated onboard data handling system are being developed at Instituto Nacional de Pesquisas Espaciais for launching on board one of the future 2U CubeSat missions. The system is a simplified and compacted version of the Langmuir Probe payloads launched on board several Brazilian SONDA III rockets and also developed for the Brazilian scientific satellites SACI-1 and SACI-2. The onboard data handling system will have the dual functions of preprocessing the data collected by the Langmuir Probe and acting as the interface between the experiment and the on board computer. The Langmuir Probe sensor in the form of two rectangular stainless steel strips of total surface area of approximately 80cm2 will be deployed soon after the injection of the CubeSat into orbit. A sweep voltage varying linearly from 0V to 3.0V in about 1.5 seconds and then remaining fixed at 3.0V for 1 second will be applied to the LP sensor to obtain both the electron density and electron temperature. A high sensitivity preamplifier will be used to convert the sensor current expected to be in the range of a few nano amperes to a few micro amperes into a varying potential. In order to cover the large dynamic range of the expected sensor current the preamplifier output will be further amplified by a logarithmic amplifier before being sampled and sent to the data handling system. The data handling system is projected to handle 8 analog channels and 4 digital words of 8 bits each. The incoming data will be stored in a RAM and later sent to the on board computer using a serial RS422 communication protocol. The interface unit will process the telecommands received from the on board computer. The interface is also projected to do FFT analysis of the LP sensor data and send the averaged FFT spectral amplitudes in place of the original unprocessed data. The system details are presented here.

  12. Langmuir probe in collisionless and collisional plasma including dusty plasma

    NASA Astrophysics Data System (ADS)

    Bose, Sayak; Kaur, Manjit; Chattopadhyay, P. K.; Ghosh, J.; Saxena, Y. C.; Pal, R.

    2017-04-01

    Measurements of local plasma parameters in dusty plasma are crucial for understanding the physics issues related to such systems. The Langmuir probe, a small electrode immersed in the plasma, provides such measurements. However, designing of a Langmuir probe system in a dusty plasma environment demands special consideration. First, the probe has to be miniaturized enough so that its perturbation on the ambient dust structure is minimal. At the same time, the probe dimensions must be such that a well-defined theory exists for interpretation of its characteristics. The associated instrumentation must also support the measurement of current collected by the probe with high signal to noise ratio. The most important consideration, of course, comes from the fact that the probes are prone to dust contamination, as the dust particles tend to stick to the probe surface and alter the current collecting area in unpredictable ways. This article describes the design and operation of a Langmuir probe system that resolves these challenging issues in dusty plasma. In doing so, first, different theories that are used to interpret the probe characteristics in collisionless as well as in collisional regimes are discussed, with special emphasis on application. The critical issues associated with the current-voltage characteristics of Langmuir probe obtained in different operating regimes are discussed. Then, an algorithm for processing these characteristics efficiently in presence of ion-neutral collisions in the probe sheath is presented.

  13. Multiple valued floating potentials of Langmuir probes

    NASA Technical Reports Server (NTRS)

    Nam, Cheol-Hee; Hershkowitz, N.; Cho, M. H.; Intrator, T.; Diebold, D.

    1988-01-01

    It is shown that Langmuir probes can have three different floating potentials in plasmas produced by a hot filament discharge in a multi-dipole device when the primary and secondary electron currents are comparable. The measured floating potential depends on the probe's initial condition - the most negative and the least negative potentials are found to be stable and the in-between value is found to be unstable. Results are compared to a simple theoretical model.

  14. Multiple valued floating potentials of Langmuir probes

    NASA Technical Reports Server (NTRS)

    Nam, Cheol-Hee; Hershkowitz, N.; Cho, M. H.; Intrator, T.; Diebold, D.

    1988-01-01

    It is shown that Langmuir probes can have three different floating potentials in plasmas produced by a hot filament discharge in a multi-dipole device when the primary and secondary electron currents are comparable. The measured floating potential depends on the probe's initial condition - the most negative and the least negative potentials are found to be stable and the in-between value is found to be unstable. Results are compared to a simple theoretical model.

  15. Dynamical Response of Continuum Regime Langmuir Probe

    NASA Astrophysics Data System (ADS)

    Rappaport, H. L.

    2009-11-01

    Probe dynamic response is sometimes used as a way to increase the amount of information obtained from Langmuir probes [1]. In this poster, the effects of frequency dependent probe capacitance and coupling of probe fields to damped Langmuir waves and damped ion acoustic waves are considered. In the continuum regime, with small Debye length to spherical probe radius ratio, the probe DC current vs. voltage characteristic displays a hard saturation at sufficiently large probe potential [2]. In this regime, the sheath thickness varies little with the applied voltage although the plasma response can still be measured. A goal of the present investigation is to show that the probe dynamical response is richer as a result of modulation of sheath thickness or shielding particularly in the larger Debye length to probe radius ratio regime. Inertia inhibits ion response at sufficiently high frequency and deviation from the DC characteristic is shown.[4pt] [1] D. N. Walker, R.F. Fernsler, D.D. Blackwell, and W.E. Amatucci, Phys. Plasmas 15, 123506 (2008).[0pt] [2] E. Baum and R.L. Chapkis, AIAA J. 8, 1073 (1970).

  16. Langmuir probe surveys of an arcjet exhaust

    NASA Technical Reports Server (NTRS)

    Zana, Lynnette M.

    1987-01-01

    Electrostatic (Langmuir) probes of both spherical and cylindrical geometry have been used to obtain electron number density and temperature in the exhaust of a laboratory arcjet. The arcjet thruster operated on nitrogen and hydrogen mixtures to simulate fully decomposed hydrazine in a vacuum environment with background pressures less than 0.05 Pa. The exhaust appears to be only slightly ionized (less than 1 percent) with local plasma potentials near facility ground. The current-voltage characteristics of the probes indicate a Maxwellian temperature distribution. Plume data are presented as a function of arcjet operating conditions and also position in the exhaust.

  17. Langmuir probe analysis in electronegative plasmas

    SciTech Connect

    Bredin, Jerome Chabert, Pascal; Aanesland, Ane

    2014-12-15

    This paper compares two methods to analyze Langmuir probe data obtained in electronegative plasmas. The techniques are developed to allow investigations in plasmas, where the electronegativity α{sub 0} = n{sub –}/n{sub e} (the ratio between the negative ion and electron densities) varies strongly. The first technique uses an analytical model to express the Langmuir probe current-voltage (I-V) characteristic and its second derivative as a function of the electron and ion densities (n{sub e}, n{sub +}, n{sub –}), temperatures (T{sub e}, T{sub +}, T{sub –}), and masses (m{sub e}, m{sub +}, m{sub –}). The analytical curves are fitted to the experimental data by adjusting these variables and parameters. To reduce the number of fitted parameters, the ion masses are assumed constant within the source volume, and quasi-neutrality is assumed everywhere. In this theory, Maxwellian distributions are assumed for all charged species. We show that this data analysis can predict the various plasma parameters within 5–10%, including the ion temperatures when α{sub 0} > 100. However, the method is tedious, time consuming, and requires a precise measurement of the energy distribution function. A second technique is therefore developed for easier access to the electron and ion densities, but does not give access to the ion temperatures. Here, only the measured I-V characteristic is needed. The electron density, temperature, and ion saturation current for positive ions are determined by classical probe techniques. The electronegativity α{sub 0} and the ion densities are deduced via an iterative method since these variables are coupled via the modified Bohm velocity. For both techniques, a Child-Law sheath model for cylindrical probes has been developed and is presented to emphasize the importance of this model for small cylindrical Langmuir probes.

  18. Plasma characterization of a test setup of RF-driven negative ion source by a Langmuir probe system

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Li, Dong; Chen, Dezhi; Liu, Kaifeng; Li, Xiaofei; Wang, Hongyi; Zuo, Chen; Fan, Mingwu

    2017-06-01

    To study the plasma properties in a test setup of RF-driven negative ion source at HUST, a Langmuir probe system has been built in-house and applied to the source. It allows for fast, multiple acquisition of the probe I-V characteristics in a diagnosis shot of several hundred milliseconds and it is also capable of evaluating the I-V data automatically. The analysis software incorporates various methods for determination of the ion density, and the analysed results are compared. Measurements of the plasma parameters at the driver center for hydrogen discharges with the transmitted RF power of 4-20 kW and source pressure of 0.2-0.8 Pa have been carried out. Besides, the distribution of the plasma parameters along the central axis of the setup has been investigated. The plasma generated in the driver exhibits non-Maxwellian electron energy distribution with density of 1016 -1017m-3 and effective electron temperature of 6-9 eV at low pressure.

  19. A fixed bias, floating double probe technique with simple Langmuir probe characteristics

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.

    1971-01-01

    A new floating double-probe method is presented which has advantages over other floated-probe systems previously described in literature. The method utilized two electrodes, one of constant area and the other with a variable area. The two-electrode configuration is separated by a fixed bias voltage. The current-voltage characteristics of the new technique, which are generated by varying the area of the one electrode, are identical to those of a simple Langmuir probe, thus coupling all the advantages of a floated-probe system with the simple analysis scheme generally applied to the Langmuir probe for the determination of plasma density and temperature.

  20. Langmuir Probe Measurements in Plasma Shadows

    SciTech Connect

    Waldmann, O.; Koch, B.; Fussmann, G.

    2006-01-15

    When immersing a target into a plasma streaming along magnetic field lines, a distinct shadow region extending over large distances is observed by the naked eye downstream of the target.In this work we present an experimental study of the effect applying Langmuir probes. In contrast to expectations, there are only marginal changes in the profiles of temperature and density behind masks that cut away about 50% of the plasma cross-section. On the other hand, the mean density is drastically reduced by an order of magnitude. First attempts to simulate the observations by solving the classical 2D diffusion equation were not successful.

  1. A Langmuir probe system for the test setup of an RF-driven negative hydrogen ion source at HUST

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Chen, D. Z.; Li, D.; Zuo, C.

    2017-08-01

    A test setup of an RF-driven negative hydrogen ion source is being constructed at HUST. It is operated at the typical pressure of 0.3 Pa, maximum RF power of 20 kW/1 MHz, with discharge pulse of 6-10 seconds. In order to diagnose the plasma parameters and evaluate the source performance, a highly integrated and automated Langmuir probe system has been developed in-house. It allows for multiple sweeping, mass data acquisition and automatic data evaluation in a fast diagnosis shot of several hundred milliseconds. Various analysis methods are investigated and compared for the ion density determination. Due to the low density and thick sheath in the plasma, OML theory is selected as the applicable one. Preliminary discharge and diagnosis experiments have been carried out in the experimental source. The plasma in the driver exhibits non-Maxwellian electron energy distribution with low density of 1017 m-3 and electron temperature of 59 eV at 20 kW/0.3 Pa.

  2. Floating Potential Probe Langmuir Probe Data Reduction Results

    NASA Technical Reports Server (NTRS)

    Morton, Thomas L.; Minow, Joseph I.

    2002-01-01

    During its first five months of operations, the Langmuir Probe on the Floating Potential Probe (FPP) obtained data on ionospheric electron densities and temperatures in the ISS orbit. In this paper, the algorithms for data reduction are presented, and comparisons are made of FPP data with ground-based ionosonde and Incoherent Scattering Radar (ISR) results. Implications for ISS operations are detailed, and the need for a permanent FPP on ISS is examined.

  3. The Dynamics Explorer Langmuir probe instrument

    NASA Technical Reports Server (NTRS)

    Krehbiel, J. P.; Brace, L. H.; Theis, R. F.; Pinkus, W. H.; Kaplan, R. B.

    1981-01-01

    The Dynamics Explorer Langmuir probe instrument (DE-LANG), a spare unit from the Pioneer Venus mission that has been modified to work with the DE spacecraft, is described. Two independent sensors are connected to individual adaptive sweep voltage circuits that continuously track the changing electron temperature and spacecraft potential while autoranging electrometers adjust their gain in response to the changing plasma density. The control signals used in achieving this automatic tracking provide a continuous monitor of the ionospheric parameters without telemetering each volt-ampere curve. In addition, internal data storage circuits permit high-resolution, high-data-rate sampling of selected volt-ampere curves for transmission to the ground to verify or correct the inflight processed data.

  4. Langmuir probe differential measurement technique in inductively coupled RF plasmas

    NASA Astrophysics Data System (ADS)

    Djermanov, I.; Djermanova, N.; Kiss'ovski, Zh; Tsankov, Ts

    2007-04-01

    A differential measurement technique has been proposed in order to reduce noise level and stray capacitance leakage usually affecting Langmuir probe data. The technique employs two identically designed and biased Langmuir probes, connected to an instrumentation amplifier. Both probes are immersed in plasma of approximately the same space potential, one of them being plasma current collecting probe, and the second one being isolated from plasma and serving as a pick-up probe, detecting leakage currents from parasitic capacitive coupling and noise. Avoiding averaging of probe current data is the main advantage of the proposed differential technique. Experiments in the plasma expansion region of inductively driven RF source are shown to achieve lower electron temperature and higher electron density as measured by conventional single Langmuir probe. Obtaining more sharpness of the "knee" on the characteristic, thus lowering the uncertainty in plasma potential is another true merit of the differential Langmuir probe technique.

  5. Fast reciprocating Langmuir probe for the DIII-D divertor

    NASA Astrophysics Data System (ADS)

    Watkins, J. G.; Hunter, J.; Tafoya, B.; Ulrickson, M.; Watson, R. D.; Moyer, R. A.; Cuthbertson, J. W.; Gunner, G.; Lehmer, R.; Luong, P.; Hill, D. N.; Mascaro, M.; Robinson, J. I.; Snider, R.; Stambaugh, R.

    1997-01-01

    A new reciprocating Langmuir probe was used to measure density and temperature profiles, ion flow, and potential fluctuation levels from the lower divertor floor up to the X point on the DIII-D Tokamak. This probe is designed to make fast (2 kHz swept, 20 kHz Mach, 500 kHz Vfloat) measurements with 2 mm spatial resolution in the region where the largest gradients on the plasma open flux tubes are found and therefore provide the best benchmarks for scrap-off layer and divertor numerical models. Profiles are constructed using the 300 ms time history of the probe measurements during the 25 cm reciprocating stroke. Both single and double null plasmas can be measured and compared with a 20 Hz divertor Thomson scattering system. The probe head is constructed of four different kinds of graphite to optimize the electrical and thermal characteristics. Electrically insulated pyrolytic graphite rings act as a heat shield to absorb the plasma heat flux on the probe shaft and are mounted on a carbon/carbon composite core for mechanical strength. The Langmuir probe sampling tips are made of a linear carbon fiber composite. The mechanical, electrical, data acquisition, and power supply systems will be described. Initial measurements will also be presented.

  6. Behavior of a Single Langmuir Probe in a Magnetic Field.

    ERIC Educational Resources Information Center

    Pytlinski, J. T.; And Others

    1978-01-01

    Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)

  7. Hardware and software systems for the determination of charged particle parameters in low pressure plasmas using impedance-tuned Langmuir probes

    NASA Astrophysics Data System (ADS)

    Ye, Yuancai; Marcus, R. Kenneth

    1997-12-01

    A computer-controlled, impedance-tuned Langmuir probe data acquisition system and processing software package have been designed for the diagnostic study of low pressure plasmas. The combination of impedance-tuning and a wide range of applied potentials (± 100 V) provides a versatile system, applicable to a variety of analytical plasmas without significant modification. The automated probe system can be used to produce complete and undistorted current-voltage (i-V) curves with extremely low noise over the wide potential range. Based on these hardware and software systems, it is possible to determine all of the important charged particle parameters in a plasma; electron number density ( ne), ion number density ( ni), electron temperature ( Te), electron energy distribution function (EEDF), and average electron energy (<ɛ>). The complete data acquisition system and evaluation software are described in detail. A LabView (National Instruments Corporation, Austin, TX) application program has been developed for the Apple Macintosh line of microcomputers to control all of the operational aspects of the Langmuir probe experiments. The description here is mainly focused on the design aspects of the acquisition system with the targets of extremely low noise and reduction of the influence of measurement noise in the calculation procedures. This is particularly important in the case of electron energy distribution functions where multiple derivatives are calculated from the obtained i-V curves. A separate C-language data processing program has been developed and is included here to allow the reader to evaluate data obtained with the described hardware, or any i-V data imported in tab separated variable format. Both of the software systems are included on a Macintosh formatted disk for their use in other laboratories desiring these capabilities.

  8. Contamination effects on fixed-bias Langmuir probes

    SciTech Connect

    Steigies, C. T.; Barjatya, A.

    2012-11-15

    Langmuir probes are standard instruments for plasma density measurements on many sounding rockets. These probes can be operated in swept-bias as well as in fixed-bias modes. In swept-bias Langmuir probes, contamination effects are frequently visible as a hysteresis between consecutive up and down voltage ramps. This hysteresis, if not corrected, leads to poorly determined plasma densities and temperatures. With a properly chosen sweep function, the contamination parameters can be determined from the measurements and correct plasma parameters can then be determined. In this paper, we study the contamination effects on fixed-bias Langmuir probes, where no hysteresis type effect is seen in the data. Even though the contamination is not evident from the measurements, it does affect the plasma density fluctuation spectrum as measured by the fixed-bias Langmuir probe. We model the contamination as a simple resistor-capacitor circuit between the probe surface and the plasma. We find that measurements of small scale plasma fluctuations (meter to sub-meter scale) along a rocket trajectory are not affected, but the measured amplitude of large scale plasma density variation (tens of meters or larger) is attenuated. From the model calculations, we determine amplitude and cross-over frequency of the contamination effect on fixed-bias probes for different contamination parameters. The model results also show that a fixed bias probe operating in the ion-saturation region is affected less by contamination as compared to a fixed bias probe operating in the electron saturation region.

  9. Continuous heatable Langmuir probe for flowing afterglow measurements

    NASA Astrophysics Data System (ADS)

    Laubé, Sylvain; Mostefaoui, Toufik; Rowe, Bertrand

    2000-02-01

    A heatable Langmuir probe consisting of a continuous dc-heating-current loop of tungsten wire is presented. This technique is efficient to keep the probe surface clean for flowing afterglow measurements. In our experimental conditions, the perturbations on the electron density determination can be considered as very small. The measurement of the well-known rate for the dissociative recombination of O2+ shows that the gas surrounding the probe is not heated for estimated probe temperature up to 700 K.

  10. Digital smoothing of the Langmuir probe I-V characteristic

    SciTech Connect

    Magnus, F.; Gudmundsson, J. T.

    2008-07-15

    Electrostatic probes or Langmuir probes are the most common diagnostic tools in plasma discharges. The second derivative of the Langmuir probe I-V characteristic is proportional to the electron energy distribution function. Determining the second derivative accurately requires some method of noise suppression. We compare the Savitzky-Golay filter, the Gaussian filter, and polynomial fitting to the Blackman filter for digitally smoothing simulated and measured I-V characteristics. We find that the Blackman filter achieves the most smoothing with minimal distortion for noisy data.

  11. Measurement of atmospheric pressure microplasma jet with Langmuir probes

    SciTech Connect

    Xu, Kunning G. Doyle, Steven J.

    2016-09-15

    A radio frequency argon microplasma jet at atmospheric-pressure is characterized using Langmuir probes. While optical methods are the typical diagnostic for these small scale plasmas, the simplicity and low cost of Langmuir probes makes them an attractive option. The plasma density and electron temperature are measured using existing high-pressure Langmuir probe theories developed for flames and arcs. The density and temperature vary from 1 × 10{sup 16} to 1 × 10{sup 19} m{sup −3} and 2.3 to 4.4 eV, respectively, depending on the operating condition. The density decreases while the electron temperature increases with axial distance from the jet exit. The applicability of the probe theories as well as the effect of collisionality and jet mixing is discussed.

  12. Revisiting plasma hysteresis with an electronically compensated Langmuir probe

    NASA Astrophysics Data System (ADS)

    Srivastava, P. K.; Singh, S. K.; Awasthi, L. M.; Mattoo, S. K.

    2012-09-01

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 μA, allowing plasma measurements to be done with ion saturation current of the order of hundreds of μA. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of ≤45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as δTpk-pk changes by ˜30%. The developed technique with swept rate ≤100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering ≤50 kHz.

  13. Revisiting plasma hysteresis with an electronically compensated Langmuir probe.

    PubMed

    Srivastava, P K; Singh, S K; Awasthi, L M; Mattoo, S K

    2012-09-01

    The measurement of electron temperature in plasma by Langmuir probes, using ramped bias voltage, is seriously affected by the capacitive current of capacitance of the cable between the probe tip and data acquisition system. In earlier works a dummy cable was used to balance the capacitive currents. Under these conditions, the measured capacitive current was kept less than a few mA. Such probes are suitable for measurements in plasma where measured ion saturation current is of the order of hundreds of mA. This paper reports that controlled balancing of capacitive current can be minimized to less than 20 μA, allowing plasma measurements to be done with ion saturation current of the order of hundreds of μA. The electron temperature measurement made by using probe compensation technique becomes independent of sweep frequency. A correction of ≤45% is observed in measured electron temperature values when compared with uncompensated probe. This also enhances accuracy in the measurement of fluctuation in electron temperature as δT(pk-pk) changes by ~30%. The developed technique with swept rate ≤100 kHz is found accurate enough to measure both the electron temperature and its fluctuating counterpart. This shows its usefulness in measuring accurately the temperature fluctuations because of electron temperature gradient in large volume plasma device plasma with frequency ordering ≤50 kHz.

  14. Miniaturization of a Combination Langmuir/Mach Probe

    NASA Astrophysics Data System (ADS)

    Melnik, P. A.; Dehart, T.; Lotz, D.

    2009-11-01

    A combination Langmuir/Mach probe has been developed to measure electron temperature and density as well as ion flow speed in TCSU. The probe is fully translatable allowing it to diagnose all radial locations of the FRC at either the mid-plane, end section, or in the exhaust jets. The 1/4'' probe stalk consists of interlocking boron nitride cylinders which encompass a 1/8'' diameter stainless steel tube that houses the probe wires. In addition to the stainless steel jacket the probe wires are twisted to minimize electromagnetic noise pickup. The tip of this combo probe is composed of a boron nitride housing and eight .020'' diameter tungsten collection leads. In TCSU, the RMF used to form and sustain the FRC makes Langmuir probe measurements difficult. To this end we have developed a drive circuit that will generate the bias voltages necessary for Langmuir probe operation. This bipolar power supply can produce steady voltages up to 200 volts at loads over 1 amp and can be swept at any frequency up to 1.5 MHz. The probe current and bias voltage will be recorded with an amplifier and transmitted via fiber optic to a receiver allowing the signals to be digitized.

  15. Langmuir Probe Diagnostics of the VASIMR Engine

    DTIC Science & Technology

    2005-12-01

    experiment is more concerned with finding the ion flux of the engine. The equation to find flux ( particles/cm2 ) from current is ionI e+ Γ = 59...where e is merely the charge of a single ion, 1.6x10+ -19 C. The ion current, ionI , comes from the probe ion saturation current. Unlike current

  16. Langmuir-probe measurements in flowing-afterglow plasmas

    SciTech Connect

    Johnsen, R.; Shun'ko, E.V.; Gougousi, T. ); Golde, M.F. )

    1994-11-01

    The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing-afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the [ital electron] densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

  17. Langmuir-Probe Measurements in Flowing-Afterglow Plasmas

    NASA Technical Reports Server (NTRS)

    Johnsen, R.; Shunko, E. V.; Gougousi, T.; Golde, M. F.

    1994-01-01

    The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing- afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

  18. Langmuir-probe measurements in flowing-afterglow plasmas

    NASA Astrophysics Data System (ADS)

    Johnsen, R.; Shun'ko, E. V.; Gougousi, T.; Golde, M. F.

    1994-11-01

    The validity of the orbital-motion theory for cylindrical Langmuir probes immersed in flowing-afterglow plasmas is investigated experimentally. It is found that the probe currents scale linearly with probe area only for electron-collecting but not for ion-collecting probes. In general, no agreement is found between the ion and electron densities derived from the probe currents. Measurements in recombining plasmas support the conclusion that only the electron densities derived from probe measurements can be trusted to be of acceptable accuracy. This paper also includes a brief derivation of the orbital-motion theory, a discussion of perturbations of the plasma by the probe current, and the interpretation of plasma velocities obtained from probe measurements.

  19. Langmuir Probe Spacecraft Potential End Item Specification Document

    NASA Technical Reports Server (NTRS)

    Gilchrist, Brian; Curtis, Leslie (Technical Monitor)

    2001-01-01

    This document describes the Langmuir Probe Spacecraft Potential (LPSP) investigation of the plasma environment in the vicinity of the ProSEDS Delta II spacecraft. This investigation will employ a group of three (3) Langmuir Probe Assemblies, LPAs, mounted on the Delta II second stage to measure the electron density and temperature (n(sub e) and T(sub e)), the ion density (n(sub i)), and the spacecraft potential (V(sub s)) relative to the surrounding ionospheric plasma. This document is also intended to define the technical requirements and flight-vehicle installation interfaces for the design, development, assembly, testing, qualification, and operation of the LPSP subsystem for the Propulsive Small Expendable Deployer System (ProSEDS) and its associated Ground Support Equipment (GSE). This document also defines the interfaces between the LPSP instrument and the ProSEDS Delta II spacecraft, as well as the design, fabrication, operation, and other requirements established to meet the mission objectives. The LPSP is the primary measurement instrument designed to characterize the background plasma environment and is a supporting instrument for measuring spacecraft potential of the Delta II vehicle used for the ProSEDS mission. Specifically, the LPSP will use the three LPAs equally spaced around the Delta II body to make measurements of the ambient ionospheric plasma during passive operations to aid in validating existing models of electrodynamic-tether propulsion. These same probes will also be used to measure Delta II spacecraft potential when active operations occur. When the electron emitting plasma contractor is on, dense neutral plasma is emitted. Effective operation of the plasma contactor (PC) will mean a low potential difference between the Delta II second stage and the surrounding plasma and represents one of the voltage parameters needed to fully characterize the electrodynamic-tether closed circuit. Given that the LP already needs to be well away from any

  20. Solar extreme ultraviolet sensor and advanced langmuir probe

    NASA Technical Reports Server (NTRS)

    Voronka, N. R.; Block, B. P.; Carignan, G. R.

    1992-01-01

    For more than two decades, the staff of the Space Physics Research Laboratory (SPRL) has collaborated with the Goddard Space Flight Center (GSFC) in the design and implementation of Langmuir probes (LP). This program of probe development under the direction of Larry Brace of GSFC has evolved methodically with innovations to: improve measurement precision, increase the speed of measurement, and reduce the weight, size, power consumption and data rate of the instrument. Under contract NAG5-419 these improvements were implemented and are what characterize the Advanced Langmuir Probe (ALP). Using data from the Langmuir Probe on the Pioneer Venus Orbiter, Brace and Walter Hoegy of GSFC demonstrated a novel method of monitoring the solar extreme ultraviolet (EUV) flux. This led to the idea of developing a sensor similar to a Langmuir probe specifically designed to measure solar EUV (SEUV) that uses a similar electronics package. Under this contract, a combined instrument package of the ALP and SEUV sensor was to be designed, constructed, and laboratory tested. Finally the instrument was to be flight tested as part of sounding rocket experiment to acquire the necessary data to validate this method for possible use in future earth and planetary aeronomy missions. The primary purpose of this contract was to develop the electronics hardware and software for this instrument, since the actual sensors were suppied by GSFC. Due to budget constraints, only a flight model was constructed. These electronics were tested and calibrated in the laboratory, and then the instrument was integrated into the rocket payload at Wallops Flight Facility where it underwent environmental testing. After instrument recalibration at SPRL, the payload was reintegrated and launched from the Poker Flat Research Range near Fairbanks Alaska. The payload was successfully recovered and after refurbishment underwent further testing and developing to improve its performance for future use.

  1. Experimental Assessment of Double Langmuir Probe Analysis Techniques in a Hall Thruster Plume

    DTIC Science & Technology

    2012-07-25

    magnitude higher than the extended far-field plume. Langmuir probes, an electrostatic diagnostic developed by Irving Langmuir in 1924 [5], are widely used...of Double Langmuir Probe Analysis Techniques in a Hall 5b. GRANT NUMBER Thruster Plume 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Brown, D.L...recent theoretical study of double Langmuir probes led to development of improved analytical techniques that account for probe electrode sheath

  2. Operation of a Langmuir Probe in a Photoelectron Plasma

    SciTech Connect

    Dove, Adrienne; Robertson, Scott; Horanyi, Mihaly; Poppe, Andrew; Wang Xu

    2011-11-29

    Dust transport on the lunar surface is likely facilitated by the variable electric fields that are generated by changing plasma conditions. We have developed an experimental apparatus to study lunar photoelectric phenomena and gain a better understanding of the conditions controlling dust transport. As an initial step, Langmuir probe measurements are used to characterize the photoelectron plasma produced above a Zr surface, and these techniques will be extended to CeO{sub 2} and lunar simulant surfaces.

  3. Results from Langmuir probe measurements in PDX and PLT

    SciTech Connect

    Budny, R.

    1982-02-01

    Fits to Langmuir probe measurements made near the midplanes of the PDX and PLT tokamaks imply density and electron temperature profiles. In ohmically heated plasmas with either circular or diverted configurations, the edge densities decrease approximately exponentially with e-folding lengths of 1-4cm. Electron temperatures are low (5 to 50 eV) and decrease more gradually than the density profiles in the outer edge.

  4. Analysis of cylindrical Langmuir probe using experiment and different theories

    SciTech Connect

    Hassouba, M. A.; Galaly, A. R.; Rashed, U. M.

    2013-03-15

    Cylindrical probe data have been analyzed using different theories in order to determine some plasma parameters (electron temperature and electron and ion densities). Langmuir probe data are obtained in a cylindrical DC glow discharge in the positive column plasma at argon gas pressures varied from 0.5 to 6 Torr and at constant discharge current equal to 10 mA. The electron density has calculated from the electron current at the space potential and from Orbital Motion Limited (OML) collisionless theory. Ion density has obtained from the OML analysis of the ion saturation currents. In addition, the electron temperature has measured by three different methods using probe and electrons currents. The electron temperature T{sub e}, plasma density n{sub e}, and space potential V{sub s}, have been obtained from the measured single cylindrical probe I-V characteristic curves. The radial distribution of the electron temperature and plasma density along the glow discharge are measured and discussed. Using the collisionless theories by Langmuir cylindrical probe and up to several Torr argon gas pressures the differences between the values of electron temperature and electron and ion densities stay within reasonable error limits.

  5. A dual-cable noise reduction method for Langmuir probes

    NASA Astrophysics Data System (ADS)

    Yang, T. F.; Zu, Q. X.; Liu, Ping

    1995-07-01

    To obtain fast time response plasma properties, electron density and electron temperature, with a Langmuir probe, the applied probe voltage has to be swept at high frequency. Due to the RC characteristics of coaxial cables, an induced noise of a square-wave form will appear when a sawtooth voltage is applied to the probe. Such a noise is very annoying and difficult to remove, particularly when the probe signal is weak. This paper discusses a noise reduction method using a dual-cable circuit. One of the cables is active and the other is a dummy. Both of them are of equal length and are laid parallel to each other. The active cable carries the applied probe voltage and the probe current signal. The dummy one is not connected to the probe. After being carefully tuned, the induced noises from both cables are nearly identical and therefore can be effectively eliminated with the use of a differential amplifier. A clean I-V characteristic curve can thus be obtained. This greatly improves the accuracy and the time resolution of the values of ne and Te.

  6. Utilization of Double Langmuir Probes on Proto-MPEX

    NASA Astrophysics Data System (ADS)

    Kafle, Nischal; Caughman, John B.; Caneses, Juan F. M.; Goulding, Richard H.; Martin, Elijah. H.; Donovan, David. C.

    2016-10-01

    Langmuir probes (LP) are a robust, simply constructed, and inexpensive diagnostic tool. They are routinely used to measure the electron temperature and density in plasmas. However, the uncompensated single-tip LP has demonstrated limitations in time fluctuating plasma potential. The measurement quality can be improved by implementing compensation or by using a double-tipped probe. Double Langmuir probes (DLPs) are referenced against each other instead of the device vessel and therefore are less susceptible to fluctuations in RF plasmas. DLPs are being used to measure plasma parameters at multiple locations in the Proto-MPEX experiment at Oak Ridge National Laboratory. Proto-MPEX is a linear plasma device that combines a helicon plasma source with additional microwave and radio frequency heating to deliver a high plasma heat flux at a target. An electron temperature of 3-6 eV and density of 3e19 - >5e19 m-3 has been measured near the target in Proto-MPEX for different magnetic field configurations, with peak magnetic fields >1 T. Plasma density and temperature tend to be higher closer to the plasma source and are strongly dependent on operating pressure. This presentation will give an overview of DLP and will provide results from multiple locations and for different operating conditions. This work was supported by the U.S. D.O.E. contract DE-AC05-00OR22725.

  7. Mirror Langmuir probe: A technique for real-time measurement of magnetized plasma conditions using a single Langmuir electrode

    SciTech Connect

    LaBombard, B.; Lyons, L.

    2007-07-15

    A new method for the real-time evaluation of the conditions in a magnetized plasma is described. The technique employs an electronic ''mirror Langmuir probe'' (MLP), constructed from bipolar rf transistors and associated high-bandwidth electronics. Utilizing a three-state bias wave form and active feedback control, the mirror probe's I-V characteristic is continuously adjusted to be a scaled replica of the ''actual'' Langmuir electrode immersed in a plasma. Real-time high-bandwidth measurements of the plasma's electron temperature, ion saturation current, and floating potential can thereby be obtained using only a single electrode. Initial tests of a prototype MLP system are reported, proving the concept. Fast-switching metal-oxide-semiconductor field-effect transistors produce the required three-state voltage bias wave form, completing a full cycle in under 1 {mu}s. Real-time outputs of electron temperature, ion saturation current, and floating potential are demonstrated, which accurately track an independent computation of these values from digitally stored I-V characteristics. The MLP technique represents a significant improvement over existing real-time methods, eliminating the need for multiple electrodes and sampling all three plasma parameters at a single spatial location.

  8. Modeling of current characteristics of segmented Langmuir probe on DEMETER

    SciTech Connect

    Imtiaz, Nadia; Marchand, Richard; Lebreton, Jean-Pierre

    2013-05-15

    We model the current characteristics of the DEMETER Segmented Langmuir probe (SLP). The probe is used to measure electron density and temperature in the ionosphere at an altitude of approximately 700 km. It is also used to measure the plasma flow velocity in the satellite frame of reference. The probe is partitioned into seven collectors: six electrically insulated spherical segments and a guard electrode (the rest of the sphere and the small post). Comparisons are made between the predictions of the model and DEMETER measurements for actual ionospheric plasma conditions encountered along the satellite orbit. Segment characteristics are computed numerically with PTetra, a three-dimensional particle in cell simulation code. In PTetra, space is discretized with an unstructured tetrahedral mesh, thus, enabling a good representation of the probe geometry. The model also accounts for several physical effects of importance in the interaction of spacecraft with the space environment. These include satellite charging, photoelectron, and secondary electron emissions. The model is electrostatic, but it accounts for the presence of a uniform background magnetic field. PTetra simulation results show different characteristics for the different probe segments. The current collected by each segment depends on its orientation with respect to the ram direction, the plasma composition, the magnitude, and the orientation of the magnetic field. It is observed that the presence of light H{sup +} ions leads to a significant increase in the ion current branch of the I-V curves of the negatively polarized SLP. The effect of the magnetic field is demonstrated by varying its magnitude and direction with respect to the reference magnetic field. It is found that the magnetic field appreciably affects the electron current branch of the I-V curves of certain segments on the SLP, whereas the ion current branch remains almost unaffected. PTetra simulations are validated by comparing the computed

  9. Langmuir probe diagnostics of plasma in high current electron cyclotron resonance proton ion source

    SciTech Connect

    Roychowdhury, P.; Kewlani, H.; Mishra, L.; Mittal, K. C.; Patil, D. S.

    2013-07-15

    A high current Electron Cyclotron Resonance (ECR) proton ion source has been developed for low energy high intensity proton accelerator at Bhabha Atomic Research Centre. Langmuir probe diagnostics of the plasma generated in this proton ion source is performed using Langmuir probe. The diagnostics of plasma in the ion source is important as it determines beam parameters of the ion source, i.e., beam current, emittance, and available species. The plasma parameter measurement in the ion source is performed in continuously working and pulsed mode using hydrogen as plasma generation gas. The measurement is performed in the ECR zone for operating pressure and microwave power range of 10{sup −4}–10{sup −3} mbar and 400–1000 W. An automated Langmuir probe diagnostics unit with data acquisition system is developed to measure these parameters. The diagnostics studies indicate that the plasma density and plasma electron temperature measured are in the range 5.6 × 10{sup 10} cm{sup −3} to 3.8 × 10{sup 11} cm{sup −3} and 4–14 eV, respectively. Using this plasma, ion beam current of tens of mA is extracted. The variations of plasma parameters with microwave power, gas pressure, and radial location of the probe have been studied.

  10. Cylindrical Langmuir probe measurements in an ion thruster plume

    SciTech Connect

    Semak, V.V.; Keefer, D.

    1995-12-31

    Cylindrical Langmuir probe measurements have been made in the exhaust plume of a 15 cm diameter three-grid ion thruster. Xenon gas was used as a propellant. The experiments were performed in a large vacuum chamber with background pressure values of 2 {times} 10{sup {minus}4} Torr and 3 {times} 10{sup {minus}6} Torr. A 250 {micro}m diameter tungsten probe 2.78 mm long was used in the experiments. The data collected for radial and axial scans were analyzed to provide measurements of electron temperature, plasma potential and electron density. It was found that, unlike the case of a stationary plasma, the electron saturation current is only several times higher than ion current. Small errors in the determination of the ion current component of the characteristic curve can result in significant overestimation of electron temperature. A method of data analysis was developed which includes an estimation of the collected ion current. This method is compared with a numerical particle simulation model for calculation of the ion current component.

  11. Theory and Capability of the Planar Langmuir Probe

    NASA Astrophysics Data System (ADS)

    Cooke, D. L.; Roddy, P. A.; Ballenthin, J.; Machuzak, J.; Albarran, R. M.; Klenzing, J.

    2014-12-01

    The Planar Langmuir Probe, PLP, in its simplest form is just a flat plate and perhaps a guard ring placed on the ram side of a Low Earth Orbit spacecraft such that it can intersect an uninterrupted flow of plasma. At small negative potential, it measures the ion ram current and thus the ion density with great accuracy, and when swept to positive potential, electrons are collected and the electron temperature may be extracted from the current-voltage characteristic. With rapid sampling, the turbulence spectrum of the plasma may also be sampled. AFRL has pioneered the development and application of the PLP for close to 2 decades. The PLP was used on numerous rocket flights in the 90's, was flown on the CHAMP satellite from 2002 to 2011, on the C/NOFS satellite from 2008 to present, and a new version is in development for possible future flights. This talk will review the design variations to date, data validation, lessons learned, and theory of operation. In particular we will present methods for extracting the electron temperature from the current-voltage characteristic, and address how the probes can measure higher moments of the electron distribution as suggested by the observations of Rother et.al. (Radio Sci, Vol 45, 2010).

  12. A fast reciprocating Langmuir probe for the DIII-D divertor

    SciTech Connect

    Watkins, J.G.; Hunter, J.; Tafoya, B.

    1996-11-01

    A new reciprocating Langmuir probe has been used to measure density and temperature profiles, ion flow, and potential fluctuation levels from the lower divertor floor up to the X-point on the DIII-D tokamak. This probe is designed to make fast (2 kHz swept, 20 kHz Mach, 500 kHz Vfloat) measurements with 2 mm spatial resolution in the region where the largest gradients on the plasma open flux tubes are found and therefore provide the best benchmarks for SOL and divertor numerical models. Profiles are constructed using the 300 ms time history of the probe measurements during the 25 cm reciprocating stroke. Both single and double null plasmas can be measured and compared with a 20 Hz divertor Thomson scattering system. The probe head is constructed of four different kinds of graphite to optimize the electrical and thermal characteristics. Electrically insulated pyrolytic graphite rings act as a heat shield to absorb the plasma heat flux on the probe shaft and are mounted on a carbon/carbon composite core for mechanical strength. The Langmuir probe sampling tips are made of a linear carbon fiber composite. The mechanical, electrical, data acquisition and power supply systems design will be described. Initial measurements will also be presented.

  13. Langmuir probe diagnostic suite in the C-2 field-reversed configuration

    NASA Astrophysics Data System (ADS)

    Roche, T.; Sun, X.; Armstrong, S.; Knapp, K.; Slepchenkov, M.

    2014-11-01

    Several in situ probes have been designed and implemented into the diagnostic array of the C-2 field-reversed configuration (FRC) at Tri Alpha Energy [M. Tuszewski et al. (the TAE Team), Phys. Rev. Lett. 108, 255008 (2012)]. The probes are all variations on the traditional Langmuir probe. They include linear arrays of triple probes, linear arrays of single-tipped swept probes, a multi-faced Gundestrup probe, and an ion-sensitive probe. The probes vary from 5 to 7 mm diameter in size to minimize plasma perturbations. They also have boron nitride outer casings that prevent unwanted electrical breakdown and reduce the introduction of impurities. The probes are mounted on motorized linear-actuators allowing for programmatic scans of the various plasma parameters over the course of several shots. Each probe has a custom set of electronics that allows for measurement of the desired signals. High frequency ( > 5MHz) analog optical-isolators ensure that plasma parameters can be measured at sub-microsecond time scales while providing electrical isolation between machine and data acquisition systems. With these probes time-resolved plasma parameters (temperature, density, spatial potential, flow, and electric field) can be directly/locally measured in the FRC jet and edge/scrape-off layer.

  14. Rocket-borne Langmuir probe for plasma density irregularities

    NASA Astrophysics Data System (ADS)

    Sinha, H. S. S.

    2013-11-01

    Ionospheric plasma density exhibits very large spatial and temporal variations known as ionosphere irregularities. These irregularities are generated by a number of processes related to plasma as well as neutral dynamics. The rocket- or satellite-borne Langmuir probe (LP) is very simple and yet a very powerful tool to measure spatial variation of plasma density enabling one to study ionosphere irregularities. This article describes how a rocket-borne LP can be used to study ionosphere irregularities. It begins with the basic principle of the LP, the ionospheric regions where it can be used, various sizes and shapes of the LP sensors, the effect of geomagnetic field and vehicle wake on LP measurements. Mechanical and electronic details of typical LP instrument are given next. Strengths, weaknesses and specifications of LP instrument are also given. Rocket-borne LP has been used by a large number of scientists in the world to study ionospheric irregularities produced through plasma instabilities in the equatorial electrojet region, in spread F and those produced by neutral turbulence. Highlights of such irregularity measurements are presented to give the reader a flavor of the type of studies which can be undertaken using a rocket-borne LP. The present capability of rocket-borne LP is to detect vertical scale sizes of ionospheric irregularities from a few km down to about 10 cm with percentage amplitudes as small as 0.001%. Finally, a few suggestions are given for the improvement the LP instrumentation for future use.

  15. The Langmuir Probe and Waves (LPW) Instrument for MAVEN

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Ergun, R. E.; Delory, G. T.; Eriksson, A.; Westfall, J.; Reed, H.; McCauly, J.; Summers, D.; Meyers, D.

    2015-12-01

    We describe the sensors, the sensor biasing and control, the signal-processing unit, and the operation of the Langmuir Probe and Waves (LPW) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. The LPW instrument is designed to measure the electron density and temperature in the ionosphere of Mars and to measure spectral power density of waves (DC-2 MHz) in Mars' ionosphere, including one component of the electric field. Low-frequency plasma waves can heat ions resulting in atmospheric loss. Higher-frequency waves are used to calibrate the density measurement and to study strong plasma processes. The LPW is part of the Particle and Fields (PF) suite on the MAVEN spacecraft. The LPW instrument utilizes two, 40 cm long by 0.635 cm diameter cylindrical sensors with preamplifiers, which can be configured to measure either plasma currents or plasma waves. The sensors are mounted on a pair of {˜}7 meter long stacer booms. The sensors and nearby surfaces are controlled by a Boom Electronics Board (BEB). The Digital Fields Board (DFB) conditions the analog signals, converts the analog signals to digital, processes the digital signals including spectral analysis, and packetizes the data for transmission. The BEB and DFB are located inside of the Particle and Fields Digital Processing Unit (PFDPU).

  16. Langmuir probe measurements aboard the International Space Station

    NASA Astrophysics Data System (ADS)

    Kirov, B.; Asenovski, S.; Bachvarov, D.; Boneva, A.; Grushin, V.; Georgieva, K.; Klimov, S. I.

    2016-12-01

    In the current work we describe the Langmuir Probe (LP) and its operation on board the International Space Station. This instrument is a part of the scientific complex "Ostonovka". The main goal of the complex is to establish, on one hand how such big body as the International Space Station affects the ambient plasma and on the other how Space Weather factors influence the Station. The LP was designed and developed at BAS-SRTI. With this instrument we measure the thermal plasma parameters-electron temperature Te, electron and ion concentration, respectively Ne and Ni, and also the potential at the Station's surface. The instrument is positioned at around 1.5 meters from the surface of the Station, at the Russian module "Zvezda", located at the farthermost point of the Space Station, considering the velocity vector. The Multi- Purpose Laboratory (MLM) module is providing additional shielding for our instrument, from the oncoming plasma flow (with respect to the velocity vector). Measurements show that in this area, the plasma concentration is two orders of magnitude lower, in comparison with the unperturbed areas. The surface potential fluctuates between-3 and-25 volts with respect to the ambient plasma. Fast upsurges in the surface potential are detected when passing over the twilight zone and the Equatorial anomaly.

  17. Langmuir probe measurements in the Hollow Cathode Magnetron

    NASA Astrophysics Data System (ADS)

    Vukovic, Mirko; Lai, Kwok-Fai

    1997-10-01

    The Hollow Cathode Magnetron (HCM) is a new kind of a high density plasma device which has been proposed as an ionized physical vapor deposition source for semiconductor device fabrication(John C. Helmer, Kwok F. Lai, Robert L. Anderson US Patent 5,482,661, Jan. 9, 1996). The target is of high purity metal machined to resemble a hollow cathode (id. 4cm, depth 6cm). It resides in a cooled metal housing. The magnetic field (several hundred Gauss) is generated by permanent magnets stacked on the outside of the metal housing, aligned parallel to the HCM axis. At the mouth of the HCM, a magnetic cusp traps a high density plasma. Beyond the cusp, a slowly diverging magnetic field produces a low temperature (T_e ~ 2-3eV), high density (n_e ~ 10^12-10^13cm-3∝ P_DC) plume. The HCM serves to both sputter and ionize metal atoms from the target. These ions may deposit onto a silicon device wafer, enabling metal deposition into the bottom of very small (<0.5μm) high aspect ratio (>=6:1) features. The unique properties of the films deposited using the HCM will be presented and related to the plasma parameters obtained from Langmuir probe data and magnetic field modeling. discharge is on the inside wall

  18. Improved optogalvanic detection with voltage biased Langmuir probes

    SciTech Connect

    Persson, A.; Salehpour, M.; Berglund, M.

    2014-12-28

    Optogalvanic detectors show great potential for infrared spectroscopy, especially in cavity enhanced techniques where they, in contrast to ordinary absorption detectors, can perform intracavity measurements. This enables them to utilize the signal-to-noise ratio improvement gained from the extended effective path length inside an optical cavity, without losing signal strength due to the limited amount of light exiting through the rear mirror. However, if optogalvanic detectors are to become truly competitive, their intrinsic sensitivity and stability has to be improved. This, in turn, requires a better understanding of the mechanisms behind the generation of the optogalvanic signal. The study presented here focuses on an optogalvanic detector based on a miniaturized stripline split-ring resonator plasma source equipped with Langmuir probes for detecting the optogalvanic signal. In particular, the effect of applying a constant bias voltage to one of the probes is investigated, both with respect to the sensitivity and stability, and to the mechanism behind the generation of the signal. Experiments with different bias voltages at different pressures and gas composition have been conducted. In particular, two different gas compositions (pure CO{sub 2} and 0.25% CO{sub 2} in 99.75% N{sub 2}) at six different pressures (100 Pa to 600 Pa) have been studied. It has been shown that probe biasing effectively improves the performance of the detector, by increasing the amplitude of the signal linearly over one order of magnitude, and the stability by about 40% compared with previous studies. Furthermore, it has been shown that relatively straightforward plasma theory can be applied to interpret the mechanism behind the generation of the signal, although additional mechanisms, such as rovibrational excitation from electron-molecule collisions, become apparent in CO{sub 2} plasmas with electron energies in the 1–6 eV range. With the achieved performance improvement and

  19. Langmuir Probe Distortions and Probe Compensation in an Inductively Coupled Plasma

    NASA Technical Reports Server (NTRS)

    Ji, J. S.; Cappelli, M. A.; Kim, J. S.; Rao, M. V. V. S.; Sharma, S. P.

    1999-01-01

    In many RF discharges, Langmuir probe measurements are usually made against a background of sinusoidal (and not so sinusoidal) fluctuations in the plasma parameters such as the plasma potential (Vp), the electron number density (ne), and the electron temperature (Te). The compensation of sinusoidal fluctuations in Vp has been extensively studied and is relatively well understood. Less attention has been paid to the possible distortions introduced by small fluctuations in plasma density and/or plasma temperature, which may arise in the sheath and pre-sheath regions of RF discharges. Here, we present the results of a model simulation of probe characteristics subject to fluctuations in both Vp and ne. The modeling of probe distortion due to possible fluctuations in Te is less straightforward. A comparison is presented of calculations with experimental measurements using a compensated and uncompensated Langmuir probe in an inductively coupled GEC reference cell plasma, operating on Ar and Ar/CF4 mixtures. The plasma parameters determined from the compensated probe characteristics are compared to previous measurements of others made in similar discharges, and to our own measurements of the average electron density derived from electrical impedance measurements.

  20. First simultaneous measurements of Reynolds stress with ball-pen and Langmuir probes

    NASA Astrophysics Data System (ADS)

    Grover, Ondrej; Adamek, Jiri; Seidl, Jakub; Devitre, Alexis; Sos, Miroslav; Vondracek, Petr; Bilkova, Petra; Hron, Martin

    2017-06-01

    A new multi-pin probe head was installed and tested at the COMPASS tokamak. The probe head consists of several ball-pen and Langmuir probes in similar geometric configurations, which enables fast, simultaneous measurements of the radial and poloidal electric field components from differences of plasma or floating potentials using appropriately positioned ball-pen or Langmuir probes, respectively. The fast measurements of the radial electric field are compared with other methods of measuring selected frequency components of the radial electric field. The radial profiles of the Reynolds stress calculated from correlations of electric field fluctuations obtained by either probe type are compared along with their spectral composition. Lower Reynolds stress values are found for Langmuir probes in comparison to ball-pen probes due to negative contributions from higher frequency fluctuations possibly associated with electron temperature fluctuations.

  1. Langmuir Probes for Obstanovka Experiment Aboard the Russian Segment of the International Space Station

    DTIC Science & Technology

    2010-08-04

    segment of the International Space Station 5a. CONTRACT NUMBER FA8655-08-1-3006 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...1 REPORT ON FA8655-08-1-3006 LANGMUIR PROBES FOR “OBSTANOVKA” EXPERIMENT ABOARD THE RUSSIAN SEGMENT OF THE INTERNATIONAL SPACE STATION August...Russian segment of the International Space Station ”. INTRODUCTION Two Langmuir electrostatic probes are included in the experiment "Obstanovka

  2. Studies on the Electrical Characteristics of a DC Glow Discharge by Using Langmuir Probe

    SciTech Connect

    Safaai, S. S.; Yap, S. L.; Wong, C. S.; Muniandy, S. V.; Smith, P. W.

    2010-07-07

    Electrical characteristics of a DC glow discharge are studied with the aim of determining the suitable parameters for stable operation of the dusty plasma system. The presence of dust particles in plasma significantly alters the charged particle equilibrium in the plasma and leads to various phenomena. Argon plasma produced by DC glow discharge is investigated with a further goal of studying dusty plasma phenomena. The discharge system has two disc-shaped parallel plate electrodes. The electrodes are enclosed in a large cylindrical stainless steel chamber filled with argon gas. Two important physical parameters affecting the condition of the discharge are the gas pressure and the inter-electrode distance. A single Langmuir probe based on the Keithley source meter is used to determine the electron temperature of the positive column. A custom designed probe is employed to determine the potential distribution between the electrodes during the discharge. The I-V characteristic curve and the Langmuir probe measurement are then used to determine the electron energy distribution of the glow discharge plasma.

  3. H-mode Edge Turbulence and Pedestal Measurements in Pegasus Plasmas using Langmuir Probes

    NASA Astrophysics Data System (ADS)

    Kriete, D. M.; Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Thome, K. E.; Thompson, D. S.

    2015-11-01

    In Pegasus discharges, L-H mode transitions are induced using Ohmic heating and high-field-side fueling. H-mode plasmas have energy confinement consistent with the ITER98pb(y,2) scaling law, indications of increased electron and ion temperature, and an increase in core rotation compared to L-mode plasmas. Electron density and temperature profiles have been measured in the edge region using a scannable triple Langmuir probe on a shot-by-shot basis. In H-mode, a pressure pedestal that has a hyperbolic tangent shape and a ~ 2 cm ∇pe scale length is observed, in contrast to a linear shape in L-mode. Autopower spectra of the collected ion saturation current in H-mode discharges show a factor of ~ 3 reduction in fluctuations in the 50-200 kHz band with respect to L-mode. Two Langmuir probes with 8 cm poloidal separation have been installed on Pegasus. The turbulence correlation length in the edge will be measured by radially scanning the probes. Knowledge of the correlation length will be used to inform the design of a future 8-channel radial multiprobe array. This system will simultaneously measure the dynamic ne (R , t) , Te (R , t) , and Φ (R , t) profiles and fluctuations across the L-H mode transition and be used to investigate nonlinear ELM dynamics. Work supported by US DOE grant DE-FG02-96ER54375.

  4. Ram-wake effects on plasma current collection of the PIX 2 Langmuir probe

    NASA Technical Reports Server (NTRS)

    Ferguson, D. C.

    1985-01-01

    The Plasma Interaction Experiment 2 (PIX 2) Langmuir probe readings of the same polar magnetospheric regions taken on consecutive orbits showed occasional apparent densities as much as 10 times lower than the average, although each pass clearly showed density structures related to the day/night boundary. At other points in the orbit, Langmuir probe currents varied by as much as a factor of 20 on a time scale of minutes. The hypothesis is advanced that these apparent inconsistencies in Langmuir probe current are the results of the probe's orientation relative to the body of the spacecraft and the velocity vector. Theoretical studies predict a possible depletion in collected electron current by a factor of 100 in the wake. Experimental results from other spacecraft indicate that a wake electron depletion by a factor of 10 or so is realistic. This amount of depletion is consistent with the PIX 2 data if the spacecraft was rotating. Both the Sun sensor and temperature sensor data on PIX 2 show a complex variation consistent with rotation of the Langmuir probe into and out of the spacecraft wake on a time scale of minutes. Furthermore, Langmuir probe data taken when the probe was not in the spacecraft wake are consistent from orbit to orbit. This supports the interpretation that ram/wake effects may be the source of apparent discrepancies at other orientations.

  5. Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

    NASA Astrophysics Data System (ADS)

    Pramila; Patel, J. J.; Rajpal, R.; Hansalia, C. J.; Anitha, V. P.; Sathyanarayana, K.

    2017-04-01

    Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (ne), the electron temperature (Te), the floating potential (Vf), and the plasma potential (Vp). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current.

  6. Means to remove electrode contamination effect of Langmuir probe measurement in space

    SciTech Connect

    Oyama, K.-I.; Lee, C. H.; Fang, H. K.; Cheng, C. Z.

    2012-05-15

    Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

  7. Means to remove electrode contamination effect of Langmuir probe measurement in space.

    PubMed

    Oyama, K-I; Lee, C H; Fang, H K; Cheng, C Z

    2012-05-01

    Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

  8. Means to remove electrode contamination effect of Langmuir probe measurement in space

    NASA Astrophysics Data System (ADS)

    Oyama, K.-I.; Lee, C. H.; Fang, H. K.; Cheng, C. Z.

    2012-05-01

    Precaution to remove the serious effect of electrode contamination in Langmuir probe experiments has not been taken in many space measurements because the effect is either not understood or ignored. We stress here that one should pay extra attention to the electrode contamination effect to get accurate and reliable plasma measurements so that the long time effort for sounding rocket/satellite missions does not end in vain or becomes less fruitful. In this paper, we describe two main features of voltage-current characteristic curves associated with the contaminated Langmuir probe, which are predicted from the equivalent circuit model, which we proposed in 1970's. We then show that fast sweeping dc Langmuir probes can give reliable results in the steady state regime. The fast sweeping probe can also give reliable results in transient situations such as satellite moves through plasma bubble in the ionosphere where the electron density drastically changes. This fact was first confirmed in our laboratory experiment.

  9. Single Langmuir probe characteristic in a magnetized plasma at the text tokamak

    SciTech Connect

    Jachmich, Stefan

    1995-05-01

    A single Langmuir probe tip was used at TEXT-Upgrade to obtain I-V characteristics in a magnetized plasma. Noisy data were reduced by a boxcar-averaging routine. Unexpected effects, namely nonsaturation of ion current, hysterises in the characteristics and I(V)-data were observed, which are in disagreement to the common single probe model. A double probe model allows parameterization of the I(V) curves and to determine the plasma properties in the scrape-off layer. It is shown in this model that a Langmuir probe does perturb the local space potential in the plasma. Comparisons were made with the triple probe technique of measuring temperatures. The nonsaturation of ion current leads to an error in the triple probe technique of order 20%.

  10. Combined Impedance Probe and Langmuir Probe Studies of the Low-Latitude E Region

    NASA Technical Reports Server (NTRS)

    Rowland, D. E.; Pfaff, R. F.; Steigies, C. T.

    2008-01-01

    The EQUIS-2 sounding rocket and radar campaign, launched from Kwajalein Atoll in 2004, included a mission to study low-latitude irregularities and electrodynamics, led by NASA GSFC. This mission included two instrumented rockets launched into the nighttime E region (apogee near 120 km), which included comprehensive electrodynamics and neutral density instrumentation. These rockets carried the first of a new generation of impedance probes, that utilize a wide-band drive signal to simultaneously measure the impedance of an antenna in a plasma as a function of frequency from 7 kEIz to 4 MHz. at a rapid cadence. This technique promises to permit true plasma spectroscopy, and resulted in the identification of multiple plasma resonances and accurate measurements of the plasma density, even in the low density nighttime E region. We present analyses of the technique and resulting spectra, and show how these data may be combined with fixed-bias Langmuir Probe data to infer the temperature structure of the E region as well as providing accurate absolute calibrations for the very high time resolution fixed-bias probe data. The data is shown to agree well with data from ionosonde, the ALTAIR radar, and the Peruvian beacon experiment.

  11. Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

    NASA Technical Reports Server (NTRS)

    Koelfgen, Syri J.; Eskridge, Richard; Lee, Michael H.; Martin, Adam; Hawk, Clark W.; Fimognan, Peter

    2004-01-01

    The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and ejecting them at high velocity. A plasmoid is a plasma with an imbedded closed magnetic field structure. The shape and magnetic field structure of the translating plasmoids have been measured with of an array of magnetic field probes. Six sets of two B-dot probes were constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes are wound on a square G10 form, and have an average (calibrated) NA of 9.37 x l0(exp -5) square meters, where N is the number of turns and A is the cross-sectional area. The probes were calibrated with a Helmholtz coil, driven by a high-voltage pulser to measure NA, and by a signal generator to determine the probe's frequency response. The plasmoid electron number density n(sub e) electron temperature T(sub e), and velocity ratio v/c(sub m), (where v is the bulk plasma flow velocity and c(sub m), is the ion thermal speed) have also been measured with a quadruple Langmuir probe. The Langmuir probe tips are 10 mm long, 20-mil diameter stainless steel wire, housed in a 6-inch long 4-bore aluminum rod. Measurements on PTX with argon and hydrogen from the magnetic field probes and quadruple Langmuir probe will be presented in this paper.

  12. Application of cylindrical Langmuir probes to streaming plasma diagnostics.

    NASA Technical Reports Server (NTRS)

    Segall, S. B.; Koopman, D. W.

    1973-01-01

    The current-voltage characteristics of cylindrical probes in a high velocity collisionless plasma flow have been investigated experimentally and theoretically. The plasma was generated by a focused laser pulse incident on a metallic target in vacuum. An analysis, developed from a stationary plasma analog to the flowing case, demonstrated a failure of plasma shielding of probe potential in the electron attracting region. Modifications of relatively simple previous treatments were found to be valid for computing electron current to a probe. The electron characteristics derived from the present analysis agree well with experimental results. The ion and electron portions of the characteristics are consistent with each other and with independent diagnostic measurements.

  13. Deriving large electron temperatures and small electron densities with the Cassini Langmuir probe at Saturn

    NASA Astrophysics Data System (ADS)

    Garnier, Philippe; Wahlund, Jan-Erik; Holmberg, Mika; Lewis, Geraint; Schippers, Patricia; Rochel Grimald, Sandrine; Gurnett, Donald; Coates, Andrew; Dandouras, Iannis; Waite, Hunter

    2014-05-01

    The Langmuir Probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigate the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), and manage to reproduce the observations with a reasonable precision through empirical and theoretical methods. Conversely, the modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). We finally show that a significant influence of the energetic electrons (larger than the contribution of thermal ions) is also expected in various plasma environments of the Solar System, such as at Jupiter (i.e near Ganymede, Europa, Callisto and Io), or even at Earth (in the plasmasheet, the magnetosheath or in plasma cavities). Large electron temperatures and small electron densities could potentially be derived in these environments, which may be of interest for Langmuir Probes in the Earth magnetosphere or onboard the future JUICE mission at Jupiter.

  14. LabVIEW software for analyzing Langmuir probe characteristics in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Gandhi, S.; Binwal, S.; Kabariya, H.; Karkari, S. K.

    2016-03-01

    This paper describes the methodology for processing Ampere-Volts (I-V) characteristics of the Langmuir probe in magnetized plasma using graphical programming language based on LabVIEW. Computing the plasma parameters from I-V characteristic involves several steps that include signal processing, interpolation, linear and non-linear curve fitting based on physical models, finding the derivatives of the experimental curve and determining the zero-crossing of the probe current as a function of the applied voltage. These operations are practically tedious to perform manually causing systematic errors in output parameters. To overcome this challenge, software is developed to analyze the planar Langmuir probe characteristics in magnetized plasma. The software allows simultaneous display of different plasma parameters that helps to verify the consistency of the analyzed plasma parameters with the standard probe theory. Using this software, plasma parameters are obtained in a linear plasma device and its characteristics are discussed.

  15. Langmuir Probe Measurements in an Inductively Coupled GEC Reference Cell Plasma

    NASA Technical Reports Server (NTRS)

    Ji, J. S.; Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

    1998-01-01

    Measurements of electron number density, electron temperature, and electron energy distribution function (EEDF) using a compensated Langmuir probe have been performed on an inductively (transformer ) coupled Gaseous Electronics Conference (GEC) reference cell plasma. The plasma source is operated with CH4, CF4, or their mixtures with argon. The effect of independently driving the electrode supporting the wafer on the probe data is studied. In particular, we find that the plasma structure depends on the phase in addition to the magnitude of the power coupled to the electrode relative to that of the transformer coil. The Langmuir probe is translated in a plane parallel to the electrode to investigate the spatial structure of the plasma. The probe data is also compared with fluid model predictions.

  16. An on-line Langmuir probe technique for the study of afterglow plasmas

    NASA Astrophysics Data System (ADS)

    Spanel, Patrik

    1995-11-01

    A new analytical technique has been developed to determine from Langmuir probe characteristics the electron number densities, electron energy distribution functions and electron temperatures in thermal and near-thermal afterglow plasmas. This technique utilises a standard personal computer equipped with a simple 12-bit analogue/digital and digital/analogue converters coupled to the Langmuire probe via a specially designed differential amplifier. The energy distribution functions are obtained by numerical differentiation of the probe characteristics using a fast noise-suppressing numerical technique, the mathematical principles of which are discussed in some detail. Some sample data, which have been obtained in truly thermalised helium flowing afterglows and in argon flowing afterglow at elevated electron temperatures, are presented to demonstrate the value of this new analytical technique.

  17. Investigation of adaptive signal processing methods for denoised I-V curve of Langmuir probe

    NASA Astrophysics Data System (ADS)

    Lee, Jung Yeol; Han, Moon-Ki; Lee, Ho-Jun; Lee, Hae June

    2016-09-01

    It is an important issue to obtain a clear second derivative of Langmuir probe I-V curve which involves the electron energy distribution function. Therefore, noise suppressions against random walk of charges are required in the experimental data. Proper numerical methods including fitting, digital smoothing, digital filtering with window function should be used to remove each types of noise to determine electron energy distribution. The calculation of electron energy distributions demands sequential algorithm of several numerical methods to reduce the noise in I-V curve. In this presentation, a new noise suppression method is suggested to achieve advanced Langmuir probe diagnostics. Combined utilization of nonlinear curve fitting and low pass filter with window function shows more precise results than the utilization of smoothing only. Therefore, results including noise analysis algorithm give new guideline of probe diagnostics.

  18. Radial Density Profile in the SSX Plasma Wind Tunnel using a Double Langmuir Probe

    NASA Astrophysics Data System (ADS)

    Weinhold, D. L.; Flanagan, K.; Gray, T.; Brown, M. R.

    2011-10-01

    We present preliminary results from a moveable double Langmuir probe in the present plasma wind tunnel configuration of SSX. The probe is designed to measure radial profiles of electron density (ne) and electron temperature (Te) across the midplane with a 1 cm resolution. Line-averaged densities from He-Ne interferometry show densities of 1 - 5 ×1015 cm-3 . In addition to mean values, we will also present electrostatic fluctuations and correlations with magnetic field measurements. The double Langmuir probe also measures local Te. Line-averaged measurements from VUV spectroscopy indicate Te ~ 10 eV . The Langmuir probe stalk diameter measures 6 . 5 mm and tip spacing is 1 . 1 mm . The SSX plasma wind tunnel has dimensions L ≅ 1 m and R = 0 . 08 m . Plasma flow speeds are v >= 50 km / s . The cylindrical copper boundary and probe surfaces are baked and cleaned in a He glow discharge to maintain excellent vacuum and surface conditions. Electrostatic measurements during merging will be presented if available. Work supported by US DOE and CMSO.

  19. On the issue of the surface contamination of a Langmuir Probe sensor: Demeter ISL results

    NASA Astrophysics Data System (ADS)

    Lebreton, J. P.

    2011-10-01

    The Demeter Instrument Sonde de Langmuir (ISL) comprises two Langmuir Probe sensors. It includes a classical cylindrical sensor and a 6-sector spherical Segmented Langmuir Probe (SLP) sensor. The CNES Demeter satellite was launched in June 2004 on a 700-km altitude high-inclination orbit. ISL worked flawlessly till the satellite was decommissioned in March 2011. It provided more than 6 years of data. For operational reasons, the science payload was only operated below magnetic latitude 65°. It was switched off twice per orbit when above 65°. A transient behavior of the ISL sensors was systematically observed each time it was turned on at the beginning of each half-orbit segment. This transient behavior is attributed to surface contamination of the sensors. Some surface contamination of the sensor is indeed inferred from the recording of a series of I-V curves at different sweep rates using a special mode designed to monitor the evolution of the surface state of the sensor during the mission. As independently observed from the comparison between Demeter ISL measurements and Ground-based radar ionospheric sounding measurements, (J.-L. Berthelier, private communication, 2011) it is shown that the electron temperature measurements performed by a contaminated Langmuir Probe are significantly higher than the true physical value. Based on the work of Piel at al., a method was developed to determine the electrical characteristics of the surface contamination layer, and to remove the effect of the contamination layer on the determination of the main plasma parameters from the analysis of the I-V curve (the plasma electron density Ne and the Electron temperature Ne). Potential contamination issues for Langmuir Probes on future planetary mission orbiters will be addressed and ways to avoid or at least mitigate the effects of will be discussed.

  20. 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.

  1. On the interpretation of Langmuir probe data inside a spacecraft sheath.

    PubMed

    Olson, J; Brenning, N; Wahlund, J-E; Gunell, H

    2010-10-01

    If a Langmuir probe is located inside the sheath of a negatively charged spacecraft, there is a risk that the probe characteristic is modified compared to that of a free probe in the ambient plasma. We have studied this probe-in-spacecraft-sheath problem in the parameter range of a small Langmuir probe (with radius r(LP)≪λ(D)) using a modified version of the orbit motion limited (OML) probe theory. We find that the ambient electron contribution I(e)(U(LP)) to the probe characteristic is suitably analyzed in terms of three regions of applied probe potential U(LP). In region I, where the probe is negatively charged (i.e., U(LP)probe position), the probe characteristic I(e)(U(LP)) is close to that of OML theory for a free probe in the ambient plasma. In the probe potential range U(LP)>U(1), there is first a transition region II in applied potential, U(1)probe and the ambient plasma. This minimum gives the depth U(pl)-U(M) of a potential barrier that prevents the lowest energy ambient electrons from reaching the probe. For a high enough positive probe potential, in region III, the barrier becomes small. Here, I(e)(U(LP)) again approaches OML theory for a free probe. The boundary U(2) between regions II and III is somewhat arbitrary; we propose a condition on the barrier, U(pl)-U(M)≪k(B)T(e)/e, as the definition of region III. The main findings in this work are qualitative rather than quantitative. The existence of the transition region points to that special care must be taken to extract plasma parameters from measured I(U(LP)) as the probe characteristic is likely to depart from usual OML in crucial respects: (1) the ambient plasma potential U(pl) falls into the transition region, but there is no obvious knee or other feature to identify it, (2) there is in this region no exponential part of I

  2. On the interpretation of Langmuir probe data inside a spacecraft sheath

    SciTech Connect

    Olson, J.; Brenning, N.; Wahlund, J.-E.; Gunell, H.

    2010-10-15

    If a Langmuir probe is located inside the sheath of a negatively charged spacecraft, there is a risk that the probe characteristic is modified compared to that of a free probe in the ambient plasma. We have studied this probe-in-spacecraft-sheath problem in the parameter range of a small Langmuir probe (with radius r{sub LP}<<{lambda}{sub D}) using a modified version of the orbit motion limited (OML) probe theory. We find that the ambient electron contribution I{sub e}(U{sub LP}) to the probe characteristic is suitably analyzed in terms of three regions of applied probe potential U{sub LP}. In region I, where the probe is negatively charged (i.e., U{sub LP}probe position), the probe characteristic I{sub e}(U{sub LP}) is close to that of OML theory for a free probe in the ambient plasma. In the probe potential range U{sub LP}>U{sub 1}, there is first a transition region II in applied potential, U{sub 1}probe and the ambient plasma. This minimum gives the depth U{sub pl}-U{sub M} of a potential barrier that prevents the lowest energy ambient electrons from reaching the probe. For a high enough positive probe potential, in region III, the barrier becomes small. Here, I{sub e}(U{sub LP}) again approaches OML theory for a free probe. The boundary U{sub 2} between regions II and III is somewhat arbitrary; we propose a condition on the barrier, U{sub pl}-U{sub M}<probe characteristic is likely to depart from usual OML in crucial respects: (1) the ambient plasma potential U{sub pl} falls into the transition

  3. Four free parameter empirical parametrization of glow discharge Langmuir probe data.

    PubMed

    Azooz, A A

    2008-10-01

    For the purpose of developing a simple empirical model capable of producing the electron energy distribution function (EEDF) from Langmuir probe I-V characteristics, a four parameter empirical equation that fits most Langmuir probe experimental data is suggested. The four free fitting parameters are related to the main plasma properties. These properties include the ion and electron saturation currents and the plasma electron temperature. This equation can be readily differentiated twice to give the EEDF according to the Druyvesteyn formula. Furthermore, a MATLAB platform based computer code based on this model yielding results for the plasma potential and all plasma parameters mentioned above is presented. The information given below can be used to write other computer codes for the same purpose in any other programming language.

  4. Four free parameter empirical parametrization of glow discharge Langmuir probe data

    NASA Astrophysics Data System (ADS)

    Azooz, A. A.

    2008-10-01

    For the purpose of developing a simple empirical model capable of producing the electron energy distribution function (EEDF) from Langmuir probe I-V characteristics, a four parameter empirical equation that fits most Langmuir probe experimental data is suggested. The four free fitting parameters are related to the main plasma properties. These properties include the ion and electron saturation currents and the plasma electron temperature. This equation can be readily differentiated twice to give the EEDF according to the Druyvesteyn formula. Furthermore, a MATLAB platform based computer code based on this model yielding results for the plasma potential and all plasma parameters mentioned above is presented. The information given below can be used to write other computer codes for the same purpose in any other programming language.

  5. Four free parameter empirical parametrization of glow discharge Langmuir probe data

    SciTech Connect

    Azooz, A. A.

    2008-10-15

    For the purpose of developing a simple empirical model capable of producing the electron energy distribution function (EEDF) from Langmuir probe I-V characteristics, a four parameter empirical equation that fits most Langmuir probe experimental data is suggested. The four free fitting parameters are related to the main plasma properties. These properties include the ion and electron saturation currents and the plasma electron temperature. This equation can be readily differentiated twice to give the EEDF according to the Druyvesteyn formula. Furthermore, a MATLAB platform based computer code based on this model yielding results for the plasma potential and all plasma parameters mentioned above is presented. The information given below can be used to write other computer codes for the same purpose in any other programming language.

  6. Langmuir Probe Measurements of Capacitive Radio Frequency Discharge for Mixture Gases

    NASA Astrophysics Data System (ADS)

    Tanisli, Murat; Sahin, Neslihan; Demir, Suleyman

    2016-10-01

    Radio frequency discharges at low pressure have been used for very much applications, but their properties have not well-known for plasma diagnostics. In this study, mixture discharges are obtained at the quartz glass reactor for different powers and flow rates under the laboratory conditions, and then the optical properties of gas discharges are examined by means of Langmuir probe. When the flow rates of gases and power values are changed, it can be investigated that how the plasma parameters change. Debye length is one of the important plasma parameters. Thus, the relationship between the mixture amount of two different gases and Debye length is determined from Langmuir probe data. The graphs obtained by using these data will give information about generating the discharge of mixture gases, in detail. Therefore, the results may be the useful reference for future works of industrial applications.

  7. Multi-surface Langmuir probe observations from the MTeX and WADIS rocket campaigns

    NASA Astrophysics Data System (ADS)

    Barjatya, A.; Collins, R. L.; Strelnikov, B.; Friedrich, M.; Varney, R. H.; Lehmacher, G. A.

    2015-12-01

    We present results from two mesospheric rocket campaigns: MTeX rockets from Poker Flat Research Range and WADIS rockets from the Andoya Rocket Range. The various payloads carried a novel multi-surface Langmuir probe: three fixed bias Langmuir probes, each with a different work function. In addition to collecting thermal electrons, each surface interacts differently with the neutral constituents of the mesosphere: neutral metal atoms, mesospheric smoke particles, ice particles, etc. The WADIS campaign had one rocket each in polar winter and summer, whereas MTeX campaign had two rockets within half hour of each other in polar winter. We show the data from all rockets and estimate various particle densities from the measured current data.

  8. Pulsed floating-type Langmuir probe for measurements of electron energy distribution function in plasmas

    NASA Astrophysics Data System (ADS)

    Choi, Ikjin; Kim, Aram; Lee, Hyo-Chang; Kim, Dong-Hwan; Chung, Chin-Wook

    2017-01-01

    A floating type Langmuir probe was studied to measure the electron energy distribution function (EEDF) in plasmas. This method measures the current (I)-voltage (V) curve with rising and falling variations based on a floating potential by using charge-discharge characteristics of the series capacitor when a square-pulse voltage is applied. In addition, this method measures the EEDF by using the alternating current (ac) superposition method. The measured EEDFs were in good agreement with results from a conventional single Langmuir probe. This technique could be applied as a plasma diagnostic method in the capacitively coupled plasma where the plasma potential is extremely high or the processing plasma where the deposition gas is used.

  9. Dynamical changes of ion current distribution for a Penning discharge source using a Langmuir probe arraya)

    NASA Astrophysics Data System (ADS)

    Li, M.; Xiang, W.; Xiao, K. X.; Chen, L.

    2012-02-01

    A paralleled plate electrode and a 9-tip Langmuir probe array located 1 mm behind the extraction exit of a cold cathode Penning ion source are employed to measure the total current and the dynamical changes of the ion current in the 2D profile, respectively. Operation of the ion source by 500 V DC power supply, the paralleled plate electrode and the Langmuir probe array are driven by a bias voltage ranging from -200 V to 200 V. The dependence of the total current and the dynamical changes of the ion current in the 2D profile are presented at the different bias voltage. The experimental results show that the distribution of ion current is axial symmetry and approximate a unimodal distribution.

  10. Characterization of helium/argon working gas systems in a radiofrequency glow discharge atomic emission source. Part II: Langmuir probe and emission intensity studies for Al, Cu and Macor samples

    NASA Astrophysics Data System (ADS)

    Belkin, Mikhail; Caruso, Joseph A.; Christopher, Steven J.; Marcus, R. Kenneth

    1998-08-01

    The application of a tuned Langmuir probe is extended to the measurement of the charged particle characteristics (electron and ion number density, average electron energy and electron temperature) in an analytical radiofrequency glow discharge (RF-GD) in helium. The effects of discharge operating conditions, such as RF power and pressure, on the charged particle characteristics for conducting (aluminum) and nonconducting (Macor) samples are studied. The differences in plasma characteristics between argon and helium working gases are discussed. Langmuir probe measurements are also performed in an argon/helium mixture. Variations of the emission intensities of sputtered analytes (copper and aluminum) are investigated when helium is introduced into an argon RF glow discharge plasma. It is recognized that, although the number of sample atoms in the plasma gradually decreases due to reduced sputtering, the emission intensities of various Al(I) and Cu(I) lines increase with helium addition. Measured electron and ion number densities also decrease with helium addition, whereas the average electron energy and electron temperature increase, accounting for the enhancement of emission intensities.

  11. Dust Impact Detection by the Cassini Langmuir Probe in Saturn's E ring

    NASA Astrophysics Data System (ADS)

    Hsu, H.-W.; Wahlund, J.-E.; Morooka, M.; Kempf, S.; Horanyi, M.

    2015-10-01

    In this work, we present preliminary analysis of dust impact detections recorded by the Cassini Langmuir probe (LP) in Saturn's E ring. These signals appear as sharp spikes in the LP current-voltage (I-V) curves and show clear correlation with the E ring dust density. The statistical analysis will help to understand the nature of these detections as well as provide an alternative method to study the densest part of the E ring.

  12. Time-resolved Langmuir Probing of a New Lanthanum Hexaboride (LaB6) Hollow Cathode

    DTIC Science & Technology

    2011-09-01

    like texture and is easily machineable with standard tooling. Competing thermally conductive but electrically insulating ceramics such as aluminum...The 32nd International Electric Propulsion Conference, Wiesbaden, Germany September 11 – 15, 2011 1 Time-resolved Langmuir Probing of a New...Lanthanum Hexaboride (LaB6) Hollow Cathode IEPC-2011-245 Presented at the 32nd International Electric Propulsion Conference, Wiesbaden

  13. Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

    NASA Astrophysics Data System (ADS)

    Shashurin, A.; Li, J.; Zhuang, T.; Keidar, M.; Beilis, I. I.

    2011-07-01

    The temporal evolution of a high pressure He arc producing nanotubes was considered and the Langmuir probe technique was applied for plasma parameter measurements. Two modes of arc were observed: cathodic arc where discharge is supported by erosion of cathode material and anodic arc which is supported by ablation of the anode packed with carbon and metallic catalysts in which carbon nanotubes are synthesized. Voltage-current (V-I) characteristics of single probes were measured and unusually low ratio of saturation current on positively biased probe to that on negatively biased of about 1-4 was observed. This effect was explained by increase of measured current at the negatively biased probe above the level of ion saturation current due to secondary electron emission from the probe surface. Since utilization of standard collisionless approach to determine plasma parameters from the measured V-I characteristic is not correct, the electron saturation current was used to estimate the plasma density.

  14. Langmuir probe measurements of double-layers in a pulsed discharge

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Crawford, F. W.

    1980-01-01

    Langmuir probe measurements were carried out which confirm the occurrence of double-layers in an argon positive column. Pulsing the discharge current permitted probe measurements to be performed in the presence of the double-layer. Supplementary evidence, obtained from DC and pulsed discharges, indicated that the double-layers formed in the two modes of operation were similar. The double-layers observed were weak and stable; their relation to other classes of double-layers are discussed, and directions for future work are suggested.

  15. Modeling a Langmuir probe in atmospheric pressure plasma at different EEDFs

    NASA Astrophysics Data System (ADS)

    Trenchev, G.; Kolev, St.; Kiss'ovski, Zh

    2017-05-01

    In this study, we present a computational model of a cylindrical electric probe in atmospheric pressure argon plasma. The plasma properties are varied in terms of density and electron temperature. Furthermore, results for plasmas with Maxwellian and non-Maxwellian electron energy distribution functions are also obtained and compared. The model is based on the fluid description of plasma within the COMSOL software package. The results for the ion saturation current are compared and show good agreement with existing analytical Langmuir probe theories. A strong dependence between the ion saturation current and electron transport properties was observed, and attributed to the effects of ambipolar diffusion.

  16. An experimental investigation of an arcjet thruster exhaust using Langmuir probes. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Carney, Lynnette M.

    1988-01-01

    Electrostatic (Langmuir) probes of both spherical and cylindrical geometry have been used to obtain electron number density and temperature in the exhaust of a laboratory arcjet. The arcjet thruster operated on nitrogen and hydrogen mixtures to simulate fully decomposed hydrazine in a vacuum environment with background pressures less than 5 x 10 to the -2 Pa. The exhaust appears to be only slightly ionized (less than 1 percent) with local plasma potentials near facility ground. The current-voltage characteristics of the probes indicate a Maxwellian temperature distribution. Plume data are presented as a function of arcjet operating condition and also position in the exhaust.

  17. Direct Vlasov simulations of electron-attracting cylindrical Langmuir probes in flowing plasmas

    SciTech Connect

    Sánchez-Arriaga, G.; Pastor-Moreno, D.

    2014-07-15

    Current collection by positively polarized cylindrical Langmuir probes immersed in flowing plasmas is analyzed using a non-stationary direct Vlasov-Poisson code. A detailed description of plasma density spatial structure as a function of the probe-to-plasma relative velocity U is presented. Within the considered parametric domain, the well-known electron density maximum close to the probe is weakly affected by U. However, in the probe wake side, the electron density minimum becomes deeper as U increases and a rarified plasma region appears. Sheath radius is larger at the wake than at the front side. Electron and ion distribution functions show specific features that are the signature of probe motion. In particular, the ion distribution function at the probe front side exhibits a filament with positive radial velocity. It corresponds to a population of rammed ions that were reflected by the electric field close to the positively biased probe. Numerical simulations reveal that two populations of trapped electrons exist: one orbiting around the probe and the other with trajectories confined at the probe front side. The latter helps to neutralize the reflected ions, thus explaining a paradox in past probe theory.

  18. Updates on Optical Emission Spectroscopy & Langmuir Probe Investigations on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    Karama, Jackson; Frank, John; Azzari, Phillip; Hopson, Jordan; James, Royce; Duke-Tinson, Omar; Paolino, Richard; Sandri, Eva; Sherman, Justin; Wright, Eva; Turk, Jeremy

    2015-11-01

    HPX is developing a to shorter lifetime (20 - 30 ns) more reproducible plasma at the Coast Guard Academy Plasma Laboratory (CGAPL). Once achieved, spectral and particle probes will help to verify plasma mode transitions to the W-mode. These optical probes utilize movable filters, and ccd cameras to gather data at selected spectral frequency bands. Once corrections for the RF field are in place for the Langmuir probe, raw data will be collected and used to measure the plasma's density, temperature, and potentially the structure and behavior during experiments. Direct measurements of plasma properties can be determined with modeling and by comparison with the state transition tables, both using Optical Emission Spectroscopy (OES). The spectral will add to HPX's data collection capabilities and be used in conjunction with the particle probes, and Thomson Scattering device to create a robust picture of the internal and external plasma parameters on HPX. Progress on the implementation of the OES and Langmuir probes will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15.

  19. High accuracy plasma density measurement using hybrid Langmuir probe and microwave interferometer method.

    PubMed

    Deline, C; Gilchrist, B E; Dobson, C; Jones, J E; Chavers, D G

    2007-11-01

    High spatial resolution plasma density measurements have been taken as part of an investigation into magnetic nozzle physics at the NASA/MSFC Propulsion Research Center. These measurements utilized a Langmuir triple probe scanned across the measurement chord of either of two stationary rf interferometers. By normalizing the scanned profile to the microwave interferometer line-integrated density measurement for each electrostatic probe measurement, the effect of shot-to-shot variation of the line-integrated density can be removed. In addition, by summing the voltage readings at each radial position in a transverse scan, the line density can be reconstituted, allowing the absolute density to be determined, assuming that the shape of the profile is constant from shot to shot. The spatial and temporal resolutions of this measurement technique depend on the resolutions of the scanned electrostatic probe and the interferometer. The measurement accuracy is 9%-15%, which is on the order of the accuracy of the rf interferometer. The measurement technique was compared directly with both scanning rf interferometer and standard Langmuir probe theory. The hybrid technique compares favorably with the scanning rf interferometer, and appears more accurate than probe theory alone. Additionally, our measurement technique is generally applicable even for nonaxisymmetric plasmas.

  20. Fast-switching Langmuir probe bias electronics for Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Lyons, L.; Labombard, B.

    2006-10-01

    In order to resolve fast-changes in edge plasma density, temperature and plasma potentials with a single Langmuir electrode, the I-V characteristic must be generated and sampled at high frequency. To this end, a custom-designed package of fast-switching electronics is being assembled for use in Alcator C-Mod, employing three principal components: (1) a master TTL ‘waveform generator’, (2) fast-switching MOSFET drive circuits (˜ 30 ns rise time), and (3) current-voltage monitor circuits. Three voltage bias states are capacitively coupled to up to 6 Langmuir probes in a sequence that samples portions of the I-V characteristic: ‘ion saturation (>= -234V), ‘electron collection’ (<= +64V), and ‘near floating’ (˜ 0V). Up to 2 amps of peak current can be supplied to each probe with waveform durations of ˜ 2 seconds. Resultant I-V characteristics are digitally sampled (<= 50MHz) by cPCI transient recorders. Three additional TTL waveforms, synchronized to the data-sampling times of the different bias states, are also supplied. These may be used to report plasma conditions in real-time using a ‘mirror Langmuir probe’ technique [1]. [1] B. LaBombard and L. Lyons, manuscript in preparation.

  1. Magnetic and Langmuir Probe Measurements on the Plasmoid Thruster Experiment (PTX)

    NASA Technical Reports Server (NTRS)

    Koelfgen, Syri J.; Eskridge, Richard; Fimognari, Peter; Hawk, Clark W.; Lee, Mike; Martin, Adam

    2004-01-01

    The Plasmoid Thruster Experiment (PTX) operates by inductively producing plasmoids in a conical theta-pinch coil and subsequently ejecting them at high velocity. An overview of PTX is described in a companion paper. The shape and magnetic field structure of the translating plasmoids will be measured with of an array of inductive magnetic field probes. Six sets of two B-dot probes (for a total of twelve probes) have been constructed for measuring B(sub z) and B(sub theta), the axial and azimuthal components of the magnetic field. The probes were calibrated with a Helmholtz coil, driven alternately by a high-voltage pulser or a signal generator. The probes are wound on a G-10 form, and have an average (calibrated) NA of 9.37 x 10(exp -5) square meters, where N is the number of turns and A is cross-sectional area. The frequency response of the probes was measured over the range from 1 kHz to 10 MHZ. The electron number density n(sub e), electron temperature T(sub e) and velocity v will be determined from measurements taken with a quadruple Langmuir probe, situated in the exhaust chamber. Three of the four probes on the quadruple probe sample the current-voltage characteristic, and from this yield measurements of T(sub e) and n(sub e). The fourth probe provides a measurement of plasma flow velocity. A 6-inch long alumina rod, hollowed with four holes to house the probe wires, is being used to construct the quadruple probe. A variety of propellants will be used, including hydrogen, nitrogen and argon. From the measurements of the plasmoid mass, density, temperature, and velocity, the basic propulsion characteristics of PTX will be evaluated.

  2. A hemispherical Langmuir probe array detector for angular resolved measurements on droplet-based laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Gambino, Nadia; Brandstätter, Markus; Rollinger, Bob; Abhari, Reza

    2014-09-01

    In this work, a new diagnostic tool for laser-produced plasmas (LPPs) is presented. The detector is based on a multiple array of six motorized Langmuir probes. It allows to measure the dynamics of a LPP in terms of charged particles detection with particular attention to droplet-based LPP sources for EUV lithography. The system design permits to temporally resolve the angular and radial plasma charge distribution and to obtain a hemispherical mapping of the ions and electrons around the droplet plasma. The understanding of these dynamics is fundamental to improve the debris mitigation techniques for droplet-based LPP sources. The device has been developed, built, and employed at the Laboratory for Energy Conversion, ETH Zürich. The experimental results have been obtained on the droplet-based LPP source ALPS II. For the first time, 2D mappings of the ion kinetic energy distribution around the droplet plasma have been obtained with an array of multiple Langmuir probes. These measurements show an anisotropic expansion of the ions in terms of kinetic energy and amount of ion charge around the droplet target. First estimations of the plasma density and electron temperature were also obtained from the analysis of the probe current signals.

  3. High heat flux Langmuir probe array for the DIII-D divertor plates

    SciTech Connect

    Watkins, J. G.; Nygren, R. E.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.

    2008-10-15

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m{sup 2} for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5 deg. surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric 'rooftop' design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of J{sub sat}, T{sub e}, and V{sub f} with 4 mm spatial resolution are shown.

  4. High heat flux Langmuir probe array for the DIII-D divertor platesa)

    NASA Astrophysics Data System (ADS)

    Watkins, J. G.; Taussig, D.; Boivin, R. L.; Mahdavi, M. A.; Nygren, R. E.

    2008-10-01

    Two modular arrays of Langmuir probes designed to handle a heat flux of up to 25 MW/m2 for 10 s exposures have been installed in the lower divertor target plates of the DIII-D tokamak. The 20 pyrolytic graphite probe tips have more than three times higher thermal conductivity and 16 times larger mass than the original DIII-D isotropic graphite probes. The probe tips have a fixed 12.5° surface angle to distribute the heat flux more uniformly than the previous 6 mm diameter domed collectors and a symmetric "rooftop" design to allow operation with reversed toroidal magnetic field. A large spring-loaded contact area improves heat conduction from each probe tip through a ceramic insulator into a cooled graphite divertor floor tile. The probe tips, brazed to molybdenum foil to ensure good electrical contact, are mounted in a ceramic tray for electrical isolation and reliable cable connections. The new probes are located 1.5 cm radially apart in a staggered arrangement near the entrance to the lower divertor pumping baffle and are linearly spaced 3 cm apart on the shelf above the in-vessel cryopump. Typical target plate profiles of Jsat, Te, and Vf with 4 mm spatial resolution are shown.

  5. The spherical segmented Langmuir probe in a flowing thermal plasma: numerical model of the current collection

    NASA Astrophysics Data System (ADS)

    Séran, E.; Berthelier, J.-J.; Saouri, F. Z.; Lebreton, J.-P.

    2005-07-01

    The segmented Langmuir probe (SLP) has been recently proposed by one of the authors (Lebreton, 2002) as an instrument to derive the bulk velocity of terrestrial or planetary plasmas, in addition to the electron density and temperature that are routinely measured by Langmuir probes. It is part of the scientific payload on the DEMETER micro-satellite developed by CNES. The basic concept of this probe is to measure the current distribution over the surface using independent collectors under the form of small spherical caps and to use the angular anisotropy of these currents to obtain the plasma bulk velocity in the probe reference frame. In order to determine the SLP capabilities, we have developed a numerical PIC (Particles In Cell) model which provides a tool to compute the distribution of the current collected by a spherical probe. Our model is based on the simultaneous determination of the charge densities in the probe sheath and on the probe surface, from which the potential distribution in the sheath region can be obtained. This method is well adapted to the SLP problem and has some advantages since it provides a natural control of the charge neutrality inside the simulation box, allows independent mesh sizes in the sheath and on the probe surface, and can be applied to complex surfaces. We present in this paper initial results obtained for plasma conditions corresponding to a Debye length equal to the probe radius. These plasma conditions are observed along the Demeter orbit. The model results are found to be in very good agreement with those published by Laframboise (1966) for a spherical probe in a thermal non-flowing plasma. This demonstrates the adequacy of the computation method and of the adjustable numerical parameters (size of the numerical box and mesh, time step, number of macro-particles, etc.) for the considered plasma-probe configuration. We also present the results obtained in the case of plasma flowing with mesothermal conditions reproducing the

  6. The Use of Langmuir Probes in Non-Maxwellian Space Plasmas

    NASA Technical Reports Server (NTRS)

    Hoegy, Walter R.; Brace, Larry H.

    1998-01-01

    Disturbance of the Maxwellian plasma may occur in the vicinity of a spacecraft due to photoemission, interactions between the spacecraft and thermospheric gases, or electron emissions from other devices on the spacecraft. Significant non-maxwellian plasma distributions may also occur in nature as a mixture of ionospheric and magnetospheric plasmas or secondaries produced by photoionization in the thermosphere or auroral precipitation. The general formulas for current collection (volt-ampere curves) by planar, cylindrical, and spherical Langmuir probes in isotropic and anisotropic non-maxwellian plasmas are examined. Examples are given of how one may identify and remove the non-maxwellian components in the Langmuir probe current to permit the ionospheric parameters to be determined. Theoretical volt-ampere curves presented for typical examples of non-maxwellian distributions include: two-temperature plasmas and a thermal plasma with an energetic electron beam. If the non-ionospheric electrons are Maxwellian at a temperature distinct from that of the ionosphere electrons, the volt-ampere curves can be fitted directly to obtain the temperatures and densities of both electron components without resorting to differenting the current. For an arbitrary isotropic distribution, the current for retarded particles is shown to be identical for the three geometries. For anisotropic distributions, the three probe geometries are not equally suited for measuring the ionospheric electron temperature and density or for determining the distribution function in the presence of non-maxwellian back-round electrons.

  7. On modified finite difference method to obtain the electron energy distribution functions in Langmuir probes

    SciTech Connect

    Kang, Hyun-Ju; Chung, Chin-Wook; Choi, Hyeok; Kim, Jae-Hyun; Lee, Se-Hun; Yoo, Tae-Ho

    2016-06-15

    A modified central difference method (MCDM) is proposed to obtain the electron energy distribution functions (EEDFs) in single Langmuir probes. Numerical calculation of the EEDF with MCDM is simple and has less noise. This method provides the second derivatives at a given point as the weighted average of second order central difference derivatives calculated at different voltage intervals, weighting each by the square of the interval. In this paper, the EEDFs obtained from MCDM are compared to those calculated via the averaged central difference method. It is found that MCDM effectively suppresses the noises in the EEDF, while the same number of points are used to calculate of the second derivative.

  8. A statistical study of the subauroral electron temperature enhancement using dynamics Explorer 2 Langmuir probe observations

    NASA Technical Reports Server (NTRS)

    Kozyra, J. U.; Cravens, T. E.; Nagy, A. F.; Brace, L. H.

    1986-01-01

    A statistical study of the subauroral electron temperature enhancement was undertaken using Langmuir probe observations during 488 traversals of the midlatitude plasmapause region by the DE-2 satellite. The subauroral electron temperature enhancement on the nightside is a quasi-permanent feature at all altitudes between 350 and 1000 km with an occurrence frequency that depends on altitude. The occurrence frequency of the subauroral electron temperature peak has a strong altitude dependence on the dayside. The position of the subauroral Te peak decreases with increasing magnetic activity in a manner similar to that of the equatorial plasmapause and other midlatitude plasmapause signatures.

  9. Thermal ion imagers and Langmuir probes in the Swarm electric field instruments

    NASA Astrophysics Data System (ADS)

    Knudsen, D. J.; Burchill, J. K.; Buchert, S. C.; Eriksson, A. I.; Gill, R.; Wahlund, J.-E.; Åhlen, L.; Smith, M.; Moffat, B.

    2017-02-01

    The European Space Agency's three Swarm satellites were launched on 22 November 2013 into nearly polar, circular orbits, eventually reaching altitudes of 460 km (Swarm A and C) and 510 km (Swarm B). Swarm's multiyear mission is to make precision, multipoint measurements of low-frequency magnetic and electric fields in Earth's ionosphere for the purpose of characterizing magnetic fields generated both inside and external to the Earth, along with the electric fields and other plasma parameters associated with electric current systems in the ionosphere and magnetosphere. Electric fields perpendicular to the magnetic field B→ are determined through ion drift velocity v→i and magnetic field measurements via the relation E→⊥=-v→i×B→. Ion drift is derived from two-dimensional images of low-energy ion distribution functions provided by two Thermal Ion Imager (TII) sensors viewing in the horizontal and vertical planes; v→i is corrected for spacecraft potential as determined by two Langmuir probes (LPs) which also measure plasma density ne and electron temperature Te. The TII sensors use a microchannel-plate-intensified phosphor screen imaged by a charge-coupled device to generate high-resolution distribution images (66 × 40 pixels) at a rate of 16 s-1. Images are partially processed on board and further on the ground to generate calibrated data products at a rate of 2 s-1; these include v→i, E→⊥, and ion temperature Ti in addition to electron temperature Te and plasma density ne from the LPs.

  10. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

    SciTech Connect

    Xu, J. C.; Jia, M. N.; Feng, W.; Deng, G. Z.; Wang, L. Xu, G. S.; Luo, G. N.; Yao, D. M.; Li, Q.; Cao, L.; Chen, L.; Zhang, W.; Liu, S. C.; Wang, H. Q.; Hu, L. Q.; Wan, B. N.; Li, J.; Sun, Y. W.; Guo, H. Y.

    2016-08-15

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

  11. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Xu, J. C.; Wang, L.; Xu, G. S.; Luo, G. N.; Yao, D. M.; Li, Q.; Cao, L.; Chen, L.; Zhang, W.; Liu, S. C.; Wang, H. Q.; Jia, M. N.; Feng, W.; Deng, G. Z.; Hu, L. Q.; Wan, B. N.; Li, J.; Sun, Y. W.; Guo, H. Y.

    2016-08-01

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

  12. Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak.

    PubMed

    Xu, J C; Wang, L; Xu, G S; Luo, G N; Yao, D M; Li, Q; Cao, L; Chen, L; Zhang, W; Liu, S C; Wang, H Q; Jia, M N; Feng, W; Deng, G Z; Hu, L Q; Wan, B N; Li, J; Sun, Y W; Guo, H Y

    2016-08-01

    In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

  13. Langmuir Probe and Waves instrument on Mars Atmosphere and Volatile EvolutioN mission

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Ergun, R.; Delory, G. T.; Eparvier, F.; Chamberlin, P. C.; Eriksson, A. I.

    2013-12-01

    To understand how the water was lost at Mars it is critical to understand the atmosphere. One important parameter that is needed and is complicated to model is the electron temperature. At present time most atmospheric models use a fixed temperature profile based on only two in-situ measurements made over 30 years ago by the Viking landers. How important the ion outflow at Mars is for the atmospheric loss depends on how much heating takes place close to the exobase. At Mars the frequencies of the fluctuations in the solar wind can couple directly to the exobase, where such frequencies are close to the heavy ions gyro motion allowing efficient energy transfer from the solar wind to the ions at the exobase. Another part of the puzzle of the atmospheric escape is the ionization rate that is mainly driven by wavelengths in EUV from the sun. Therefore, the newest NASA mission, Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, to be launched in November 2013 and arrive at Mars September 2014, has included a Langmuir Probe and Waves (LPW) instrument which incudes and EUV detector. This instrument measures (1) electron temperature and density via a Langmuir probe; (2) DC and AC electric fields; and (3) the most critical EUV bands of the solar irradiance with a separate detector. This presentation describes the instrument capabilities and the expected impact the data will have on the field.

  14. Probe diagnostics in low pressure dc discharge. Does the Langmuir Paradox exist?

    NASA Astrophysics Data System (ADS)

    Godyak, Valery; Alexandrovich, Ben; Rahman, Abdur

    2006-10-01

    Maxwellian electron energy distributions in a highly non-equilibrium plasma of low pressure dc discharges is one the oldest and fascinating mysteries of gas discharge physics. There is extensive literature and many hypotheses attempting to explain this paradox, but the problem still remains unsolved. In this report we present results on the EEDF measurement in the positive column of a dc discharge in mercury vapor with differently oriented probes placed along the positive column over a wide range of discharge current showed that: a) - the EEDF is not Maxwellian, b) - is essentially anisotropic, c) - is not in equilibrium with discharge current (i.e. EEDF changes along the positive column), d) - the electron temperature inferred from the measured EEDF and that determined by the slope of the probe characteristic in semi-log scale are essentially different, e) - the linearity of the probe characteristic in semi-log scale (the sign of a Maxwellian EEDF) may occurs at essentially nonlinear dependence of the second derivative of the probe characteristic on the probe voltage in semi-log scale. The main conclusions of this study are: a) - the absence of Maxwellian EEDF in the low pressure dc discharge and b) - the Druyvesteyn method is not applicable for measurement of highly anisotropic EEDF typical for the Langmuir Paradox condition.

  15. Identification of when a Langmuir probe is in the sheath of a spacecraft: The effects of secondary electron emission from the probe

    NASA Astrophysics Data System (ADS)

    Wang, X.; Hsu, H.-W.; Horányi, M.

    2015-04-01

    Langmuir probes on spacecraft have been used for characterizing the ambient plasma parameters in space. When their boom is short compared to the Debye length, the probes remain immersed in the spacecraft sheath, causing the current-voltage (I-V) characteristics to deviate from that of a probe far away from the spacecraft. We present identification of when a Langmuir probe is in a sheath, based on the secondary electron (SE) emission from the probe itself. The I-V characteristics of a spherical probe are investigated in a plasma sheath above a conducting plate. Plasmas with cold and hot electrons (1 eV and 10 eV), as well as monoenergetic electrons (50-100 eV), are created. The derivative (dI/dV) of the probe I-V curves shows that in addition to a "knee" at a potential more positive than the plasma potential, an additional knee appears at a sheath potential at the probe location. This additional knee is created due to the SE emission from the probe and is identified as an indication of the probe being immersed in the sheath. Our experimental results reproduced the aspects of the Cassini Langmuir probe I-V characteristics, suggesting that at times, the probe may have been immersed in the sheath of the spacecraft in Saturn's magnetosphere, and SE emission from the probe itself may have significantly altered its I-V characteristics.

  16. Plasma diagnostics with Langmuir probes in the equatorial ionosphere: II. Evaluation of DEOS flight F06

    NASA Astrophysics Data System (ADS)

    Hirt, M.; Steigies, C. T.; Piel, A.

    2001-09-01

    The flight data of an ionospheric sounding rocket (DEOS campaign flight F06) are evaluated with respect to electron density and temperature profiles. The probe characteristic is analysed in the frame of a model that takes the influence of the geomagnetic field and of a contamination layer into account, as described in part I (Piel et al 2001 J. Phys. D: Appl. Phys.). The electron temperature of the night-time ionosphere is found to be higher (1300 K) than that predicted by the IRI-95 model (Bilitza D 1999 J. Atmos. Terr. Phys. 61 167), but in general agreement with the model of Watanabe et al (Watanabe et al 1995 J. Geophys. Res. 100 14 581). It is also found that the electron temperature in depleted plasma regions (plasma bubbles) is lower than in the unperturbed plasma. This is a hint at the action of the Rayleigh-Taylor mechanism that convects cold low-density plasma from the bottomside of the F-layer to higher altitudes inside the plasma bubbles. An absolute comparison of the electron density profiles from the analysis of the Langmuir probe and by an independent impedance probe is performed. Excellent agreement of the profile shape and of absolute density values can be achieved over the entire altitude regime. It is demonstrated which steps in the evaluation procedure of the probe characteristic may lead to systematic errors in electron density.

  17. Dust impact detection by the Cassini Langmuir probe in Saturn's E ring

    NASA Astrophysics Data System (ADS)

    Hsu, S.; Wahlund, J. E.; Kempf, S.; Wang, X.; Horanyi, M.; Morooka, M. W.

    2015-12-01

    Individual examination reveals the existence of sharp spikes in the Cassini Radio and Plasma Wave Science / Langmuir probe (RPWS/LP) I-V (current-voltage) sweeps. These spikes are characterized as a sudden increase or decrease in the probe current, with many of them appearing as one-point anomalies lasting less than a millisecond. Their occurrence generally correlates with the E ring dust density - the closer to the ring plane and Enceladus, the more frequent the appearance of spikes. These characteristics suggest that the LP spike signals are caused by dust impacts - most likely the collection of plasma produced from high velocity dust-probe impacts. Because of the low detection rate and the flexibility regarding to the spacecraft attitude, LP spikes provide an alternative way to explore the densest part of the E ring. Here we will present a preliminary statistical analysis of the LP spike appearance as a function of the spacecraft location, the relative dust speed, the spacecraft and probe potentials, and other relevant parameters. Comparison with measurements carried out by the High Rate Detector, a subsystem of the Cassini Cosmic Dust Analyser, will provide constraints on the dust grain size responsible for these detections. We will also examine their spatial distribution to identify features that may associate with ring dynamical effects, such as the seasonal variation or the noon-to-midnight electric field.

  18. I-V characteristics of the Langmuir probe in flowing afterglow plasmas

    NASA Astrophysics Data System (ADS)

    Shun'ko, E. V.

    2003-04-01

    The specific features of the probe I-V characteristics in flowing-afterglow plasmas are studied experimentally and in theory. As it was found at a probe potential equal to the plasma one, V=0, an electron concentration in a probe vicinity (and a probe current) is decreased due to a predominant outflow of the electrons into an electrical circuit of the probe from the probe vicinity. The expression allowing one to reconstruct the undisturbed-by-probe electron concentration from only experimental data is derived. The reconstructed values of the electron concentration enable one to find from the experiments the semiempiric expressions allowing to describe quantitatively the behavior of the probe I-V characteristics at the electron-attracting as well as at the ion-attracting potential, respectively. The expressions found (both for electron-attracting and ion-attracting potential) include the "separating length," which merely is the Langmuir length with a factor equal to the square root of the electron mass over the ion mass ratio for two-component plasma. The intermediate part of the probe I-V characteristics is discovered for probes operating with afterglow plasmas. This intermediate part is described in terms of the experimental parameter L0 having a dimension of the length (presumably electron-orbital length). The value of the parameter L0 does not depend on plasma parameters to within the ranges of plasma parameter variations for experimentally investigated plasmas as it was found. The experiments were performed with two cylindrical probes of 10 and 25 μm diam and ˜3 mm lengths in the experimentally investigated ranges of the afterglow plasma parameters: 105 cm-3

  19. Measurements of plasma profiles using a fast swept Langmuir probe in the VINETA-II magnetic reconnection experiment

    NASA Astrophysics Data System (ADS)

    Shesterikov, I.; Von Stechow, A.; Grulke, O.; Stenzel, R.; Klinger, T.

    2017-07-01

    A fast-swept Langmuir probe capable to be biased at a high voltages has been constructed and successfully operated at the VINETA-II magnetic reconnection experiment. The presented circuit has two main features beneficial for fast transient parameter changes in laboratory experiments as, e.g., plasma guns or magnetic reconnection: the implementation simplicity and the high voltage sweep range. This work presents its design and performance for time-dependent measurements of VINETA-II plasmas. The probe is biased with a sinusoidal voltage at a fixed frequency. Current - voltage characteristics are measured along the falling and rising slopes of the probe bias. The sweep frequency is fsweep= 150 kHz. The spatiotemporal evolution of radial plasma profiles is obtained by evaluation of the probe characteristics. The plasma density measurements agree with those derived from a microwave interferometer, demonstrating the reliability of the measurements. As a model plasma system, a plasma gun discharge with typical pulse times of 60 μ s is chosen.

  20. Understanding narrow SOL power flux component in COMPASS limiter plasmas by use of Langmuir probes

    NASA Astrophysics Data System (ADS)

    Dejarnac, R.; Stangeby, P. C.; Goldston, R. J.; Gauthier, E.; Horacek, J.; Hron, M.; Kocan, M.; Komm, M.; Panek, R.; Pitts, R. A.; Vondracek, P.

    2015-08-01

    The narrow scrape-off layer power component observed in COMPASS inner wall limiter circular discharges by means of IR thermography is investigated by Langmuir probes embedded in the limiter. The power flux profiles are in good agreement with IR observations and can be described by a double-exponential decay with a short decay length (<5 mm) just outside the separatrix and a longer one (∼50 mm) for the rest of the profile in the main scrape-off layer. Non-ambipolar currents measured at the limiter apex play a relatively modest role in the formation of the narrow component. The fraction of the deposited power due to non-ambipolarity varies between 2% and 45%. On the other hand, the measured power widths are roughly consistent in magnitude with a model that takes into account drift effects, suggesting these effects may be dominant.

  1. Langmuir probe study of an inductively coupled magnetic-pole-enhanced helium plasma

    NASA Astrophysics Data System (ADS)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Naeem, M.; Zaka-ul-Islam, M.; Zakaullah, M.

    2017-03-01

    This study reports the effects of RF power and filling gas pressure variation on the plasma parameters, including the electron number density n e , electron temperature T e , plasma potential V p , skin depth δ, and electron energy probability functions (EEPFs) in a low-pressure inductively coupled helium plasma source with magnetic pole enhancement. An RF compensated Langmuir probe is used to measure these plasma parameters. It is observed that the electron number density increases with both the RF power and the filling gas pressure. Conversely, the electron temperature decreases with increasing RF power and gas pressure. It is also noted that, at low RF powers and gas pressures, the EEPFs are non-Maxwellian, while at RF powers of ≥50 W, they evolve into a Maxwellian distribution. The dependences of the skin depth and plasma potential on the RF power are also studied and show a decreasing trend.

  2. Langmuir Probe Ion density and spacecraft potential analysis for low velocity ions at comet 67P

    NASA Astrophysics Data System (ADS)

    Leffe Johansson, Fredrik; Vigren, Erik; Eriksson, Anders; Henri, Pierre; Vallières, Xavier

    2017-04-01

    The RPC-LAP Langmuir Probe instrument on-board Rosetta monitored the evolution of the plasma around comet 67P/Churyumov-Gerasimenko for more than two years. As the neutral gas density was too low to support efficient electron cooling, the electron temperature remained around 10 eV which drove the spacecraft to negative potential of the same order, complicating the interpretation of the LAP data. To support data interpretation, spacecraft-plasma interaction simulations including simulated I-V curves were carried out using the SPIS code package and we find that the often highly negatively charged (-20V) Rosetta spacecraft accelerate ions towards the spacecraft. If not taken into account, this could lead to an overestimate of the ion speed in the I-V curves. The spacecraft-plasma interaction result is then applied to interpret and constrain cometary ion velocities and densities at perihelion in August 2015.

  3. Soft Particle Spectrometer, Langmuir Probe, and Data Analysis for Aerospace Magnetospheric/Thermospheric Coupling Rocket Program

    NASA Technical Reports Server (NTRS)

    Sharber, J. R.; Frahm, R. A.; Scherrer, J. R.

    1997-01-01

    Under this grant two instruments, a soft particle spectrometer and a Langmuir probe, were refurbished and calibrated, and flown on three instrumented rocket payloads as part of the Magnetosphere/Thermosphere Coupling program. The flights took place at the Poker Flat Research Range on February 12, 1994 (T(sub o) = 1316:00 UT), February 2, 1995 (T(sub o) = 1527:20 UT), and November 27, 1995 (T(sub o) = 0807:24 UT). In this report the observations of the particle instrumentation flown on all three of the flights are described, and brief descriptions of relevant geophysical activity for each flight are provided. Calibrations of the particle instrumentation for all ARIA flights are also provided.

  4. Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir probe

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Hoegy, W. R.; Theis, R. F.

    1988-01-01

    Data from the Pioneer Venus Langmuir probe, collected since 1979 (and thus, including the period between solar maximum in 1979-1980 and solar minimum in 1986-1987) are examined. Calculations show that about 51 percent of the solar emission at Venus is due to Lyman alpha (1216 A), 46 percent is produced by wavelengths between 550 and 1100 A, and less than 3 percent is due to wavelengths longer than Lyman alpha. The photocurrents were found to exhibit variations related to the solar cycle and solar rotation, as well as a major 7.2-month periodicity. Three different indices of solar EUV behavior at Venus were derived, which include the photoemission current itself, the total EUV flux, and an F(10.7)-like solar index, and are compared with related measurements made simultaneously at earth.

  5. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    SciTech Connect

    Brombin, M. Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

    2014-11-15

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors’ holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  6. Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from Radio Frequency plasma) experiment: tests in BATMAN (BAvarian Test Machine for Negative ions).

    PubMed

    Brombin, M; Spolaore, M; Serianni, G; Pomaro, N; Taliercio, C; Dalla Palma, M; Pasqualotto, R; Schiesko, L

    2014-11-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  7. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    NASA Astrophysics Data System (ADS)

    Brombin, M.; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

    2014-11-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  8. Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir Probe

    SciTech Connect

    Brace, L.H.; Hoegy, W.R.; Theis, R.F. )

    1988-07-01

    The photoelectron current from the Pioneer Venus Langmuir probe has provided measurements of the solar extreme ultraviolet flux at Venus since 1979. This current is the product of the photoelectric yield of the collector and the solar spectrum at wavelengths short enough to cause emission. Calculations show that approximately 51% of the emission is due to Lyman {alpha} (1,216 {angstrom}), 46% is produced by wavelengths between 550 and 1,100 {angstrom}, and less than 3% is due to wavelengths longer than Lyman {alpha}. Thus, the Langmuir probe provides a direct measure of the total solar EUV flux, including most of the wavelengths that produce the Venus ionosphere and heat and excite neutrals in the thermosphere. The measurement technique is described, and the daily average measurements of photocurrent obtained between 1979 and 1987 are presented. The photocurrents exhibit variations related to the solar cycle and solar rotation, as well as a major 7.2-month periodicity. The authors present three indices of EUV based on the measurements: (1) the photoemission current itself, (2) the total EUV flux, and (3) an F{sub 10.7}-like solar index. These are compared with related measurements made simultaneously at Earth. These data may also help solar physicists track the intensity of EUV emission regions on the Sun while they are not visible from the Earth. The EUV flux profile of a solar flare event is also illustrated. In the future the method also could be applied on a comet mission to obtain the incident solar EUV flux, to measure the EUV extinction profiles of the cometary atmosphere, and to sample directly the dust and gas environment of the comet through the ionization the dust and gas produce when they impact the collector.

  9. Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

    DOE PAGES

    Boedo, J. A.; Rudakov, D. L.

    2017-03-20

    Here we present a method to calculate the ion saturation current, Isat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of Isat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating Te. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips tomore » arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and it’s use in reducing arcs.« less

  10. On the Measurement of Electron Temperature by Single Langmuir Probes in High Recycling Divertors

    NASA Astrophysics Data System (ADS)

    Pitts, Richard; Horacek, Jan; Loarte, Alberto

    2000-10-01

    Under high recycling and detached conditions, divertor Langmuir probes often yield a significantly higher value of Te than expected. The influence of plasma turbulence and the effect of fast electrons/plasma collisionality are two reasons why this might occur. We concentrate on these two candidates, with particular reference to observations on the TCV tokamak. A systematic study of the effects of noise on simulated probe characteristics at low T_e, shows that the asymmetric, exponential nature of the characteristic favours electron collection such that fluctuations in Vf alone actually tend to reduce the derived Te from that which would otherwise be found. We have also studied the effects of correlated density and potential fluctuations, finding no effect on the fitted T_e. The sheath potential fall energetically filters electrons such that at high densities, the probe measured Te may be characteristic of hotter, more distant zones in the plasma. We use model parallel field profiles of Te and ne generated from B2-Eirene simulations of TCV discharges as input to the analytic theory of Wesson [1] to show how a divertor plate measurement of Te in TCV can exceed the expected value by factors of up to 6 as detachment is approached. [1] J. A. Wesson, Plasma Phys. and Contr. Fusion 37 (1995) 1459

  11. Estimation of plasma ion saturation current and reduced tip arcing using Langmuir probe harmonics

    NASA Astrophysics Data System (ADS)

    Boedo, J. A.; Rudakov, D. L.

    2017-03-01

    We present a method to calculate the ion saturation current, Isat, for Langmuir probes at high frequency (>100 kHz) using the harmonics technique and we compare that to a direct measurement of Isat. It is noted that the Isat estimation can be made directly by the ratio of harmonic amplitudes, without explicitly calculating Te. We also demonstrate that since the probe tips using the harmonic method are oscillating near the floating potential, drawing little power, this method reduces tip heating and arcing and allows plasma density measurements at a plasma power flux that would cause continuously biased tips to arc. A multi-probe array is used, with two spatially separated tips employing the harmonics technique and measuring the amplitude of at least two harmonics per tip. A third tip, located between the other two, measures the ion saturation current directly. We compare the measured and calculated ion saturation currents for a variety of plasma conditions and demonstrate the validity of the technique and its use in reducing arcs.

  12. Langmuir probe diagnostics of an atmospheric pressure, vortex-stabilized nitrogen plasma jet

    SciTech Connect

    Prevosto, L.; Mancinelli, B. R.; Kelly, H.

    2012-09-15

    Langmuir probe measurements in an atmospheric pressure direct current (dc) plasma jet are reported. Sweeping probes were used. The experiment was carried out using a dc non-transferred arc torch with a rod-type cathode and an anode of 5 mm diameter. The torch was operated at a nominal power level of 15 kW with a nitrogen flow rate of 25 Nl min{sup -1}. A flat ion saturation region was found in the current-voltage curve of the probe. The ion saturation current to a cylindrical probe in a high-pressure non local thermal equilibrium (LTE) plasma was modeled. Thermal effects and ionization/recombination processes inside the probe perturbed region were taken into account. Averaged radial profiles of the electron and heavy particle temperatures as well as the electron density were obtained. An electron temperature around 11 000 K, a heavy particle temperature around 9500 K and an electron density of about 4 Multiplication-Sign 10{sup 22} m{sup -3}, were found at the jet centre at 3.5 mm downstream from the torch exit. Large deviations from kinetic equilibrium were found throughout the plasma jet. The electron and heavy particle temperature profiles showed good agreement with those reported in the literature by using spectroscopic techniques. It was also found that the temperature radial profile based on LTE was very close to that of the electrons. The calculations have shown that this method is particularly useful for studying spraying-type plasma jets characterized by electron temperatures in the range 9000-14 000 K.

  13. Measurement of electronegativity at different laser wavelengths: accuracy of Langmuir probe assisted laser photo-detachment

    NASA Astrophysics Data System (ADS)

    Sirse, N.; Oudini, N.; Bendib, A.; Ellingboe, A. R.

    2016-08-01

    Langmuir probe (LP) assisted pulsed laser photo-detachment (LPD) of negative ions is one of the frequently used diagnostic techniques in electronegative plasmas. The technique is based on measuring the rise in electron saturation current following photo-detachment. During the photo-detachment process it is assumed that the background electron parameters (temperature and density) remain unchanged in the laser channel and the photo-detached electrons thermalize instantaneously with the background electrons (same temperature). Therefore, the measured electronegativity should be independent of laser wavelengths. However, our recent simulation results (2015 Phys. Plasmas 22 073509) demonstrates a failure of these assumptions and suggests that the measured rise in electron saturation current has a dependence on the laser wavelength. This letter presents experimental evidence in support of these simulation results. In this work, photo-detachment is performed at two different laser wavelengths in an oxygen inductively coupled plasma discharge. Electronegativity measured by LP assisted LPD is compared with those obtained by the hairpin probe (HPP) assisted LPD which is based on quasi-neutrality assumption. The experimental results reveal that the electronegativities measured by LP assisted LPD are affected by the laser wavelength, whereas, electronegativities measured by HPP assisted LPD are almost independent. The discrepancy between the measurements is higher at high electronegativities. In conclusion, the experimental results validate the weakness of assumptions to estimate electronegativity from LPD combined with LP and therefore emphasizes the need of a more realistic model to analyze raw data or an alternate solution is to utilize HPP.

  14. Langmuir Probe Measurements of Inductively Coupled Plasmas in CF4/Ar/O2 Mixtures

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Meyyappan, M.; Sharma, S. P.

    2000-01-01

    Fluorocarbon gases, such as CF4, and their mixtures are widely used in contemporary low-pressure and high-density plasma processing techniques. In such plasmas Langmuir probe is one of the most commonly employed diagnostic techniques to obtain electron number density (ne), electron temperature (Te), electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp). In this paper we report probe data for planar inductively coupled plasmas in CF4/O2/Ar mixtures. By varying the relative concentrations in the mixture, radial profiles of ne, ni, Te, Ee, Vp, EEDF were measured in the mid-plane of the plasma at 10 mTorr and 20 mTorr of gas pressures, and 200 W and 300 W of RF powers. Data show that ne and ni decrease with increase of CF4 content and decrease of gas-pressure but they increase with increase of RF-power, whereas Vp increases with decrease of gas-pressure and remains independent of RF-power. However, they all peak at the center of the plasma and decrease towards the edge while Te follows the other way and increases a little with increase of power. The measured EEDFs exhibit Druyvesteyn-like distribution at all pressures and powers. Data are analyzed and will be presented.

  15. Design of a Miniaturized Langmuir Plasma Probe for the QuadSat/PnP

    NASA Astrophysics Data System (ADS)

    Landavazo, M.; Jorgensen, A. M.; Del Barga, C.; Ferguson, D.; Guillette, D.; Huynh, A.; Klepper, J.; Kuker, J.; Lyke, J. C.; Marohn, B.; Mason, J.; Quiroga, J.; Ravindran, V.; Yelton, C.; Zagrai, A. N.; Zufelt, B.

    2011-12-01

    We have developed a miniaturized Langmuir plasma probe for measuring plasma density in low-earth orbit. Measuring plasma density in the upper ionosphere is important as a diagnostic for the rest of the ionosphere and as an input to space weather forecasting models. Developing miniaturized instrumentation allows easier deployment of a large number of small satellites for monitoring space weather. Our instrument was designed for the Swedish QuadSat/PnP, with the following constraints: A volume constraint of 5x5x1.25cm for the electronics enclosure, a mass budget 100 g, and a power budget of 0.5 W. We met the volume and mass constraints and where able to use less power than budgeted, only 0.25 W. We designed the probe for a bias range of +/-15V and current measurements in the 1 nA to 1 mA range (6 orders of magnitude). Necessary voltage of +/- 15 V and 3.3 V were generated on-board from a single 5 V supply. The electronics suite is based off carefully selected yet affordable commercial components that exhibit low noise, low leakage currents and low power consumption. Size constraints, low noise and low leakage requirements called for a carefully designed four layer PCB with a properly guarded current path using surface mount components on both sides. An ultra-low power microcontroller handles instrument functionality and is fully controllable over i2c using SPA-1 space plug and play. We elected for a probe launched deployed, which required careful design to survive launch vibrations while staying within the mass budget. The QuadSat/PnP has not been launched at the time of writing. We will present details of the instrument design and initial calibration data.

  16. Second derivative Langmuir probe measurements in Faraday dark space in Argon d.c. gas discharge at intermediate pressures

    NASA Astrophysics Data System (ADS)

    Dimitrova, M.; Popov, Tsv K.; Todorovand, J.; Naydenova, Tsv G.

    2006-07-01

    In a d.c. discharge tube with sectional cathodes and a common grid anode, second derivative Langmuir probe measurements were performed in the Faraday dark space in argon gas discharge at intermediate pressures. Experimental results for different radial probe positions and different distances from the cathode in axial direction are presented. It is shown that the electron energy distribution function is bi-Maxwellian. Taking into account the electron depletion caused by their sinking on the probe surface, an extension of the Druyvesteyn formula is applied for more accurate determination of the electron temperature value, T, the electron density, n, and the plasma potential, Upl, from the experimental results acquired.

  17. Effect of fast drifting electrons on electron temperature measurement with a triple Langmuir probe

    SciTech Connect

    Biswas, Subir Chowdhury, Satyajit; Pal, Rabindranath

    2015-08-14

    Triple Langmuir Probe (TLP) is a widely used diagnostics for instantaneous measurement of electron temperature and density in low temperature laboratory plasmas as well as in edge region of fusion plasma devices. Presence of a moderately energetic flowing electron component, constituting only a small fraction of the bulk electrons, is also a generally observed scenario in plasma devices, where plasmas are produced by electron impact ionization of neutrals. A theoretical analysis of its effect on interpretation of the TLP data for bulk electron temperature measurement is presented here assuming electron velocity distribution is not deviating substantially from a Maxwellian. The study predicts conventional expression from standard TLP theory to give overestimated value of bulk electron temperature. Correction factor is significant and largely depends on population density, temperature, and energy of the fast component. Experimental verification of theoretical results is obtained in the magnetized plasma linear experimental device of Saha Institute of Nuclear Physics where plasma is produced by an electron cyclotron resonance method and known to have a fast flowing electron component.

  18. Statistical results from 10 years of Cassini Langmuir probe plasma measurements

    NASA Astrophysics Data System (ADS)

    Holmberg, M.; Shebanits, O.; Wahlund, J. E.; Morooka, M.; Andre, N.

    2016-12-01

    We use a new analysis method to obtain 10 years of Cassini RPWS Langmuir probe (LP) measurements to study the structure and dynamics of the inner plasma disk of Saturn. The LP plasma density measurements show good agreement with electron densities derived from the RPWS electric field power spectra and confirms and/or improves a number of previous findings about the structure of the plasma disk. E.g., the Enceladus plume is detected as a localised density maximum at the orbit of Enceladus, but the peak density of the inner plasma disk, excluding Enceladus plume passages, is located closer to 4.7 Rs. No density peaks are recorded at the orbits of the moons Mimas, Tethys, Dione, and Rhea. We confirm the previously detected plasma density dayside/nightside asymmetry, which is likely due to a particle drift in the dusk to dawn direction. Presented is also the LP result on the seasonal dependence of the plasma disk within Enceladus' orbit.

  19. A new technique for studying ion-ion recombination in a flowing afterglow Langmuir probe apparatus

    NASA Astrophysics Data System (ADS)

    Miller, Thomas M.; Friedman, Jeffrey F.; Viggiano, A. A.

    2007-11-01

    We present a new technique for measuring ion-ion recombination rate constants in a flowing afterglow Langmuir probe (FALP) apparatus. The technique involves measuring the fractional negative ion product distribution following electron attachment versus the initial electron density when two or more products are formed. The concentration of reactant gas is kept low enough that the plasma retains its electron-Ar+, ambipolar diffusion character along the entire length of the flow tube. If only polyatomic anions are formed, accurate relative rates are obtained. When one of the species is atomic, absolute rates are also possible by doing a detailed model of the plasma kinetics. Here we present rate constants for Ar+ recombining with Cl2- ((5.3 ± 1.6) × 10-8 cm3 s-1 at 302 K), Br2- ((3.9 ± 1.2) × 10-8 cm3 s-1 at 302 K), the phosgene negative ion CCl2O- ((8.9 ± 2.7) × 10-8 cm3 s-1 at 302 K), and relative rate constants for Ar+ + SF6- and SF5- (ratio 1.2 at 550 K, with an uncertainty of +0.3 and -0.1). The diatomic negative ions are found to recombine slower than the polyatomic ones, in agreement with earlier indications.

  20. Rocket-borne Langmuir Probe response to an applied periodic potential

    NASA Astrophysics Data System (ADS)

    Muralikrishna, P.; Abdu, M. A.; Kantor, I. J.

    1988-10-01

    A Langmuir Probe (LP), payload designed and developed at Instituto de Pesuisas Espaciais (INPE/MCT) was flown on board a SONDA III rocket at 2259 hrs. (LST) on October 31, 1986 from the Centro de Lancamento da Barreira do Inferno in Natal, RN, Brazil, under a collaborative program between INPE and Instituto de Atividades Espaciais (IAE/CTA). The rocket reached an apogee of about 444 km and the LP payload functioned satisfactorily during the ascent as well as descent of the rocket. A sweep voltage varying between -1V and +4V in a period of about 2.6 seconds was applied to the LP sensor. As the applied voltage increased from -1V to +4V, the LP sensor current first showed an increase, reached a saturation level, and then, though the sensor potential increased towards a steady value, the current showed a systematic decrease. This sensor current characteristic also showed a clear dependence on altitude and hence on the ambient plasma parameters. Possible physical mechanisms responsible for these LP response characteristics are analyzed and discussed here.

  1. Hall thruster plume measurements from High-speed Dual Langmuir Probes with Ion Saturation Reference

    NASA Astrophysics Data System (ADS)

    Sekerak, M.; McDonald, M.; Hofer, R.; Gallimore, A.

    The plasma plume of a 6 kW Hall Effect Thruster (HET) has been investigated in order to determine time-averaged and time-resolved plasma properties in a 2-D plane. HETs are steady-state devices with a multitude of kilohertz and faster plasma oscillations that are poorly understood yet impact their performance and may interact with spacecraft subsystems. HETs are known to operate in different modes with differing efficiencies and plasma characteristics, particularly the axial breathing mode and the azimuthal spoke mode. In order to investigate these phenomena, high-speed diagnostics are needed to observe time-resolved plasma properties and correlate them to thruster operating conditions. A new technique called the High-speed Dual Langmuir Probe with Ion Saturation Reference (HDLP-ISR) builds on recent results using an active and an insulated or null probe in conjunction with a third, fixed-bias electrode maintained in ion saturation for ion density measurements. The HDLP-ISR was used to measure the plume of a 6-kW-class single-channel HET called the H6 operated at 300 V and 20 A at 200 kHz. Time-averaged maps of electron density, electron temperature and plasma potential were determined in a rectangular region from the exit plane to over five channel radii downstream and from the centrally mounted cathode radially out to over three channel radii. The power spectral density (PSD) of the time-resolved plasma density oscillations showed four discrete peaks between 16 and 28 kHz which were above the broad breathing mode peak between 10 and 15 kHz. Using a high-speed camera called FastCam imaging at 87,500 frames per second, the plasma oscillations were correlated with visible rotating spokes in the discharge channel. Probes were vertically spaced in order to identify azimuthal plasma transients around the discharge channel where density delays of 14.4 μ s were observed correlating to a spoke velocity of 1800 m/s in the E× B direction. The results presented- here are

  2. Characterization of RF He-N2/Ar mixture plasma via Langmuir probe and optical emission spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Hussain, S. S.; Zakaullah, M.; Zaka-ul-Islam, M.

    2016-08-01

    A Magnetic Pole Enhanced inductively coupled RF H e - N 2 / A r plasma is characterized using a Langmuir probe and optical emission spectroscopy (OES) techniques. The effect of helium mixing on electron density ( n e ) and temperature ( T e ) , electron energy probability functions (EEPFs), [ N ] atomic density, and N 2 dissociation is investigated. A Langmuir probe and a zero slope method based on trace rare gas-optical emission spectroscopy (TRG-OES) are employed to measure the electron temperature. It is noted that the electron temperature shows an increasing trend for both methods. However, the temperature measured by a zero slope method T e ( Z . S ) approaches the temperature measured by a Langmuir probe; T e ( L . P ) at 56% and above helium concentration in the discharge. "Advance actinometry" is employed to monitor the variation in [ N ] atomic density with helium concentration and gas pressure. It is noted that [ N ] atomic density increases at 56% and above helium in the discharge, which is consistent with the trend of electron temperature and EEPFs. A drastic enhancement in N 2 dissociation fraction D 1 determined by "advance actinometry" is noted at 56% and above helium concentration in the mixture due to modifications in different population and depopulation mechanisms. However, it is also noted that the dissociation fraction D 2 determined by intensity ratio method increases linearly with helium addition.

  3. Langmuir Probe and Mass Spectroscopic Measurements in Inductively Coupled CF4 Plasmas

    NASA Technical Reports Server (NTRS)

    Rao, M. V. V. S.; Sharma, Surendra; Cruden, B. A.; Meyyappan, M.

    2001-01-01

    Abstract Electron and ion energy distribution functions and other plasma parameters such as plasma potential (V(sub p)) , electron temperature (T(sub e)), and electron and ion number densities (n (sub e) and n(sub i)) in low pressure CF4 plasmas have been measured. The experiments were conducted in a GEC cell using an inductively coupled plasma (ICP) device powered by a 13.56 MHz radio-frequency (rf) power source. The measurements were made at 300 W of input rf power at 10, 30 and 50 mTorr gas pressures. Langmuir probe measurements suggest that n(sub e), n(sub i) and V(sub p) remain constant over 60% of the central electrode area, beyond which they decrease. Within the limits of experimental error (+/- 0.25 eV), T(sub e) remains nearly constant over the electrode area. T(sub e) and V(sub p) increase with a decrease in pressure. n(sub e) and n(sub i) are not affected as significantly as T(sub e) or V(sub p) by variation in the gas pressure. The electron energy distribution function (EEDF) measurements indicate a highly non-Maxwellian plasma. CF3+ is the most dominant ion product of the plasma, followed by CF2+ and CF+. The concentrations of CF2+ and CF+ are much larger than that is possible from direct electron impact ionization of the parent gas. The cross-section data suggest that the direct electron impact ionization of fragment neutrals and negative ion production by electron attachment may be responsible for increase of the minor ions.

  4. Progress on Langmuir Probe, Data Analysis, Acquisition and Optimization Innovations at the Coast Guard Academy Plasma Lab (CGAPL)

    NASA Astrophysics Data System (ADS)

    Wright, Erin; Frank, John; Azzari, Phil; James, Royce; Hopson, Jordan; Duke-Tinson, Omar; Paolino, Richard; Sandi, Eva; Sherman, Justin; Turk, Jeremy

    2016-10-01

    CGAPL houses four major plasma experiments that span large temperature, density, energy and functionality regimes. Often automation and remote operation of intelligent devices are required in adverse operating environments for digital and analogue systems. Plasma data collected by a multitude of diagnostics and sensors (to include Langmuir probes) over long timescales mandates CGAPL's 40-channel Data Acquisition (DAQ) system that collects and stores data plus controls CGAPL. The ability to remotely control and operate lab diagnostics then collect and store data through a LabView collective Graphic User Interface (GUI) currently under construction, enable users to remotely control, collect, and store CGAPL experimental data. Innovative solutions to optimize data collection and apparatus command and control, will enhance the ability to run experiments remotely, improve the validity of results, and advance participation in fusion grade diagnostic development. Instrument automation, optimization, and data collection obstacles, solutions, and procedures will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15-16.

  5. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA 300M Hall Thruster

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA 300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 DT,m downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 DT,m from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the nearfield, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was small, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA 300 M.

  6. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-300M Hall Thruster

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    In order to aid in the design of high-power Hall thrusters and provide experimental validation for existing modeling efforts, plasma potential and Langmuir probe measurements were performed in the near-field plume of the NASA-300M Hall thruster. A probe array consisting of a Faraday probe, Langmuir probe, and emissive probe was used to interrogate the plume from approximately 0.1 - 2.0 mean thruster diameters downstream of the thruster exit plane at four operating conditions: 300 V, 400 V, and 500 V at 20 kW as well as 300 V at 10 kW. Results show that the acceleration zone and high-temperature region were contained within 0.3 mean thruster diameters from the exit plane at all operating conditions. Isothermal lines were shown to strongly follow magnetic field lines in the near-field, with maximum temperatures ranging from 19 - 27 eV. The electron temperature spatial distribution created large drops in measured floating potentials in front of the magnetic pole surfaces where the plasma density was low, which suggests strong sheaths at these surfaces. The data taken have provided valuable information for future design and modeling validation, and complements ongoing internal measurement efforts on the NASA-300M.

  7. Plasma Potential and Langmuir Probe Measurements in the Near-field Plume of the NASA-457Mv2 Hall Thruster

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    In order to further the design of future high-power Hall thrusters and provide experimental validation for ongoing modeling efforts, plasma potential and Langmuir probe measurements were performed on the 50-kW NASA-457Mv2. An electrostatic probe array comprised of a near-field Faraday probe, single Langmuir probe, and emissive probe was used to interrogate the near-field plume from approximately 0.1 - 2.0 mean thruster diameters downstream of the thruster exit plane at the following operating conditions: 300 V, 400 V and 500 V at 30 kW and 500 V at 50 kW. Results have shown that the acceleration zone is limited to within 0.4 mean thruster diameters of the exit plane while the high-temperature region is limited to 0.25 mean thruster diameters from the exit plane at all four operating conditions. Maximum plasma potentials in the near-field at 300 and 400 V were approximately 50 V with respect to cathode potential, while maximum electron temperatures varied from 24 - 32 eV, depending on operating condition. Isothermal lines at all operating conditions were found to strongly resemble the magnetic field topology in the high-temperature regions. This distribution was found to create regions of high temperature and low density near the magnetic poles, indicating strong, thick sheath formation along these surfaces. The data taken from this study are considered valuable for future design as well as modeling validation.

  8. Plasma Potential and Langmuir Probe Measurements in the Near-Field Plume of the NASA-457Mv2 Hall Thruster

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    In order to further the design of future high-power Hall thrusters and provide experimental validation for ongoing modeling efforts, plasma potential and Langmuir probe measurements were performed on the 50-kW NASA-457Mv2. An electrostatic probe array comprised of a near-field Faraday probe, single Langmuir probe, and emissive probe was used to interrogate the near-field plume from approximately 0.1 ? 2.0 mean thruster diameters downstream of the thruster exit plane at the following operating conditions: 300 V, 400 V and 500 V at 30 kW and 500 V at 50 kW. Results have shown that the acceleration zone is limited to within 0.4 mean thruster diameters of the exit plane while the high-temperature region is limited to 0.25 mean thruster diameters from the exit plane at all four operating conditions. Maximum plasma potentials in the near-field at 300 and 400 V were approximately 50 V with respect to cathode potential, while maximum electron temperatures varied from 24 ? 32 eV, depending on operating condition. Isothermal lines at all operating conditions were found to strongly resemble the magnetic field topology in the high-temperature regions. This distribution was found to create regions of high temperature and low density near the magnetic poles, indicating strong, thick sheath formation along these surfaces. The data taken from this study are considered valuable for future design as well as modeling validation.

  9. Comparison of Langmuir probe and multipole resonance probe measurements in argon, hydrogen, nitrogen, and oxygen mixtures in a double ICP discharge

    NASA Astrophysics Data System (ADS)

    Fiebrandt, Marcel; Oberberg, Moritz; Awakowicz, Peter

    2017-07-01

    The results of a Multipole Resonance Probe (MRP) are compared to a Langmuir probe in measuring the electron density in Ar, H2, N2, and O2 mixtures. The MRP was designed for measurements in industry processes, i.e., coating or etching. To evaluate a possible influence on the MRP measurement due to molecular gases, different plasmas with increasing molecular gas content in a double inductively coupled plasma at 5 Pa and 10 Pa at 500 W are used. The determined electron densities from the MRP and the Langmuir probe slightly differ in H2 and N2 diluted argon plasmas, but diverge significantly with oxygen. In pure molecular gas plasmas, electron densities measured with the MRP are always higher than those measured with the Langmuir Probe, in particular, in oxygen containing mixtures. The differences can be attributed to etching of the tungsten wire in the Ar:O2 mixtures and rf distortion in the pure molecular discharges. The influence of a non-Maxwellian electron energy distribution function, negative ions or secondary electron emission seems to be of no or only minor importance.

  10. On the interpretation of fluctuation and ExB turbulent transport measured by Langmuir probes in fusion plasmas

    SciTech Connect

    Calderon, E.; Hidalgo, C.; Pedrosa, M.A.; Silva, C.

    2004-10-01

    Plasma fluctuations and fluctuation-induced particle fluxes have been investigated in the plasma edge of the TJ-II stellarator using Langmuir probes. Simultaneous measurements of plasma fluctuations carried out by probes located in and out of the probe body sheath show similar results in the normalized level of fluctuations in the ion saturation current. However, floating potential fluctuations measured in the co and counter direction of the magnetic field on the sheath probe body show slight but significant differences. The local radial electrostatic turbulent driven transport measured in and out of the probe body sheath shows consistent results, within the errors bars due to uncertainties in the determination of the effective probe collecting area; the normalized local radial transport to the average ion saturation current (the effective velocity which is not affected by uncertainties in the probe area) show consistent results. These results and previous findings call into question the recent interpretation of probe measurements on the basis of the influence of the probe's pre-sheath zone [B. Labombard, Phys. Plasmas. 9, 1300 (2002)].

  11. Improvement of the noise level of the Split Langmuir Probe - a spatial current density meter

    NASA Astrophysics Data System (ADS)

    Marusenkov, Andriy; Dudkin, Fedor; Shuvalov, Valentyn

    2013-04-01

    One of the main tasks at the experimental investigations of the wave processes in space plasma is the determination of the dispersion relations between their wave vector and frequency. The frequency analysis of the magnetic field fluctuations and the electric current density in plasma is very efficient in this case. It had been shown that the simultaneous measurements of the magnetic field orthogonal components and the spatial current density fluctuations can give the wave vector k values for the plane wave spectra, by which a wave field in a plasma reference frame can be represented. The measurements of the magnetic field fluctuations usually are made by a variety of magnetometers using well developed methods. Unfortunately, up to the moment the methods and instruments for the reliable measurements of the space current density are not so good developed as the magnetic ones. There are three independent techniques to study the spatial current density in plasma: the contactless Rogovsky coil, the Faraday cap and the Split Langmuir Probe (SLP). The attempt to compare the different approaches and instruments was carried out during the experiment "Variant" onboard Ukrainian remote sensing satellite SICH-1M launched 2004. The clear advantages of the SLP over other instruments were revealed and proved. Using whistler as a test signal the very good consistency between the magnetic and electric fields and the spatial electric current density was obtained. However, the signal-to-noise ratio of the current density meters has to be further improved. In this report we analyze the sources of the SLP noises and propose the ways to decrease it. The computer simulation of the improved current density meter reveals that the introduced changes have almost no influence on the sensor matching with the space plasma and, as a result, the minor changes of the transformation factor in operation frequency band are expected. The modernized version of the SLP was successfully tested in the

  12. Development of a novel sweeping Langmuir probe instrument for monitoring the upper ionosphere on board a pico-satellite

    NASA Astrophysics Data System (ADS)

    Ranvier, Sylvain; De Keyser, Johan; Cardoen, Pepijn; Pieroux, Didier

    2014-05-01

    A novel Langmuir probe instrument, which will fly on board the Pico-Satellite for Atmospheric and Space Science Observations (PICASSO), is under development at the Belgian Institute for Space Aeronomy. PICASSO was initiated to join the QB50 project as scientific in-orbit demonstrator. The sweeping Langmuir probe (SLP) instrument is designed to measure both plasma density and electron temperature at an altitude varying from about 400 km up to 700 km from a high inclination orbit. Therefore, the plasma density is expected to fluctuate over a wide range, from about 1e6/m³ at high latitude and high altitude up to 1e12/m³ at low/mid latitude and low altitude. The electron temperature is expected to lie between approximately 1000 K and 3000 K. Given the high inclination of the orbit, the SLP instrument will allow a global monitoring of the ionosphere with a maximum spatial resolution of the order of 150 m. The main goals are to study 1) the ionosphere-plasmasphere coupling, 2) the subauroral ionosphere and corresponding magnetospheric features, 3) auroral structures, 4) polar caps, and 5) ionospheric dynamics via coordinated observations with EISCAT's heating radar. To achieve the scientific objectives described above, the instrument includes four thin cylindrical probes whose electrical potential is swept in such a way that both plasma density and electron temperature can be derived. In addition, since at least two probes will be out of the spacecraft's wake at any given time, differential measurements can be performed to increase the accuracy. Along the orbit, the Debye length is expected to vary from a few millimetres up to a few meters. Due to the tight constraints in terms of mass and volume inherent to pico-satellites, the use of long booms, which would guarantee that the probes are outside the sheath of the spacecraft (several Debye lengths away), is not possible. Consequently, the probes might be in the sheath of the spacecraft in polar regions. Extensive

  13. Evaluation of the scrape-off-layer plasma parameters by a horizontal reciprocating Langmuir probe in the COMPASS tokamak

    NASA Astrophysics Data System (ADS)

    Dimitrova, M.; Popov, Tsv K.; Ivanova, P.; Vasileva, E.; Hasan, E.; Horáček, J.; Vondráček, P.; Dejarnac, R.; Stöckel, J.; Weinzettl, V.; Havlicek, J.; Janky, F.; Panek, R.

    2014-05-01

    The scrape-off-layer (SOL) parameters in the COMPASS tokamak are studied by using a Langmuir probe mounted on a horizontal reciprocating manipulator. The radial profiles of the plasma potential, the electron energy distribution function and the electron densities are derived from the measured current-voltage probe characteristics by applying the firstderivative probe technique (FDPT). It is shown that close to the tokamak wall the electron energy distribution function is Maxwellian, while in the SOL, in the vicinity of the last closed flux surface and inside the confined plasma, the electron energy distribution function is bi-Maxwellian with a low-energy electron fraction dominating over a higher energy one. The radial profiles of the electron pressure and the parallel electron power flux density in COMPASS are also presented.

  14. Electron density and electron temperature measurement in a bi-Maxwellian electron distribution using a derivative method of Langmuir probes

    SciTech Connect

    Choi, Ikjin; Chung, ChinWook; Youn Moon, Se

    2013-08-15

    In plasma diagnostics with a single Langmuir probe, the electron temperature T{sub e} is usually obtained from the slope of the logarithm of the electron current or from the electron energy probability functions of current (I)-voltage (V) curve. Recently, Chen [F. F. Chen, Phys. Plasmas 8, 3029 (2001)] suggested a derivative analysis method to obtain T{sub e} by the ratio between the probe current and the derivative of the probe current at a plasma potential where the ion current becomes zero. Based on this method, electron temperatures and electron densities were measured and compared with those from the electron energy distribution function (EEDF) measurement in Maxwellian and bi-Maxwellian electron distribution conditions. In a bi-Maxwellian electron distribution, we found the electron temperature T{sub e} obtained from the method is always lower than the effective temperatures T{sub eff} derived from EEDFs. The theoretical analysis for this is presented.

  15. A Langmuir Probe Diagnostic for Use in Inhomogeneous, Time-Varying Plasmas Produced by High-Energy Laser Ablation

    SciTech Connect

    Patterson, J R; Emig, J A; Fournier, K B; Jenkins, P P; Trautz, K M; Seiler, S W; Davis, J F

    2012-05-01

    Langmuir probes (LP) are used extensively to characterize plasma environments produced by radio frequency, pulsed plasma thrusters, and laser ablation. We discuss here the development of a LP diagnostic to examine high-density, high-temperature inhomogeneous plasmas such as those that can be created at the University of Rochester's Laboratory for Laser Energetics OMEGA facility. We have configured our diagnostic to examine the velocity of the plasma expanding from the target. We observe velocities of approximately 16-17 cm/{micro}s, with individual LP currents displaying complex structures, perhaps due to the multiple atomic species and ionization states that exist.

  16. Method for obtaining electron energy-density functions from Langmuir-probe data using a card-programmable calculator

    SciTech Connect

    Longhurst, G.R.

    1981-01-01

    This paper presents a method for obtaining electron energy density functions from Langmuir probe data taken in cool, dense plasmas where thin-sheath criteria apply and where magnetic effects are not severe. Noise is filtered out by using regression of orthogonal polynomials. The method requires only a programmable calculator (TI-59 or equivalent) to implement and can be used for the most general, nonequilibrium electron energy distribution plasmas. Data from a mercury ion source analyzed using this method are presented and compared with results for the same data using standard numerical techniques.

  17. A method for obtaining electron energy density functions from Langmuir probe data using a card-programable calculator

    NASA Astrophysics Data System (ADS)

    Longhurst, G. R.

    1981-04-01

    This paper presents a method for obtaining electron energy density functions from Langmuir probe data taken in cool, dense plasmas where thin-sheath criteria apply and where magnetic effects are not severe. Noise is filtered out by using regression of orthogonal polynomials. The method requires only a programable calculator (TI-59 or equivalent) to implement and can be used for the most general, nonequilibrium electron energy distribution plasmas. Data from a mercury ion source analyzed using this method are presented and compared with results for the same data using standard numerical techniques.

  18. An experimental study of plasma density determination by cylindrical Langmuir probe in a flowing afterglow plasma at elevated pressures

    SciTech Connect

    Kudrna, P.; Chudacek, O.; Sicha, M.; Tichy, M.

    1995-12-31

    The collection of positive ions by a cylindrical Langmuir probe at the pressures when the ion mean free path is much shorter than the probe sheath thickness (usually called the collisional case of positive ion collection) has been treated by several authors. The idea, that the ions can only be scattered by collisions with neutral particles and hence the effect of collisions results in the reduction of the ion current to the probe had to be corrected owing to the experimental facts which showed that the ion current in the presence of collisions can be greater than in the collisionless; case and hence results in greater apparent ion density compared to the electron one. A simple explanation of the fact that the ion current can be increased by the effect of collisions of positive ions with neutrals, has been brought up by Zakrzewski and Kopiczynski in and was based on the fact that the collisions can destroy the ion orbital motion in the space charge sheath surrounding the Langmuir probe and the ions have hence greater chance to be collected by the probe. The upper limit for the ion current increase has been set in to be the current calculated by the radial motion theory by Allen, the collisionless, current limit has been taken after Laframboise. Quantitatively this effect is described by a factor {gamma}{sub 1} which ranges from 1 in the collisionless case to the ratio I{sub A}/I{sub L}, where I{sub A} and I{sub L} are the ion collisionless. Simultaneously it is supposed in the work that the collisions can scatter ions which leads to the decrease of the ion current, the effect is described quantitatively by a factor {gamma}{sub 2}.

  19. Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

    SciTech Connect

    Zanáška, M.; Kudrna, P.; Tichý, M.; Adámek, J.; Peterka, M.

    2015-03-15

    The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I{sub sat}{sup −}/I{sub sat}{sup +} to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

  20. Galileo Probe Battery System

    NASA Technical Reports Server (NTRS)

    Dagarin, B. P.; Taenaka, R. K.; Stofel, E. J.

    1997-01-01

    The conclusions of the Galileo probe battery system are: the battery performance met mission requirements with margin; extensive ground-based and flight tests of batteries prior to probe separation from orbiter provided good prediction of actual entry performance at Jupiter; and the Li-SO2 battery was an important choice for the probe's main power.

  1. Statistics of Widths and Separations of Equatorial Plasma Bubbles Detected by the C/NOFS Planar Langmuir Probe

    NASA Astrophysics Data System (ADS)

    Costa, E.; Roddy, P. A.; Ballenthin, J.; Groves, K. M.

    2016-12-01

    Summary data from the Planar Langmuir Probe (PLP) onboard the Communication/Navigation Outage Forecasting System (C/NOFS) satellite are immediately available in individual daily files with 1-Hz resolution. Each 1-s record associates the Universal Time (s) to the corresponding average ion density Ni (cm-3), standard deviation of the ion density DNi (cm-3), ratio DNi/Ni, as well as satellite latitude (degrees), longitude (degrees), and altitude (km). Two different years of PLP data from (01 October 2008 to 30 September 2009 and 01 January 2012 to 31 December 2012) were selected for analysis. The first data set corresponds to solar minimum conditions and the second one is close to solar maximum conditions of solar cycle 24. Initially, a low-pass filtered version i> of the one-second average ion density Ni data will be determined to represent the slowly varying ambient ion density. The time series (i>-Ni) and Ni/i> (absolute and normalized time series, respectively) will indicate depths and durations of plasma bubbles with respect to the ambient ion density. A level-crossing analysis will then be applied to these time series, as well as to that of a smoothed version of the standard deviation of the ion density DNi, assuming different thresholds. The results from the analysis will describe the statistical distributions of durations of (i>-Ni), Ni/i> and DNi, both below (within a depletion) and above (between consecutive depletions) for each assumed threshold. Since the C/NOFS satellite position can be determined from the data, the time baseline can also be mapped into distance along the orbit. Thus, statistics of numbers and widths of plasma bubbles, as well as of separations between them will also be determined. This study will classify results according to different combinations of: (i) solar activity; (ii) altitude range; (iii) longitude sector; (iv) local time interval; (v) geomagnetic latitude interval; and (vi) season, when applicable.

  2. Assessment of the effect of parallel temperature gradients in the JET SOL on Te measured by divertor target Langmuir probes

    NASA Astrophysics Data System (ADS)

    Ďuran, I.; Ješko, K.; Fuchs, V.; Groth, M.; Guillemaut, C.; Gunn, J. P.; Horacek, J.; Pitts, R. A.; Tskhakaya, D.

    2015-08-01

    Higher than expected electron temperatures (Te) are often measured by divertor Langmuir probes (LP) in high recycling and detached regimes in JET and other tokamaks. As a possible mechanism to explain this discrepancy, we investigate the effect of penetration of fast, almost collisionless electrons connecting the hot upstream scrape-off layer (SOL) region to the divertor targets in JET. We simulate the electron velocity distribution function (EVDF) near the divertor targets using a simple 1D kinetic model using parallel SOL profiles from EDGE2D-EIRENE simulations. The resulting EVDF is used to construct synthetic LP current-voltage (IV) characteristics and evaluation of Te is performed in the same way as for experimental data. Results indicate that the process does not explain the anomalously high Te values estimated from the target probe measurements if the EDGE2D-EIRENE simulated parallel profiles are a good representation of reality.

  3. An improved model to analyze Langmuir probe assisted photo-detachment signal for measuring electronegative plasma parameters

    NASA Astrophysics Data System (ADS)

    Sirse, Nishant; Oudini, Noureddine; Bendib, Abderrezeg; Ellingboe, Albert R.

    2016-09-01

    A diagnostic technique for measuring negative ion parameters based on Langmuir probe assisted laser photo-detachment relies on a theoretical model which relates the rise in the electron saturation current to electronegativity in the plasma. The existing model depend on various assumptions and neglect electrostatic potential barrier formed between the laser column (electropositive column) and the surrounding electronegative plasma in order to prevent the outward flow of electrons from the electropositive plasma column. These assumptions leads to erroneous estimation of the plasma electronegativity. In the present work, we present an analytical model to analyze Langmuir probe assisted photo-detachment signal in order to improve the accuracy of measured electronegativity and extended this technique for measuring electron temperature and charged species density. The analytical model is validated using both experiments and particle-in-cell simulation. The results shows improved accuracy in the measured parameters when compared to existing model. This work was supported by the Korea Institute for the Advancement of Technology and Ministry of Knowledge Economy (L-2010-1438-000), Republic of Korea, Enterprise Ireland and the European Regional Development Fund (ERDF) under NSRF 2007-2013.

  4. Comparison of currents predicted by NASCAP/LEO model simulations with elementary Langmuir-type bare probe models for an insulated cable containing a single pinhole

    NASA Technical Reports Server (NTRS)

    Galofaro, Joel T.

    1990-01-01

    The behavior of a defect in the insulation of a short biased section of cable in a Low Earth Orbit (LEO) space environment was examined. Such studies are of the utmost importance for large space power systems where great quantities of cabling will be deployed. An insulated probe containing a pinhole was placed into a hypothetical high speed LEO plasma. The NASA Charging Analyzer Program (NASCAP/LEO) was used to explore sheath growth about the probe as a function of applied voltage and to predict I-V behavior. A set of independent current calculations using Langmuir's formulations for concentric spheres and coaxial cylinders were also performed. The case of concentric spheres was here extended to include the case of concentric hemispheres. Several simple Langmuir-type models were then constructed to bracket the current collected by the cable. The space-charge sheath radius and impact parameters were used to determine the proper current regime. I-V curves were plotted for the models and comparisons were made with NASCAP/LEO results. Finally, NASCAP/LEO potential contours and surface cell potential plots were examined to explain interesting features in the NASCAP/LEO I-V curve.

  5. The Influence of Energetic Electrons on the Cassini Langmuir Probe at Saturn : Deriving Large Electron Temperatures and Small Electron Densities

    NASA Astrophysics Data System (ADS)

    Garnier, P.; Wahlund, J.; Holmberg, M.; Lewis, G.; Schippers, P.; Thomsen, M. F.; Rochel Grimald, S.; Gurnett, D. A.; Coates, A. J.; Dandouras, I. S.; Waite, J. H.

    2013-12-01

    The Langmuir probes (LPs) are commonly used to investigate the cold plasma characteristics in planetary ionospheres/magnetospheres. The LPs performances are limited to low temperatures (i.e. below 5-10 eV at Saturn) and large densities (above several particles/cm3). A strong sensitivity of the Cassini LP measurements to energetic electrons (hundreds eV) may however be observed at Saturn in the L Shell range L=6-10 RS. These electrons impact the surface of the probe and generate a detectable current of secondary electrons. We investigated the influence of such electrons on the current-voltage (I-V) characteristics (for negative potentials), showing that both the DC level and slope of the I-V curve are modified. The influence of energetic electrons may be interpreted in terms of the critical and anticritical temperatures concept that is important for spacecraft charging studies. Estimations of the maximum secondary yield value for the LP surface are obtained without using laboratory measurements. Empirical and theoretical methods were developed to reproduce the influence of the energetic electrons with a reasonable precision. Conversely, this modelling allows us to derive useful information about the energetic electrons from the LP observations : some information about their pitch angle anisotropy (if combined with the data from a single CAPS ELS anode), as well as an estimate of the electron temperature (in the range 100-300 eV) and of the electron density (above 0.1 particles/cm3). This enlarges the LP measurements capabilities when the influence of the energetic electrons is large (essentially near L=6-10 RS at Saturn). The understanding of this influence may be used for other missions using Langmuir probes, such as the future missions JUICE at Jupiter, BepiColombo at Mercury, or even the probes in the Earth magnetosphere.

  6. A direct Vlasov code to study the non-stationary current collection by a cylindrical Langmuir probe

    SciTech Connect

    Sanchez-Arriaga, G.

    2013-01-15

    The time-dependent current collection by a cylindrical Langmuir probe, whose bias is suddenly changed from zero to a positive or negative finite value, is studied with a novel direct Vlasov code. The numerical algorithm is based on finite-difference formulas to approximate spatial and velocity derivatives and the time integration is carried out with an explicit Runge-Kutta method, or in the case of probe radius small compared with the Debye length, by using the unconditionally stable backward Euler scheme. Both electrons and ions are treated kinetically by the code, which implements initial and boundary conditions that are consistent with the presence of the probe. Within the considered parameter range, the plasma sheath around the probe exhibited an overshoot and it later recovered a steady state. Phase space diagrams of the particle trajectories revealed the presence of a trapped population of particles. The dependence of this population as a function of the probe radius is presented as well as a comparison with the stationary theory. The performance of the code and a comparison with previously used particle-in-cell algorithms are discussed.

  7. Advances in Langmuir probe diagnostics of the plasma potential and electron-energy distribution function in magnetized plasma

    NASA Astrophysics Data System (ADS)

    Popov, Tsv K.; Dimitrova, M.; Ivanova, P.; Kovačič, J.; Gyergyek, T.; Dejarnac, R.; Stöckel, J.; Pedrosa, M. A.; López-Bruna, D.; Hidalgo, C.

    2016-06-01

    Advanced Langmuir probe techniques for evaluating the plasma potential and electron-energy distribution function (EEDF) in magnetized plasma are reviewed. It is shown that when the magnetic field applied is very weak and the electrons reach the probe without collisions in the probe sheath the second-derivative Druyvesteyn formula can be used for EEDF evaluation. At low values of the magnetic field, an extended second-derivative Druyvesteyn formula yields reliable results, while at higher values of the magnetic field, the first-derivative probe technique is applicable for precise evaluation of the plasma potential and the EEDF. There is an interval of intermediate values of the magnetic field when both techniques—the extended second-derivative and the first-derivative one—can be used. Experimental results from probe measurements in different ranges of magnetic field are reviewed and discussed: low-pressure argon gas discharges in the presence of a magnetic field in the range from 0.01 to 0.08 T, probe measurements in circular hydrogen plasmas for high-temperature fusion (magnetic fields from 0.45 T to 1.3 T) in small ISTTOK and CASTOR tokamaks, D-shape COMPASS tokamak plasmas, as well as in the TJ-II stellarator. In the vicinity of the last closed flux surface (LCFS) in tokamaks and in the TJ-II stellarator, the EEDF obtained is found to be bi-Maxwellian, while close to the tokamak chamber wall it is Maxwellian. The mechanism of the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is discussed. Comparison of the results from probe measurements with those obtained from calculations using the ASTRA and EIRENE codes shows that the main reason for the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is the ionization of the neutral atoms.

  8. Langmuir probe diagnostics of electron energy distributions with optical emission spectroscopy in capacitively coupled rf discharge in nitrogen

    SciTech Connect

    Abdel-Fattah, E.; Bazavan, M.; Sugai, H.

    2011-12-01

    Measurements with a rf compensated Langmuir probe and optical emission spectroscopy are carried out in capacitively coupled rf (13.56 MHz) pure nitrogen N{sub 2} discharges at fixed rf voltage over a wide range of pressure, 30 to 400 mTorr. The electron energy probability function (EEPF) measured below 100 mTorr resembles a bi-Maxwellian-type distribution. At pressure range of 100-200 mTorr, the EEPF has non-Maxwellian distribution with a ''dip'' near 4.5 eV. At the highest pressure of 400 mTorr, the EEPF evolves into a Druyvestein-like distribution and the ''dip'' disappears. The electron density significantly decreases with increase in the N{sub 2} pressure. On the other hand, the electron temperatures gradually decrease with an increase in N{sub 2} pressure, reaching minimum at 150 mTorr, beyond which it abruptly increases. Such evolution of the EEPFs shape with gas pressure has been discussed in terms of non-local electron kinetics and heating mode transition. The emission intensities of nitrogen (0-0) band of second positive system at 337.1 nm and (0-0) band of first negative systems at 391.4 nm are used to determine the dependence of their radiative states N{sub 2}(C{sup 3}{Pi}{sub u}) and N{sub 2}{sup +}(B{sup 2}{Sigma}{sub u}{sup +}) with nitrogen pressure. It is observed that the pressure influences the radiative states differently owing to their different populating mechanisms. The vibrational temperature T{sub {nu}ib} and rotational temperature T{sub rot} are measured for the sequence ({Delta}{nu}=-2) of N{sub 2} second positive system (C{sup 3}{Pi}{yields}B{sup 3}{Pi}{sub g}) using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. It was found that both T{sub {nu}ib} and T{sub rot} have similar dependences with N{sub 2} pressure; peaked at 100 mTorr beyond which it monotonically decreases with increase in the N{sub 2} pressure. The correlation between the observed maximum value of T{sub {nu}ib} around

  9. Application of Langmuir Probe Method to the Atmospheric Pressure Discharge Plasma

    SciTech Connect

    Matsuura, Hiroto; Matsumura, Yasuhiro; Nakano, Ken

    2008-12-31

    The heat balance model in the probe tip applied to atmospheric pressure plasma is constructed. Considering the natural convective heat loss, the limitation of plasma density for probe application to such a plasma is estimated. The rough limit is about n{sub e} = 10{sup 18} m{sup -3}. Four kind of materials (Cu, SUS, W, Al) are used for probe tips, and are tested in DC atmospheric pressure discharge. Heat conductivity is found to be a more important property than melting point in design of probes in high pressure discharge. DC atmospheric pressure discharge plasma parameters are obtained with our test probes. Obtained density is the order of 10{sup 17} m{sup -3} and does not contradict with the above density limitation. Change of space potential in air/Ar plasma is also confirmed.

  10. Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers--spectroscopic investigations.

    PubMed

    Bursa, B; Wróbel, D; Biadasz, A; Kędzierski, K; Lewandowska, K; Graja, A; Szybowicz, M; Durmuş, M

    2014-07-15

    The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

  11. PICASSO-SLP: a Langmuir probe instrument for monitoring the upper ionosphere on board a pico-satellite

    NASA Astrophysics Data System (ADS)

    Ranvier, Sylvain; Anciaux, Michel; Cardoen, Pepijn; Gamby, Emmanuel; Bonnewijn, Sabrina; De Keyser, Johan; Echim, Marius; Pieroux, Didier

    2016-04-01

    A novel Langmuir probe instrument, which will fly on board the Pico-Satellite for Atmospheric and Space Science Observations (PICASSO), is under development at the Royal Belgian Institute for Space Aeronomy. PICASSO, an ESA in-orbit demonstrator, is a triple unit CubeSat of dimensions 340.5x100x100 mm. The sweeping Langmuir probe (SLP) instrument, which includes four thin cylindrical probes whose electrical potential is swept, is designed to measure both plasma density and electron temperature at an altitude varying from about 400 km up to 700 km from a high inclination orbit. Therefore, the plasma density is expected to fluctuate over a wide range, from about 1e8/m³ at high latitude and high altitude up to several times 1e12/m³ at low/mid latitude and low altitude. The electron temperature is expected to lie between approximately 1.000 K and 10.000 K. Given the high inclination of the orbit, the SLP instrument will allow a global monitoring of the ionosphere with a maximum spatial resolution of the order of 150 m for the electron density and temperature, and up to a few meters for electron density only. The main goals are to study 1) the ionosphere-plasmasphere coupling, 2) the subauroral ionosphere and corresponding magnetospheric features, 3) auroral structures, 4) polar caps, 5) for the density, the multi-scale behaviour, spectral properties and turbulence of processes typical for the auroral regions, and 6) ionospheric dynamics via coordinated observations with EISCAT's heating radar. Along the orbit, the Debye length is expected to vary from a few millimetres up to a few meters. Due to the tight constraints in terms of mass and volume inherent to pico-satellites, the use of long booms, which would guarantee that the probes are outside the sheath of the spacecraft (several Debye lengths away), is not possible. Consequently, the probes might be in the sheath of the spacecraft in polar regions. Extensive modelling and simulations of the sheath effects on the

  12. Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen

    SciTech Connect

    Abdel-Fattah, E.; Bazavan, M.; Sugai, H.

    2012-11-15

    By using a rf compensated Langmuir probe and optical emission spectroscopy, the effects of driving frequency (13.56-50 MHz) on the electron energy probability function (EEPF), electron density, electron temperature, and the vibrational and rotational temperatures in capacitively coupled nitrogen discharge were investigated. Measurements were performed in the pressure range 60-200 mTorr, and at a fixed voltage of 140 V (peak-to-peak). With increasing the driving frequency, the dissipated power and electron density markedly increased along with the intensity of the optical emission lines belonging to the 2nd positive (337.1 nm) and 1st negative systems (391.4 nm) of N{sub 2}. The EEPF at low pressure 60 mTorr is two-temperature (bi-Maxwellian) distribution, irrespective of the driving frequency, in contrast with argon and helium discharges in the similar conditions. The mechanism forming such bi-Maxwellian shape was explained by two combined effects: one is the collisionless sheath-heating effect enhancing the tail electron population, and the other is the collision-induced reduction of electrons at the energy 2-4 eV where the collision cross-section for the vibrational excitation has a resonantly large peak. The two-temperature EEPF structure was basically retained at moderate pressure 120 mTorr and high pressure 200 mTorr. The vibrational temperature T{sub vib} and rotational temperature T{sub rot} are measured for the sequence ({Delta}{nu}=-2) of N{sub 2} second positive system (C{sup 3}{Pi}{sub u}{yields}B{sup 3}{Pi}{sub g}) using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. It was found that, both of T{sub vib} and T{sub rot} are a weakly dependent on driving frequency at low pressure 60 mTorr. At higher pressure (120 and 200 mTorr), T{sub vib} rises monotonically with the driving frequency, whereas the T{sub rot} slightly decreases with frequency below 37 MHz, beyond which it relatively increases or

  13. Detection of electron energy distribution function anisotropy in a magnetized electron cyclotron resonance plasma by using a directional Langmuir probe

    SciTech Connect

    Shikama, T. Hasuo, M.; Kitaoka, H.

    2014-07-15

    Anisotropy in the electron energy distribution function (EEDF) in an electron cyclotron resonance plasma with magnetized electrons and weakly magnetized ions is experimentally investigated using a directional Langmuir probe. Under an assumption of independent EEDFs in the directions parallel and perpendicular to the magnetic field, the directional variation of the EEDF is evaluated. In the measured EEDFs, a significantly large population density of electrons with energies larger than 30 eV is found in one of the cross-field directions depending on the magnetic field direction. With the aid of an electron trajectory calculation, it is suggested that the observed anisotropic electrons originate from the EEDF anisotropy and the cross-field electron drift.

  14. Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

    NASA Astrophysics Data System (ADS)

    Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

    2016-09-01

    In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

  15. Theory of cylindrical and spherical Langmuir probes in the limit of vanishing Debye number

    SciTech Connect

    Parrot, M.J.M.; Storey, L.R.O.; Parker, L.W.; Laframboise, J.G.

    1982-12-01

    A theory has been developed for cylindrical and spherical probes and other collectors in collisionless plasmas, in the limit where the ratio of Debye length to probe radius (the Debye number lambda/sub D/) vanishes. Results are presented for the case of equal electron and ion temperatures. On the scale of the probe radius, the distributions of potential and density in the presheath appear to have infinite slope at the probe surface. The dimensionless current--voltage characteristic is the same for the cylinder as for the sphere, within the limits of error of the numerical results, although no physical reason for this is evident. As the magnitude of probe potential (relative to space) increases, the current does not saturate abruptly but only asymptotically; its limiting value is about 45% larger than at space potential. Probe currents for small nonzero lambda/sub D/ approach those for zero lambda/sub D/ only very slowly, showing power-law behavior as function of lambda/sub D/ in the limit as lambda/sub D/ ..-->.. 0, with power-law exponents less than unity, resulting in infinite limiting derivatives with respect to lambda/sub D/.

  16. Characterization of O2/Ar inductively coupled plasma studied by using a Langmuir probe and global model

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Wen, De-Qi; Zhao, Shu-Xia; Gao, Fei; Wang, You-Nian

    2015-04-01

    An O2/Ar inductively coupled plasma is investigated by a Langmuir probe and a global model (volume averaged model). The electron density, electron temperature and electron energy distribution function (EEDF) are measured at different O2 contents, gas pressures and applied powers. At fixed pressure and power, the electron density first drops quickly with the O2 ratio and then tends to saturate in the high O2 ratio range. The effective electron temperature exhibits completely opposite behaviors at low and high pressures. This is caused by the different evolving behaviors of low and high energy electrons of the EEDFs with the O2 ratio. Both the Langmuir probe and the global model predict that the electron density of O2/Ar mixed plasma first increases, peaks and then drops constantly, upon increasing the pressure. An analysis based on the simulation reveals that the non-monotonic variation of electron density with the pressure is due to the non-monotonic variation of the ionizations from both ground state O and metastable O*. Due to the strong ionizations, the electron density increases linearly with the power. The effective electron temperature is unchanged because the EEDF shape that determines the electron temperature is not varied upon increasing the power. The calculated electron density and temperature when varying the power agree better with the experiments at high pressure, i.e. 45 mTorr. The quantitative deviation between the model and the experiment when varying the pressure and the O2 ratio can be explained by two aspects. (1) The electron energy probability function is assumed to have a Maxwellian distribution in the global model while the realistic EEDFs vary significantly with the pressure and/or the O2 ratio, as revealed by the experiment. (2) The power transfer efficiency (i.e. the fraction of the power coupled into plasma) increases with the pressure.

  17. First electron density and temperature estimates from the Swarm Langmuir probes and a comparison with IS measurements

    NASA Astrophysics Data System (ADS)

    Buchert, Stephan C.; Eriksson, Anders; Gill, Reine; Nilsson, Thomas; Åhlen, Lennart; Wahlund, Jan-Erik; Knudsen, David; Burchill, Johnathan; Archer, William; Kouznetsov, Alexei; Stricker, Nico; Bouridah, Abderrazak; Bock, Ralph; Häggström, Ingemar; Rietveld, Michael; Gonzalez, Sixto; Aponte, Nestor

    2014-05-01

    The Langmuir Probes (LP) on the Swarm satellites are part of the Electric Field Instruments (EFI), which are featuring thermal ion imagers (TII) and so are measuring 3-d ion distributions. The main task of the Langmuir probes is to provide measurements of spacecraft potentials influencing the ions before they enter the TIIs. In addition also electron density (Ne) and temperature (Te) are estimated from EFI LP data. The design of the Swarm LP includes a standard current sampling under sweeps of the bias voltage, and also a novel ripple technique yielding derivatives of the current-voltage characteristics at three points in a rapid cycle. In normal mode the time resolution of the Ne and Te measurements so becomes only 0.5 s. We show first Ne and Te estimates from the EFI LPs obtained in the commissioning phase in December 2013, when all three satellites were following each other at about 500 km altitude at mutual distances of a few tens of kilometers. The LP data are compared with observations by incoherent scatter radars, namely EISCAT UHF, VHF, the ESR, and also Arecibo. Acknowledgements: The EFIs were developed and built by a consortium that includes COM DEV Canada, the University of Calgary, and the Swedish Institute for Space Physics in Uppsala. The Swarm EFI project is managed and funded by the European Space Agency with additional funding from the Canadian Space Agency. EISCAT is an international association supported by research organisations in China (CRIRP), Finland (SA), Japan (NIPR and STEL), Norway (NFR), Sweden (VR), and the United Kingdom (NERC). The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association.

  18. Determination of the plasma potential and the EEDF by Langmuir probes in the divertor region of COMPASS tokamak

    NASA Astrophysics Data System (ADS)

    Ivanova, P.; Dimitrova, M.; Vasileva, E.; Popov, Tsv K.; Dejarnac, R.; Stockel, J.; Imríšfsek, M.; Hacek, P.; Panek, R.

    2016-10-01

    This paper reports experimental data obtained on the COMPASS tokamak by an array of Langmuir probes embedded in the divertor tiles. The measured current-voltage probe characteristics were processed by the recently published first-derivative probe technique for precise determination of the plasma potential and the electron energy distribution function (EEDF). The measurements were performed during L-mode hydrogen and deuterium plasma with a toroidal magnetic field Bt = 1.15 T, plasma current Ip = 180 kA and average electron density ne = 8*1019 m-3. The spatial profile of the electron temperatures shows that in the vicinity of the inner and outer strike points in hydrogen plasma the EEDF can be approximated by a bi-Maxwellian distribution, with a dominating low-energy electron population (4 - 7 eV) and a minority of electrons with higher energies (12 - 18 eV). In the private flux region between the two strike points, the EEDF is found to be Maxwellian with temperatures in the range of 7 - 9 eV. In the case of deuterium plasma under similar discharge conditions, the EEDFs in the vicinity of the inner and outer strike points, as well as in the private flux region between the two strike points, are found to be bi-Maxwellian.

  19. Measurement of plasma parameters in the exhaust of a magnetoplasma rocket by gridded energy analyzer and emissive Langmuir probe

    NASA Astrophysics Data System (ADS)

    Glover, Timothy Ward

    2002-01-01

    The 10 kilowatt prototype of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine, abbreviated as VX-10, is designed to eject plasma at exhaust velocities of tens of kilometers per second. In this device, energy is imparted to the plasma ions by two mechanisms: ion cyclotron resonant heating (ICRH), and acceleration in an ambipolar electric field. Measurements from two different electrostatic probes are combined to determine how much each mechanism contributes to the total ion energy. The first probe is a gridded retarding potential analyzer (RPA) that incorporates a multi-channel collimator to obtain precise measurement of the ion and electron parallel energy distributions. The second is an emissive Langmuir probe that measures the DC and RF components of the plasma potential. The plasma potential obtained from the emitting probe allows calculation of the parallel velocity distribution once the parallel energy distribution is obtained from the energy analyzer data. Biasing the RPA housing is shown to minimize the plasma perturbation, as monitored by an auxiliary probe. When this minimization is done, the RPA measurements become compatible with the emissive probe's measurement of plasma potential. The collimated RPA and emissive probe have been used to examine the effects of a double dual half-turn (DDHT) antenna encircling the plasma. When power at the ion cyclotron frequency is applied, changes are seen in the saturation current and mean ion energy of the collimated RPA characteristic. The evolution of these changes as the RPA is moved downstream from the antenna is interpreted as firm evidence of ion cyclotron heating, albeit at absorbed energies of less than 1 electronvolt per ion. The emissive probe shows that, within experimental error, all of the increased ion energy is accounted for by an increase in the plasma potential that occurs when the ICRF power is applied. The combined RPA and emissive probe data also show that there is a jet of

  20. Driven diffusive systems with mutually interactive Langmuir kinetics

    NASA Astrophysics Data System (ADS)

    Vuijk, H. D.; Rens, R.; Vahabi, M.; MacKintosh, F. C.; Sharma, A.

    2015-03-01

    We investigate the simple one-dimensional driven model, the totally asymmetric exclusion process, coupled to mutually interactive Langmuir kinetics. This model is motivated by recent studies on clustering of motor proteins on microtubules. In the proposed model, the attachment and detachment rates of a particle are modified depending upon the occupancy of neighboring sites. We first obtain continuum mean-field equations and in certain limiting cases obtain analytic solutions. We show how mutual interactions increase (decrease) the effects of boundaries on the phase behavior of the model. We perform Monte Carlo simulations and demonstrate that our analytical approximations are in good agreement with the numerics over a wide range of model parameters. We present phase diagrams over a selective range of parameters.

  1. Formation and characterization of Langmuir and Langmuir-Blodgett films of Newkome-type dendrons in presence and absence of a therapeutic compound, for the development of surface mediated drug delivery systems.

    PubMed

    Dib, Nahir; Reviglio, Ana Lucia; Fernández, Luciana; Morales, Gustavo; Santo, Marisa; Otero, Luis; Alustiza, Fabrisio; Liaudat, Ana Cecilia; Bosch, Pablo; Calderón, Marcelo; Martinelli, Marisa; Strumia, Miriam

    2017-06-15

    Organic macromolecules with dendrimeric architectures are polymeric materials potentially useful as nanocarriers for therapeutic drugs. In this work, we evaluate a series of Newkome-type dendrons in Langmuir and Langmuir-Blodgett films as platforms capable of interacting with a potential antitumoral agent. The nanocomposite is proposed as model for the development of surface mediated drug delivery systems. We were successful in the formation and characterization of pure (dendrons) and composite (drug-dendron) stable and reproducible monolayers, and their transfer to solid substrates. A detailed study of topographic characteristics of the generated surfaces by atomic force microscopy was conducted. Furthermore, we probed dendron monolayer films as anchorage surfaces for mammalian cells. Normal cell attachment and proliferation on the surfaces were observed. No evident cytotoxic effects were detected, demonstrating the adequate biocompatibility of the surfaces.

  2. Predictions of VRF on a Langmuir Probe under the RF Heating Spiral on the Divertor Floor on NSTX-U

    SciTech Connect

    Hosea, J C; Perkins, R J; Jaworski, M A; Kramer, G J; Ahn, J-W

    2014-07-01

    RF heating deposition spirals are observed on the divertor plates on NSTX as shown in for a NB plus RF heating case. It has been shown that the RF spiral is tracked quite well by the spiral mapping of the strike points on the divertor plate of magnetic field lines passing in front of the high harmonic fast wave (HHFW) antenna on NSTX. Indeed, both current instrumented tiles and Langmuir probes respond to the spiral when it is positioned over them. In particular, a positive increment in tile current (collection of electrons) is obtained when the spiral is over the tile. This current can be due to RF rectification and/or RF heating of the scrape off layer (SOL) plasma along the magnetic field lines passing in front of the the HHFW antenna. It is important to determine quantitatively the relative contributions of these processes. Here we explore the properties of the characteristics of probes on the lower divertor plate to determine the likelyhood that the primary cause of the RF heat deposition is RF rectification.

  3. Application of an RF Biased Langmuir Probe to Etch Reactor Chamber Matching, Fault Detection and Process Control

    NASA Astrophysics Data System (ADS)

    Keil, Douglas; Booth, Jean-Paul; Benjamin, Neil; Thorgrimsson, Chris; Brooks, Mitchell; Nagai, Mikio; Albarede, Luc; Kim, Jung

    2008-10-01

    Semiconductor device manufacturing typically occurs in an environment of both increasing equipment costs and per unit sale price shrinkage. Profitability in such a conflicted economic environment depends critically on yield, throughput and cost-of-ownership. This has resulted in increasing interest in improved fault detection, process diagnosis, and advanced process control. Achieving advances in these areas requires an integrated understanding of the basic physical principles driving the processes of interest and the realities of commercial manufacturing. Following this trend, this work examines the usefulness of an RF-biased planar Langmuir probe^1. This method delivers precise real-time (10 Hz) measurements of ion flux and tail weighted electron temperature. However, it is also mechanically non-intrusive, reliable and insensitive to contamination and deposition on the probe. Since the measured parameters are closely related to physical processes occurring at the wafer-plasma interface, significant improvements in process control, chamber matching and fault detection are achieved. Examples illustrating the improvements possible will be given. ^1J.P. Booth, N. St. J. Braithwaite, A. Goodyear and P. Barroy, Rev.Sci.Inst., Vol.71, No.7, July 2000, pgs. 2722-2727.

  4. Extraction of electron energy distribution functions from Langmuir probes using integrated step function response and regularized least squares solver

    NASA Astrophysics Data System (ADS)

    Elsaghir, Ahmed; Shannon, Steve

    2008-10-01

    Electron energy distribution function (EEDF) extraction from Langmuir probe data is an ill-posed problem due to the integral relationship between electron current and EEDF with respect to probe voltage. Curve fitting solutions to extract this EEDF assume a specific type of distribution. Point by point extraction of the second derivative relationship uses a small fraction of the integrated data to extract the EEDF. Recently EEDF extraction techniques have been evaluated using regularized solutions to the integral problem.ootnotetextGuti'errez-Tapia and Flores-Llamas, Phys. Plasmas 11 5102 (2004) These techniques do not assume any mathematical representation of the EEDF and solve the integral problem for any function that best represents the EEDF. In this paper the electron current for arbitrary functions is derived assuming that the electron density is a sum of step functions representing such a function. This technique for EEDF extraction is validated by adding noise to numerically generated data and using a regularized least squares method to calculate the original function by solving for the individual step function contribution to the total electron current. The methodology, reconstruction, and comparison to current best-known methods will be presented.

  5. The behavior of the plasmapause at mid-latitudes - Isis 1 Langmuir probe measurements

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Theis, R. F.

    1974-01-01

    Observations of the electron concentration and the temperature from the electrostatic probes on the Isis 1 satellite were used to examine the location and behavior of the plasmapause at about 3000-km altitude in the vicinity of L = 4. At these altitudes the electron concentration measurements are equivalent to measurements of H(+), since the satellite is well into the protonosphere. The plasmapause is evident as a sharp drop in electron concentration by a factor of 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the earth. An enhancement of temperature is also observed at the plasmapause, an effect that is most visible at night, when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to Kp than is the equatorial plasmapause.

  6. The behavior of the plasmapause at mid-latitudes - Isis 1 Langmuir probe measurements

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Theis, R. F.

    1974-01-01

    Observations of the electron concentration and the temperature from the electrostatic probes on the Isis 1 satellite were used to examine the location and behavior of the plasmapause at about 3000-km altitude in the vicinity of L = 4. At these altitudes the electron concentration measurements are equivalent to measurements of H(+), since the satellite is well into the protonosphere. The plasmapause is evident as a sharp drop in electron concentration by a factor of 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the earth. An enhancement of temperature is also observed at the plasmapause, an effect that is most visible at night, when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to Kp than is the equatorial plasmapause.

  7. Real-time control of divertor detachment in H-mode with impurity seeding using Langmuir probe feedback in JET-ITER-like wall

    NASA Astrophysics Data System (ADS)

    Guillemaut, C.; Lennholm, M.; Harrison, J.; Carvalho, I.; Valcarcel, D.; Felton, R.; Griph, S.; Hogben, C.; Lucock, R.; Matthews, G. F.; Perez Von Thun, C.; Pitts, R. A.; Wiesen, S.; contributors, JET

    2017-04-01

    Burning plasmas with 500 MW of fusion power on ITER will rely on partially detached divertor operation to keep target heat loads at manageable levels. Such divertor regimes will be maintained by a real-time control system using the seeding of radiative impurities like nitrogen (N), neon or argon as actuator and one or more diagnostic signals as sensors. Recently, real-time control of divertor detachment has been successfully achieved in Type I ELMy H-mode JET-ITER-like wall discharges by using saturation current (I sat) measurements from divertor Langmuir probes as feedback signals to control the level of N seeding. The degree of divertor detachment is calculated in real-time by comparing the outer target peak I sat measurements to the peak I sat value at the roll-over in order to control the opening of the N injection valve. Real-time control of detachment has been achieved in both fixed and swept strike point experiments. The system has been progressively improved and can now automatically drive the divertor conditions from attached through high recycling and roll-over down to a user-defined level of detachment. Such a demonstration is a successful proof of principle in the context of future operation on ITER which will be extensively equipped with divertor target probes.

  8. The behavior of the plasmapause at mid-latitudes: ISIS-1 Langmuir probe measurements

    NASA Technical Reports Server (NTRS)

    Brace, L. H.; Theis, R. F.

    1973-01-01

    Observations of the electron concentration, N sub e, and temperature, T sub e, from the electrostatic probes on the ISIS-1 satellite were used to examine the location and behavior of the plasmapause at about 3000 kilometers altitude in the vicinity of L = 4. At these altitudes, the N sub e measurements are equivalent to measurements of H(+) since the satellite is well into the protonosphere. The plasmapause as is evident as a sharp drop in N sub e by a factor of 10 to 100 as the satellite passes into the polar cap, and a corresponding increase is observed as it enters the plasmasphere on the opposite side of the Earth. An enhancement of T sub e is also observed at the plasmapause, an effect that is most visible at night when the temperatures at latitudes above and below the plasmapause are usually very low. The position of the plasmapause decreases with magnetic activity but is found to be somewhat less sensitive to K sub p than is the equatorial plasmapause. Also unlike its equatorial behavior, the mid-latitude plasmapause exhibits no detectable late afternoon bulge. These differences imply rather complex coupling of the thermal plasma along the field lines that link these two regions of the plasmasphere. An additional factor may be the recently observed axial asymmetry in the geomagnetic field at high altitudes.

  9. Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probe.

    PubMed

    Schmitzer, C; Kronberger, M; Lettry, J; Sanchez-Arias, J; Störi, H

    2012-02-01

    The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H(-) volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e(-) and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H(-) ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H(-) ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

  10. Langmuir probe-based observables for plasma-turbulence code validation and application to the TORPEX basic plasma physics experiment

    SciTech Connect

    Ricci, Paolo; Theiler, C.; Fasoli, A.; Furno, I.; Labit, B.; Mueller, S. H.; Podesta, M.; Poli, F. M.

    2009-05-15

    The methodology for plasma-turbulence code validation is discussed, with focus on the quantities to use for the simulation-experiment comparison, i.e., the validation observables, and application to the TORPEX basic plasma physics experiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. The considered validation observables are deduced from Langmuir probe measurements and are ordered into a primacy hierarchy, according to the number of model assumptions and to the combinations of measurements needed to form each of them. The lowest levels of the primacy hierarchy correspond to observables that require the lowest number of model assumptions and measurement combinations, such as the statistical and spectral properties of the ion saturation current time trace, while at the highest levels, quantities such as particle transport are considered. The comparison of the observables at the lowest levels in the hierarchy is more stringent than at the highest levels. Examples of the use of the proposed observables are applied to a specific TORPEX plasma configuration characterized by interchange-driven turbulence.

  11. Langmuir Probe Measurements of Inductively Coupled CHF3/Ar and Ar/CHF3/O2 Plasmas

    NASA Technical Reports Server (NTRS)

    Sharma, S. P.; Rao, M. V. V. S.; Meyyappan, M.

    2000-01-01

    Plasma parameters, such as, electron number density (ne), electron temperature (Te), y electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp), have been measured by using Langmuir probe in low-pressure (10-50 mTorr) inductively coupled CHF3/Ar and CHF3/Ar/O2 plasmas generated in the GEC cell. The measurements were made at the center of the plasma, keeping the lower electrode grounded, for various CHF3/Ar and Ar/CHF3/O2 mixtures operating at 10-50 mTorr pressures and two input RF power levels, 200 and 300 W. EEDF data show a strong Druyvesteyn distribution with relatively lower number of low energy electrons as compared to a Maxwell distribution and a large electron population with energies higher than the plasma potential. The results further show that at low CHF3 concentrations (less than 50%) the electron number density remains nearly constant with increase in pressure. At higher CHF3 concentrations, however, it decreases with increase in pressure. Plasma potential and electron temperature increase with decrease in pressure and with increase in CHF3 concentration. An analysis of the above observations and mechanisms will be presented.

  12. Langmuir probe study of a magnetically enhanced RF plasma source at pressures below 0.1 Pa

    NASA Astrophysics Data System (ADS)

    Kousal, Jaroslav; Tichý, Milan; Šebek, Ondřej; Čechvala, Juraj; Biederman, Hynek

    2011-08-01

    The majority of plasma polymerization sources operate at pressures higher than 1 Pa. At these pressures most common deposition methods do not show significant directionality. One way of enhancing the directional effects is to decrease the working pressure to increase the mean free path of the reactive molecules. The plasma source used in this work was designed to study the plasma polymerization process at pressures below 0.1 Pa. The source consists of the classical radio frequency (RF) (13.56 MHz, capacitive coupled) tubular reactor enhanced by an external magnetic circuit. The working gas is introduced into the discharge by a capillary. This forms a relatively localized zone of higher pressure where the monomer is activated. Due to the magnetic field, the plasma is constricted near the axis of the reactor with nearly collisionless gas flow. The plasma parameters were obtained using a double Langmuir probe. Plasma density in the range ni = 1013-1016 m-3 was obtained in various parts of the discharge under typical conditions. The presence of the magnetic field led to the presence of relatively strong electric fields (103 V m-1) and relatively high electron energies up to several tens of eV in the plasma.

  13. Estimation of Al2O3 critical temperature using a Langmuir probe in laser ablation

    NASA Astrophysics Data System (ADS)

    Yahiaoui, K.; Abdelli-Messaci, S.; Messaoud Aberkane, S.; Kellou, A.

    2016-11-01

    Pulsed laser deposition (PLD) has demonstrated its capacity in thin films growing under the moderate laser intensity. But when the laser intensity increases, the presence of droplets on the thin film limits the PLD efficiency such that the process needs an optimization study. In this way, an experimental study has been conducted in order to correlate between the appearance of those droplets and the laser fluence. The comprehension of the physical mechanism during ablation and the control of the deposition parameters allowed to get a safe process. Our experiment consists in measuring the amount of ejected matter from polycrystalline alumina target as a function of the laser fluence when irradiated by a KrF laser. According to laser fluence, several kinds of ablation regimes have been identified. Below a threshold value found as 12 J/cm2, the mechanism of ablation was assigned to normal evaporation, desorption and nonthermal processes. While above this threshold value, the mechanism of ablation was assigned to phase explosion phenomenon which is responsible of droplets formation when the surface temperature approaches the critical temperature T tc. A negative charge collector was used to collect the positive ions in the plume. Their times of flight (TOF) signal were used to estimate the appropriate T tc for alumina target. Ions yield, current as well as kinetic energy were deduced from the TOF signal. Their evolutions show the occurrence of an optical breakdown in the vapor plume which is well correlated with the onset of the phase explosion phenomenon. At 10 J/cm2, the ions velocities collected by the probe have been compared to those obtained from optical emission spectroscopy diagnostic and were discussed. To prove the occurrence of phase explosion by the appearance of droplets, several thin films were elaborated on Si (100) substrate at different laser fluence into vacuum. They have been characterized by scanning electron microscope. The results were well

  14. Probing the Solar System

    ERIC Educational Resources Information Center

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  15. Probing the Solar System

    ERIC Educational Resources Information Center

    Wilkinson, John

    2013-01-01

    Humans have always had the vision to one day live on other planets. This vision existed even before the first person was put into orbit. Since the early space missions of putting humans into orbit around Earth, many advances have been made in space technology. We have now sent many space probes deep into the Solar system to explore the planets and…

  16. Optical emission spectroscopy and Langmuir probe diagnostics of CH3F/O2 inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Karakas, Erdinc; Donnelly, Vincent M.; Economou, Demetre J.

    2013-06-01

    A CH3F:O2 (50%:50%) inductively coupled discharge, sustained in a compact plasma reactor, was investigated as a function of power (20-400 W) and pressure (9-30 mTorr), using optical emission spectroscopy and Langmuir probe measurements. The electron density increased linearly with power but only weakly with pressure. The effective electron temperature was nearly independent of power and pressure. The gas temperature, obtained from the rotational structure of N2 (C → B) optical emission, increased from 400 to 900 K as a function of inductive mode power between 75 and 400 W at 10 mTorr. For constant feed gas flow, the absolute H, F, and O atom densities, estimated by optical emission rare gas actinometry, increased linearly with power. The absolute number density ratios H/Ar, F/Ar, and O/Ar, increased, decreased, and remained constant, respectively, with pressure. The H-atom density was estimated to be 5.4 × 1013 cm-3 at 400 W and 10 mTorr (gas temperature = 900 K), implying a high degree of dissociation of the CH3F feedstock gas. The F and O atom number densities were much lower (8.3 × 1012 cm-3 and 5.9 × 1012 cm-3, respectively) for the same conditions, suggesting that most of the fluorine and oxygen is contained in reaction products HF, CO, CO2, H2O, and OH. The relative number densities of HF, CO, and CO2 were observed to first rapidly increase with power, and then reach a plateau or decay slightly at higher power. Reaction mechanisms were proposed to explain the observed behavior of the number density of F and HF vs. power and pressure.

  17. A measurement of the TPMU - PROBA II Microsatellite Instrument and its comparison with the SWARM Langmuir Probes results

    NASA Astrophysics Data System (ADS)

    Podolska, Katerina; Hruska, Frantisek; Truhlik, Vladimir

    2016-04-01

    This contribution deals with the long-term measurement of the floating potential (FP) and the electron temperature (Te) provided by the Thermal Plasma Measurement Unit (TPMU) scientific instrument on-board the PROBA II microsatellite. The device is working with limitations of scientific measurements caused very probably by installed on-board software. This brings lower data volume as it was planned. Affected are the ion measurement and partially the electron temperature measurement. We present comparisons of the TPMU long-term measurement of the FP and the Te with the Te and the FP SWARM Langmuir Probes measured data. We implement the method of stochastic comparison of the probability distribution between measurements of FP and Te of both instruments to recognize seasonal and solar activity similarities. The analysis is performed for all seasons of the period from the years 2013 - 2015 for the Equatorial region, North and South hemisphere. The data are divided into the three groups by the geographical latitude to the Nothern hemisphere (lat>15'), the Southern hemisphere (lat<-5') and Equatorial zone (lat 15'- -15') and to four groups by season. This comparison confirms that the TPMU PROBAII Te and FP measurement statistically corresponds to the SWARM Te and FP measurement. The annual seasonal changes in the floating potential are observed in this analysis. Changes in the beginning, the end and duration of seasons over a period of years reflect also changes of the Kp index. Changes over the solar cycle are also visible. The main TPMU goal is the validation and testing of new design of the instrument which is necessary for possible applications of TPMU design for future scientific missions.

  18. Investigation of the electron kinetics in O2 capacitively coupled plasma with the use of a Langmuir probe

    NASA Astrophysics Data System (ADS)

    Kechkar, S.; Swift, P.; Kelly, S.; Kumar, S.; Daniels, S.; Turner, M.

    2017-06-01

    A Langmuir probe was used to measure various electron plasma parameters in O2 capacitively coupled plasma. It was shown that the variation in these plasma parameters was due to changes in the electron heating mechanisms as the discharge conditions varied. The so called ‘α-γ’ mode transition in O2 plasma (100 mTorr) was identified from the power evolution (30-600 W) of the electron energy probability function (EEPF), electron density (n e) and effective electron temperature (T eff). The EEPF evolved from Druyvesteyn to bi-Maxwellian with increasing applied power which resulted in a rapid decrease and an abrupt increase in T eff and n e respectively. Comparisons were made to the same mode transition for similar conditions in Ar plasma. The EEPFs were Druyvesteyn in the α mode and evolved into a Maxwellian like EEPF in the γ mode of an Ar plasma. Two distinct trends of n e versus power was observed, it was shown that the measured rf current and rf voltage had a similar behavior. The pressure evolution of the EEPF, n e, and T eff was also investigated in O2 plasma operated at both 30 and 200 W. At 30 W the number of high energy electrons decreased and flattening of the low energy portion of the EEPF occurred with increasing gas pressure (10-100 mTorr) which indicates a collisionless to collisional heating transition. However, at 200 W the right combination of rf voltage and pressure was met for the discharge to evolve into the γ mode as the pressure increased. This was evident from significant narrowing of the EEPF as the pressure increased.

  19. Observed Coupling Between the International Space Station PCU Plasma and a FPMU Langmuir Probe Facilitated by the Geomagnetic Field

    NASA Technical Reports Server (NTRS)

    Hartman, William; Koontz, Steven L.

    2010-01-01

    Electrical charging of the International Space Station (ISS) is a matter of serious concern resulting from the possibility of vehicle arcing and electrical shock hazard to crew during extravehicular activity (EVA). A Plasma Contactor Unit (PCU) was developed and integrated into ISS in order to control the ISS floating potential, thereby, minimize vehicle charging and associated hazards. One of the principle factors affecting ISS electrical charging is the ionosphere plasma state (i.e., electron temperature and density). To support ISS electrical charging studies a Floating Potential Monitoring Unit (FPMU) is also integrated into ISS in order to measure the ionosphere properties using Langmuir probes (LP). The FPMU was located on the Starboard side of ISS. The PCU is located near the center of ISS with its plasma exhaust pointed to port. From its integration on ISS in 2006 through November of 2009, the FPMU data exhibited nominal characteristics during PCU operation. On November 21, 2009 the FPMU was relocated from the Starboard location to a new Port location. After relocation significant enhanced noise was observed in both the LP current-voltage sweeps and the derived electron temperature data. The enhanced noise only occurred when the PCU was in discharge and at unique and repeatable locations of the ISS orbit. The cause of this enhanced noise was investigated. It was found that there is coupling occurring between the PCU plasma and the FPMU LP. In this paper we shall 1) present the on-orbit data and the presence of enhanced noise, 2) demonstrate that the coupling of the PCU plasma and the FPMU measurements is geomagnetically organized, 3) show that coupling of the PCU plasma and the FPMU is primarily due to and driven by particle-wave interaction and 4) show that the ionosphere conditions are adequate for Alfven waves to be generated by the PCU plasma.

  20. Diagnostics of capacitively-coupled hydrocarbon plasmas for deposition of diamond-like carbon films using quadrupole mass spectrometry and Langmuir probe

    NASA Astrophysics Data System (ADS)

    Oda, Akinori; Fukai, Shun; Kousaka, Hiroyuki; Ohta, Takayuki

    2015-09-01

    Diamond-like carbon (DLC) films are the hydrogenated amorphous carbon films, which contains a mixture of sp2- and sp3-bonded carbon. The DLC films have been widely used for various applications, such as automotive, semiconductors, medical devices, since have excellent material properties in lower friction, higher chemical stability, higher hardness, higher wear resistance. Until now, numerous investigations on the DLC films using plasma assisted chemical vapor deposition have been done. For precise control of coating technique of DLC films, it is enormously important to clarify the fundamental properties in hydrocarbon plasmas, as a source of hydrocarbon ions and radicals. In this paper, the fundamental properties in a low pressure radio-frequency hydrocarbon (Ar/CH4 (1 %) gas mixture) plasmas have been diagnosed using a quadrupole mass spectrometer (HIDEN ANARYTICAL Ltd., EQP-300) and Langmuir probe system (HIDEN ANARYTICAL Ltd., ESPion). This work was partly supported by KAKENHI (No.26420247), and a ``Grant for Advanced Industrial Technology Development (No.11B06004d)'' in 2011 from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

  1. Divertor sheath power studies in DIII-D using fixed Langmuir probes and three-dimensional modeling of tile heat flows

    NASA Astrophysics Data System (ADS)

    Donovan, D.; Nygren, R.; Buchenauer, D.; Watkins, J.; Rudakov, D.; Leonard, A.; Wong, C. P. C.; Makowski, M.

    2014-04-01

    Experimental results are presented from the three-Langmuir probe (LP) diagnostic head of the divertor material evaluation system (DiMES) on DIII-D that confirm the size of the projected current collection area of the LPs, which is essential for properly measuring ion saturation current density (Jsat) and the sheath power transmission factor (SPTF). Also using the 3-LP DiMES head, the hypothesis that collisional effects on plasma density occurring in the magnetic sheath of the tile are responsible for a lower than expected SPTF is tested and deemed not to have a significant impact on the SPTF. Three-dimensional thermal modeling of wall tiles is presented that accounts for lateral heat conduction, temperature dependence of tile material properties and radiative heat loss from the tile surface. This modeling was developed to be used in the analysis of temperature profiles of the divertor embedded thermocouple (TC) array to obtain more accurate interpretations of TC temperature profiles to infer divertor surface heat flux than have previously been accomplished using more basic one-dimensional methods.

  2. [Characteristics of interaction of adenylate cyclase modulators and phosphoinositide cell signaling systems with lipid langmuir monolayers].

    PubMed

    Liakhov, O M; Prokopenko, V V; Prokopenko, R A; Mohylevych, S Ie

    2006-01-01

    Interaction of two groups of bioregulators, which oppositely affect activity of adenylate cyclase and phosphoinositide cellular signaling systems, with the Langmuir monolayer films made of natural lecithin was studied. Most significant influence on the structural and energy characteristics of lipid monolayers was revealed for the group of bioregulators, which inhibit polyphosphoinositide signaling system or/and activate adenylate cyclase signaling system. It is shown, that using the cluster analysis the bioregulators can be divided into two groups according to general orientation of their action on the considered systems of transduction of a signal.

  3. Traversing probe system

    DOEpatents

    Mashburn, Douglas N.; Stevens, Richard H.; Woodall, Harold C.

    1977-01-01

    This invention comprises a rotatable annular probe-positioner which carries at least one radially disposed sensing probe, such as a Pitot tube having a right-angled tip. The positioner can be coaxially and rotatably mounted within a compressor casing or the like and then actuated to orient the sensing probe as required to make measurements at selected stations in the annulus between the positioner and compressor casing. The positioner can be actuated to (a) selectively move the probe along its own axis, (b) adjust the yaw angle of the right-angled probe tip, and (c) revolve the probe about the axis common to the positioner and casing. A cam plate engages a cam-follower portion of the probe and normally rotates with the positioner. The positioner includes a first-motor-driven ring gear which effects slidable movement of the probe by rotating the positioner at a time when an external pneumatic cylinder is actuated to engage the cam plate and hold it stationary. When the pneumatic cylinder is not actuated, this ring gear can be driven to revolve the positioner and thus the probe to a desired circumferential location about the above-mentioned common axis. A second motor-driven ring gear included in the positioner can be driven to rotate the probe about its axis, thus adjusting the yaw angle of the probe tip. The positioner can be used in highly corrosive atmosphere, such as gaseous uranium hexafluoride.

  4. Deriving the characteristics of warm electrons (100-500 eV) in the magnetosphere of Saturn with the Cassini Langmuir probe

    NASA Astrophysics Data System (ADS)

    Garnier, P.; Holmberg, M. K. G.; Wahlund, J.-E.; Lewis, G. R.; Schippers, P.; Coates, A.; Gurnett, D. A.; Waite, J. H.; Dandouras, I.

    2014-12-01

    agreement with the CAPS measurements than the values derived from the proxy technique (Morooka et al., 2009) based on the floating potential of the LP. Both the electron temperature and the density estimates lie outside the classical capabilities of the LP, which are essentially ne > 5 cc and Te < 5 eV at Saturn. This approximate derivation technique may be used in the regions where the cold plasma component is small with an average temperature in the range ~ [ 100 - 500 ] eV, which occurs often in the L range 6.4-9.4 RS when Cassini is off the equator, but may occur anywhere in the magnetosphere. This technique may be all the more interesting since the CAPS instrument was shut down, and, though it cannot replace the CAPS instrument, the technique can provide useful information about the electron moments, with probably even better estimates than CAPS in some cases (when the plasma is strongly anisotropic). Finally, a simple modeling approach allows us to predict the impact of the energetic contributions on LP measurements in any plasma environment whose characteristics (density, temperature, etc.) are known. LP observations may thus be influenced by warm electrons in several planetary plasma regions in the solar system, and ambient magnetospheric electron density and temperature could be estimated in some of them (e.g. around several galilean satellites) through the use of Langmuir probes.

  5. Electron energy distribution function in plasma determined using numerical simulations of multiple harmonic components on Langmuir probe characteristic: efficiency of the method.

    PubMed

    Jauberteau, J L; Jauberteau, I

    2007-04-01

    The method proposed to determine the electron energy distribution is based on the numerical simulation of the effect induced by a sinusoidal perturbation superimposed to the direct current voltage applied to the probe. The simulation is generating a multiple harmonic components signal over the rough experimental data. Each harmonic component can be isolated by means of finite impulse response filters. Then, the second derivative is deduced from the second harmonic component using the Taylor expansion. The efficiency of the method is proved first on simple cases and second on typical Langmuir probes characteristics recorded in the expansion of a microwave plasma containing argon or nitrogen-hydrogen gas mixture. Results obtained using this method are compared to those, which are determined using a classical Savitzsky-Golay filter.

  6. Electron energy distribution function in plasma determined using numerical simulations of multiple harmonic components on Langmuir probe characteristic--Efficiency of the method

    SciTech Connect

    Jauberteau, J. L.; Jauberteau, I.

    2007-04-15

    The method proposed to determine the electron energy distribution is based on the numerical simulation of the effect induced by a sinusoidal perturbation superimposed to the direct current voltage applied to the probe. The simulation is generating a multiple harmonic components signal over the rough experimental data. Each harmonic component can be isolated by means of finite impulse response filters. Then, the second derivative is deduced from the second harmonic component using the Taylor expansion. The efficiency of the method is proved first on simple cases and second on typical Langmuir probes characteristics recorded in the expansion of a microwave plasma containing argon or nitrogen-hydrogen gas mixture. Results obtained using this method are compared to those, which are determined using a classical Savitzsky-Golay filter.

  7. Studies on the radical species in inductively coupled Ar/CH4 plasma using improved single Langmuir probe diagnostic methods and fluid simulation

    NASA Astrophysics Data System (ADS)

    Cha, Ju-Hong; Seo, Kwon-Sang; Lee, Jung Yeol; Lee, Hae June; Lee, Ho-Jun

    2016-09-01

    An inductively coupled plasma source driven by 13.56MHz was prepared for the deposition of a-C:H thin film. Properties of the plasma source are investigated by fluid simulation including Navier-Stokes equation and home-made tuned single Langmuir probe. Signal attenuation ratios of the Langmuir probe at first and second harmonic frequency were 49dB and 46dB respectively. Numerical methods including fitting, digital smoothing, digital filter with window function were used to calculate the electron energy distribution accurately. Dependencies of plasma parameters on process were well agreed with simulation results. It was found that RF power, inlet pressure and composition ratio significantly affect to the electron density, temperature and energy distribution. Electron density and plasma potential profile were changed along the input power and gas pressure. Below the input power density of 0.1W/cm3 , higher plasma potential was observed at higher pressure. However, over the 0.1W/cm3 , lower plasma potential was observed along the higher pressure. This result was occurred owing to the change of electron energy distribution. And from the simulation results, the specific chemical reaction channel, not CxHy but CHx, affect to the radical density profile.

  8. RF power deposition effects observed for the scrape off layer in NSTX/NSTX_U and EAST and the accompanying RF effects on divertor Langmuir probes

    NASA Astrophysics Data System (ADS)

    Hosea, J.; Perkins, R. J.; Jaworski, M.; Bertelli, N.; Taylor, G.; Qin, C.; Wang, L.; Yang, J.; Zhang, X. J.

    2016-10-01

    Strong RF power deposition effects in the divertor regions have been observed in NSTX for the HHFW regime and in EAST for the minority ICRF regime. On NSTX the RF power deposition in the scrape off layer (SOL) follows the magnetic field lines from in front of the antenna to an RF heat deposition spiral on the divertor regions. The strong SOL deposition and the spiral formation occur for edge densities above the cutoff density in front of the antenna. On EAST the RF heat deposition appears to be less intense as predicted with AORSA simulations. At coupled powers on EAST up to 700 kW here, bands of deposition are observed on the lower divertor. RF deposition is also indicated on Langmuir probes on the lower outer divertors. For divertor probes in NSTX located to intercept field lines passing in the SOL away from the antenna, the floating potential is pushed negatively as expected for RF rectification. Similarly, on EAST the floating potential is pushed negatively for the field lines out in front of the antenna, but more positively for field lines that intercept the antenna/wall. To understand this latter behavior, probe IV characteristics will be investigated on NSTX-U to establish the electron energy distribution and space potential at a set of probes covering the entire SOL field strike point range. This work is supported by USDOE Contract No. DE-AC02-09CH11466.

  9. Langmuir probe investigation of transient plasmas generated by femtosecond laser ablation of several metals: Influence of the target physical properties on the plume dynamics

    NASA Astrophysics Data System (ADS)

    Irimiciuc, S. A.; Gurlui, S.; Bulai, G.; Nica, P.; Agop, M.; Focsa, C.

    2017-09-01

    Langmuir probe measurements were performed on transient plasmas generated by femtosecond laser ablation of several metallic targets (Al, Cu, Mn, Ni, In, Te, W). The analysis of current-voltage characteristics at various delays after the laser pulse gave access to the temporal evolution of ion density, electron temperature and plasma potential. The time-of-flight profile of the current recorded by the probe was also discussed in terms of a shifted Maxwell-Boltzmann velocity distribution, considering both thermal and drift velocities. The plasma parameters derived by these approaches were correlated with the electrical conductivity of the investigated metals. Assuming a direct dependence between the probe ionic signal and the charge carrier mobility in the target, a logarithmic fit was proposed for the plasma potential variation with electrical conductivity, whereas a derivative of this function was applied for the electron temperature. The saturation charge derived from the time-integrated probe ionic signals was influenced by the electrical conductivity of the target and also by the atomic weight of the metal. A steep increase of the thermal and drift velocities with conductivity was observed.

  10. Langmuir-Blodgett films of a pyrrole and ferrocene mixed surfactant system

    SciTech Connect

    Samuelson, L.; Rahman, A.K.M.; Clough, S.; Tripathy, S.; Hale, P.D.; Inagaki, T.; Skotheim, T.A.; Okamoto, Y. . Dept. of Chemistry; Brookhaven National Lab., Upton, NY; Polytechnic Univ., Brooklyn, NY . Dept. of Chemistry)

    1989-01-01

    The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization, it appears, leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization. Near Edge X-Ray Absorption Fine Structure (NEXAFS) studies revealed that highly ordered multilayer structures are being formed. Electrochemical studies have been initiated to determine the feasibility of these films in molecular electronic device applications. 13 refs., 6 figs., 1 tab.

  11. Response of Venus exospheric temperature measured by neutral mass spectrometer to solar EUV flux measured by Langmuir probe on the Pioneer Venus orbiter

    NASA Technical Reports Server (NTRS)

    Mahajan, K. K.; Kasprzak, W. T.; Brace, L. H.; Niemann, H. B.; Hoegy, W. R.

    1990-01-01

    The photoelectron current from the Pioneer Venus Langmuir probe has provided measurements of the total flux of solar EUV photons at Venus since 1979. The neutral oxygen scale height measured by the orbiter neutral mass spectrometer has permitted the exospheric temperature to be derived during the same mission. In this paper, the EUV observations are used to examine the response of exospheric temperature to changes in solar activity, primarily those related to solar rotation. It is found that the dayside exospheric temperature quite faithfully tracks variations in the EUV flux. Comparison is also made with the earth-based solar activity index F10.7 adjusted to the position of Venus. This index varied from 142 to 249 flux units during the period of measurements. The exospheric temperature is better correlated with EUV flux than with the 10.7-cm solar radio flux.

  12. The Huygens Probe System Design

    NASA Astrophysics Data System (ADS)

    Clausen, K. C.; Hassan, H.; Verdant, M.; Couzin, P.; Huttin, G.; Brisson, M.; Sollazzo, C.; Lebreton, J.-P.

    2002-07-01

    The Huygens Probe is the ESA-provided element of the joint NASA/ESA Cassini/Huygens mission to Saturn and its largest moon Titan. Huygens is an entry probe designed to enter Titan's atmosphere and descend under parachute down to the surface. The Probe is carried to Titan on board the Cassini Saturn Orbiter. Huygens is dormant for 7.2 years, during the interplanetary journey and during the first 6 months around Saturn. It is activated about every 6 months for an in-flight checkout to verify and monitor its health and to perform a periodic maintenance and calibration of the payload instruments. The Probe will be targeted to Titan and released from the Orbiter about 3 weeks before the Titan encounter on the third Orbit around Saturn. During the 3-week coast phase the Probe is ‘OFF’, except a timer unit that has the task to awaken Huygens before it enters Titan's atmosphere. The Probe's aeroshell will decelerate it in less than 2 minutes from the entry speed of about 6 km s-1 to 400 m s-1 (Mach 1.5) at an altitude of 150 180 km. From that point onwards, a pre-programmed sequence will trigger the parachute deployment and the heat-shield ejection. The main part of the scientific mission will then start, lasting for a descent of 2 21/2 hours. The Orbiter will listen to the Probe for a total duration of at least 3 hours, which includes time to receive data from the surface, should the Probe continue to transmit data after touchdown. Huygens' transmissions are received and stored aboard the Orbiter for later retransmission to the Earth. This paper presents a technical description of the elements of the Huygens Probe System. The reader is invited to refer to the companion paper (Lebreton and Matson, 2002) for further background information about the Huygens mission, and the payload. The early in-flight performance of the Probe is briefly discussed. During in-flight testing in 2000, a technical anomaly was found with the Probe-to-Orbiter telecommunication system that

  13. Long-range excitation energy transfer in Langmuir-Blodgett multilayer systems

    NASA Astrophysics Data System (ADS)

    Draxler, Sonja; Lippitsch, Max E.; Aussenegg, Franz R.

    1989-07-01

    In Langmuir-Blodgett films containing organic dyes, efficient energy transfer over distances exceeding 100 nm is observed. This exceptionally long-range transfer is interpreted as due to special mutual orientation of the dye molecules.

  14. Langmuir Probe Measurements Within the Discharge Channel of the 20-kW NASA-300M and NASA-300MS Hall Thrusters

    NASA Technical Reports Server (NTRS)

    Shastry, Rohit; Huang, Wensheng; Haag, Thomas W.; Kamhawi, Hani

    2013-01-01

    NASA is presently developing a high-power, high-efficiency, long-lifetime Hall thruster for the Solar Electric Propulsion Technology Demonstration Mission. In support of this task, studies have been performed on the 20-kW NASA-300M Hall thruster to aid in the overall design process. The ability to incorporate magnetic shielding into a high-power Hall thruster was also investigated with the NASA- 300MS, a modified version of the NASA-300M. The inclusion of magnetic shielding would allow the thruster to push existing state-of-the-art technology in regards to service lifetime, one of the goals of the Technology Demonstration Mission. Langmuir probe measurements were taken within the discharge channels of both thrusters in order to characterize differences at higher power levels, as well as validate ongoing modeling efforts using the axisymmetric code Hall2De. Flush-mounted Langmuir probes were also used within the channel of the NASA-300MS to verify that magnetic shielding was successfully applied. Measurements taken from 300 V, 10 kW to 600 V, 20 kW have shown plasma potentials near anode potential and electron temperatures of 4 to 12 eV at the walls near the thruster exit plane of the NASA-300MS, verifying magnetic shielding and validating the design process at this power level. Channel centerline measurements on the NASA-300M from 300 V, 10 kW to 500 V, 20 kW show the electron temperature peak at approximately 0.1 to 0.2 channel lengths upstream of the exit plane, with magnitudes increasing with discharge voltage. The acceleration profiles appear to be centered about the exit plane with a width of approximately 0.3 to 0.4 channel lengths. Channel centerline measurements on the NASA-300MS were found to be more challenging due to additional probe heating. Ionization and acceleration zones appeared to move downstream on the NASA-300MS compared to the NASA-300M, as expected based on the shift in peak radial magnetic field. Additional measurements or alternative

  15. Investigation of Radio Frequency Discharges and Langmuir Probe Diagnostic Methods in a Fast Flowing Electronegative Background Gas

    DTIC Science & Technology

    2007-12-01

    B. F. Gordiets, and A. I. Osipov, Plasma Kinetics in Atmospheric Gases. New York: Springer-Verlag, 2000. Carroll olomon, W.C., “Recent...Transition from diffusion-convection to sheath- convection of a cold Clemen lanmuir probe in a moving compressible plasma ,” J. of Phys., 14 : 1001...collisionless plasma ,” Phys. of Plasmas 12: 062109-1-062109-20 (2005). orales , C. R., J. I. Fernandez Palop, S. Borrego del Pino, and J

  16. Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe.

    PubMed

    Prevosto, L; Kelly, H; Mancinelli, B

    2013-12-01

    This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.

  17. Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: Analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe

    SciTech Connect

    Prevosto, L.; Mancinelli, B.; Kelly, H.

    2013-12-15

    This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.

  18. Numerical experiment to estimate the validity of negative ion diagnostic using photo-detachment combined with Langmuir probing

    SciTech Connect

    Oudini, N.; Sirse, N.; Ellingboe, A. R.; Benallal, R.; Taccogna, F.; Bendib, A.

    2015-07-15

    This paper presents a critical assessment of the theory of photo-detachment diagnostic method used to probe the negative ion density and electronegativity α = n{sub -}/n{sub e}. In this method, a laser pulse is used to photo-detach all negative ions located within the electropositive channel (laser spot region). The negative ion density is estimated based on the assumption that the increase of the current collected by an electrostatic probe biased positively to the plasma is a result of only the creation of photo-detached electrons. In parallel, the background electron density and temperature are considered as constants during this diagnostics. While the numerical experiments performed here show that the background electron density and temperature increase due to the formation of an electrostatic potential barrier around the electropositive channel. The time scale of potential barrier rise is about 2 ns, which is comparable to the time required to completely photo-detach the negative ions in the electropositive channel (∼3 ns). We find that neglecting the effect of the potential barrier on the background plasma leads to an erroneous determination of the negative ion density. Moreover, the background electron velocity distribution function within the electropositive channel is not Maxwellian. This is due to the acceleration of these electrons through the electrostatic potential barrier. In this work, the validity of the photo-detachment diagnostic assumptions is questioned and our results illustrate the weakness of these assumptions.

  19. Optimized design of recycle chromatography to isolate intermediate retained solutes in ternary mixtures: Langmuir isotherm systems.

    PubMed

    Lee, Ju Weon; Wankat, Phillip C

    2009-10-09

    Batch chromatography with a recycle stream is a popular and simple technique to separate a single target component in a complex mixture with moderate operating conditions. Design of recycle chromatography depends on the retention behaviors of the mixture components. In this work, four nucleosides were considered as solutes. Feed concentration and recycle methods were optimized to isolate only the intermediate retained solute in ternary and pseudo-ternary mixtures. Two recycle methods introduced in our previous work for linear isotherms, the desorbent and feed recycle methods, were compared in terms of productivity and desorbent to feed ratio, D/F, with various feed concentrations for competitive Langmuir isotherm systems. The simulation results show that the target (intermediate retained solute) was separated with over 99.76% purity and 99.88% yield. Productivity of the feed recycle method was increased by up to 162% and D/F was decreased by up to 59% compared to the desorbent recycle method. For the separation of nucleosides, recycle chromatography was compared to eight column simulated moving bed (SMB) cascades with a recycle stream and D/F of the SMB cascades was 58% lower than D/F of recycle chromatography at the same productivity. However, recycle chromatography is much simpler.

  20. Fiberoptic probe and system for spectral measurements

    DOEpatents

    Dai, Sheng; Young, Jack P.

    1998-01-01

    A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferrably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0.degree., an inverted cone-shaped probe tip, and a lens head.

  1. Fiberoptic probe and system for spectral measurements

    DOEpatents

    Dai, S.; Young, J.P.

    1998-10-13

    A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0{degree}, an inverted cone-shaped probe tip, and a lens head. 12 figs.

  2. Experimental estimation of tungsten impurity sputtering due to Type I ELMs in JET-ITER-like wall using pedestal electron cyclotron emission and target Langmuir probe measurements

    NASA Astrophysics Data System (ADS)

    Guillemaut, C.; Jardin, A.; Horacek, J.; Borodkina, I.; Autricque, A.; Arnoux, G.; Boom, J.; Brezinsek, S.; Coenen, J. W.; De La Luna, E.; Devaux, S.; Eich, T.; Harting, D.; Kirschner, A.; Lipschultz, B.; Matthews, G. F.; Meigs, A.; Moulton, D.; O'Mullane, M.; Stamp, M.; contributors, JET

    2016-02-01

    The ITER baseline scenario, with 500 MW of DT fusion power and Q = 10, will rely on a Type I ELMy H-mode and will be achieved with a tungsten (W) divertor. W atoms sputtered from divertor targets during mitigated ELMs are expected to be the dominant source in ITER. W impurity concentration in the plasma core can dramatically degrade its performance and lead to potentially damaging disruptions. Understanding the physics of the target W source due to sputtering during ELMs and inter-ELMs is important and can be helped by experimental measurements with improved precision. It has been established that the ELMy target ion impact energy has a simple linear dependence with the pedestal electron temperature measured by Electron Cyclotron Emission (ECE). It has also been shown that Langmuir Probes (LP) ion flux measurements are reliable during ELMs due to the surprisingly low electron temperature. Therefore, in this paper, LP and ECE measurements in JET-ITER-Like-Wall (ILW) unseeded Type I ELMy H-mode experiments have been used to estimate the W sputtering flux from divertor targets in ELM and inter-ELM conditions. Comparison with similar estimates using W I spectroscopy measurements shows a reasonable agreement for the ELM and inter-ELM W source. The main advantage of the method involving LP measurements is the very high time resolution of the diagnostic (˜10 μs) allowing very precise description of the W sputtering source during ELMs.

  3. New insights on boundary plasma turbulence and the quasi-coherent mode in Alcator C-Mod using a Mirror Langmuir Probe

    SciTech Connect

    LaBombard, B.; Golfinopoulos, T.; Terry, J. L.; Brunner, D.; Davis, E.; Greenwald, M.; Hughes, J. W.

    2014-05-15

    A new “Mirror Langmuir Probe” diagnostic, combined with a double-coil scanning magnetic probe, is used to interrogate Alcator C-Mod's quasi-coherent mode (QCM) with unprecedented detail. In ohmic EDA H-modes, the QCM is found to reside in a region of positive radial electric field, with a radial width (∼3 mm) that spans open and closed field line regions. Large amplitude, in-phase sinusoidal bursts (∼100 kHz) in density, electron temperature, and plasma potential are observed, with potential lagging density by ∼16°, producing an outward radial transport velocity of ∼10 m/s. Mode propagation corresponds to the sum of local E × B and electron diamagnetic drift velocities. Poloidal magnetic field fluctuations project to current filaments carrying peak current densities of ∼25 A/cm{sup 2}. An evaluation of parallel electron force balance (Ohm's law) over a fluctuation cycle indicates a significant electromotive component. Interchange drive is also a contributor in the current continuity (vorticity) equation. Thus, the QCM is primarily a separatrix-spanning electron drift-wave with interchange and electromagnetic contributions.

  4. Mass Spectrometric and Langmuir Probe Measurements in Inductively Coupled Plasmas in Ar, CHF3/Ar and CHF3/Ar/O2 Mixtures

    NASA Technical Reports Server (NTRS)

    Kim, J. S.; Rao, M. V. V. S.; Cappelli, M. A.; Sharma, S. P.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2000-01-01

    Absolute fluxes and energy distributions of ions in inductively coupled plasmas of Ar, CHF3/Ar, and CHF3/Ar/O2 have been measured. These plasmas were generated in a Gaseous Electronics Conference (GEC) cell modified for inductive coupling at pressures 10-50 mTorr and 100-300 W of 13.56 MHz radio frequency (RF) power in various feedgas mixtures. In pure Ar plasmas, the Ar(+) flux increases linearly with pressure as well as RF-power. Total ion flux in CHF3 mixtures decreases with increase in pressure and also CHF3 concentration. Relative ion fluxes observed in the present studies are analyzed with the help of available cross sections for electron impact ionization and charge-exchange ion-molecule reactions. Measurements of plasma potential, electron and ion number densities, electron energy distribution function, and mean electron energy have also been made in the center of the plasma with a RF compensated Langmuir probe. Plasma potential values are compared with the mean ion energies determined from the measured ion energy distributions and are consistent. Electron temperature, plasma potential, and mean ion energy vary inversely with pressure, but increase with CHF3 content in the mixture.

  5. Langmuir probe plasma parameters and kinetic rates in a Ar-SiH4-H2 plasma during nc-Si films deposition for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Moiseev, T.; Isella, G.; Chrastina, D.; Cavallotti, C.

    2009-11-01

    An assessment of main electron-impact and secondary (homogeneous) gas-phase reaction rates of silane in an argon-silane-hydrogen plasma during nano-crystalline silicon deposition is presented. Radially resolved Langmuir probe plasma parameters (electron temperature and density) and electron energy distribution functions (eedfs) have been evaluated for Ar, Ar-H2 and Ar-SiH4-H2 plasma in a low-energy plasma-enhanced chemical vapour deposition reactor. Input flow rates of 50 sccm Ar, 10 sccm SiH4 and 0-50 sccm H2 have been used for a reactor pressure range 1-4 Pa. The eedfs are used to evaluate kinetic rate constants for electron-impact dissociative processes of SiH4 and H2 and to infer the amount of atomic H available for the silane-hydrogen gas-phase reaction, observing trends with an increase in H2 input flow. The evolution of silane kinetic rates with an increase in H2 input indicates that conditions corresponding to nc-Si deposition are characterized by a dominance of silane-hydrogen gas-phase rates over electron-impact dissociation rates up to about two orders of magnitude.

  6. Edge transport studies in the edge and scrape-off layer of the National Spherical Torus Experiment with Langmuir probes

    SciTech Connect

    Boedo, J. A. Rudakov, D. L.; Myra, J. R.; D'Ippolito, D. A.; Zweben, S.; Maingi, R.; Maqueda, R. J.; Bell, R.; Kugel, H.; Leblanc, B.; Roquemore, L. A.; Soukhanovskii, V. A.; Ahn, J. W.; Canik, J.; Crocker, N.

    2014-04-15

    Transport and turbulence profiles were directly evaluated using probes for the first time in the edge and scrape-off layer (SOL) of NSTX [Ono et al., Nucl. Fusion 40, 557 (2000)] in low (L) and high (H) confinement, low power (P{sub in}∼ 1.3 MW), beam-heated, lower single-null discharges. Radial turbulent particle fluxes peak near the last closed flux surface (LCFS) at ≈4×10{sup 21} s{sup −1} in L-mode and are suppressed to ≈0.2×10{sup 21} s{sup −1} in H mode (80%–90% lower) mostly due to a reduction in density fluctuation amplitude and of the phase between density and radial velocity fluctuations. The radial particle fluxes are consistent with particle inventory based on SOLPS fluid modeling. A strong intermittent component is identified. Hot, dense plasma filaments 4–10 cm in diameter, appear first ∼2 cm inside the LCFS at a rate of ∼1×10{sup 21} s{sup −1} and leave that region with radial speeds of ∼3–5 km/s, decaying as they travel through the SOL, while voids travel inward toward the core. Profiles of normalized fluctuations feature levels of 10% inside LCFS to ∼150% at the LCFS and SOL. Once properly normalized, the intermittency in NSTX falls in similar electrostatic instability regimes as seen in other devices. The L-H transition causes a drop in the intermittent filaments velocity, amplitude and number in the SOL, resulting in reduced outward transport away from the edge and a less dense SOL.

  7. Galileo probe battery systems design

    NASA Technical Reports Server (NTRS)

    Dagarin, B. P.; Van Ess, J. S.; Marcoux, L. S.

    1986-01-01

    NASA's Galileo mission to Jupiter will consist of a Jovian orbiter and an atmospheric entry probe. The power for the probe will be derived from two primary power sources. The main source is composed of three Li-SO2 battery modules containing 13 D-size cell strings per module. These are required to retain capacity for 7.5 years, support a 150 day clock, and a 7 hour mission sequence of increasing loads from 0.15 to 9.5 amperes for the last 30 minutes. This main power source is supplemented by two thermal batteries (CaCrO4-Ca) for use in firing the pyrotechnic initiators during the atmospheric staging events. This paper describes design development and testing of these batteries at the system level.

  8. Galileo probe battery systems design

    NASA Technical Reports Server (NTRS)

    Dagarin, B. P.; Van Ess, J. S.; Marcoux, L. S.

    1986-01-01

    NASA's Galileo mission to Jupiter will consist of a Jovian orbiter and an atmospheric entry probe. The power for the probe will be derived from two primary power sources. The main source is composed of three Li-SO2 battery modules containing 13 D-size cell strings per module. These are required to retain capacity for 7.5 years, support a 150 day clock, and a 7 hour mission sequence of increasing loads from 0.15 to 9.5 amperes for the last 30 minutes. This main power source is supplemented by two thermal batteries (CaCrO4-Ca) for use in firing the pyrotechnic initiators during the atmospheric staging events. This paper describes design development and testing of these batteries at the system level.

  9. Ion beam probe diagnostic system

    NASA Astrophysics Data System (ADS)

    Hickok, R. L.; Jennings, W. C.; Woo, J. T.; Connor, K. A.

    1980-07-01

    Tokomak plasmas suitable for diagnostic development were produced in RENTOR following technological improvements in the vacuum chamber and discharge cleaning systems. Secondary ion signals were obtained from the heavy ion beam probe on RENTOR leading to initial estimates of the plasma space potential, which appears to vary by several hundred volts during the plasma pulse. The principle of measuring space potential in a minimum-B geometry was established using an ion gun mounted at the center of the ALEX baseball coil. The neutral beam probe was installed for measuring the space potential using actual secondary ion signals from a hollow cathode arc in ALEX and preliminary tests have begun. The ion beam test stand was significantly altered to allow more flexibility in testing energy analyzers, ion guns, and ion focusing concepts.

  10. Application of Langmuir Probe for Study of Recombination of D3+ Ions with Electrons in He-Ar-D2 Stationary and Flowing Afterglow Plasma

    NASA Astrophysics Data System (ADS)

    Tichy, M.; Poterya, V.; Plasil, R.; Pysanenko, A.; Kudrna, P.; Novotny, O.; Zakouril, P.; Glosik, J.

    2003-06-01

    We report measurements of the rate coefficient for recombination of D3+ and D5+ with electrons in He-Ar-D2 plasma. Two afterglow experiments, flowing afterglow and stationary afterglow were used to cover large extent of pressures of He buffer gas (2-10 Torr) and large extent of partial number densities of D2 (5×1010-3×1015cm-3). Langmuir probes and mass spectrometers were used to monitor decay of the plasma during the afterglow. The observed rate coefficient is dependent on the deuterium number density indicating that third-body-assisted recombination is efficient and significantly contributes to recombination when sufficient number density of deuterium is present. At low D2 number densities the ions D3+ dominate the ion composition and electron density decay is controlled by recombination of D3+ with recombination rate coefficient α(D3+). At higher D2 number densities and lower temperatures D5+ are formed and electron density decay is controlled by recombination of D5+ ions with recombination rate coefficient α(D5+). The overall effective recombination rate coefficient αeff as a function of D2 number density was measured and from this dependence the rates α(D3+) and α(D5+) at several temperatures were determined. Obtained pressure dependencies are in good agreement with thermodynamic data. When the deuterium number density is decreased down to 5×1010cm-3, the rate coefficient also decreases to αeff ˜4×10-9 cm3s-1. These data indicate that the binary dissociative recombination of D3+ is very slow with αDR <4×10-9 cm3s-1. The observation of an additional de-ionization process proceeding via formation of D5+ and its recombination is also reported.

  11. Cross Comparison of Electron Density and Electron Temperature Observations from the DICE CubeSat Langmuir Probes and the Millstone Hill Incoherent Scatter Radar.

    NASA Astrophysics Data System (ADS)

    Swenson, C.; Erickson, P. J.; Crowley, G.; Pilinski, M.; Barjatya, A.; Fish, C. S.

    2014-12-01

    The Dynamic Ionosphere CubeSat Experiment (DICE) consists of two identical 1.5U CubeSats deployed simultaneously from a single P-POD (Poly Picosatellite Orbital Deployer) into the same orbit. Several observational campaigns were planned between the DICE CubeSats and the mid-latitude Millstone Hill Incoherent Scatter Radar (ISR) in order to calibrate the DICE measurements of electron density and electron temperature. In this presentation, we compare in-situ observations from the Dynamic Ionosphere CubeSat Experiment (DICE) and from the Millstone Hill ISR. Both measurements are cross-calibrated against an assimilative model of the global ionospheric electron density. The electron density and electron temperature were obtained for three Millstone Hill DICE overflights (2013-03-12, 2013-03-15, 2013-03-17). We compare the data during quiet and geomagnetically disturbed conditions and find evidence of an storm enhanced density (SED) plume in the topside ionosphere on 2013-03-17 at 19? UTC. During this disturbed interval, American longitude sector high density plasma was convected near 15 SLT towards the noontime cusp. DICE was selected for flight under the NSF "CubeSat-based Science Mission for Space Weather and Atmospheric Research" program. The DICE twin satellites were launched on a Delta II rocket on October 28, 2011. The satellites are flying in a "leader-follower" formation in an elliptical orbit which ranges from 820 to 400 km in altitude. Each satellite carries a fixed-bias DC Langmuir Probe (DCP) to measure in-situ ionospheric plasma densities and a science grade magnetometer to measure DC and AC geomagnetic fields. The purpose of these measurements was to permit accurate identification of storm-time features such as the SED bulge and plume. The mission team combines expertise from ASTRA, Utah State University/Space Dynamics Laboratory (USU/SDL), and Embry-Riddle Aeronautical University. In this paper we present a comparison of data from DICE and Millstone Hill

  12. Parametric decay of Langmuir waves in an electron beam-plasma system

    NASA Astrophysics Data System (ADS)

    Willett, J. E.; Aktas, Y.

    1984-06-01

    Backscattering of Langmuir waves from the low-frequency electrostatic waves in a plasma traversed by an electron beam is studied. The analysis is based on the use of beam electron, plasma electron, and ion susceptibilities provided by kinetic theory. For the case of a warm electron beam, formulae are derived for the growth rate and threshold associated with resonant backscattering from an ion-acoustic wave modified by the presence of the beam. For the case of a cold electron beam, formulae are derived from the growth rates associated with resonant backscattering from a modified ion-acoustic wave and from a higher-frequency beam-plasma mode. A numerical study of the effects of an electron beam on these parametric instabilities is included.

  13. Different Adsorption Behavior of Rare Earth and Metallic Ion Complexes on Langmuir Mono layers Probed by Sum-Frequency Generation Spectroscopy

    SciTech Connect

    Song, Woongmo; Vaknin, David; Kim, Doseok

    2013-02-25

    Adsorption behavior of counterions under a Langmuir monolayer was investigated by sum-frequency generation (SFG) spectroscopy. By comparing SFG spectra of arachidic acid (AA) Langmuir monolayer/water interface with and without added salt, it was found that the simple trivalent cation La3+ adsorbed on AA monolayer only when the carboxylic headgroups are charged (deprotonated), implying that counterion adsorption is induced by Coulomb interaction. On the other hand, metal hydroxide complex Fe(OH)3 adsorbed even on a charge-neutral AA monolayer, indicating that the adsorption of iron hydroxide is due to chemical interaction such as covalent or hydrogen bonding to the headgroup of the molecules at the monolayer.

  14. Three axis velocity probe system

    DOEpatents

    Fasching, George E.; Smith, Jr., Nelson S.; Utt, Carroll E.

    1992-01-01

    A three-axis velocity probe system for determining three-axis positional velocities of small particles in fluidized bed systems and similar applications. This system has a sensor head containing four closely-spaced sensing electrodes of small wires that have flat ends to establish a two axis plane, e.g. a X-Y plane. Two of the sensing electrodes are positioned along one of the axes and the other two are along the second axis. These four sensing electrodes are surrounded by a guard electrode, and the outer surface is a ground electrode and support member for the sensing head. The electrodes are excited by, for example, sinusoidal voltage having a peak-to-peak voltage of up to 500 volts at a frequency of 2 MHz. Capacitive currents flowing between the four sensing electrodes and the ground electrode are influenced by the presence and position of a particle passing the sensing head. Any changes in these currents due to the particle are amplified and synchronously detected to produce positional signal values that are converted to digital form. Using these digital forms and two values of time permit generation of values of the three components of the particle vector and thus the total velocity vector.

  15. Biopolymer-induced calcium phosphate scaling in membrane-based water treatment systems: Langmuir model films studies.

    PubMed

    Dahdal, Yara N; Oren, Yoram; Schwahn, Dietmar; Pipich, Vitaliy; Herzberg, Moshe; Ying, Wang; Kasher, Roni; Rapaport, Hanna

    2016-07-01

    Biofouling and scaling on reverse osmosis (RO) or nanofiltration (NF) membranes during desalination of secondary and tertiary effluents pose an obstacle that limits the reuse of wastewater. In this study we explored the mineral scaling induced by biopolymers originated from bacterial biofilms: bovine serum albumin (BSA), fibrinogen, lysozyme and alginic acid, as well as an extracts of extracellular polymeric substances (EPS) from bio-fouled RO membranes from wastewater treatment facility. Mineralization studies were performed on Langmuir films of the biopolymers deposited at the interface of a solution simulating RO desalination of secondary-treated wastewater effluents. All studied biopolymers and EPS induced heterogeneous mineralization of mainly calcium phosphate. Using IR spectroscopy coupled with systematic quantitative analysis of the surface pressure versus molecular-area isotherms, we determined the mineralization tendencies of the biopolymers to be in the order of: fibrinogen>lysozyme>BSA>alginic acid. The biopolymers and EPS studied here were found to be accelerators of calcium-phosphate mineralization. This study demonstrates the utilization of Langmuir surface-pressure area isotherms and a model solution in quantitatively assessing the mineralization tendencies of various molecular components of EPS in context of membrane-based water treatment systems.

  16. Langmuir Mixing Affects Global Climate

    NASA Astrophysics Data System (ADS)

    Li, Q.; Webb, A.; Fox-Kemper, B.; Arbetter, T. E.; Craig, A.; Danabasoglu, G.; Large, W.; Vertenstein, M.

    2016-02-01

    The effects of Langmuir turbulence on the surface ocean mixing and thereby the global climate are assessed in the CESM earth system model by adding a parameterization of Langmuir mixing to the K-Profile Parameterization (KPP). A global wave field is needed by this Langmuir mixing parameterization to provide the Stokes drift that drives Langmuir mixing. Both a prognostic wave model, WAVEWATCH III, and a climatological data wave model have been coupled with CESM and tested. Nearly identical and substantial improvements in the simulated mixed layer depth and intermediate water ventilation are found in both cases when Langmuir mixing is included. The greatest improvement occurs in the Southern Ocean. A climatological data wave model, which responds to simulated winds, but with fixed wind-wave relationships, can therefore reproduce the primary improvements of Langmuir mixing, but with much less computational cost than even a coarse-resolution prognostic wave model. Progress toward an improved wave-induced entrainment through the bottom of ocean surface boundary layer will also be discussed.

  17. Probing Signal Design for Power System Identification

    SciTech Connect

    Pierre, John W.; Zhou, Ning; Tuffner, Francis K.; Hauer, John F.; Trudnowski, Daniel J.; Mittelstadt, William

    2010-05-31

    This paper investigates the design of effective input signals for low-level probing of power systems. In 2005, 2006, and 2008 the Western Electricity Coordinating Council (WECC) conducted four large-scale system wide tests of the western interconnected power system where probing signals were injected by modulating the control signal at the Celilo end of the Pacific DC intertie. A major objective of these tests is the accurate estimation of the inter-area electromechanical modes. A key aspect of any such test is the design of an effective probing signal that leads to measured outputs rich in information about the modes. This paper specifically studies low-level probing signal design for power-system identification. The paper describes the design methodology and the advantages of this new probing signal which was successfully applied during these tests. This probing input is a multi-sine signal with its frequency content focused in the range of the inter-area modes. The period of the signal is over two minutes providing high-frequency resolution. Up to 15 cycles of the signal are injected resulting in a processing gain of 15. The resulting system response is studied in the time and frequency domains. Because of the new probing signal characteristics, these results show significant improvement in the output SNR compared to previous tests.

  18. An ion thruster internal discharge chamber electrostatic probe diagnostic technique using a high-speed probe positioning system.

    PubMed

    Herman, Daniel A; Gallimore, Alec D

    2008-01-01

    Extensive resources have been allocated to diagnose and minimize lifetime-limiting factors in gridded ion thrusters. While most of this effort has focused on grid erosion, results from wear tests indicate that discharge cathode erosion may also play an important role in limiting the lifetime of ring-cusp ion thrusters proposed for future large flagship missions. The detailed characterization of the near-cathode discharge plasma is essential for mitigating discharge cathode erosion. However, severe difficulty is encountered when attempting to measure internal discharge plasma parameters during thruster operation with conventional probing techniques. These difficulties stem from the high-voltage, high-density discharge cathode plume, which is a hostile environment for probes. A method for interrogating the discharge chamber plasma of a working ion thruster over a two-dimensional grid is demonstrated. The high-speed axial reciprocating probe positioning system is used to minimize thruster perturbation during probe insertion and to reduce heating of the probe. Electrostatic probe measurements from a symmetric double Langmuir probe are presented over a two-dimensional spatial array in the near-discharge cathode assembly region of a 30-cm-diameter ring-cusp ion thruster. Electron temperatures, 2-5 eV, and number density contours, with a maximum of 8 x 10(12) cm(-3) on centerline, are measured. These data provide detailed electron temperature and number density contours which, when combined with plasma potential measurements, may shed light on discharge cathode erosion processes and the effect of thruster operating conditions on erosion rates.

  19. Characterization of Fiber Optic CMM Probe System

    SciTech Connect

    K.W.Swallow

    2007-05-15

    This report documents a study completed on the fiber optic probe system that is a part of the Werth optical CMM. This study was necessary due to a lack of documentation from the vendor for the proper use and calibration of the fiber probe, and was performed in support of the Lithographie Galvanoformung Abformung (LIGA) development program at the FM&T. As a result of this study, a better understanding of the fiber optic probe has been developed, including guidelines for its proper use and calibration.

  20. Laboratory plasma probe studies

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.

    1975-01-01

    Diagnostic experiments performed in a collisionless plasma using CO2 as the working gas are described. In particular, simultaneous measurements that have been performed by means of Langmuir- and RF-probes are presented. A resonance occurring above the parallel resonance in the frequency characteristic of a two electrode system is interpreted as being due to the resonant excitation of electroacoustic waves.

  1. Fluid to soft-glass transition in a quasi-2D system: thermodynamic and rheological evidences for a Langmuir monolayer.

    PubMed

    Maestro, Armando; Guzmán, Eduardo; Chuliá, Raquel; Ortega, Francisco; Rubio, Ramón G; Miller, Reinhard

    2011-05-28

    We report an experimental study that points out the existence of a fluid to soft-glass transition in Langmuir polymer monolayers of poly(methyl methacrylate) (PMMA), for which the water/air interface behaves as a poor-solvent. The temperature dependence of surface pressure vs. surface area equilibrium isotherms shows a glass-like transition temperature at T(g,2D)≈ 298 K, significantly lower than the value for bulk PMMA (T(g,bulk)≈ 378 K). The plot of the film thickness h vs. temperature shows a sharp change of slope at about the same temperature, 298 K, which is a typical hallmark of a glass transition in thin polymer films [J. L. Keddie, R. A. L. Jones, R. A. Cory, Europhys. Lett., 1996, 27, 59-64]. Furthermore, slightly above T(g,2D), the temperature dependence of the dilational viscosity does not follow an Arrhenius law, but instead can be described by a Vogel-Fulcher-Tamman equation with parameters that are typical of a fragile glass. Not only the qualitative behavior of three distinct equilibrium and dynamic properties, but also the quantitative agreement of the values of T(g) obtained, are a strong evidence of the existence of a fluid to soft-glass transition in this quasi-2D system.

  2. Scattering, Adsorption, and Langmuir-Hinshelwood Desorption Models for Physisorptive and Chemisorptive Gas-Surface Systems

    NASA Astrophysics Data System (ADS)

    Bentley, Brook I.

    Surface effects limit the performance of hypersonic vehicles, micro-electro-mechanical devices, and directed energy systems. This research develops methods to predict adsorption, scattering, and thermal desorption of molecules on a surface. These methods apply to physisorptive (adsorption and scattering) and chemisorptive (thermal desorption) gas-surface systems. Engineering and design applications will benefit from these methods, hence they are developed under the Direct Simulation Monte Carlo construct. The novel adsorption and scattering contribution, the Modified Kisliuk with Scattering method, predicts angular and energy distributions, and adsorption probabilities. These results agree more closely with experiment than the state-of-the-art Cercignani-Lampis-Lord scattering kernel. Super-elastic scattering is predicted. Gas-adlayer interactions are included for the first time. Accommodation coefficents can be determined by fitting simulations to experimental data. The new thermal desorption model accurately calculates angular, translational, rotational, and vibrational distributions, and the rotational alignment parameter. The model is validated by comparing with experiments. Multiple transition states are considered in a set of non-dimensionalized equations of motion, linked with temporally-accurate event timing. Initial conditions are chosen from a new truncated Maxwell-Boltzmann distribution. Run times are improved by eliminating the Gaussian Weighting of desorbing products. The absorption energy barrier is shown to significantly contribute only to the translational energy of desorbing molecules by contributing energy to each adatom in a similar manner.

  3. Langmuir monolayers of cerebroside originated from Linckia laevigata: binary systems of cerebrosides and phospholipid.

    PubMed

    Maruta, Tomoki; Hoda, Kazuki; Inagaki, Masanori; Higuchi, Ryuichi; Shibata, Osamu

    2005-08-01

    The surface pressure (pi)-area (A), the surface potential (DeltaV)-A and the dipole moment (mu( perpendicular))-A isotherms were obtained for six cerebrosides of LLC-2, LLC-2-1, LLC-2-8, LLC-2-10, LLC-2-12, and LLC-2-15, which were isolated from Linckia laevigata, and two-component monolayers of two different cerebrosides (LLC-2 and LLC-2-8) with phospholipid of dipalmitoylphosphatidylcholine (DPPC) on a subphase of 0.15 M sodium chloride solution as a function of cerebroside compositions in the two-component systems by employing the Wilhelmy method, the ionizing electrode method, and the fluorescence microscopy. The new finding was that LLC-2 showed a stable and liquid expanded type film. Four of them (LLC-2-8, -10, -12, and -15) had the phase transition from the liquid-expanded (LE) to the liquid-condensed (LC) states at 298.2 K. The apparent molar quantity changes (Deltas(gamma), Deltah(gamma), and Deltau(gamma)) on their phase transition on 0.15M at 298.2 K were calculated. The miscibility of cerebroside and phospholipid in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the cerebroside molar fraction (X(cerebroside)), using the additivity rule. From the A-X(cerebroside) and DeltaV(m)-X(phospholipid) plots, a partial molecular surface area (PMA) and an apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible systems. Judging from the two-dimensional phase diagrams, these were found to be one type, a positive azeotropic type; all the cerebrosides were miscible with DPPC. Furthermore, assuming a regular surface mixture, the Joos equation for the analysis of the collapse pressure of two-component monolayers allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltavarepsilon) between the cerebrosides and DPPC. The

  4. Raman spectroscopy system with hollow fiber probes

    NASA Astrophysics Data System (ADS)

    Liu, Bing-hong; Shi, Yi-Wei

    2012-11-01

    A Raman remote spectroscopy system was realized using flexible hollow optical fiber as laser emittion and signal collection probes. A silver-coated hollow fiber has low-loss property and flat transmission characteristics in the visible wavelength regions. Compared with conventional silica optical fiber, little background fluorescence noise was observed with optical fiber as the probe, which would be of great advantages to the detection in low frequency Raman shift region. The complex filtering and focusing system was thus unnecessary. The Raman spectra of CaCO3 and PE were obtained by using the system and a reasonable signal to noise ratio was attained without any lens. Experiments with probes made of conventional silica optical fibers were also conducted for comparisons. Furthermore, a silver-coated hollow glass waveguide was used as sample cell to detect liquid phase sample. We used a 6 cm-long hollow fiber as the liquid cell and Butt-couplings with emitting and collecting fibers. Experiment results show that the system obtained high signal to noise ratio because of the longer optical length between sample and laser light. We also give the elementary theoretical analysis for the hollow fiber sample cell. The parameters of the fiber which would affect the system were discussed. Hollow fiber has shown to be a potential fiber probe or sample cell for Raman spectroscopy.

  5. Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Brunner, D.; Kuang, A. Q.; LaBombard, B.; Burke, W.

    2017-07-01

    A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density—through use of a mirror Langmuir probe bias system—combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. In addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.

  6. Saturn Probe: Revealing Solar System Origins

    NASA Astrophysics Data System (ADS)

    Spilker, T. R.

    2015-12-01

    Comparative studies of the gas giant and ice giant planets are needed to reliably discriminate among competing theories of the origin and evolution of giant planets and the solar system, but we lack critical measurements. A Saturn atmospheric entry probe mission would fill a vital part of that gap, allowing comparative studies of Jupiter and Saturn, providing the basis for later comparisons with the ice giants Uranus and Neptune, and informing studies of extrasolar planetary systems now being characterized. The Galileo Probe mission provided the first in situ studies of Jupiter's atmosphere. Similar measurements at Saturn, Uranus and Neptune would provide an important comparative planetology context for the Galileo results. Cassini's "Proximal Orbits" in 2017 will reveal Saturn's internal structure to complement the Juno mission's similar measurements at Jupiter. A Saturn entry probe, complementing the Galileo Probe investigations at Jupiter, would complete a solid basis for improved understanding of both Jupiter and Saturn, an important stepping stone to understanding Uranus and Neptune and solar system formation and evolution. The 2012 Decadal Survey ("DS") added Saturn Probe science objectives to NASA's New Frontiers Program: highest-priority Tier 1 objectives any New Frontiers implementation must achieve, and Tier 2, high priority but lower than Tier 1. A DS mission concept study using extremely conservative assumptions concluded that a Saturn Probe project could fit within New Frontiers resource constraints, giving a PI confidence that they could pursue some Tier 2 objectives, customizing for the proper balance of science return, science team composition, procured or contributed instruments, etc. Contributed instruments could significantly enhance the payload and the science team for greater science return. They also provide international collaboration opportunities, with science benefits well demonstrated by missions such as Cassini-Huygens and Rosetta.

  7. Outer planet entry probe system study. Volume 1: Summary

    NASA Technical Reports Server (NTRS)

    1972-01-01

    General mission considerations and science prospectus, which are of a general nature that applies to several or all planetary applications, are presented. Five probe systems are defined: nominal Jupiter probe system, and Jupiter probe-dedicated alternative probe system, Jupiter spacecraft radiation-compatible alternative probe system, Saturn probe system, and Saturn probe applicability for Uranus. Parametric analysis is summarized for mission analysis of a general nature, and then for specific missions to Jupiter, Saturn, Uranus, and Neptune. The program is also discussed from the hardware availability viewpoint and the aspect of commonality.

  8. Galileo probe battery system -- An update

    SciTech Connect

    Dagarin, B.P.; Taenaka, R.K.; Stofel, E.J.

    1996-11-01

    NASA`s Galileo 6-year trip to Jupiter is in its final phase. The mission consists of a Jovian Orbiter and an atmospheric entry Probe. The Probe is designed to coast autonomously for up to 190 days and turn itself on 6 hours prior to entry. It will then descend through the upper atmosphere for 50 to 75 minutes with the aid of an 8-foot parachute. This paper discusses sources of electrical power for the Probe and battery testing at the systems level. Described are the final production phase, qualification, and systems testing prior to and following launch, as well as decisions made regarding the Probe separation Li/SO{sub 2} battery configuration. In addition, the paper briefly describes the thermal battery verification program. The main power source comprises three Li/SO{sub 2} battery modules containing 13 D-sized cell strings per module. These modules are required to retain capacity for 7.5 years and support a 150-day clock, ending with a 7-hour mission sequence of increasing loads from 0.15 A to 9.5 A during the last 30 minutes. The main power source is supplemented by two thermal batteries (CaCrO{sub 4}-Ca), which will be used for firing the pyrotechnic initiators during the atmospheric entry.

  9. Modelling and simulation of photocatalytic oxidation mechanism of chlorohalogenated substituted phenols in batch systems: Langmuir-Hinshelwood approach.

    PubMed

    Khuzwayo, Z; Chirwa, E M N

    2015-12-30

    This study investigated, modelled and simulated the influence of multi-chlorohalogenation in heterogeneous photocatalytic degradation of substituted phenols (pentachlorophenol (PCP), trichlorophenol (TCP), dichlorophenol (DCP), and monochlorophenol (CP)). The Langmuir-Hinshelwood approach was applied to determine oxidation kinetics. Aquasim 2.0 computational software was used to model, simulate and estimate model parameters of the different chlorophenols. Chemical adsorption equilibrium isotherms for the four chlorophenols and phenol were studied and modelled for adsorption onto titanium dioxide (TiO2) semiconductor catalyst. Langmuir adsorption parameters were determined and used to calculate adsorption constant and maximum adsorption capacity. The adsorption of chloride phenolics onto titanium dioxide catalyst increased in the order of 4 - CP < DCP < Ph < TCP < PCP. Photocatalytic studies analysed the efficiency of oxidation and found improved degradation with higher chloride substituted phenolics in the order of PCP > TCP > DCP ≥ 4 - CP. Photocatalytic parameters were calculated and estimated along with sensitivity and uncertainty analyses.

  10. A Langmuir film approach to elucidating interactions in lipid membranes: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine/cholesterol/metal cation systems.

    PubMed

    Korchowiec, Beata; Paluch, Maria; Corvis, Yohann; Rogalska, Ewa

    2006-01-01

    The interactions between two membrane lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and cholesterol (CHOL), were studied in Langmuir films using surface pressure isotherms and Brewster angle microscopy. The DPPE/CHOL interactions were probed for chosen monolayer and subphase (Na(+), Ca(2+)) composition at 20, 25, and 30 degrees C. The results obtained show that DPPE and CHOL are miscible for the cholesterol mol fractions x(CHOL)=0.3-0.5. Cholesterol induces condensation of the DPPE monolayers. The most significant condensation of the DPPE/CHOL monolayers was observed in the presence of Ca(2+) ions in the subphase at x(CHOL)=0.4. The negative deviation of the molecular surface area (MMA) additivity from the ideal behavior together with negative values of excess free enthalpy of mixing in the monolayers were interpreted in terms of attractive interactions between lipid molecules.

  11. Concepts in strong Langmuir turbulence theory

    SciTech Connect

    DuBois, D.F.; Rose, H.A.

    1990-01-01

    Some of the basic concepts of strong Langmuir turbulence (SLT) theory are reviewed. In SLT system, a major fraction of the turbulent energy is carried by local, time-dependent, nonlinear excitations called cavitons. Modulational instability, localization of Langmuir fields by density fluctuations, caviton nucleation, collapse, and burnout and caviton correlations are reviewed. Recent experimental evidence will be presented for SLT phenomena in the interaction of powerful HF waves with the ionosphere and in laser-plasma interaction experiments. 38 refs., 11 figs.

  12. Gravity Probe B gyroscope readout system

    NASA Astrophysics Data System (ADS)

    Muhlfelder, B.; Lockhart, J.; Aljabreen, H.; Clarke, B.; Gutt, G.; Luo, M.

    2015-11-01

    We describe the Gravity Probe B London-moment readout system successfully used on-orbit to measure two gyroscope spin axis drift rates predicted by general relativity. The system couples the magnetic signal of a spinning niobium-coated rotor into a low noise superconducting quantum interference device. We describe the multi-layered magnetic shield needed to attenuate external fields that would otherwise degrade readout performance. We discuss the ∼35 nrad/yr drift rate sensitivity that was achieved on-orbit.

  13. Outer planet entry probe system study. Volume 4: Common Saturn/Uranus probe studies

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Results are summarized of a common scientific probe study to explore the atmospheres of Saturn and Uranus. This was a three-month follow-on effort to the Outer Planet Entry Probe System study. The report presents: (1) a summary, conclusions and recommendations of this study, (2) parametric analysis conducted to support the two system definitions, (3) common Saturn/Uranus probe system definition using the Science Advisory Group's exploratory payload and, (4) common Saturn/Uranus probe system definition using an expanded science complement. Each of the probe system definitions consists of detailed discussions of the mission, science, system and subsystems including telecommunications, data handling, power, pyrotechnics, attitude control, structures, propulsion, thermal control and probe-to-spacecraft integration. References are made to the contents of the first three volumes where it is feasible to do so.

  14. Langmuir polymer films: recent results and new perspectives.

    PubMed

    Monroy, F; Arriaga, L R; Langevin, D

    2012-11-14

    Langmuir polymer films (LPFs) are very interesting systems to probe quasi-two dimensional dynamics. Although adsorbed on water, the substrate is fluid enough to avoid irreversible pinning at adsorption sites, as with solid substrates. LPFs in dense states can exhibit a high degree of metastability, however reproducible measurements can be performed on films which have not been previously compressed. The shear rheology is one of the most active fields of research, especially because it allows investigation of flow behaviour in LPFs, thus of possible reptation motion in semidilute films under good solvent conditions. It also allows probing glassy behaviour in dense films under poor solvent conditions. In this perspective article, we review the recent literature and discuss unpublished results on the dynamics of the glass transition, recently observed in these quasi-2D systems at low temperatures. We conclude by listing new problems and open questions emerging from this research area.

  15. MicroProbe Small Unmanned Aerial System

    NASA Technical Reports Server (NTRS)

    Bland, Geoffrey; Miles, Ted

    2012-01-01

    The MicroProbe unmanned aerial system (UAS) concept incorporates twin electric motors mounted on the vehicle wing, thus enabling an aerodynamically and environmentally clean nose area for atmospheric sensors. A payload bay is also incorporated in the fuselage to accommodate remote sensing instruments. A key feature of this concept is lightweight construction combined with low flying speeds to minimize kinetic energy and associated hazards, as well as maximizing spatial resolution. This type of aerial platform is needed for Earth science research and environmental monitoring. There were no vehicles of this type known to exist previously.

  16. Did Irving Langmuir Observe Langmuir Circulations?

    NASA Astrophysics Data System (ADS)

    D'Asaro, E. A.; Harcourt, R. R.; Shcherbina, A.; Thomson, J. M.; Fox-Kemper, B.

    2012-12-01

    Although surface waves are known to play an important role in mixing the upper ocean, the current generation of upper ocean boundary layer parameterizations does not include the explicit effects of surface waves. Detailed simulations using LES models which include the Craik-Leibovich wave-current interactions, now provide quantitative predictions of the enhancement of boundary layer mixing by waves. Here, using parallel experiments in Lake Washington and at Ocean Station Papa, we show a clear enhancement of vertical kinetic energy across the entire upper ocean boundary layer which can be attributed to surface wave effects. The magnitude of this effect is close to that predicted by LES models, but is not large, less than a factor of 2 on average, and increased by large Stokes drift and shallow mixed layers. Global estimates show the largest wave enhancements occur on the equatorial side of the westerlies in late Spring, due to the combination of large waves, shallow mixed layers and weak winds. In Lakes, however, the waves and the Craik-Leibovich interactions are weak, making it likely that the counter-rotating vortices famously observed by Irving Langmuir in Lake George were not driven by wave-current interactions.

  17. Proposed Solar Probe telecommunications system concept

    NASA Technical Reports Server (NTRS)

    Kellogg, K.; Devereaux, A.; Vacchione, J.; Kapoor, V.; Crist, R.

    1992-01-01

    A proposed telecommunications system concept for NASA's Solar Probe mission is described. Key system requirements include 70 kbps data rate at perihelion and operation at X-band (uplink/downlink) and Ka-band (downlink). A design control table is presented to demonstrate design compliance with telecommunication needs. The Ka-band feed is to be a hexagonal array of 37 active elements, each containing 1/4W HEMT amplifiers. The array is located at the Cassegrain point of a 0.75-m reflector. When compared to the TWTA-based system, the Ka-band active array feed provides advantages of reduced mass, increased dc power efficiency, enhanced reliability, graceful degradation, and reduced volume requirements.

  18. Proposed Solar Probe telecommunications system concept

    NASA Technical Reports Server (NTRS)

    Kellogg, K.; Devereaux, A.; Vacchione, J.; Kapoor, V.; Crist, R.

    1992-01-01

    A proposed telecommunications system concept for NASA's Solar Probe mission is described. Key system requirements include 70 kbps data rate at perihelion and operation at X-band (uplink/downlink) and Ka-band (downlink). A design control table is presented to demonstrate design compliance with telecommunication needs. The Ka-band feed is to be a hexagonal array of 37 active elements, each containing 1/4W HEMT amplifiers. The array is located at the Cassegrain point of a 0.75-m reflector. When compared to the TWTA-based system, the Ka-band active array feed provides advantages of reduced mass, increased dc power efficiency, enhanced reliability, graceful degradation, and reduced volume requirements.

  19. Cognition and order in Langmuir-Blodgett films of a 3-hexadecyl pyrrole and ferrocene-derivatized pyrrole mixed monolayer system

    NASA Astrophysics Data System (ADS)

    Samuelson, L.; Rahman, A. K. M.; Puglia, G. P.; Clough, S.; Tripathy, S.; Inagaki, T.; Yang, X. Q.; Skotheim, T. A.; Okamoto, Y.

    Novel, self-assembled materials were designed and produced from first principle to possess unique structural hierarchy and electronic and optical properties. The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. The pyrrole moiety was chosen for its' well established electronic and optical properties when polymerized, while ferrocene, it is theorized, if properly oriented into a Langmuir-Blodgett monolayer film may show a layered array of transition metals which would be extremely valuable as a model for 2-D magnets. The ferrocene group may also provide the possibility of charge coupling between neutral ferrocene and oxidized ferricenium which could be controlled electrochemically or photochemically. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization using synchrotron radiation. Near Edge X-Ray Absorption Fine Structure studies revealed that highly ordered multilayer structures are being formed.

  20. Cognition and order in Langmuir-Blodgett films of a 3-hexadecyl pyrrole and ferrocene-derivatized pyrrole mixed monolayer system

    SciTech Connect

    Samuelson, L.; Rahman, A.K.M.; Puglia, G.P.; Clough, S.; Tripathy, S.; Inagaki, T.; Yang, X.Q.; Skotheim, T.A.; Okamoto, Y.

    1989-01-01

    Novel, self-assembled materials have been designed and produced from first principle to possess unique structural hierarchy and electronic and optical properties. The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. The pyrrole moiety was chosen for its' well established electronic and optical properties when polymerized, while ferrocene, it is theorized, if properly oriented into a Langmuir-Blodgett monolayer film may show a layered array of transition metals which would be extremely valuable as a model for two-dimensional magnets. The ferrocene group may also provide the possibility of charge coupling between neutral ferrocene and oxidized ferricenium which could be controlled electrochemically or photochemically. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization using synchrotron radiation. Near Edge X-Ray Absorption Fine Structure studies revealed that highly ordered multilayer structures are being formed. 8 refs., 4 figs., 1 tab.

  1. Gravity Probe B data system description

    NASA Astrophysics Data System (ADS)

    Bennett, Norman R.

    2015-11-01

    The Gravity Probe B data system, developed, integrated, and tested by Lockheed Missiles & Space Company, and later Lockheed Martin Corporation, included flight and ground command, control, and communications software. The development was greatly facilitated, conceptually and by the transfer of key personnel, through Lockheed’s earlier flight and ground test software development for the Hubble Space Telescope (HST). Key design challenges included the tight mission timeline (17 months, 9 days of on-orbit operation), the need to tune the system once on-orbit, and limited 2 Kbps real-time data rates and ground asset availability. The result was a completely integrated space vehicle and Stanford mission operations center, which successfully collected and archived 97% of the ‘guide star valid’ data to support the science analysis. Lessons learned and incorporated from the HST flight software development and on-orbit support experience, and Lockheed’s independent research and development effort, will be discussed.

  2. Galileo Atmospheric Entry Probe System - Design, development, and test

    NASA Technical Reports Server (NTRS)

    Givens, J. J.; Nolte, L. J.; Pochettino, L. R.

    1983-01-01

    The overall development of the Galileo Atmospheric Entry Probe System is described. The Probe will be carried to Jupiter by the Galileo Orbiter and released on an entry trajectory 150 days before entry. A complement of seven science instruments will measure the near-Jupiter radiation field and the characteristics of the Jovian atmosphere from a distance of about 5 Jupiter radii above the 1-bar level down to levels in the 10-20-bar range. Probe data are to be transmitted to earth via the Orbiter. System requirements are discussed. Probe design features and those features of the development test program peculiar to entry probes are described.

  3. Domain Relaxation in Langmuir Films

    NASA Astrophysics Data System (ADS)

    Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth K.; Mann, J. Adin; Zou, Lu; Wintersmith, Jacob R.

    2007-11-01

    We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer domain on the surface of a subfluid. When stretched (by a transient stagnation flow), the Langmuir layer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the circular minimum energy configuration. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments as a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. We process the digital images of the experiment to extract the domain shape, use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics, and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%.

  4. Study of new systems concepts for a Titan atmospheric probe

    NASA Technical Reports Server (NTRS)

    Bernard, Doug; Citron, Todd; Drean, Robert; Lewis, Scott; Lo, Martin; Mccarthy, John; Soderblom, Robert; Steffy, Dave; Vargas, Tina; Wolff, Marty

    1986-01-01

    Results of a systems concepts study for a Titan Probe were examined. The key tradeoffs performed are described in detail. Mass breakdown of each Probe subsystem or major element were given. The mission analysis performed to determine compliance with the high altitude sampling and descent time requirements are described. The baseline Descent Module design was derived. The element of the Probe System left on the Carrier after separation were described.

  5. Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.

    PubMed

    Sostarecz, Audra G; Gaidamauskas, Ernestas; Distin, Steve; Bonetti, Sandra J; Levinger, Nancy E; Crans, Debbie C

    2014-04-22

    We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats.

  6. Domain relaxation in Langmuir films

    NASA Astrophysics Data System (ADS)

    Alexander, James C.; Bernoff, Andrew J.; Mann, Elizabeth K.; Mann, J. Adin; Wintersmith, Jacob R.; Zou, Lu

    We report on theoretical studies of molecularly thin Langmuir films on the surface of a quiescent subfluid and qualitatively compare the results to both new and previous experiments. The film covers the entire fluid surface, but domains of different phases are observed. In the absence of external forcing, the compact domains tend to relax to circles, driven by a line tension at the phase boundaries. When stretched (by a transient applied stagnation-point flow or by stirring), a compact domain elongates, creating a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape will then relax slowly to the minimum-energy configuration of a circular domain. The tether is never observed to rupture, even when it is more than a hundred times as long as it is wide. We model these experiments by taking previous descriptions of the full hydrodynamics, identifying the dominant effects via dimensional analysis, and reducing the system to a more tractable form. The result is a free boundary problem for an inviscid Langmuir film whose motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. Using this model we derive relaxation rates for perturbations of a uniform strip and a circular patch. We also derive a boundary integral formulation which allows an efficient numerical solution of the problem. Numerically this model replicates the formation of a bola and the subsequent relaxation observed in the experiments. Finally, we suggest physical properties of the system (such as line tension) that can be deduced by comparison of the theory and numerical simulations to the experiment. Two movies are available with the online version of the paper.

  7. Beyond Sedna: Probing the Distant Solar System

    NASA Astrophysics Data System (ADS)

    Schwamb, Megan E.

    This thesis presents studies in observational planetary astronomy probing the structure of the Kuiper belt and beyond. The discovery of Sedna on a highly eccentric orbit beyond Neptune challenges our understanding of the solar system and suggests the presence of a population of icy bodies residing past the Kuiper belt. With a perihelion of 76 AU, Sedna is well beyond the reach of the gas-giants and could not be scattered onto its highly eccentric orbit from interactions with Neptune alone. Sedna's aphelion at ˜1000 AU is too far from the edge of the solar system to feel the perturbing effects of passing stars or galactic tides in the present-day solar neighborhood. Sedna must have been emplaced in its orbit at an earlier time when massive unknown bodies were present in or near the solar system. The orbits of distant Sedna-like bodies are dynamically frozen and serve as the relics of their formation process. We have performed two surveys to search for additional members of the Sedna population. In order to find the largest and brightest Sedna-like bodies we have searched ˜12,000 deg² within +/-30 degrees of the ecliptic to a limiting R magnitude of 21.3 using the QUEST camera on the 1.2m Samuel Oschin Telescope. To search for the fainter, more common members of this distant class of solar system bodies, we have performed an deep survey using the Subaru Prime Focus Camera on the 8.2m Subaru telescope covering 43 deg² to a limiting R magnitude of 25.3. Searching over a two-night baseline, we were sensitive to motions out to distances of approximately 1000 AU. We present the results of these surveys. We discuss the implications for a distant Sedna-like population beyond the Kuiper belt and discuss future prospects for detecting and studying these distant bodies, focusing in particular on the constraints we can place on the embedded stellar cluster environment the early Sun may have been born in, where the location and distribution of Sedna-like orbits sculpted by

  8. Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography II: Investigation of separation systems with competitive Langmuir adsorption isotherms.

    PubMed

    Forssén, Patrik; Samuelsson, Jörgen; Fornstedt, Torgny

    2014-06-20

    In this study we investigated how the maximum productivity for commonly used, realistic separation system with a competitive Langmuir adsorption isotherm is affected by changes in column length, packing particle size, mobile phase viscosity, maximum allowed column pressure, column efficiency, sample concentration/solubility, selectivity, monolayer saturation capacity and retention factor of the first eluting compound. The study was performed by generating 1000 random separation systems whose optimal injection volume was determined, i.e., the injection volume that gives the largest achievable productivity. The relative changes in largest achievable productivity when one of the parameters above changes was then studied for each system and the productivity changes for all systems were presented as distributions. We found that it is almost always beneficial to use shorter columns with high pressure drops over the column and that the selectivity should be greater than 2. However, the sample concentration and column efficiency have very limited effect on the maximum productivity. The effect of packing particle size depends on the flow rate limiting factor. If the pumps maximum flow rate is the limiting factor use smaller packing, but if the pressure of the system is the limiting factor use larger packing up to about 40μm.

  9. Development of a reciprocating probe servomotor control system with real-time feedback on plasma position for the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Brunner, D.; Kuang, A. Q.; Labombard, B.; Burke, W.

    2015-11-01

    Reciprocating probe drives are one of the diagnostic workhorses in the boundary of magnetic confinement fusion experiments. The probe is scanned into an exponentially increasing heat flux, which demands a prompt and precise turn around to maintain probe integrity. A new linear servomotor controlled reciprocating drive utilizing a commercial linear servomotor and drive controller has been developed for the Alcator C-Mod tokamak. The quick response of the controller (able to apply an impulse of 50A in about 1ms) along with real-time plasma measurements from a Mirror Langmuir Probe (MLP) allows for real-time control of the probe trajectory based on plasma conditions at the probe tip. Since the primary concern for probe operation is overheating, an analog circuit has been created that computes the surface temperature of the probe from the MLP measurements. The probe can be programmed to scan into the plasma at various times and then turns around when the computed surface temperature reaches a set threshold, maximizing the scan depth into the plasma while avoiding excessive heating. Design, integration, and first measurements with this new system will be presented. This work was supported by U.S. Department of Energy award DE-FC02-99ER54512, using Alcator C-Mod, A DOE SC User Facility.

  10. Characterizing Water Quenching Systems with a Quench Probe

    NASA Astrophysics Data System (ADS)

    Ferguson, B. Lynn; Li, Zhichao; Freborg, Andrew M.

    2014-12-01

    Quench probes have been used effectively to characterize the quality of quenchants for many years. For this purpose, a variety of commercial probes, as well as the necessary data acquisition system for determining the time-temperature data for a set of standardized test conditions, are available for purchase. The type of information obtained from such probes provides a good basis for comparing media, characterizing general cooling capabilities, and checking media condition over time. However, these data do not adequately characterize the actual production quenching process in terms of heat transfer behavior in many cases, especially when high temperature gradients are present. Faced with the need to characterize water quenching practices, including conventional and intensive practices, a quench probe was developed. This paper describes that probe, the data collection system, the data gathered for both intensive quenching and conventional water quenching, and the heat transfer coefficients determined for these processes. Process sensitivities are investigated and highlight some intricacies of quenching.

  11. Tamm-Langmuir surface waves

    NASA Astrophysics Data System (ADS)

    Golenitskii, K. Â. Yu.; Koshelev, K. Â. L.; Bogdanov, A. Â. A.

    2016-10-01

    In this work we develop a theory of surface electromagnetic waves localized at the interface of periodic metal-dielectric structures. We have shown that the anisotropy of plasma frequency in metal layers lifts the degeneracy of plasma oscillations and opens a series of photonic band gaps. This results in appearance of surface waves with singular density of states—we refer to them as Tamm-Langmuir waves. Such naming is natural since we have found that their properties are very similar to the properties of both bulk Langmuir and surface Tamm waves. Depending on the anisotropy parameters, Tamm-Langmuir waves can be either forward or backward waves. Singular density of states and high sensitivity of the dispersion to the anisotropy of the structure makes Tamm-Langmuir waves very promising for potential applications in nanophotonics and biosensing.

  12. A Universal Spring-Probe System for Reliable Probing of Electrochemical Lab-on-a-Chip Devices

    PubMed Central

    Lee, Moon-Keun; Lee, Tae Jae; Choi, Ho Woon; Shin, Su Jeong; Park, Jung Youn; Lee, Seok Jae

    2014-01-01

    For achieve sensitivity in lab-on-a-chip electrochemical detection, more reliable probing methods are required, especially for repeated measurements. Spring-probes are a promising candidate method which can replace needle-like probes and alligator clips that usually produce scratches on the surface of gold electrodes due to the strong physical contacts needed for electrochemical measurements. The superior reliability of amperometric measurements by a spring-probe system was compared with results by conventional probing methods. We demonstrated that a universal spring-probe system would be potentially suitable to achieve high performance in lab-on-a-chip devices using electrochemical detection. PMID:24406857

  13. Phenomenological Modeling for Langmuir Monolayers

    NASA Astrophysics Data System (ADS)

    Baptiste, Dimitri; Kelly, David; Safford, Twymun; Prayaga, Chandra; Varney, Christopher N.; Wade, Aaron

    Experimentally, Langmuir monolayers have applications in molecular optical, electronic, and sensor devices. Traditionally, Langmuir monolayers are described by a rigid rod model where the rods interact via a Leonard-Jones potential. Here, we propose effective phenomenological models and utilize Monte Carlo simulations to analyze the phase behavior and compare with experimental isotherms. Research reported in this abstract was supported by UWF NIH MARC U-STAR 1T34GM110517-01.

  14. Systems vaccinology: probing humanity's diverse immune systems with vaccines.

    PubMed

    Pulendran, Bali

    2014-08-26

    Homo sapiens are genetically diverse, but dramatic demographic and socioeconomic changes during the past century have created further diversification with respect to age, nutritional status, and the incidence of associated chronic inflammatory disorders and chronic infections. These shifting demographics pose new challenges for vaccination, as emerging evidence suggests that age, the metabolic state, and chronic infections can exert major influences on the immune system. Thus, a key public health challenge is learning how to reprogram suboptimal immune systems to induce effective vaccine immunity. Recent advances have applied systems biological analysis to define molecular signatures induced early after vaccination that correlate with and predict the later adaptive immune responses in humans. Such "systems vaccinology" approaches offer an integrated picture of the molecular networks driving vaccine immunity, and are beginning to yield novel insights about the immune system. Here we discuss the promise of systems vaccinology in probing humanity's diverse immune systems, and in delineating the impact of genes, the environment, and the microbiome on protective immunity induced by vaccination. Such insights will be critical in reengineering suboptimal immune systems in immunocompromised populations.

  15. Compact and high-particle-flux thermal-lithium-beam probe system for measurement of two-dimensional electron density profile

    SciTech Connect

    Shibata, Y. Manabe, T.; Ohno, N.; Takagi, M.; Kajita, S.; Tsuchiya, H.; Morisaki, T.

    2014-09-15

    A compact and high-particle-flux thermal-lithium-beam source for two-dimensional measurement of electron density profiles has been developed. The thermal-lithium-beam oven is heated by a carbon heater. In this system, the maximum particle flux of the thermal lithium beam was ∼4 × 10{sup 19} m{sup −2} s{sup −1} when the temperature of the thermal-lithium-beam oven was 900 K. The electron density profile was evaluated in the small tokamak device HYBTOK-II. The electron density profile was reconstructed using the thermal-lithium-beam probe data and this profile was consistent with the electron density profile measured with a Langmuir electrostatic probe. We confirm that the developed thermal-lithium-beam probe can be used to measure the two-dimensional electron density profile with high time and spatial resolutions.

  16. Computational characterization of cutoff probe system for the measurement of electron density

    SciTech Connect

    Na, Byung-Keun; Kim, Dae-Woong; Kwon, Jun-Hyuk; Chang, Hong-Young; Kim, Jung-Hyung; You, Shin-Jae

    2012-05-15

    The wave cutoff probe, a precise measurement method for measuring the electron density, was recently proposed. To characterize the cutoff probe system, in this paper, the microwave simulations of a cutoff probe system were performed at various configurations of the cutoff probe system. The influence of the cutoff probe spectrum stemming from numerous parametric elements such as the probe tip length, probe tip distance, probe tip plane orientation, chamber volume/geometry, and coaxial cable length is presented and discussed. This article is expected to provide qualitative and quantitative insight into cutoff probe systems and its optimization process.

  17. Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces

    NASA Technical Reports Server (NTRS)

    Guevorkian, Karine; Wurzel, Sam; Mihalusova, Mariana; Valles, Jim

    2003-01-01

    At Brown University, we are developing the use of magnetic body forces as a means to simulate variable gravity body forces on biological systems. This tool promises new means to probe gravi-sensing and the gravi-response of biological systems. It also has the potential as a technique for screening future systems for space flight experiments.

  18. Langmuir wave harmonics due to driven nonlinear currents

    NASA Astrophysics Data System (ADS)

    Malaspina, David M.; Graham, Daniel B.; Ergun, Robert E.; Cairns, Iver H.

    2013-11-01

    The conversion of Langmuir waves into electromagnetic radiation near the local plasma frequency (fpe) and twice the local plasma frequency (2fpe) occurs in diverse heliospheric environments including along the path of type III radio bursts, at interplanetary shocks, and in planetary foreshocks. This radiation has the potential to act as a probe of remote plasma conditions, provided that the conversion mechanism is well understood. One candidate conversion mechanism is the antenna radiation of localized Langmuir waves. Antenna radiation near 2fpe requires the presence of nonlinear currents at 2fpe. In this work, properties of these currents are predicted from theory and compared with observations of Langmuir wave electric fields made using the WAVES instrument on the STEREO spacecraft. It is found that the observed frequency structure, polarization, and wave number ratio are consistent with nonlinear current predictions, once electric fields near 2fpeconsistent with sheath effects are taken into account.

  19. Situ soil sampling probe system with heated transfer line

    DOEpatents

    Robbat, Jr., Albert

    2002-01-01

    The present invention is directed both to an improved in situ penetrometer probe and to a heated, flexible transfer line. The line and probe may be implemented together in a penetrometer system in which the transfer line is used to connect the probe to a collector/analyzer at the surface. The probe comprises a heater that controls a temperature of a geologic medium surrounding the probe. At least one carrier gas port and vapor collection port are located on an external side wall of the probe. The carrier gas port provides a carrier gas into the geologic medium, and the collection port captures vapors from the geologic medium for analysis. In the transfer line, a flexible collection line that conveys a collected fluid, i.e., vapor, sample to a collector/analyzer. A flexible carrier gas line conveys a carrier gas to facilitate the collection of the sample. A system heating the collection line is also provided. Preferably the collection line is electrically conductive so that an electrical power source can generate a current through it so that the internal resistance generates heat.

  20. Fast reciprocating probe system on the EAST superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Chang, J. F.; Wan, B. N.; Xu, G. S.; Xiao, C. J.; Li, B.; Xu, C. S.; Yan, N.; Wang, L.; Liu, S. C.; Jiang, M.; Liu, P.

    2010-11-01

    A new fast reciprocating probe system (FRPS) has been built and installed on the outer midplane of the EAST tokamak to investigate the profiles of the boundary plasma parameters such as electron density and temperature. The system consists of a two-stage motion drive mechanism: slow motion and fast motion. The fast motion is powered by a servo motor, which drives the probe horizontally up to 50 cm to scan the edge region of the EAST tokamak. The maximum velocity achieved is 2 m/s. High velocity and flexible control of the fast motion are the remarkable features of this FRPS. A specially designed connector installed at the front end of the probe shaft makes it easy to install or replace the probe head on FRPS. During the latest experimental campaign in the spring of 2010, a probe head with seven tips, including two tips for a Mach probe, has been used. An example is given for simultaneous profile measurements of the plasma temperature, plasma density, and the plasma flow velocity.

  1. Fast reciprocating probe system on the EAST superconducting tokamak.

    PubMed

    Zhang, W; Chang, J F; Wan, B N; Xu, G S; Xiao, C J; Li, B; Xu, C S; Yan, N; Wang, L; Liu, S C; Jiang, M; Liu, P

    2010-11-01

    A new fast reciprocating probe system (FRPS) has been built and installed on the outer midplane of the EAST tokamak to investigate the profiles of the boundary plasma parameters such as electron density and temperature. The system consists of a two-stage motion drive mechanism: slow motion and fast motion. The fast motion is powered by a servo motor, which drives the probe horizontally up to 50 cm to scan the edge region of the EAST tokamak. The maximum velocity achieved is 2 m/s. High velocity and flexible control of the fast motion are the remarkable features of this FRPS. A specially designed connector installed at the front end of the probe shaft makes it easy to install or replace the probe head on FRPS. During the latest experimental campaign in the spring of 2010, a probe head with seven tips, including two tips for a Mach probe, has been used. An example is given for simultaneous profile measurements of the plasma temperature, plasma density, and the plasma flow velocity.

  2. Probe Measurements of Electrostatic Fluctuations in LDX

    NASA Astrophysics Data System (ADS)

    Ortiz, E. E.; Mauel, M. E.; Garnier, D. T.; Hansen, A. K.; Levitt, B. J.; Kesner, J.; Boxer, A.; Ellsworth, J. L.; Karim, I.; Mahar, S.; Roach, A. H.; Zimmermann, M.

    2004-11-01

    Electrostatic fluctuations play an important role in the equilibrium and stability of a high-beta plasma confined in a dipolar magnetic field. Initial plasma experiments in LDX will use movable edge probes to measure plasma potential, plasma characteristics, and plasma mass flow. Three probe systems have been installed: a triple Langmuir probe (constructed of 1 cm long, 0.5 mm dia. tungsten wire probe tips), an emissive probe (constructed of 0.9 cm long, 1 mm dia. thoriated tungsten wire), and a Mach probe (constructed with two 0.7 cm long, 1.5 mm dia. tungsten wires). Each probe is mounted on an adjustable feed-through capable of scanning parameters along a 40 cm cord at the plasma edge. Initial measurements and interpretations from first plasma experiments will be presented.

  3. Solar Power System Design for the Solar Probe+ Mission

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A.; Schmitz, Paul C.; Kinnison, James; Fraeman, Martin; Roufberg, Lew; Vernon, Steve; Wirzburger, Melissa

    2008-01-01

    Solar Probe+ is an ambitious mission proposed to the solar corona, designed to make a perihelion approach of 9 solar radii from the surface of the sun. The high temperature, high solar flux environment makes this mission a significant challenge for power system design. This paper summarizes the power system conceptual design for the solar probe mission. Power supplies considered included nuclear, solar thermoelectric generation, solar dynamic generation using Stirling engines, and solar photovoltaic generation. The solar probe mission ranges from a starting distance from the sun of 1 AU, to a minimum distance of about 9.5 solar radii, or 0.044 AU, from the center of the sun. During the mission, the solar intensity ranges from one to about 510 times AM0. This requires power systems that can operate over nearly three orders of magnitude of incident intensity.

  4. Surface moisture measurement system electromagnetic induction probe calibration technique

    SciTech Connect

    Crowe, R.D., Westinghouse Hanford

    1996-07-08

    The Surface Moisture Measurement System (SMMS) is designed to measure the moisture concentration near the surfaces of the wastes located in the Hanford Site tank farms. This document describes a calibration methodology to demonstrate that the Electromagnetic Induction (EMI) moisture probe meets relevant requirements in the `Design Requirements Document (DRD) for the Surface Moisture Measurement System.` The primary purpose of the experimental tests described in this methodology is to make possible interpretation of EMI in-tank surface probe data to estimate the surface moisture.

  5. Langmuir rogue waves in electron-positron plasmas

    SciTech Connect

    Moslem, W. M.

    2011-03-15

    Progress in understanding the nonlinear Langmuir rogue waves which accompany collisionless electron-positron (e-p) plasmas is presented. The nonlinearity of the system results from the nonlinear coupling between small, but finite, amplitude Langmuir waves and quasistationary density perturbations in an e-p plasma. The nonlinear Schroedinger equation is derived for the Langmuir waves' electric field envelope, accounting for small, but finite, amplitude quasistationary plasma slow motion describing the Langmuir waves' ponderomotive force. Numerical calculations reveal that the rogue structures strongly depend on the electron/positron density and temperature, as well as the group velocity of the envelope wave. The present study might be helpful to understand the excitation of nonlinear rogue pulses in astrophysical environments, such as in active galactic nuclei, in pulsar magnetospheres, in neutron stars, etc.

  6. Probing CPT violation in B systems

    SciTech Connect

    Kundu, Anirban; Patra, Sunando Kumar; Nandi, Soumitra

    2010-04-01

    We discuss how a possible violation of the combined symmetry CPT in the B meson system can be investigated at the LHC. We show how a tagged and an untagged analysis of the decay modes of both B{sub d} and B{sub s} mesons can lead not only to a possible detection of a CPT-violating new physics but also to an understanding of its precise nature. The implication of CPT violation to a large mixing phase in the B{sub s} system is also discussed.

  7. Design study for electronic system for Jupiter Orbit Probe (JOP)

    NASA Technical Reports Server (NTRS)

    Elero, B. P., Jr.; Carignan, G. R.

    1978-01-01

    The conceptual design of the Jupiter probe spectrometer is presented. Block and circuit diagrams are presented along with tabulated parts lists. Problem areas are considered to be (1) the schedule, (2) weight limitations for the electronic systems, and (3) radiation hardness of the electronic devices.

  8. Probing and mapping plasmonic systems by spectroscopic methods (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Noginova, Natalia; Hussain, Rabia; Mashhadi, Soheila

    2016-09-01

    Rare earth ions having both electric and magnetic dipole transitions in emission spectra can be used as local probe to provide information on degree of modification and local distribution of optical electric and magnetic fields in plasmonic systems. In our research, we use highly luminescent organic systems with Eu3+ to study and analyze modification of magnetic and electric dipoles emission in different environment, including systems having plasmonic electric resonance or magnetic resonance in the range of Eu3+ emission, and flat metal. Experimental setup based on selective detection of the particular transition was built and used for probing and mapping of electric and magnetic fields in plasmonic systems and metasurfaces. The method developed can find applications in characterization of plasmonic systems and metamaterials, and engineering of emission properties of rare earth ions and other emitters.

  9. Dichromatic Langmuir waves in degenerate quantum plasma

    SciTech Connect

    Dubinov, A. E. Kitayev, I. N.

    2015-06-15

    Langmuir waves in fully degenerate quantum plasma are considered. It is shown that, in the linear approximation, Langmuir waves are always dichromatic. The low-frequency component of the waves corresponds to classical Langmuir waves, while the high-frequency component, to free-electron quantum oscillations. The nonlinear problem on the profile of dichromatic Langmuir waves is solved. Solutions in the form of a superposition of waves and in the form of beatings of its components are obtained.

  10. Dynamic Force Sensing Using an Optically Trapped Probing System

    PubMed Central

    Huang, Yanan; Cheng, Peng; Menq, Chia-Hsiang

    2013-01-01

    This paper presents the design of an adaptive observer that is implemented to enable real-time dynamic force sensing and parameter estimation in an optically trapped probing system. According to the principle of separation of estimation and control, the design of this observer is independent of that of the feedback controller when operating within the linear range of the optical trap. Dynamic force sensing, probe steering/clamping, and Brownian motion control can, therefore, be developed separately and activated simultaneously. The adaptive observer utilizes the measured motion of the trapped probe and input control effort to recursively estimate the probe–sample interaction force in real time, along with the estimation of the probing system’s trapping bandwidth. This capability is very important to achieving accurate dynamic force sensing in a time-varying process, wherein the trapping dynamics is nonstationary due to local variations of the surrounding medium. The adaptive estimator utilizes the Kalman filter algorithm to compute the time-varying gain in real time and minimize the estimation error for force probing. A series of experiments are conducted to validate the design of and assess the performance of the adaptive observer. PMID:24382944

  11. Probing peripheral and central cholinergic system responses.

    PubMed Central

    Naranjo, C A; Fourie, J; Herrmann, N; Lanctôt, K L; Birt, C; Yau, K K

    2000-01-01

    OBJECTIVE: The pharmacological response to drugs that act on the cholinergic system of the iris has been used to predict deficits in central cholinergic functioning due to diseases such as Alzheimer's disease, yet correlations between central and peripheral responses have not been properly studied. This study assessed the effect of normal aging on (1) the tropicamide-induced increase in pupil diameter, and (2) the reversal of this effect with pilocarpine. Scopolamine was used as a positive control to detect age-dependent changes in central cholinergic functioning in the elderly. DESIGN: Randomized double-blind controlled trial. PARTICIPANTS: Ten healthy elderly (mean age 70) and 9 young (mean age 33) volunteers. INTERVENTIONS: Pupil diameter was monitored using a computerized infrared pupillometer over 4 hours. The study involved 4 sessions. In 1 session, tropicamide (20 microL, 0.01%) was administered to one eye and placebo to the other. In another session, tropicamide (20 microL, 0.01%) was administered to both eyes, followed 23 minutes later by the application of pilocarpine (20 microL, 0.1%) to one eye and placebo to the other. All eye drops were given in a randomized order. In 2 separate sessions, a single dose of scopolamine (0.5 mg, intravenously) or placebo was administered, and the effects on word recall were measured using the Buschke Selective Reminding Test over 2 hours. OUTCOME MEASURES: Pupil size at time points after administration of tropicamide and pilocarpine; scopolamine-induced impairment in word recall. RESULTS: There was no significant difference between elderly and young volunteers in pupillary response to tropicamide at any time point (p > 0.05). The elderly group had a significantly greater pilocarpine-induced net decrease in pupil size 85, 125, 165 and 215 minutes after administration, compared with the young group (p < 0.05). Compared with the young group, the elderly group had greater scopolamine-induced impairment in word recall 60, 90

  12. Topics in strong Langmuir turbulence

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.

    1983-01-01

    Progress in two approaches to the study of strong Langmuir turbulence is reported. In two spatial dimensions, numerical solution of the Zakharov equations yields a steady state involving linear growth, linear damping, and a collection of coherent, long-lived entities which might loosely be called solitons. In one spatial dimension, a statistical theory is applied to the cubically nonlinear Schroedinger equation and is solved analytically in a special case.

  13. Topics in strong Langmuir turbulence

    NASA Technical Reports Server (NTRS)

    Nicholson, D. R.

    1982-01-01

    Progress in two approaches to the study of strong Langmuir turbulence is reported. In two spatial dimensions, numerical solution of the Zakharov equations yields a steady state involving linear growth, linear damping, and a collection of coherent, long-lived entities which might loosely be called solitons. In one spatial dimension, a statistical theory is applied to the cubically nonlinear Schroedinger equation and is solved analytically in a special case.

  14. Multi-function diamond film fiber optic probe and measuring system employing same

    DOEpatents

    Young, J.P.

    1998-11-24

    A fused fiber optic probe having a protective cover, a fiber optic probe system, and embodiments thereof for conducting electromagnetic spectral measurements are disclosed. The fused fiber optic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferably silica, with a protective cover disposed over at least a portion of the probe tip. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0{degree}, an inverted cone-shaped probe tip, and a lens head. 9 figs.

  15. Multi-function diamond film fiberoptic probe and measuring system employing same

    DOEpatents

    Young, Jack P.

    1998-01-01

    A fused fiberoptic probe having a protective cover, a fiberoptic probe system, and embodiments thereof for conducting electromagnetic spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferrably silica, with a protective cover disposed over at least a portion of the probe tip. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0.degree., an inverted cone-shaped probe tip, and a lens head.

  16. Langmuir and langmuir-blodgett films of metallosupramolecular polyelectrolyte-amphiphile complexes.

    PubMed

    Lehmann, Pit; Symietz, Christian; Brezesinski, Gerald; Krass, Henning; Kurth, Dirk G

    2005-06-21

    A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.

  17. High resolution imaging systems for spin-stabilized Probe spacecraft

    NASA Astrophysics Data System (ADS)

    Danielson, G. E.; Malin, M. C.; Delamere, W. A.

    1981-01-01

    A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ('Probes'). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57 km/sec encounter velocity with a small, 10 km diameter, object) coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or nonspinning platforms are not necessary to acquire high resolution, high quality planetary images.

  18. Two-axis probing system for atomic force microscopy.

    PubMed

    Jayanth, G R; Jhiang, Sissy M; Menq, Chia-Hsiang

    2008-02-01

    A novel two-axis probing system is proposed for multiaxis atomic force microscopy (AFM). It employs a compliant manipulator that is optimally designed in terms of geometries and kinematics, and is actuated by multiple magnetic actuators to simultaneously control tip position and change tip orientation to achieve greater accessibility of the sample surface when imaging surfaces having large geometric variations. It leads to the creation of a multiaxis AFM system, which is a three-dimensional surface tool rather than a two-dimensional planar surface tool. The use of the system to scan the bottom corner of a grating step is reported.

  19. 2D Langmuir Maps of Kinked UW-RWM Plasma

    NASA Astrophysics Data System (ADS)

    Hannum, David; Brookhart, Matt; Forest, Cary; Kendrick, Roch; Mengin, Gabriel; Paz-Soldan, Carlos

    2009-11-01

    The rotating wall machine is a linear screw-pinch built to study the role of different wall boundary conditions on the Resistive Wall Mode (RWM). Its plasma is created by a hexagonal array of seven electrostatic guns. The guns can be biased to discharge up to 1 kA of current each, firing independently or in tandem. The 20 cm diameter, 1.2 m long plasma column is held in place by a 500 G (max) axial guide field. A singletip Langmuir probe inserted from the opposite end of the chamber yields measurements of Te, ne and Vp in r and z. Though it is tied to the guns at the cathode end, the plasma column is free to slip over the anode end. At higher plasma currents, the kinking column oscillates past the probe tip. Ensemble averaging of the I-V curves is required to derive reliable Langmuir measurements for these plasmas. I will present 2D Langmuir profiles in configurations scanning the plasma current Ip, guide field Bz, and number of plasma sources (one gun / seven guns).

  20. Evaluation of the NDP (neutron diagnostic probe) system

    SciTech Connect

    Pentaleri, E.A.; Eisen, Y.Y.

    1990-12-01

    The neutron diagnostic probe (NDP), an explosive detection system developed by Consolidated Controls Corporation and based on the associated-alpha-particle technique, was evaluated. Although many problems were found with the prototype system that make it useless for most practical applications, the NDP system may be considered a successful proof-of-principle for the basic explosive detection system design. In addition to evaluating the design and performance of the present system, models were developed to estimate the performance that might reasonably be expected from full scale systems of different conceptual design. Specific examples involved various types of bulk and sheet explosives contained in a suitcase and a large crate. Also considered were the effects of innocuous materials surrounding explosives in different scenarios, including the deliberate use of shielding materials as a countermeasure to detection. 11 refs., 46 figs., 24 tabs.

  1. The Microwave Anisotropy Probe (MAP) Attitude Control System

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Ericsson, Aprille J.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an Inertial Reference Unit, two Autonomous Star Trackers, a Digital Sun Sensor, twelve Coarse Sun Sensors, three Reaction Wheel Assemblies, and a propulsion system. This paper describes the design of the attitude control system that carries out this mission and presents some early flight experience.

  2. Luminescent Organic Semiconducting Langmuir Monolayers.

    PubMed

    Agina, Elena V; Mannanov, Artur A; Sizov, Alexey S; Vechter, Olga; Borshchev, Oleg V; Bakirov, Artem V; Shcherbina, Maxim A; Chvalun, Sergei N; Konstantinov, Vladislav G; Bruevich, Vladimir V; Kozlov, Oleg V; Pshenichnikov, Maxim S; Paraschuk, Dmitry Yu; Ponomarenko, Sergei A

    2017-05-31

    In recent years, monolayer organic field-effect devices such as transistors and sensors have demonstrated their high potential. In contrast, monolayer electroluminescent organic field-effect devices are still in their infancy. One of the key challenges here is to create an organic material that self-organizes in a monolayer and combines efficient charge transport with luminescence. Herein, we report a novel organosilicon derivative of oligothiophene-phenylene dimer D2-Und-PTTP-TMS (D2, tetramethyldisiloxane; Und, undecylenic spacer; P, 1,4-phenylene; T, 2,5-thiophene; TMS, trimethylsilyl) that meets these requirements. The self-assembled Langmuir monolayers of the dimer were investigated by steady-state and time-resolved photoluminescence spectroscopy, atomic force microscopy, X-ray reflectometry, and grazing-incidence X-ray diffraction, and their semiconducting properties were evaluated in organic field-effect transistors. We found that the best uniform, fully covered, highly ordered monolayers were semiconducting. Thus, the ordered two-dimensional (2D) packing of conjugated organic molecules in the semiconducting Langmuir monolayer is compatible with its high-yield luminescence, so that 2D molecular aggregation per se does not preclude highly luminescent properties. Our findings pave the way to the rational design of functional materials for monolayer organic light-emitting transistors and other optoelectronic devices.

  3. Singletip Langmuir Measurements of UW-RWM Plasma

    NASA Astrophysics Data System (ADS)

    Hannum, David; Forest, C. B.; Kendrick, R.

    2008-11-01

    The rotating wall machine is a linear screw-pinch built to study the role of different wall boundary conditions on the resistive wall mode (RWM). Its plasma is created by a hexagonal array of electrostatic guns. The central seven guns can be biased to discharge up to 1 kA of current each. The 20 cm diameter, 1.2 m long plasma column is held in place by a 600 G (max) axial guide field. A singletip Langmuir probe inserted from the opposite end of the chamber yields measurements of Te, ne and Vp in r and z. Several multivariable fitting routines are employed on the I-V curve to derive the standard measurements. I will present 2D Langmuir profiles of the unbiased plasma column in several density and field configurations; biased plasma current measurements are an ongoing concern.

  4. Child-Langmuir flow with periodically varying anode voltage

    NASA Astrophysics Data System (ADS)

    Rokhlenko, A.

    2015-02-01

    Using the Lagrangian technique, we study settled Child-Langmuir flows in a one dimensional planar diodes whose anode voltages periodically vary around given positive values. Our goal is to find analytically if the average currents in these systems can exceed the famous Child-Langmuir limit found for the stationary current a long time ago. The main result of our study is that in a periodic quasi-stationary regime the average current can be larger than the Child-Langmuir maximum even by 50% compared with its adiabatic average value. The cathode current in this case has the form of rectangular pulses which are formed by a very special triangular voltage modulation. This regime, i.e., periodicity, shape of pulses, and their amplitude, needs to be carefully chosen for the best performance.

  5. Child-Langmuir flow with periodically varying anode voltage

    SciTech Connect

    Rokhlenko, A.

    2015-02-15

    Using the Lagrangian technique, we study settled Child-Langmuir flows in a one dimensional planar diodes whose anode voltages periodically vary around given positive values. Our goal is to find analytically if the average currents in these systems can exceed the famous Child-Langmuir limit found for the stationary current a long time ago. The main result of our study is that in a periodic quasi-stationary regime the average current can be larger than the Child-Langmuir maximum even by 50% compared with its adiabatic average value. The cathode current in this case has the form of rectangular pulses which are formed by a very special triangular voltage modulation. This regime, i.e., periodicity, shape of pulses, and their amplitude, needs to be carefully chosen for the best performance.

  6. Measuring correlations of cold-atom systems using multiple quantum probes

    NASA Astrophysics Data System (ADS)

    Streif, Michael; Buchleitner, Andreas; Jaksch, Dieter; Mur-Petit, Jordi

    2016-11-01

    We present a nondestructive method to probe a complex quantum system using multiple-impurity atoms as quantum probes. Our protocol provides access to different equilibrium properties of the system by changing its coupling to the probes. In particular, we show that measurements with two probes reveal the system's nonlocal two-point density correlations, for probe-system contact interactions. We illustrate our findings with analytic and numerical calculations for the Bose-Hubbard model in the weakly and strongly interacting regimes, under conditions relevant to ongoing experiments in cold-atom systems.

  7. Probing TRAPPIST-1-like Systems with K2

    NASA Astrophysics Data System (ADS)

    Demory, Brice-Olivier; Queloz, Didier; Alibert, Yann; Gillen, Ed; Gillon, Michael

    2016-07-01

    The search for small planets orbiting late M dwarfs holds the promise of detecting Earth-size planets for which their atmospheres could be characterized within the next decade. The recent discovery of TRAPPIST-1 entertains hope that these systems are common around hosts located at the bottom of the main sequence. In this Letter, we investigate the ability of the repurposed Kepler mission (K2) to probe planetary systems similar to TRAPPIST-1. We perform a consistent data analysis of 189 spectroscopically confirmed M5.5 to M9 late M dwarfs from Campaigns 1-6 to search for planet candidates and inject transit signals with properties matching TRAPPIST-1b and c. We find no transiting planet candidates across our K2 sample. Our injection tests show that K2 is able to recover both TRAPPIST-1 planets for 10% of the sample only, mainly because of the inefficient throughput at red wavelengths resulting in Poisson-limited performance for these targets. Increasing injected planetary radii to match GJ 1214b’s size yields a recovery rate of 70%. The strength of K2 is its ability to probe a large number of cool hosts across the different campaigns, out of which the recovery rate of 10% may turn into bona fide detections of TRAPPIST-1-like systems within the next two years.

  8. Langmuir wave damping decreases slowly

    NASA Astrophysics Data System (ADS)

    Rose, Harvey

    2006-10-01

    The onset of stimulated Raman scatter in a single laser speckle occurs (D. S. Montgomery et al., Phys. Plasmas, 9, 2311 (2002)) at lower laser intensity, I, than predicted by linear theory based on classical Landau damping, νL, of the SRS daughter Langmuir wave. Does this imply that SRS onset in a speckled laser beam, propagating through long scale length plasma, is also at odds with linear theory? It has been shown (Harvey A. Rose and D. F. DuBois, Phys. Rev. Lett. 72, 2883 (1994)) that linear convective gain in speckles with large fluctuations of I about the average, , leads to onset at a value of , Ic, small compared to that for onset in a uniform beam. While nonlinear electron trapping effects may occur in very intense speckles, whether or not these effects are sufficient to lower the onset value of below Ic depends on how strongly electrons must be trapped before there is significant reduction in νL. As the amplitude of an SRS daughter Langmuir wave increases, its νL decreases by the factor ν/φb, due to the competition between electron trapping, with electron bounce frequency, φb, and escape of these trapped electrons by advection out of a speckle's side, at rate ν. This result (Harvey A. Rose and David A. Russell, Phys. Plasmas, 8, 4784 (2001)) is valid for ν/φb 1. In this talk I present a nonlinear, transit time damping, calculation of νL and find that reduction by a factor of two does not occur until φb/ν 5. This slow turn on of trapping effects suggests that the linear calculation of Ic is NIF relevant.

  9. Excitation of electron Langmuir frequency harmonics in the solar atmosphere

    SciTech Connect

    Fomichev, V. V.; Fainshtein, S. M.; Chernov, G. P.

    2013-05-15

    An alternative mechanism for the excitation of electron Langmuir frequency harmonics as a result of the development of explosive instability in a weakly relativistic beam-plasma system in the solar atmosphere is proposed. The efficiency of the new mechanism as compared to the previously discussed ones is analyzed.

  10. Limitations to Using Linearized Langmuir Equations

    USDA-ARS?s Scientific Manuscript database

    One of the most commonly used models for describing solute sorption to soils is the Langmuir model. Because the Langmuir model is nonlinear, fitting the model to sorption data requires that the model be solved iteratively using an optimization program. To avoid the use of optimization programs, a li...

  11. Measurement of electron density using reactance cutoff probe

    NASA Astrophysics Data System (ADS)

    You, K. H.; You, S. J.; Kim, D. W.; Na, B. K.; Seo, B. H.; Kim, J. H.; Seong, D. J.; Chang, H. Y.

    2016-05-01

    This paper proposes a new measurement method of electron density using the reactance spectrum of the plasma in the cutoff probe system instead of the transmission spectrum. The highly accurate reactance spectrum of the plasma-cutoff probe system, as expected from previous circuit simulations [Kim et al., Appl. Phys. Lett. 99, 131502 (2011)], was measured using the full two-port error correction and automatic port extension methods of the network analyzer. The electron density can be obtained from the analysis of the measured reactance spectrum, based on circuit modeling. According to the circuit simulation results, the reactance cutoff probe can measure the electron density more precisely than the previous cutoff probe at low densities or at higher pressure. The obtained results for the electron density are presented and discussed for a wide range of experimental conditions, and this method is compared with previous methods (a cutoff probe using the transmission spectrum and a single Langmuir probe).

  12. Measurement of electron density using reactance cutoff probe

    SciTech Connect

    You, K. H.; Seo, B. H.; Kim, J. H.; Seong, D. J.; You, S. J.; Kim, D. W.; Na, B. K.; Chang, H. Y.

    2016-05-15

    This paper proposes a new measurement method of electron density using the reactance spectrum of the plasma in the cutoff probe system instead of the transmission spectrum. The highly accurate reactance spectrum of the plasma-cutoff probe system, as expected from previous circuit simulations [Kim et al., Appl. Phys. Lett. 99, 131502 (2011)], was measured using the full two-port error correction and automatic port extension methods of the network analyzer. The electron density can be obtained from the analysis of the measured reactance spectrum, based on circuit modeling. According to the circuit simulation results, the reactance cutoff probe can measure the electron density more precisely than the previous cutoff probe at low densities or at higher pressure. The obtained results for the electron density are presented and discussed for a wide range of experimental conditions, and this method is compared with previous methods (a cutoff probe using the transmission spectrum and a single Langmuir probe).

  13. Periodontal probing systems: a review of available equipment.

    PubMed

    Ramachandra, Srinivas Sulugodu; Mehta, Dhoom Singh; Sandesh, Nagarajappa; Baliga, Vidya; Amarnath, Janardhan

    2011-03-01

    The periodontal pocket, one of the definitive signs of periodontal disease, is the most common parameter to be assessed by dental clinicians. Periodontal probes have been the instruments most commonly used to locate and measure these pockets. Regular use of periodontal probes in routine dental practice facilitates and increases the accuracy of the process of diagnosing the condition, formulating the treatment, and predicting the outcome of therapy. Advances in the field of periodontal probing have led to the development of probes that may help reduce errors in determining this parameter used to define the state of active periodontal disease. One such advance is the emergence of probes that purportedly assess periodontal disease activity noninvasively. The selection of periodontal probe depends on the type of dental practice: a general dental practitioner would require first- or second-generation probes, while third- through fifth-generation probes generally are used in academic and research institutions as well as specialty practices.

  14. The Jupiter System Observer: Probing the Foundations of Planetary Systems

    NASA Astrophysics Data System (ADS)

    Senske, D.; Prockter, L.; Collins, G.; Cooper, J.; Hendrix, A.; Hibbitts, K.; Kivelson, M.; Orton, G.; Schubert, G.; Showman, A.; Turtle, E.; Williams, D.; Kwok, J.; Spilker, T.; Tan-Wang, G.

    2007-12-01

    Galileo's observations in the 1600's of the dynamic system of Jupiter and its moons launched a revolution in understanding the way planetary systems operate. Now, some 400 years later, the discovery of extra solar planetary systems with Jupiter-sized bodies has led to a similar revolution in thought regarding how these systems form and evolve. From the time of Galileo, the Jovian system has been viewed as a solar system in miniature, providing a laboratory to study, diverse and dynamic processes in a single place. The icy Galilean satellites provide a window into solar system history by preserving in their cratering records a chronology dating back nearly 4.5 By and extending to the present. The continuously erupting volcanoes of Io may provide insight into the era when magma oceans were common. The discovery of an internally generated magnetic field at Ganymede, one of only three terrestrial bodies to possess such a field, is a place to gain insight as to how dynamos work. The confirmation and characterization of icy satellite subsurface oceans impacts the way habitability is considered. Understanding the composition and volatile inventory of Jupiter can shed light into how planets accrete from the solar nebulae. Finally, like our sun, Jupiter influences its system through its extensive magnetic field. In early 2007, NASA's Science Mission Directorate formed four Science Definition Teams (SDTs) to formulate science goals and objectives in anticipation of the initiation of a flagship-class mission to the outer solar system (Europa, Jupiter system, Titan and Enceladus). The Jupiter System Observer (JSO) mission concept emphasizes overall Jupiter system science: 1) Jupiter and its atmosphere, 2) the geology and geophysics of the Galilean satellites (Io, Europa, Ganymede and Callisto), 3) the magnetosphere environment - both Jupiter's and Ganymede's&pand 4) interactions within the system. Focusing on the unique geology, presence of an internal magnetic field and

  15. Spreading dynamics of 2D dipolar Langmuir monolayer phases.

    PubMed

    Heinig, P; Wurlitzer, S; Fischer, Th M

    2004-07-01

    We study the spreading of a liquid 2D dipolar droplet in a Langmuir monolayer. Interfacial tensions (line tensions) and microscopic contact angles depend on the scale on which they are probed and obey a scaling law. Assuming rapid equilibration of the microscopic contact angle and ideal slippage of the 2D solid/liquid and solid/gas boundary, the driving force of spreading is merely expressed by the shape-dependent long-range interaction integrals. We obtain good agreement between experiment and numerical simulations using this theory.

  16. Synthetic fluorescent probes for studying copper in biological systems

    PubMed Central

    Cotruvo, Joseph A.; Aron, Allegra T.; Ramos-Torres, Karla M.; Chang, Christopher J.

    2015-01-01

    The potent redox activity of copper is required for sustaining life. Mismanagement of its cellular pools, however, can result in oxidative stress and damage connected to aging, neurodegenerative diseases, and metabolic disorders. Therefore, copper homeostasis is tightly regulated by cells and tissues. Whereas copper and other transition metal ions are commonly thought of as static cofactors buried within protein active sites, emerging data points to the presence of additional loosely bound, labile pools that can participate in dynamic signalling pathways. Against this backdrop, we review advances in sensing labile copper pools and understanding their functions using synthetic fluorescent indicators. Following brief introductions to cellular copper homeostasis and considerations in sensor design, we survey available fluorescent copper probes and evaluate their properties in the context of their utility as effective biological screening tools. We emphasize the need for combined chemical and biological evaluation of these reagents, as well as the value of complementing probe data with other techniques for characterizing the different pools of metal ions in biological systems. This holistic approach will maximize the exciting opportunities for these and related chemical technologies in the study and discovery of novel biology of metals. PMID:25692243

  17. Generalized Langmuir Waves in Magnetized Kinetic Plasmas

    NASA Technical Reports Server (NTRS)

    Willes, A. J.; Cairns, Iver H.

    2000-01-01

    The properties of unmagnetized Langmuir waves and cold plasma magnetoionic waves (x, o, z and whistler) are well known. However, the connections between these modes in a magnetized kinetic plasma have not been explored in detail. Here, wave properties are investigated by numerically solving the dispersion equation derived from the Vlasov equations both with and without a beam instability present. For omega(sub p)>Omega(sub e), it is shown that the generalized Langmuir mode at oblique propagation angles has magnetic z-mode characteristics at low wave numbers and thermal Langmuir mode characteristics at high wave numbers. For omega(sub p)Langmuir mode instead connects to the whistler mode at low wave numbers. The transition from the Langmuir/z mode to the Langmuir/whistler mode near omega(sub p) = Omega(sub e) is rapid. In addition, the effects on wave dispersion and polarization after adding a beam are investigated. Applications of this theory to magnetized Langmuir waves in Earth's foreshock and the solar wind, to waves observed near the plasma frequency in the auroral regions, and to solar type III bursts are discussed.

  18. Development of a system for aerodynamic fast-response probe measurements

    NASA Astrophysics Data System (ADS)

    Gossweiler, C.; Humm, H.; Kupferschmied, P.

    This paper describes the development of a fast-response probe measurement system. Small pressure probes have been equipped with up to 4 miniature pressure sensors. The high frequency response of such sensors allied to minimized cavities between the flow and the sensing diaphragm enables the probe system to take measurements up to 40 kHz bandwidth (typical blade passing frequency: 2-10 kHz). First results of investigations on the aerodynamic of high frequency response measurement probes are presented including experiments in a water towing channel with unsteady flows around different probe geometries. The packaging of the sensor chip into the probe, the properties of the sensors and the measurement errors are examined. Probe calibration methods and aerodynamic evaluation procedures are discussed, followed by a presentation of the data acquisition system and of the data evaluation software. Measurements in a radial compressor test rig and in a fully developed pipe flow are shown as applications.

  19. Transportation System Options For The Interstellar Probe Mission

    NASA Technical Reports Server (NTRS)

    Johnson, Charles Les

    2000-01-01

    NASA is considering a mission to explore near-interstellar space early in the next decade as the first step toward a vigorous interstellar exploration program. A key enabling technology for such an ambitious science and exploration effort is the development of propulsion systems capable of providing fast trip times. Advanced propulsion technologies that might support an interstellar precursor mission early in the next century include some combination of solar sails, nuclear electric propulsion systems, and aerogravity assists. For years, the scientific community has been interested in the development of solar sail technology to support exploration of the inner and outer planets. Progress in thin-film technology and the development of technologies that may enable the remote assembly of lar2e sails in space are only now maturing to the point where ambitious interstellar precursor missions can be considered. Electric propulsion is now being demonstrated for planetary exploration by the Deep Space I mission. The primary issues for it's adaptation to interstellar precursor applications include the nuclear reactor that would be required and the engine lifetime. A propulsion system concept for the proposed Interstellar Probe mission will be described for each.

  20. Abegg, Lewis, Langmuir, and the Octet Rule.

    ERIC Educational Resources Information Center

    Jensen, William B.

    1984-01-01

    Discusses major events leading to the development of the octet rule. Three conclusions based on the work of Mendeleev, Abegg, Thompson, Kossel, Lewis, and Langmuir are considered as is the debate over the rule's validity. (JN)

  1. Relativistically modulational instability by strong Langmuir waves

    SciTech Connect

    Liu, X. L.; Liu, S. Q.; Li, X. Q.

    2012-09-15

    Based on the set of nonlinear coupling equations, which has considered the relativistic effects of electrons, modulational instability by strong Langmuir waves has been investigated in this paper. Both the characteristic scale and maximum growth rate of the Langmuir field will enhance with the increase in the electron relativistic effect. The numerical results indicate that longitudinal perturbations induce greater instability than transverse perturbations do, which will lead to collapse and formation of the pancake-like structure.

  2. Eigenmode Structure in Solar Wind Langmuir Waves

    NASA Astrophysics Data System (ADS)

    Malaspina, D. M.; Ergun, R.; Bougeret, J.; Kaiser, M. L.; Bale, S.; Cairns, I. H.; Cattell, C. A.; Kellogg, P. J.; Newman, D. L.

    2007-12-01

    Bursty Langmuir waves associated with space plasma phenomena including type II and type III solar radio bursts, auroral field-aligned electrons, and radiation from shocks often exhibit localized beat-type waveforms. A consensus view on the modulation mechanism remains elusive. Current theories include multi-wave interactions, turbulence, or non-linear growth such as kinetic localization. Most of these theories start with the assumption that the density of the background plasma is near-uniform, in spite of numerous observations to the contrary. An alternative approach is to start with the assumption that density perturbations pre-exist. We construct an analytical electric field solution, describing Langmuir waves as a combination of trapped eigenmodes within a parabolic density well. This hypothesis is supported by discreet frequency structure in auroral Langmuir wave observations observed to be associated with density fluctuations, and by the high degree of localization observed in solar wind borne Langmuir waves. This simple, one-dimensional model can reproduce waveform and frequency structure of localized Langmuir waves observed by STEREO/SWAVES. The waveforms can be reasonably reproduced using linear combinations of only a few low-mode eigenmode solutions. The eigenmode solutions are sensitive to plasma environmental parameters such as the electron temperature and solar wind velocity. The trapped-eigenmode solutions can form a theoretical basis to explore the non-linear behavior of Langmuir waves which may allow for efficient conversion and escape of electromagnetic emissions and second harmonic production.

  3. All-optical photoacoustic imaging system using fiber ultrasound probe and hollow optical fiber bundle.

    PubMed

    Miida, Yusuke; Matsuura, Yuji

    2013-09-23

    An all-optical 3D photoacoustic imaging probe that consists of an optical fiber probe for ultrasound detection and a bundle of hollow optical fibers for excitation of photoacoustic waves was developed. The fiber probe for ultrasound is based on a single-mode optical fiber with a thin polymer film attached to the output end surface that works as a Fabry Perot etalon. The input end of the hollow fiber bundle is aligned so that each fiber in the bundle is sequentially excited. A thin and flexible probe can be obtained because the probe system does not have a scanning mechanism at the distal end.

  4. The Attitude Control System for the Wilkinson Microwave Anisotropy Probe

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe mission produces a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an inertial reference unit, two star trackers, a digital sun sensor, twelve coarse sun sensors, three reaction wheel assemblies, and a propulsion system. Sufficient attitude knowledge is provided to yield instrument pointing to a standard deviation (l sigma) of 1.3 arc-minutes per axis. In addition, the spacecraft acquires and holds the sunline at initial acquisition and in the event of a failure, and slews to the proper orbit adjust orientations and to the proper off-sunline attitude to start the compound spin. This paper presents an overview of the design of the attitude control system to carry out this mission and presents some early flight experience.

  5. Restoring Redundancy to the Wilkinson Microwave Anisotrophy Probe Propulsion System

    NASA Technical Reports Server (NTRS)

    O'Donnell, James R., Jr.; Davis, Gary T.; Ward, David K.

    2004-01-01

    The Wilkinson Microwave Anisotropy Probe is a follow-on to the Differential Microwave Radiometer instrument on the Cosmic Background Explorer. Attitude control system engineers discovered sixteen months before launch that configuration changes after the critical design review had resulted in a significant migration of the spacecraft's center of mass. As a result, the spacecraft no longer had a viable backup control mode in the event of a failure of the negative pitch-axis thruster. A tiger team was formed and identified potential solutions to this problem, such as adding thruster-plume shields to redirect thruster torque, adding or removing mass from the spacecraft, adding an additional thruster, moving thrusters, bending thruster nozzles or propellant tubing, or accepting the loss of redundancy. The project considered the impacts on mass, cost, fuel budget, and schedule for each solution, and decided to bend the propellant tubing of the two roll-control thrusters to allow the pair to be used for backup control in the negative pitch axis. This paper discusses the problem and the potential solutions, and documents the hardware and software changes and verification performed. Flight data are presented to show the on-orbit performance of the propulsion system and lessons learned are described.

  6. The CRRES Langmuir Probe and Fluxgate Magnetometer Instrument

    DTIC Science & Technology

    1989-05-09

    VOLTAGE’CURRENT MODE MT • m 0015 PIAYFIA6 EQU 80H PLAYBACK ENABLE BIT »00 0017 KÜHN E8U 8 MIR rRANSHIT OVERRIDE 0000 0018 I •:• oe ooi9 mil...RAH34+AN6SHP 1B1A C9 0065 RET 1B1B 0066 * 181B 0067 t COHHAND ENTRY IN CHL1 1816 0068 t 181B 7C 0069 SNPCHD HOV A,H IF REBIAS COHHAND, SETRESULT

  7. Domain Relaxation in Polymer Langmuir Layers

    NASA Astrophysics Data System (ADS)

    Bernoff, Andrew J.; Alexander, James C.; Mann, Elizabeth; Mann, J. Adin, Jr.; Pugh, Jacob M.; Zou, Lu

    2005-11-01

    We report on an experimental, theoretical and computational study of a molecularly thin polymer Langmuir layer on the surface of a subfluid. When stretched (by a transient stagnation flow), the monolayer takes the form of a bola consisting of two roughly circular reservoirs connected by a thin tether. This shape relaxes to the minimum energy configuration of a circular domain. The tether is never observed to rupture, even when it is more than a hundred times as long as it is thin. We model these experiments by taking previous descriptions of the full hydrodynamics (primarily those of Stone & McConnell and Lubensky & Goldstein ), identifying the dominant effects via dimensional analysis, and reducing the system to a more tractable form. The result is a free boundary problem where motion is driven by the line tension of the domain and damped by the viscosity of the subfluid. The problem has a boundary integral formulation which allows us to numerically simulate the tether relaxation; comparison with the experiments allows us to estimate the line tension in the system.

  8. Probe based confocal laser endomicroscopy of the pancreatobiliary system

    PubMed Central

    Almadi, Majid A; Neumann, Helmut

    2015-01-01

    AIM: To review applications of confocal laser endomicroscopy (CLE) in pancreatobiliary lesions and studies that assessed training and interpretation of images. METHODS: A computerized literature search was performed using OVID MEDLINE, EMBASE, Cochrane library, and the ISI Web of Knowledge from 1980 to October 2014. We also searched abstracts from major meetings that included the Digestive Disease Week, Canadian Digestive Disease Week and the United European Gastroenterology Week using a combination of controlled vocabulary and text words related to pCLE, confocal, endomicroscopy, probe-based confocal laser endomicroscopy, and bile duct to identify reports of trials. In addition, recursive searches and cross-referencing was performed, and manual searches of articles identified after the initial search was also completed. We included fully published articles and those in abstract form. Given the relatively recent introduction of CLE we included randomized trials and cohort studies. RESULTS: In the evaluation of indeterminate pancreatobiliary strictures CLE with ERCP compared to ERCP alone can increase the detection of cancerous strictures with a sensitivity of (98% vs 45%) and has a negative predictive value (97% vs 69%), but decreased the specificity (67% vs 100%) and the positive predictive value (71% vs 100%) when compared to index pathology. Modifications in the classification systems in indeterminate biliary strictures have increased the specificity of pCLE from 67% to 73%. In pancreatic cystic lesions there is a need to develop similar systems to interpret and characterize lesions based on CLE images obtained. The presence of superficial vascular network predicts serous cystadenomas accurately. Also training in acquiring and interpretation of images is feasible in those without any prior knowledge in CLE in a relatively simple manner and computer-aided diagnosis software is a promising innovation. CONCLUSION: The role of pCLE in the evaluation of

  9. Probe based confocal laser endomicroscopy of the pancreatobiliary system.

    PubMed

    Almadi, Majid A; Neumann, Helmut

    2015-11-28

    To review applications of confocal laser endomicroscopy (CLE) in pancreatobiliary lesions and studies that assessed training and interpretation of images. A computerized literature search was performed using OVID MEDLINE, EMBASE, Cochrane library, and the ISI Web of Knowledge from 1980 to October 2014. We also searched abstracts from major meetings that included the Digestive Disease Week, Canadian Digestive Disease Week and the United European Gastroenterology Week using a combination of controlled vocabulary and text words related to pCLE, confocal, endomicroscopy, probe-based confocal laser endomicroscopy, and bile duct to identify reports of trials. In addition, recursive searches and cross-referencing was performed, and manual searches of articles identified after the initial search was also completed. We included fully published articles and those in abstract form. Given the relatively recent introduction of CLE we included randomized trials and cohort studies. In the evaluation of indeterminate pancreatobiliary strictures CLE with ERCP compared to ERCP alone can increase the detection of cancerous strictures with a sensitivity of (98% vs 45%) and has a negative predictive value (97% vs 69%), but decreased the specificity (67% vs 100%) and the positive predictive value (71% vs 100%) when compared to index pathology. Modifications in the classification systems in indeterminate biliary strictures have increased the specificity of pCLE from 67% to 73%. In pancreatic cystic lesions there is a need to develop similar systems to interpret and characterize lesions based on CLE images obtained. The presence of superficial vascular network predicts serous cystadenomas accurately. Also training in acquiring and interpretation of images is feasible in those without any prior knowledge in CLE in a relatively simple manner and computer-aided diagnosis software is a promising innovation. The role of pCLE in the evaluation of pancreatobiliary disorders might be better

  10. A comparative study of electrical probe techniques for plasma diagnostics

    NASA Technical Reports Server (NTRS)

    Szuszczewicz, E. P.

    1972-01-01

    Techniques for using electrical probes for plasma diagnostics are reviewed. Specific consideration is given to the simple Langmuir probe, the symmetric double probe of Johnson and Malter, the variable-area probe of Fetz and Oeschsner, and a floating probe technique. The advantages and disadvantages of each technique are discussed.

  11. Performance Assessment of a New Variable Stiffness Probing System for Micro-CMMs.

    PubMed

    Alblalaihid, Khalid; Kinnell, Peter; Lawes, Simon; Desgaches, Dorian; Leach, Richard

    2016-04-08

    When designing micro-scale tactile probes, a design trade-off must be made between the stiffness and flexibility of the probing element. The probe must be flexible enough to ensure sensitive parts are not damaged during contact, but it must be stiff enough to overcome attractive surface forces, ensure it is not excessively fragile, easily damaged or sensitive to inertial loads. To address the need for a probing element that is both flexible and stiff, a novel micro-scale tactile probe has been designed and tested that makes use of an active suspension structure. The suspension structure is used to modulate the probe stiffness as required to ensure optimal stiffness conditions for each phase of the measurement process. In this paper, a novel control system is presented that monitors and controls stiffness, allowing two probe stiffness values ("stiff" and "flexible") to be defined and switched between. During switching, the stylus tip undergoes a displacement of approximately 18 µm, however, the control system is able ensure a consistent flexible mode tip deflection to within 12 nm in the vertical axis. The overall uncertainty for three-dimensional displacement measurements using the probing system is estimated to be 58 nm, which demonstrates the potential of this innovative variable stiffness micro-scale probe system.

  12. Development and Testing of Prototype Giant Magnetoresistive (GMR) Rotating Probe System

    NASA Astrophysics Data System (ADS)

    Wincheski, Buzz; Simpson, John; Namkung, Min; Perey, Dan; Callahan, John

    2003-03-01

    Continued development of the giant magnetoresistive based rotating probe system has resulted in the fabrication of a fieldable prototype instrument. The system, designed for the detection of deeply buried flaws under installed fasteners, utilizes a giant magnetoresistive sensor within the self-nulling probe design for improved low frequency capabilities. The prototype unit incorporates a new probe design for deep penetration and reduced edge effects along with new electronics and system software. Testing of the prototype system has been performed at SANDIA National Laboratories Aging Aircraft NDI Validation Center. The complete system configuration along with field testing results are presented.

  13. Langmuir solitons in a plasma with inhomogeneous electron temperature

    NASA Astrophysics Data System (ADS)

    Gromov, Evgeny M.; Malomed, Boris A.

    2015-06-01

    Dynamics of Langmuir solitons is considered in plasmas with spatially inhomogeneous electron temperature. An underlying Zakharov-type system of two unidirectional equations for the Langmuir and ion-sound fields is reduced to an inhomogeneous nonlinear Schrödinger equation with spatial variation of the second-order dispersion and self-phase modulation coefficients, induced by a spatially inhomogeneous profile of the electron temperature. Analytical trajectories of motion of a soliton in the plasma with an electron-temperature hole, barrier, or cavity between two barriers are found, using the method of integral moments. The possibility of the soliton to pass a high-temperature barrier is shown too. Analytical results are well corroborated by numerical simulations.

  14. Extended oil spill spreading with Langmuir circulation.

    PubMed

    Simecek-Beatty, Debra; Lehr, William J

    2017-09-15

    When spilled in the ocean, most crude oils quickly spread into a thin film that ruptures into smaller slicks distributed over a larger area. Observers have also reported the film tearing apart into streaks that eventually merge forming fewer but longer bands of floating oil. Understanding this process is important to model oil spill transport. First, slick area is calculated using a spreading model. Next, Langmuir circulation models are used to approximate the merging of oiled bands. Calculations are performed on Troll blended and Alaska North Slope crude oils and results compared with measurements from the 1990s North Sea field experiments. Langmuir circulation increases the oil area but decreases the surface coverage of oil. This work modifies existing oil spreading formulas by providing a surface area correction due to the effects of Langmuir circulation. The model's simplicity is advantageous in situations with limited data, such as emergency oil spill response. Published by Elsevier Ltd.

  15. Determination of interphase line tension in Langmuir films

    NASA Astrophysics Data System (ADS)

    Wintersmith, Jacob R.; Zou, Lu; Bernoff, Andrew J.; Alexander, James C.; Mann, J. Adin, Jr.; Kooijman, Edgar E.; Mann, Elizabeth K.

    2007-06-01

    A Langmuir film is a molecularly thin film on the surface of a fluid; we study the evolution of a Langmuir film with two coexisting fluid phases driven by an interphase line tension and damped by the viscous drag of the underlying subfluid. Experimentally, we study a 4' -8-alkyl[1, 1' -biphenyl]-4-carbonitrile (8CB) Langmuir film via digitally imaged Brewster angle microscopy in a four-roll mill setup which applies a transient strain and images the response. When a compact domain is stretched by the imposed strain, it first assumes a bola shape with two tear-drop shaped reservoirs connected by a thin tether which then slowly relaxes to a circular domain which minimizes the interfacial energy of the system. We process the digital images of the experiment to extract the domain shapes. We then use one of these shapes as an initial condition for the numerical solution of a boundary-integral model of the underlying hydrodynamics and compare the subsequent images of the experiment to the numerical simulation. The numerical evolutions first verify that our hydrodynamical model can reproduce the observed dynamics. They also allow us to deduce the magnitude of the line tension in the system, often to within 1%. We find line tensions in the range of 200-600pN ; we hypothesize that this variation is due to differences in the layer depths of the 8CB fluid phases.

  16. Saturn Uranus atmospheric entry probe mission spacecraft system definition study

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The modifications required of the Pioneer F/G spacecraft design for it to deliver an atmospheric entry probe to the planets Saturn and Uranus are investigated. It is concluded that it is feasible to conduct such a mission within the constraints and interfaces defined. The spacecraft required to perform the mission is derived from the Pioneer F/G design, and the modifications required are generally routinely conceived and executed. The entry probe is necessarily a new design, although it draws on the technology of past, present, and imminent programs of planetary atmospheric investigations.

  17. AuNP-CTG based probing system targeting CAG repeat DNA and RNA sequences.

    PubMed

    Le, Binh Huy; Joo, Han Na; Hwang, Do Won; Kim, Kyu Wan; Seo, Young Jun

    2017-08-15

    We have developed a AuNP-CTG based probing system that is applicable to the detection of many units of CAG repeat sequences which was synthesized by a rolling circle amplification (RCA) system with changes in fluorescence. We also demonstrate that our AuNP-CTG based probing system could transfect without using transfection reagent and detect target CAG repeat sequences in HeLa cells with dramatic changes in fluorescence. This AuNP-CTG based probing system could also be used, in conjunction with the CAG repeat RCA system, to detect target DNA. This system was so sensitive to the target DNA that it could detect even picomolar amounts with amplification of the fluorescence signal. Furthermore, we have used our gold-based CAG probing system for the detection of RNA CAG repeat sequences. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Volatiles in comets as probes to the early solar system

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hitomi

    2014-03-01

    Comets are considered as the remnants of the planetesimals (building blocks of the planets) formed in the proto-planetary disk of the Sun. They have retained the information about the formation and evolutional history of the early solar system. To investigate the chemical and physical conditions of the proto-planetary disk, comets have been studied as probes to the solar system formation. In the last two decades, thanks to advances in technology, near-infrared (NIR) observations have been carried out to detect the various kinds of molecules (with and without permanent electric dipole moments) released directly from the nucleus. As the physical temperature could control chemical reactions, we expect to find chemical diversity among comets that have different dynamical origins. To investigate chemical diversity in the proto-planetary disk, we have observed several comets with NIR high-dispersion spectrometry. Although the number of samples is still small relative to the number of samples obtained by optical studies, the HCN, C2H2, CH4, C2H6, CH3OH, H2CO, and CO content in more than 10 comets have been measured. We compared our samples with other samples obtained by NIR observations and found no clear differences in the chemical compositions of the comets, even though the comets originated in different dynamical reservoirs (i.e., the Oort Cloud and the trans-Neptunian regions). Although there was a small variation in the mixing ratios among the OC comets, all the samples were consistent within error limits. This variation (if it exists) may be supporting evidence for the Nice model. The sublimation temperature of H2O is relatively higher than that of other hyper volatiles, such as CO, CO2, and CH4. Thus, in the proto-planetary disk, there was a region where H2O could exist as ice and be incorporated into the planetesimals, while other hyper volatiles were in gas phase and could not be incorporated into the planetesimals. Alternatively, the differences in the chemical

  19. Singletip Langmuir Measurements of UW-RWM Plasma

    NASA Astrophysics Data System (ADS)

    Hannum, David; Forest, Cary; Kendrick, Roch

    2009-05-01

    The rotating wall machine is a linear screw-pinch built to study the role of different wall boundary conditions on the resistive wall mode (RWM). Its plasma is created by a hexagonal array of seven electrostatic guns. The guns can be biased to discharge up to 1 kA of current each, firing independently or in tandem. The 20 cm diameter, 1.2 m long plasma column is held in place by a 600 G (max) axial guide field. A singletip Langmuir probe inserted from the opposite end of the chamber yields measurements of Te, ne and Vp in r and z. The density fired from a single gun on the magnetic axis diffuses to the wall as it travels down the column, while the plasma from seven guns condenses in the center. I will present 2D Langmuir profiles and animations of the unbiased plasma column in several density and field configurations; biased plasma current measurements are an ongoing concern.

  20. Outer planet entry probe system study. Volume 2: Supporting technical studies

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The environment, science investigations, and general mission analysis considerations are given first. These data are followed by discussions of the studies pertaining to the planets Jupiter, Saturn, Uranus, and Neptune. Except for Neptune, each planet discussion is divided into two parts: (1) parametric activities and (2) probe definition for that planet, or the application of a given probe for that planet. The Neptune discussion is limited to parametrics in the area of science and mission analysis. Each of the probe system definitions consists of system and subsystem details including telecommunications, data handling, power pyrotechnics, attitude control, structures, propulsion, thermal control, and probe to spacecraft integration. The first configuration is discussed in detail and the subsequent configuration discussions are limited to the differences. Finally, the hardware availability to support a probe system and commonality of science, missions, and subsystems for use at the various planets are considered.

  1. Fibre Fabry - Perot cavity-based aperture probe for near-field optical microscopy systems

    SciTech Connect

    Kulchin, Yurii N; Vitrik, O B; Bezverbnyi, A V; Pustovalov, E V; Kuchmizhak, A A; Nepomnyashchii, A V

    2011-03-31

    We report a theoretical analysis and experimental study of the possibility of producing a novel type of interferometric near-field aperture probe for near-field optical microscopy systems using a fibre Fabry - Perot microcavity with a nanometre-scale aperture made in one of its output mirrors. The probe ensures a spatial resolution no worse than {lambda}/14. (fibre optics)

  2. Langmuir and Langmuir-Blodgett films containing a porphyrin-ruthenium complex.

    PubMed

    Wohnrath, Karen; Dinelli, Luis R; Mello, Sarita V; Constantino, Carlos J L; Leblanc, Roger M; Batista, Alzir A; Oliveira, Osvaldo N

    2005-06-01

    The fabrication of supramolecular structures from the tetraruthenated porphyrin-containing phosphines, {TPyP[RuCl3(dppb)]4}, RuTPyP, is demonstrated with Langmuir and Langmuir-Blodgett films. The surface pressure-molecular area isotherms (pi-A) point to an edge-on arrangement for the RuTPyP molecules in the condensed state. Weak aggregation in the Langmuir films was indicated by non-zero surface potentials at large areas per molecule and a slight red shift in the ultraviolet-visible absorption spectrum in comparison to the spectrum in solution. Further aggregation occurs in the Z-type Langmuir-Blodgett films, which was confirmed with ultraviolet-visible spectroscopy of the deposited films. Fourier transform infrared and Raman spectroscopic data for powder and Langmuir-Blodgett films indicate that the RuTPyP molecules are chemically stable in Langmuir-Blodgett films regardless of the contact with water during film fabrication. The nanostructured nature of the Langmuir-Blodgett films was manifested in cyclic voltammetry due to the high sensitivity of the metallic centers in RuTPyP. Electrodes modified with Langmuir-Blodgett films exhibit an anodic peak at 100 mV and a cathodic peak at 7 mV, which is assigned to RuIII/RuII redox processes. Furthermore, Langmuir-Blodgett films from RuTPyP showed electrocatalytic activity for oxidation of benzyl alcohol, illustrated by a large shift of 100 mV in the anodic peak at 400 mV, while electropolymerized and cast films of the same compound displayed smaller and no activities, respectively.

  3. Langmuir films of petroleum at the air-water interface.

    PubMed

    Vieira, Vinícius C C; Severino, Divinomar; Oliveira, Osvaldo N; Pavinatto, Felippe J; Zaniquelli, Maria E D; Ramos, Ana Paula; Baptista, Maurício S

    2009-11-03

    Understanding the behavior of petroleum films at the air/water interface is crucial for dealing with oil slicks and reducing the damages to the environment, which has normally been attempted with studies of Langmuir films made of fractions of petroleum. However, the properties of films from whole petroleum samples may differ considerably from those of individual fractions. Using surface pressure and surface potential measurements and Brewster angle and fluorescence microscopy, we show that petroleum forms a nonhomogeneous Langmuir film at the air-water interface. The surface pressure isotherms for petroleum Langmuir films exhibit gas (G), liquid-expanded (LE), and liquid-condensed phases, with almost no hysteresis in the compression-decompression cycles. Domains formed upon compression from the G to the LE phase were accompanied by an increase in fluorescence intensity with excitation at 400-440 nm owing to an increase in the surface density of the chromophores in the petroleum film. The surface pressure and the fluorescence microscopy data pointed to self-assembling domains into a pseudophase in thermodynamic equilibrium with other less emitting petroleum components. This hypothesis was supported by Brewster angle microscopy images, whereby the appearance of water domains even at high surface pressures confirms the tendency of petroleum to stabilize emulsion systems. The results presented here suggest that, for understanding the interaction with water, it may be more appropriate to use the whole petroleum samples rather than its fractions.

  4. Langmuir mixing effects on global climate: WAVEWATCH III in CESM

    NASA Astrophysics Data System (ADS)

    Li, Qing; Webb, Adrean; Fox-Kemper, Baylor; Craig, Anthony; Danabasoglu, Gokhan; Large, William G.; Vertenstein, Mariana

    2016-07-01

    Large-Eddy Simulations (LES) have shown the effects of ocean surface gravity waves in enhancing the ocean boundary layer mixing through Langmuir turbulence. Neglecting this Langmuir mixing process may contribute to the common shallow bias in mixed layer depth in regions of the Southern Ocean and the Northern Atlantic in most state-of-the-art climate models. In this study, a third generation wave model, WAVEWATCH III, has been incorporated as a component of the Community Earth System Model, version 1.2 (CESM1.2). In particular, the wave model is now coupled with the ocean model through a modified version of the K-Profile Parameterization (KPP) to approximate the influence of Langmuir mixing. Unlike past studies, the wind-wave misalignment and the effects of Stokes drift penetration depth are considered through empirical scalings based on the rate of mixing in LES. Wave-Ocean only experiments show substantial improvements in the shallow biases of mixed layer depth in the Southern Ocean. Ventilation is enhanced and low concentration biases of pCFC-11 are reduced in the Southern Hemisphere. A majority of the improvements persist in the presence of other climate feedbacks in the fully coupled experiments. In addition, warming of the subsurface water over the majority of global ocean is observed in the fully coupled experiments with waves, and the cold subsurface ocean temperature biases are reduced.

  5. Thermal behavior of H-aggregate in a mixed Langmuir-Blodgett film of merocyanine dye, arachidic acid, and n-octadecane ternary system investigated by UV-visible and IR absorption spectroscopy.

    PubMed

    Hirano, Yoshiaki; Tateno, Shinsuke; Yamashita, Yoshihide; Ozaki, Yukihiro

    2008-11-13

    We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.

  6. Sungrazing comets: Probing the inner extremes of the Solar System

    NASA Astrophysics Data System (ADS)

    Knight, M.

    2014-07-01

    /Machholz 1. The third group, Meyer, has not been linked to any known solar system object and has an unknown orbital period. The remaining known sungrazing comets have a variety of orbits and, with the notable exception of ISON, are generally not observed extensively. Due to their extreme orbits, sungrazing comets offer unique opportunities for understanding evolutionary processes in our solar system. During their perihelion passages they experience equilibrium temperatures exceeding 1500 K, resulting in sublimation of their dust and potentially allowing the least volatile components of our solar system to be cataloged. In fact, while all of the near-Sun objects discovered by SOHO and STEREO are designated ''comets'', many of those not associated with other known cometary objects may be asteroids or defunct comets whose apparent activity at these distances is due to sublimation of their bare surfaces. Sungrazing comets also experience strong tidal forces, resulting in frequent fragmentation. Such breakups expose the unprocessed interiors, potentially allowing intercomparison of the compositions of discrete fragments and revealing the size distribution of the planetessimals out of which the parent comet formed. Finally, it has recently become possible to use comets as ''solar probes'', treating them as test particles that can reveal properties of the solar environment such as the coronal temperature and density, magnetic field strength, and solar wind speed and direction.

  7. Langmuir and Langmuir-Blodgett films of a maleic anhydride derivative: effect of subphase divalent cations.

    PubMed

    Martín-García, B; Velázquez, M Mercedes; Pérez-Hernández, J A; Hernández-Toro, J

    2010-09-21

    We report the study of the equilibrium and dynamic properties of Langmuir monolayers of poly(styrene-co-maleic anhydride) partial 2-buthoxyethyl ester cumene terminated polymer and the effect of the Mg(NO(3))(2) addition in the water subphase on the film properties. Results show that the polymer monolayer becomes more expanded when the electrolyte concentration in the subphase increases. Dense polymer films aggregate at the interface. The aggregates are transferred onto silicon wafers using the Langmuir-Blodgett methodology and the morphology is observed by AFM. The structure of aggregates depends on the subphase composition of the Langmuir film transferred onto the silicon wafer.

  8. Systems-level study of a nonsurvivable Jupiter turbopause probe. Volume 1: Summary

    NASA Technical Reports Server (NTRS)

    Wiltshire, R. S.

    1972-01-01

    The design of a space probe to explore the atmosphere of the planet Jupiter is discussed. Five major areas were considered: (1) definition of science requirements, (2) mission evaluation, (3) definition of probe system, (4) definition of spacecraft support requirements, and (5) nonequilibrium flow field analysis for communications blackout evaluation. The overall mission and system design are emphasized. The integration of the various technologies into complete systems designs is described. Results showed that a nonsurvivable turbopause probe mission to Jupiter with adequate data return to meet the science objectives is feasible and practical.

  9. Nanopatterned cadmium selenide Langmuir-Blodgett platform for leukemia detection.

    PubMed

    Sharma, Aditya; Pandey, Chandra M; Matharu, Zimple; Soni, Udit; Sapra, Sameer; Sumana, Gajjala; Pandey, Manoj K; Chatterjee, Tathagat; Malhotra, Bansi D

    2012-04-03

    We present results of the studies relating to preparation of Langmuir-Blodgett (LB) monolayers of tri-n-octylphosphine oxide-capped cadmium selenide quantum dots (QCdSe) onto indium-tin oxide (ITO) coated glass substrate. The monolayer behavior has been studied at the air-water interface under various subphase conditions. This nanopatterned platform has been explored to fabricate an electrochemical DNA biosensor for detection of chronic myelogenous leukemia (CML) by covalently immobilizing the thiol-terminated oligonucleotide probe sequence via a displacement reaction. The results of electrochemical response studies reveal that this biosensor can detect target DNA in the range of 10(-6) to 10(-14) M within 120 s, has a shelf life of 2 months, and can be used about 8 times. Further, this nucleic acid sensor has been found to distinguish the CML-positive and the control negative clinical patient samples.

  10. Observations of Langmuir Circulation From FLIP

    NASA Astrophysics Data System (ADS)

    Smith, J. A.

    2002-12-01

    Langmuir circulation has significance across the marine disciplines. Enhanced deepening and inhibited re-stratification can alter the surface temperature and hence net air-sea exchanges. Organization of bubbles into windrows introduces dramatic sound speed variability and also affects air/sea gas fluxes. Organization of seaweed and plankton affects marine life, including pelagic fisheries. Finally, dispersal by Langmuir circulation is a major component in models for oil-spill tracking and for search-and-rescue operations. To get an adequate picture of the forcing and response of Langmuir circulation (and the wind-mixed layer in general), the observations needed include windstress, directional waves, wave breaking, heat and moisture fluxes, stratification (temperature and salinity profiles), velocity profiles across the mixed layer and thermocline, spacing and orientation of windrows, and a measure of the strength of the circulation (e.g., surface rms velocities). These measurements span both the air/sea interface and the thermocline, and must be maintained continuously for many days to span storms and daily, tidal, and inertial cycles. In addition, the total power requirements exceed that comfortably supplied by batteries or local generation by wind or solar energy. It appears that FLIP is uniquely qualified as a platform from which the required range of measurements may all be made. Findings concerning the evolution and dynamics of Langmuir circulation that were facilitated by FLIP are reviewed and summarized, with emphasis on observations from 1990, 1995, and 2002.

  11. Nonlinear, relativistic Langmuir waves in astrophysical magnetospheres

    NASA Technical Reports Server (NTRS)

    Chian, Abraham C.-L.

    1987-01-01

    Large amplitude, electrostatic plasma waves are relevant to physical processes occurring in the astrophysical magnetospheres wherein charged particles are accelerated to relativistic energies by strong waves emitted by pulsars, quasars, or radio galaxies. The nonlinear, relativistic theory of traveling Langmuir waves in a cold plasma is reviewed. The cases of streaming electron plasma, electronic plasma, and two-streams are discussed.

  12. Ultrasonic probe system for the bore-side inspection of tubes and welds therein

    DOEpatents

    Cook, K. Von; Koerner, Dan W.; Cunningham, Jr., Robert A.; Murrin, Jr., Horace T.

    1977-07-26

    A probe system is provided for the bore-side inspection of tube-to-header welds and the like for small diameter tubes. The probe head of the system includes an ultrasonic transmitter-receiver transducer, a separate ultrasonic receiver, a reflector associated with the transducer to properly orient the ultrasonic signal with respect to a tube wall, a baffle to isolate the receiver from the transducer, and means for maintaining the probe head against the tube wall under investigation. Since the probe head must rotate to inspect along a helical path, special ultrasonic signal connections are employed. Through the use of the probe, flaws at either the inner or outer surfaces may be detected.

  13. A heavy ion beam probe system for investigation of a modified Penning discharge

    NASA Technical Reports Server (NTRS)

    Kambic, G. X.; Krawczonek, W. M.

    1977-01-01

    An ion beam probe diagnostic system can measure time- and space-resolved profiles of plasma space potential and electron density. In combination with a computer iterative technique, the ion beam probe can determine both the space potential profile in plasmas containing strong electric fields and potentials comparable in magnitude to the energy of the probing ion beam. During ion beam probing of a modified Penning discharge, several groups of secondary ions were observed coming from the plasma with a fixed primary beam energy and momentum. The energies of these ions were within 10 percent of the values predicted by a computer-generated model of the potential profile in the plasma. The mechanical and electronic components of the system are described, with particular emphasis on those features required to probe plasma potentials comparable in magnitude to the ion beam energy.

  14. Probing nanoscale oxygen ion motion in memristive systems

    NASA Astrophysics Data System (ADS)

    Yang, Yuchao; Zhang, Xiaoxian; Qin, Liang; Zeng, Qibin; Qiu, Xiaohui; Huang, Ru

    2017-05-01

    Ion transport is an essential process for various applications including energy storage, sensing, display, memory and so on, however direct visualization of oxygen ion motion has been a challenging task, which lies in the fact that the normally used electron microscopy imaging mainly focuses on the mass attribute of ions. The lack of appropriate understandings and analytic approaches on oxygen ion motion has caused significant difficulties in disclosing the mechanism of oxides-based memristors. Here we show evidence of oxygen ion migration and accumulation in HfO2 by in situ measurements of electrostatic force gradient between the probe and the sample, as systematically verified by the charge duration, oxygen gas eruption and controlled studies utilizing different electrolytes, field directions and environments. At higher voltages, oxygen-deficient nano-filaments are formed, as directly identified employing a CS-corrected transmission electron microscope. This study could provide a generalized approach for probing ion motions at the nanoscale.

  15. Probing nanoscale oxygen ion motion in memristive systems

    PubMed Central

    Yang, Yuchao; Zhang, Xiaoxian; Qin, Liang; Zeng, Qibin; Qiu, Xiaohui; Huang, Ru

    2017-01-01

    Ion transport is an essential process for various applications including energy storage, sensing, display, memory and so on, however direct visualization of oxygen ion motion has been a challenging task, which lies in the fact that the normally used electron microscopy imaging mainly focuses on the mass attribute of ions. The lack of appropriate understandings and analytic approaches on oxygen ion motion has caused significant difficulties in disclosing the mechanism of oxides-based memristors. Here we show evidence of oxygen ion migration and accumulation in HfO2 by in situ measurements of electrostatic force gradient between the probe and the sample, as systematically verified by the charge duration, oxygen gas eruption and controlled studies utilizing different electrolytes, field directions and environments. At higher voltages, oxygen-deficient nano-filaments are formed, as directly identified employing a CS-corrected transmission electron microscope. This study could provide a generalized approach for probing ion motions at the nanoscale. PMID:28469257

  16. Probing nanoscale oxygen ion motion in memristive systems.

    PubMed

    Yang, Yuchao; Zhang, Xiaoxian; Qin, Liang; Zeng, Qibin; Qiu, Xiaohui; Huang, Ru

    2017-05-04

    Ion transport is an essential process for various applications including energy storage, sensing, display, memory and so on, however direct visualization of oxygen ion motion has been a challenging task, which lies in the fact that the normally used electron microscopy imaging mainly focuses on the mass attribute of ions. The lack of appropriate understandings and analytic approaches on oxygen ion motion has caused significant difficulties in disclosing the mechanism of oxides-based memristors. Here we show evidence of oxygen ion migration and accumulation in HfO2 by in situ measurements of electrostatic force gradient between the probe and the sample, as systematically verified by the charge duration, oxygen gas eruption and controlled studies utilizing different electrolytes, field directions and environments. At higher voltages, oxygen-deficient nano-filaments are formed, as directly identified employing a CS-corrected transmission electron microscope. This study could provide a generalized approach for probing ion motions at the nanoscale.

  17. Basic Questions About the Solar System: The Need for Probes

    NASA Technical Reports Server (NTRS)

    Ingersoll, Andrew P.

    2005-01-01

    Probes are an essential element in the scientific study of planets with atmospheres. In-situ measurements provide the most accurate determination of composition, winds, temperatures, clouds, and radiative fluxes. They address fundamental NASA objectives concerning volatile compounds, climate, and the origin of life. Probes also deliver landers and aerobots that help in the study of planetary surfaces. This talk focuses on Venus, Titan, and the giant planets. I review the basic science questions and discuss the recommended missions. I stress the need for a balanced program that includes an array of missions that increase in size by factors of two. Gaps in this array lead to failures and cancellations that are harmful to the program and to scientific exploration.

  18. STEREO database of interplanetary Langmuir electric waveforms

    NASA Astrophysics Data System (ADS)

    Briand, C.; Henri, P.; Génot, V.; Lormant, N.; Dufourg, N.; Cecconi, B.; Nguyen, Q. N.; Goetz, K.

    2016-02-01

    This paper describes a database of electric waveforms that is available at the Centre de Données de la Physique des Plasmas (CDPP, http://cdpp.eu/). This database is specifically dedicated to waveforms of Langmuir/Z-mode waves. These waves occur in numerous kinetic processes involving electrons in space plasmas. Statistical analysis from a large data set of such waves is then of interest, e.g., to study the relaxation of high-velocity electron beams generated at interplanetary shock fronts, in current sheets and magnetic reconnection region, the transfer of energy between high and low frequencies, the generation of electromagnetic waves. The Langmuir waveforms were recorded by the Time Domain Sampler (TDS) of the WAVES radio instrument on board the STEREO mission. In this paper, we detail the criteria used to identify the Langmuir/Z-mode waves among the whole set of waveforms of the STEREO spacecraft. A database covering the November 2006 to August 2014 period is provided. It includes electric waveforms expressed in the normalized frame (B,B × Vsw,B × (B × Vsw)) with B and Vsw the local magnetic field and solar wind velocity vectors, and the local magnetic field in the variance frame, in an interval of ±1.5 min around the time of the Langmuir event. Quicklooks are also provided that display the three components of the electric waveforms together with the spectrum of E∥, together with the magnitude and components of the magnetic field in the 3 min interval, in the variance frame. Finally, the distribution of the Langmuir/Z-mode waves peak amplitude is also analyzed.

  19. Study of a high-resolution PET system using a Silicon detector probe

    NASA Astrophysics Data System (ADS)

    Brzeziński, K.; Oliver, J. F.; Gillam, J.; Rafecas, M.

    2014-10-01

    A high-resolution silicon detector probe, in coincidence with a conventional PET scanner, is expected to provide images of higher quality than those achievable using the scanner alone. Spatial resolution should improve due to the finer pixelization of the probe detector, while increased sensitivity in the probe vicinity is expected to decrease noise. A PET-probe prototype is being developed utilizing this principle. The system includes a probe consisting of ten layers of silicon detectors, each a 80 × 52 array of 1 × 1 × 1 mm3 pixels, to be operated in coincidence with a modern clinical PET scanner. Detailed simulation studies of this system have been performed to assess the effect of the additional probe information on the quality of the reconstructed images. A grid of point sources was simulated to study the contribution of the probe to the system resolution at different locations over the field of view (FOV). A resolution phantom was used to demonstrate the effect on image resolution for two probe positions. A homogeneous source distribution with hot and cold regions was used to demonstrate that the localized improvement in resolution does not come at the expense of the overall quality of the image. Since the improvement is constrained to an area close to the probe, breast imaging is proposed as a potential application for the novel geometry. In this sense, a simplified breast phantom, adjacent to heart and torso compartments, was simulated and the effect of the probe on lesion detectability, through measurements of the local contrast recovery coefficient-to-noise ratio (CNR), was observed. The list-mode ML-EM algorithm was used for image reconstruction in all cases. As expected, the point spread function of the PET-probe system was found to be non-isotropic and vary with position, offering improvement in specific regions. Increase in resolution, of factors of up to 2, was observed in the region close to the probe. Images of the resolution phantom showed

  20. Mode of interaction of ganglioside Langmuir monolayer originated from echinoderms: three binary systems of ganglioside/DPPC, ganglioside/DMPE, and ganglioside/cholesterol.

    PubMed

    Hoda, Kazuki; Ikeda, Yuriko; Kawasaki, Hideya; Yamada, Koji; Higuchi, Ryuichi; Shibata, Osamu

    2006-09-01

    The surface pressure (pi)-area (A), the surface potential (DeltaV)-A, and the dipole moment (mu( perpendicular))-A isotherms were obtained for monolayers made from a ganglioside originated from echinoderms [Diadema setosum ganglioside (DSG-1)], dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylethanolamine (DMPE), cholesterol (Ch), and their combinations. Monolayers spread on several different substrates were investigated at the air/water interface by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM) and atomic force microscopy (AFM). Surface potentials (DeltaV) of pure components were analyzed using the three-layer model proposed by Demchak and Fort [R.J. Demchak, T. Fort, J. Colloid Interface Sci. 46 (1974) 191-202]. The new finding was that DSG-1 was stable and showed a liquid-expanded film and that its monolayer behavior of DeltaV was sensitive for the change of the NaCl concentration in the subphase. Moreover, the miscibility of DSG-1 and three major lipids in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the DSG-1 molar fraction (X(DSG-1)), using the additivity rule. From the A-X(DSG-1) and DeltaV(m)-X(DSG-1) plots, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible system. The miscibility was also investigated from the two-dimensional phase diagrams. Furthermore, a regular surface mixture, for which the Joos equation was used for the analysis of the collapse pressure of two-component monolayers, allowed calculation of the interaction parameter (xi) and the interaction energy (-Deltavarepsilon) between them. The observations using fluorescence microscopy and AFM image also provide us the miscibility in the monolayer state.

  1. Unmanned Multiple Exploratory Probe System (MEPS) for Mars observation. Volume 2: Calculations and derivations

    NASA Technical Reports Server (NTRS)

    Adams, Daniel E.; Crumbly, Christopher M.; Delp, Steve E.; Guidry, Michelle A.; Lisano, Michael E.; Packard, James D.; Striepe, Scott A.

    1988-01-01

    This volume of the final report on the unmanned Multiple Exploratory Probe System (MEPS) details all calculations, derivations, and computer programs that support the information presented in the first volume.

  2. On statistics of electric field amplitudes in Langmuir turbulence

    NASA Astrophysics Data System (ADS)

    Voshchepynets, Andrii; Volokitin, Alexander; Krasnoselskikh, Vladimir; Krafft, Catherine

    2017-04-01

    A systematic study of the properties of Langmuir wave turbulence generated by electron beams via bump-on-tail instabilities in strongly non-homogeneous plasmas is presented. A statistical analysis of the Langmuir waves' fields' amplitudes using numerical simulations based on two different theoretical models is performed : a probabilistic one and a dynamical one. The former describes the self-consistent dynamics of wave-particle and wave-wave interactions in inhomogeneous plasmas. The latter is a modified version of the standard quasi-linear theory which requires much less computational resources. To analyze the simulation data provided by the probabilistic model, a Pearson technique is used to classify the calculated probability distribution functions (PDFs) of the logarithm of the wave fields' intensities. It is demonstrated that the core parts of the PDFs belong to the Pearson types I, IV and VI distributions, depending on the spatial profiles of the density fluctuations, rather than to the normal distribution. Moreover it is shown that the high-amplitude parts of the PDFs follow power-law or exponential decay distributions, depending on the type of the corresponding cores' distributions. The PDFs of the fields' amplitudes calculated using the numerical simulations based on the dynamical model are in the whole consistent with those provided by the probabilistic model. Moreover, these simulations lead to a series of additional results. First, in the small fields' amplitudes' parts of the PDFs (i.e. in the linear stage of the system's evolution), an universal scaling parameter is found, with a value not depending on the average levels of the density fluctuations and of the Langmuir turbulence. Second, the PDFs are obtained in the presence of wave 28 decay processes, which are not taken into account in the probabilistic model. When those are weak, the PDFs show at large fields' amplitudes an exponential asymptotic behavior; during the time evolution, the

  3. The fast reciprocating magnetic probe system on the J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Li, Fuming; Chen, Zhipeng; Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-01

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  4. The fast reciprocating magnetic probe system on the J-TEXT tokamak.

    PubMed

    Li, Fuming; Chen, Zhipeng; Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-01

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  5. Improved thermometry of low-temperature quantum systems by a ring-structure probe

    NASA Astrophysics Data System (ADS)

    Guo, Li-Sha; Xu, Bao-Ming; Zou, Jian; Shao, Bin

    2015-11-01

    The thermometry precision of a sample is a question of both fundamental and technological importance. In this paper, we consider a ring-structure system as our probe to estimate the temperature of a bath. Based on the Markovian master equation of the probe, we calculate the quantum Fisher information (QFI) of the probe at any time. We find that for the thermal equilibrium thermometry, the ferromagnetic structure can measure a lower temperature of the bath with a higher precision compared with the nonstructure probe, while for the dynamical thermometry, the antiferromagnetic structure can make the QFI of the probe in the dynamical process much larger than that in equilibrium with the bath, which is somewhat counterintuitive. Moreover, the best accuracy for the thermometry achieved in the antiferromagnetic structure case can be much higher than that in the nonstructure case. The physical mechanisms of the above phenomena are given in this paper.

  6. The fast reciprocating magnetic probe system on the J-TEXT tokamak

    SciTech Connect

    Li, Fuming; Chen, Zhipeng Zhuang, Ge; Liu, Hai; Zhu, Lizhi

    2016-11-15

    The fast reciprocating magnetic probe (FRMP) system is newly developed on the Joint Texas Experimental Tokamak (J-TEXT) to measure the local magnetic fluctuations at the plasma edge. The magnetic probe array in the FRMP consists of four 2-dimensional magnetic probes arranged at different radial locations to detect local poloidal and radial magnetic fields. These probes are protected by a graphite and boron nitride casing to improve the frequency response of each probe; they are mounted on the head of a movable rod, which is oriented along radial direction at the top of the torus. In the experiments, multiple core diagnostics show that the insertion of the FRMP has little impact on the equilibrium of the plasma. Local magnetic fluctuations inside the last closed flux surface are successfully measured by the FRMP.

  7. Channel direction information probing for multi-antenna cognitive radio system

    NASA Astrophysics Data System (ADS)

    Yuan, Fang; Villardi, Gabriel Porto; Kojima, Fumihide; Yano, Hiroyuki

    2015-12-01

    This work studies the problem of channel direction information (CDI) probing for multi-antenna cognitive radio system. The CDI of the channel from the secondary transmitter (ST) to primary receiver (PR) is elementary information in designing the beamforming at the ST for mitigating the interference to the PR. However, lacking the explicit cooperation between primary and secondary systems, the CDI has to be acquired by probing at the ST, which is challenging. To solve this, we consider the line of sight (LoS) channel between the ST and the PR, and propose one CDI probing scheme for the ST. Specifically, the ST sends two types of probing signals by beamforming towards an interested region where both the secondary receiver (SR) and the PR are located and then actively learns the hidden feedback information from the primary system to acquire the CDI. The proposed scheme has a closed-form solution, and avoids the iteration between the probing and acquisition, which is desirable for practical system. Moreover, we show that the proposed probing scheme can be extended for primary systems working under multi-access channel and broadcasting channel. Simulation results demonstrate that the proposed scheme can improve the accuracy of the acquired CDI at the ST in cognitive ratio system remarkably.

  8. Fusion Propulson System Requirements for an Interstellar Probe

    NASA Technical Reports Server (NTRS)

    Spencer, D. F.

    1963-01-01

    An examination of the engine constraints for a fusion-propelled vehicle indicates that minimum flight times for a probe to a 5 light-year star will be approximately 50 years. The principal restraint on the vehicle is the radiator weight and size necessary to dissipate the heat which enters the chamber walls from the fusion plasma. However, it is interesting, at least theoretically, that the confining magnetic field strength is of reasonable magnitude, 2 to 3 x 10(exp5) gauss, and the confinement time is approximately 0.1 sec.

  9. Sounding-Rocket Studies of Langmuir-Wave Microphysics in the Auroral Ionosphere

    NASA Astrophysics Data System (ADS)

    Dombrowski, Micah P.

    agreement with expected signatures of beating between pure, field-aligned, linearly polarized Langmuir waves and obliquely propagating, elliptically polarized, hybrid whistler-Langmuir waves. Finally, an autonomous digital signal processor/receiver has been refined and augmented to achieve high time- and frequency-resolution radio observations, synchronized sampling between multiple receivers, and on-board processing of data. This system was deployed on the CHARM-II rocket, resulting in measurements of the polarization of fine structures in auroral roar emissions.

  10. Multiphoton microscopy system with a compact fiber-based femtosecond-pulse laser and handheld probe

    PubMed Central

    Liu, Gangjun; Kieu, Khanh; Wise, Frank W.; Chen, Zhongping

    2012-01-01

    We report on the development of a compact multiphoton microscopy (MPM) system that integrates a compact and robust fiber laser with a miniature probe. The all normal dispersion fiber femtosecond laser has a central wavelength of 1.06 μm, pulse width of 125 fs and average power of more than 1 W. A double cladding photonic crystal fiber was used to deliver the excitation beam and to collect the two-photon signal. The hand-held probe included galvanometer-based mirror scanners, relay lenses and a focusing lens. The packaged probe had a diameter of 16 mm. Second harmonic generation (SHG) images and two-photon excited fluorescence (TPEF) images of biological tissues were demonstrated using the system. MPM images of different biological tissues acquired by the compact system which integrates an FBFP laser, an DCPCF and a miniature handheld probe. PMID:20635426

  11. Langmuir Circulations in a Coastal Environment During CBLAST

    DTIC Science & Technology

    2004-09-01

    dynamical cascade from smaller scales towards dominant larger scales. Langmuir (1938) and the most of the following studies related the spacing (L...MOTIVATION OF THIS STUDY .................................................................1 II. TURBULENCE FLOW AND LANGMUIR CIRCULATIONS...detection algorithm of upwelling / downwelling regions related to Langmuir circulations

  12. Irving Langmuir and the light bulb

    NASA Astrophysics Data System (ADS)

    Lister, Graeme

    2009-02-01

    Irving Langmuir's principal contribution to lighting was a major improvement in the efficiency of the incandescent lamp. He also used experiments on these lamps to provide fundamental new insight into a number of other areas of physics, including evaporation of metals, the space charge limited current in a vacuum and thermionic emission of electrons from metallic surfaces. This paper describes his experiments, and the chain of ideas which led him to new discoveries.

  13. Langmuir Films of Polycyclic Molecules on Mercury

    SciTech Connect

    Tamam,L.; Kraack, H.; Sloutskin, E.; Ocko, B.; Pershan, P.; Deutsch, M.

    2007-01-01

    Langmuir films (LFs) of biphenyl and anthracene derivatives on the surface of liquid mercury were studied by surface-specific X-ray and surface tension measurements. Phases of lying-down, side-lying and standing-up molecules were found, some of which exhibit long-range lateral order. The molecular symmetry and the position and nature of the side-, end-, and headgroups are shown to dominate the structural evolution of the LFs with surface coverage.

  14. Caviton dynamics in strong Langmuir turbulence

    SciTech Connect

    DuBois, D.; Rose, H.A.; Russell, D.

    1989-01-01

    Recent studies based on long time computer simulations of Langmuir turbulence as described by Zakharov's model will be reviewed. These show that for strong to moderate ion sound samping the turbulent energy is dominantly in nonlinear ''caviton'' excitations which are localized in space and time. A local caviton model will be presented which accounts for the nucleation-collapse-burnout cycles of individual cavitons as well as their space-time correlations. This model is in detailed agreement with many features of the electron density fluctuation spectra in the ionosphere modified by powerful hf waves as measured by incoherent scatter radar. Recently such observations have verified a prediction of the theory that ''free'' Langmuir waves are emitted in the caviton collapse process. These observations and theoretical considerations also strongly imply that cavitons in the heated ionosphere, under certain conditions, evolve to states in which they are ordered in space and time. The sensitivity of the high frequency Langmuir field dynamics to the low frequency ion density fluctuations and the related caviton nucleation process will be discussed. 40 refs., 19 figs.

  15. Dynamics of cavitons in strong Langmuir turbulence

    SciTech Connect

    DuBois, D.F.; Rose, H.A.; Russell, D.

    1990-01-01

    Recent studies of Langmuir turbulence as described by Zakharov's model will be reviewed. For parameters of interest in laser-plasma experiments and for ionospheric hf heating experiments a significant fraction of the turbulent energy is in nonlinear caviton'' excitations which are localized in space and time. A local caviton model will be presented which accounts for the nucleation-collapse-burnout cycles of individual cavitons as well as their space-time correlations. This model is in detailed agreement with many features of the electron density fluctuation spectra in the ionosphere modified by powerful hf waves as measured by incoherent scatter radar. Recently such observations have verified a prediction of the theory that free'' Langmuir waves are emitted in the caviton collapse process. Observations and theoretical considerations also imply that when the pump frequency is slightly lower than the ambient electron plasma frequency cavitons may evolve to states in which they are ordered in space and time. The sensitivity of the high frequency Langmuir field dynamics to the low frequency ion density fluctuations and the related caviton nucleation process will be discussed. 42 refs., 12 figs.

  16. Langmuir-Blodgett films - From micron to angstrom

    NASA Astrophysics Data System (ADS)

    Bourdieu, L.; Silberzan, P.; Chatenay, D.

    1991-10-01

    Combining optical microscopy and atomic force microscopy, a complete characterization of Langmuir-Blodgett bilayers made of arachidic acid has been performed. At macroscopic scales, both techniques can be used to control the homogeneity of the transferred films. By atomic force microscopy, roughness and thickness of the bilayers could be determined. These are compatible with a normal orientation of the fully extended aliphatic chains with respect to the substrate. Molecular-resolution images give the first direct experimental evidence for the presence of pairs of dislocations in those systems.

  17. Miniaturized probe based on a microelectromechanical system mirror for multiphoton microscopy

    PubMed Central

    Jung, Woonggyu; Tang, Suo; McCormic, Daniel T.; Xie, Tiquiang; Ahn, Yeh-Chan; Su, Jianping; Tomov, Ivan V.; Krasieva, Tatiana B.; Tromberg, Bruce J.; Chen, Zhongping

    2008-01-01

    A factor that limits the use of multiphoton microscopy (MPM) in clinical and preclinical studies is the lack of a compact and flexible probe. We report on a miniaturized MPM probe employing a microelectromechanical system (MEMS) scanning mirror and a double-clad photonic crystal fiber (DCPCF). The use of a MEMS mirror and a DCPCF provides many advantages, such as size reduction, rapid and precise scanning, efficient delivery of short pulses, and high collection efficiency of fluorescent signals. The completed probe was 1 cm in outer diameter and 14 cm in length. The developed probe was integrated into an MPM system and used to image fluorescent beads, paper, and biological specimens. PMID:18552946

  18. Common-path optical coherence tomography using a microelectromechanical-system-based endoscopic probe.

    PubMed

    Wang, Donglin; Duan, Can; Zhang, Xiaoyang; Yun, Zhao; Pozzi, Antonio; Xie, Huikai

    2016-09-01

    This paper presents a common-path (CP) swept-source optical coherence tomography (SSOCT) system based on a special endoscopic probe design with an in-line internal reflection as the reference and a two-axis electrothermal microelectromechanical system mirror for image scanning. The rear surface of a gradient reflective index (GRIN) lens inside the probe is set as the reference reflection plane. The length of the GRIN lens is optimized to eliminate the artifacts in SSOCT images successfully. Doppler OCT is also demonstrated based on the CP endoscopic probe. The diameter of the probe is only 2.5 mm, so it can be easily inserted into the biopsy channel of traditional endoscopes to access human internal organs for in vivo diagnoses.

  19. Compact probing system using remote imaging for industrial plant maintenance

    NASA Astrophysics Data System (ADS)

    Ito, F.; Nishimura, A.

    2014-03-01

    Laser induced breakdown spectroscopy (LIBS) and endoscope observation were combined to design a remote probing device. We use this probing device to inspect a crack of the inner wall of the heat exchanger. Crack inspection requires speed at first, and then it requires accuracy. Once Eddy Current Testing (ECT) finds a crack with a certain signal level, another method should confirm it visually. We are proposing Magnetic particle Testing (MT) using specially fabricated the Magnetic Particle Micro Capsule (MPMC). For LIBS, a multichannel spectrometer and a Q-switch YAG laser were used. Irradiation area is 270 μm, and the pulse energy was 2 mJ. This pulse energy corresponds to 5-2.2 MW/cm2. A composite-type optical fiber was used to deliver both laser energy and optical image. Samples were prepared to heat a zirconium alloy plate by underwater arc welding in order to demonstrate severe accidents of nuclear power plants. A black oxide layer covered the weld surface and white particles floated on water surface. Laser induced breakdown plasma emission was taken into the spectroscope using this optical fiber combined with telescopic optics. As a result, we were able to simultaneously perform spectroscopic measurement and observation. For MT, the MPMC which gathered in the defective area is observed with this fiber. The MPMC emits light by the illumination of UV light from this optical fiber. The size of a defect is estimated with this amount of emission. Such technology will be useful for inspection repair of reactor pipe.

  20. Thermal characteristics of sapphire contact probe delivery systems for laser angioplasty.

    PubMed

    Ashley, S; Brooks, S G; Gehani, A A; Kester, R C; Rees, M R

    1990-01-01

    Contact probes made from synthetic sapphire crystal, designed for general laser surgery, are currently being evaluated for use in laser angioplasty. Their mode of action and safety in the context of arterial recanalisation is unknown, particularly with respect to the degree of probe and catheter heating. Infrared thermal imaging was used to investigate the surface temperature rise of various rounded sapphire probes during emission of continuous wave Nd-YAG (1,064 nm) laser energy. Catheter safety was addressed by analyzing the temperature of the metal interface between the optical fiber and sapphire, as well as the catheter proximal to this junction. Transmission of Nd-YAG energy through each probe was also measured. Five rounded probes of 1.8-3.0 mm diameter (three supplied by Surgical Laser Technologies [SLT], two by Living Technology [LT]), along with their respective optical catheters, were compared. There was a large temperature gradient between the front and rim of the probes. The maximum surface temperature rise of the sapphire (at 20 W, 5-second exposure) was 314-339 degrees C (SLT) and 90-108 degrees C (LT) [P less than 0.001, 3-way ANOVA]. The reason for this difference may be related to "crazing" of the front surface of the SLT sapphires. At all energy levels sapphire temperatures were considerably lower than attained by metal laser thermal angioplasty probes. Forward transmission was slightly higher in the SLT probes (75-85%) than the LT sapphires (54-69%). With fiber perfusion at 2 ml/minute, a minor degree of heating of the metal sapphire holders was recorded (maximum rise 35 degrees C), but heating of the catheter proximal to this was negligible. Therefore, it would appear that the risk of tip detachment or arterial injury due to heating of the connecting metal interface is extremely low. Without perfusion, however, there was a greater degree of interface heating in the LT delivery system suggestive of more laser backscattering by these sapphires

  1. Bulk organisation and alignment in Langmuir and Langmuir-Blodgett films of tetrachloroperylene tetracarboxylic acid esters

    NASA Astrophysics Data System (ADS)

    Modlińska, Anna; Filipowicz, Marek; Martyński, Tomasz

    2016-12-01

    Perylene derivatives with chlorine atoms attached at the bay position to the dye core are expected to affect organisation and tendency to aggregation in Langmuir and Langmuir-Blodgett (LB) films. Therefore, newly synthesized core-twisted homologous series of tetrachloroperylene tetracarboxylic acid esters with n = 1,4,5,6,9 carbon atoms in terminal alkyl chains were studied. Phase transitions and crystalline structures were specified by differential scanning calorimetry (DSC) and single crystal X-ray diffraction (XRD), respectively. Intermolecular interactions and organisation of the dyes in monomolecular films were investigated by means of Brewster angle microscope (BAM), UV-Vis absorption and emission spectroscopy, fluorescence microscopy and atomic force microscopy (AFM). The dyes investigated do not form thermotropic mesogenic phases in bulk. The crystalline triclinic elementary cell with P-1 symmetry is revealed from X-ray experiments. In Langmuir and Langmuir-Blodgett films molecular tilted head-on alignment is postulated. Spectroscopic research confirmed by AFM texture images of the LB films show that in the Langmuir and LB films the dyes, depending on length of terminal chains, have a tendency to create H or I molecular aggregates. The impact of the twisted core on the molecular behavior in a bulk and thin films is discussed.

  2. Oxygen transport as a structure probe for heterogeneous polymeric systems

    NASA Astrophysics Data System (ADS)

    Hu, Yushan

    Although permeability of small molecules is often measured as an important performance property, deeper analysis of the transport characteristics provides insight into polymer structure, especially if used in combination with other characterization techniques. Transport of small gas molecules senses the permeable amorphous structure and probes the nature of free volume. This work focuses on oxygen transport, supplemented with other methods of physical analysis, as a probe for: (1) the nature of free volume and crystalline morphology in the crystallized glassy state, (2) the nature of free volume and hierarchical structure in liquid crystalline polymers, and (3) the role of dispersed polyamide phase geometry on oxygen barrier properties of poly(ethylene terephthalate) (PET)/polyamide blends. In the first part, the improvement in oxygen-barrier properties of glassy polyesters by crystallization was examined. Examples included poly(ethylene naphthalate) (PEN), and a copolymer based on PET in which 55 mol% terephthalate was replaced with 4,4'-bibenzoate. Explanation of the unexpectedly high solubility of crystallized PEN required a two-phase transport model consisting of an impermeable crystalline phase of constant density and a permeable amorphous phase of variable density. The resulting relationship between oxygen solubility and amorphous phase density was consistent with free volume concepts of gas sorption. In the second part, oxygen barrier properties of liquid crystalline (LC) polyesters based on poly(diethylene glycol 4,4'-bibenzoate) (PDEGBB) were studied. This study extended the 2-phase transport model for oxygen transport of non-LC crystalline polymers to a smectic LCP. It was possible to systematically vary the solid state structure of (PDEGBB) from LC glass to crystallized LC glass. The results were consistent with a liquid crystalline state intermediate between the permeable amorphous glass and the impermeable 3-dimensional crystal. In this interpretation

  3. RECON - A new system for probing the outer solar system with stellar occultations

    NASA Astrophysics Data System (ADS)

    Buie, M. W.; Keller, J. M.; Wasserman, L. H.

    2015-10-01

    The Research and Education Collaborative Occultation Network (RECON) is a new system for coordinated occultation observations of outer solar system objects. Occultations by objects in the outer solar system are more difficult to predict due to their large distance and limited duration of the astrometric data used to determine their orbits and positions. This project brings together the research and educational community into a unique citizen-science partnership to overcome the difficulties of observing these distant objects. The goal of the project is to get sizes and shapes for TNOs with diameters larger than 100 km. As a result of the system design it will also serve as a probe for binary systems with spatial separations too small to be resolved directly. Our system takes the new approach of setting up a large number of fixed observing stations and letting the shadows come to the network. The nominal spacing of the stations is 50 km. The spread of the network is roughly 2000 km along a roughly north-south line in the western United States. The network contains 56 stations that are committed to the project and we get additional ad hoc support from the International Occultation Timing Association. At our minimum size, two stations will record an event while the other stations will be probing for secondary events. Larger objects will get more chords and will allow determination of shape profiles. The stations are almost exclusively sited and associated with schools, usually at the 9-12 grade level. We have successfully completed our first TNO observation which is presented in the compainion paper by G. Rossi et al (this conference).

  4. Flight Performance of Gravity Probe B Cryogenic System

    NASA Astrophysics Data System (ADS)

    Murray, D. O.; Taber, M. A.; Burns, K. M.

    2006-04-01

    Gravity Probe B (GP-B) is a cryogenic and space-based test of Einstein's General Theory of Relativity by means of precision gyroscopes, The GP-B spacecraft was launched into a polar orbit from Vandenberg AFB on April 20, 2004. The launch and operation of GP-B represented the culmination of forty years of planning, technology development, hardware fabrication, and testing. The superfluid liquid helium became depleted on September 29, 2005, giving a lifetime of 17.3 months compared to the requirement of 16.5 months and a thermal model prediction of 16.6 months. The flight dewar contained 2320 liters of ~1.8 K superfluid helium at launch and housed the science instrument consisting of four precision gyroscopes and a telescope. A porous plug phase separator effected the venting of the helium boiloff gas. This venting helium was used to operate 16 thrusters, which are the actuators that effect precision pointing on a fixed star and adjust the orbit to be drag free or close to true zero-g.

  5. Isokinetic TWC Evaporator Probe: Calculations and Systemic Uncertainty Analysis

    NASA Technical Reports Server (NTRS)

    Davison, Craig R.; Strapp, J. Walter; Lilie, Lyle; Ratvasky, Thomas P.; Dumont, Christopher

    2016-01-01

    A new Isokinetic Total Water Content Evaporator (IKP2) was downsized from a prototype instrument, specifically to make airborne measurements of hydrometeor total water content (TWC) in deep tropical convective clouds to assess the new ice crystal Appendix D icing envelope. The probe underwent numerous laboratory and wind tunnel investigations to ensure reliable operation under the difficult high altitude/speed/TWC conditions under which other TWC instruments have been known to either fail, or have unknown performance characteristics and the results are presented in a companion paper. This paper presents the equations used to determine the total water content (TWC) of the sampled atmosphere from the values measured by the IKP2 or necessary ancillary data from other instruments. The uncertainty in the final TWC is determined by propagating the uncertainty in the measured values through the calculations to the final result. Two techniques were used and the results compared. The first is a typical analytical method of propagating uncertainty and the second performs a Monte Carlo simulation. The results are very similar with differences that are insignificant for practical purposes. The uncertainty is between 2 percent and 3 percent at most practical operating conditions. The capture efficiency of the IKP2 was also examined based on a computational fluid dynamic simulation of the original IKP and scaled down to the IKP2. Particles above 24 microns were found to have a capture efficiency greater than 99 percent at all operating conditions.

  6. Isokinetic TWC Evaporator Probe: Calculations and Systemic Uncertainty Analysis

    NASA Technical Reports Server (NTRS)

    Davison, Craig R.; Strapp, John W.; Lilie, Lyle E.; Ratvasky, Thomas P.; Dumont, Christopher

    2016-01-01

    A new Isokinetic Total Water Content Evaporator (IKP2) was downsized from a prototype instrument, specifically to make airborne measurements of hydrometeor total water content (TWC) in deep tropical convective clouds to assess the new ice crystal Appendix D icing envelope. The probe underwent numerous laboratory and wind tunnel investigations to ensure reliable operation under the difficult high altitude/speed/TWC conditions under which other TWC instruments have been known to either fail, or have unknown performance characteristics and the results are presented in a companion paper (Ref. 1). This paper presents the equations used to determine the total water content (TWC) of the sampled atmosphere from the values measured by the IKP2 or necessary ancillary data from other instruments. The uncertainty in the final TWC is determined by propagating the uncertainty in the measured values through the calculations to the final result. Two techniques were used and the results compared. The first is a typical analytical method of propagating uncertainty and the second performs a Monte Carlo simulation. The results are very similar with differences that are insignificant for practical purposes. The uncertainty is between 2 and 3 percent at most practical operating conditions. The capture efficiency of the IKP2 was also examined based on a computational fluid dynamic simulation of the original IKP and scaled down to the IKP2. Particles above 24 micrometers were found to have a capture efficiency greater than 99 percent at all operating conditions.

  7. Langmuir wave electric fields induced by electron beams in the heliosphere

    NASA Astrophysics Data System (ADS)

    Reid, Hamish A. S.; Kontar, Eduard P.

    2017-01-01

    Solar electron beams responsible for type III radio emission generate Langmuir waves as they propagate out from the Sun. The Langmuir waves are observed via in situ electric field measurements. These Langmuir waves are not smoothly distributed but occur in discrete clumps, commonly attributed to the turbulent nature of the solar wind electron density. Exactly how the density turbulence modulates the Langmuir wave electric fields is understood only qualitatively. Using weak turbulence simulations, we investigate how solar wind density turbulence changes the probability distribution functions, mean value and variance of the beam-driven electric field distributions. Simulations show rather complicated forms of the distribution that are dependent upon how the electric fields are sampled. Generally the higher magnitude of density fluctuations reduce the mean and increase the variance of the distribution in a consistent manor to the predictions from resonance broadening by density fluctuations. We also demonstrate how the properties of the electric field distribution should vary radially from the Sun to the Earth and provide a numerical prediction for the in situ measurements of the upcoming Solar Orbiter and Solar Probe Plus spacecraft.

  8. Use of the WECC WAMS in Wide Area Probing Tests for Validation of System Performance & Modeling

    SciTech Connect

    Hauer, John F.; Mittelstadt, William; Martin, Kenneth E.; Burns, J. W.; Lee, Harry; Pierre, John W.; Trudnowski, Daniel

    2009-02-01

    During 2005 and 2006 the Western Electricity Coordinating Council (WECC) performed three major tests of western system dynamics. These tests used a Wide Area Measurement System (WAMS) based primarily on Phasor Measurement Units (PMUs) to determine response to events including the insertion of the 1400-MW Chief Joseph braking resistor, probing signals, and ambient events. Test security was reinforced through real-time analysis of wide area effects, and high-quality data provided dynamic profiles for interarea modes across the entire western interconnection. The tests established that low-level optimized pseudo-random ±20-MW probing with the Pacific DC Intertie (PDCI) roughly doubles the apparent noise that is natural to the power system, providing sharp dynamic information with negligible interference to system operations. Such probing is an effective alternative to use of the 1400-MW Chief Joseph dynamic brake, and it is under consideration as a standard means for assessing dynamic security.

  9. Systems vaccinology: Probing humanity’s diverse immune systems with vaccines

    PubMed Central

    Pulendran, Bali

    2014-01-01

    Homo sapiens are genetically diverse, but dramatic demographic and socioeconomic changes during the past century have created further diversification with respect to age, nutritional status, and the incidence of associated chronic inflammatory disorders and chronic infections. These shifting demographics pose new challenges for vaccination, as emerging evidence suggests that age, the metabolic state, and chronic infections can exert major influences on the immune system. Thus, a key public health challenge is learning how to reprogram suboptimal immune systems to induce effective vaccine immunity. Recent advances have applied systems biological analysis to define molecular signatures induced early after vaccination that correlate with and predict the later adaptive immune responses in humans. Such “systems vaccinology” approaches offer an integrated picture of the molecular networks driving vaccine immunity, and are beginning to yield novel insights about the immune system. Here we discuss the promise of systems vaccinology in probing humanity’s diverse immune systems, and in delineating the impact of genes, the environment, and the microbiome on protective immunity induced by vaccination. Such insights will be critical in reengineering suboptimal immune systems in immunocompromised populations. PMID:25136102

  10. Monte Carlo studies of model Langmuir monolayers

    NASA Astrophysics Data System (ADS)

    Opps, S. B.; Yang, B.; Gray, C. G.; Sullivan, D. E.

    2001-04-01

    This paper examines some of the basic properties of a model Langmuir monolayer, consisting of surfactant molecules deposited onto a water subphase. The surfactants are modeled as rigid rods composed of a head and tail segment of diameters σhh and σtt, respectively. The tails consist of nt~4-7 effective monomers representing methylene groups. These rigid rods interact via site-site Lennard-Jones potentials with different interaction parameters for the tail-tail, head-tail, and head-head interactions. In a previous paper, we studied the ground-state properties of this system using a Landau approach. In the present paper, Monte Carlo simulations were performed in the canonical ensemble to elucidate the finite-temperature behavior of this system. Simulation techniques, incorporating a system of dynamic filters, allow us to decrease CPU time with negligible statistical error. This paper focuses on several of the key parameters, such as density, head-tail diameter mismatch, and chain length, responsible for driving transitions from uniformly tilted to untilted phases and between different tilt-ordered phases. Upon varying the density of the system, with σhh=σtt, we observe a transition from a tilted (NNN)-condensed phase to an untilted-liquid phase and, upon comparison with recent experiments with fatty acid-alcohol and fatty acid-ester mixtures [M. C. Shih, M. K. Durbin, A. Malik, P. Zschack, and P. Dutta, J. Chem. Phys. 101, 9132 (1994); E. Teer, C. M. Knobler, C. Lautz, S. Wurlitzer, J. Kildae, and T. M. Fischer, J. Chem. Phys. 106, 1913 (1997)], we identify this as the L'2/Ov-L1 phase boundary. By varying the head-tail diameter ratio, we observe a decrease in Tc with increasing mismatch. However, as the chain length was increased we observed that the transition temperatures increased and differences in Tc due to head-tail diameter mismatch were diminished. In most of the present research, the water was treated as a hard surface, whereby the surfactants are only

  11. Monte Carlo studies of model Langmuir monolayers.

    PubMed

    Opps, S B; Yang, B; Gray, C G; Sullivan, D E

    2001-04-01

    This paper examines some of the basic properties of a model Langmuir monolayer, consisting of surfactant molecules deposited onto a water subphase. The surfactants are modeled as rigid rods composed of a head and tail segment of diameters sigma(hh) and sigma(tt), respectively. The tails consist of n(t) approximately 4-7 effective monomers representing methylene groups. These rigid rods interact via site-site Lennard-Jones potentials with different interaction parameters for the tail-tail, head-tail, and head-head interactions. In a previous paper, we studied the ground-state properties of this system using a Landau approach. In the present paper, Monte Carlo simulations were performed in the canonical ensemble to elucidate the finite-temperature behavior of this system. Simulation techniques, incorporating a system of dynamic filters, allow us to decrease CPU time with negligible statistical error. This paper focuses on several of the key parameters, such as density, head-tail diameter mismatch, and chain length, responsible for driving transitions from uniformly tilted to untilted phases and between different tilt-ordered phases. Upon varying the density of the system, with sigma(hh)=sigma(tt), we observe a transition from a tilted (NNN)-condensed phase to an untilted-liquid phase and, upon comparison with recent experiments with fatty acid-alcohol and fatty acid-ester mixtures [M. C. Shih, M. K. Durbin, A. Malik, P. Zschack, and P. Dutta, J. Chem. Phys. 101, 9132 (1994); E. Teer, C. M. Knobler, C. Lautz, S. Wurlitzer, J. Kildae, and T. M. Fischer, J. Chem. Phys. 106, 1913 (1997)], we identify this as the L'(2)/Ov-L1 phase boundary. By varying the head-tail diameter ratio, we observe a decrease in T(c) with increasing mismatch. However, as the chain length was increased we observed that the transition temperatures increased and differences in T(c) due to head-tail diameter mismatch were diminished. In most of the present research, the water was treated as a hard

  12. Modular system for measuring a speech quality in the IP telephony infrastructures using autonomous probes

    NASA Astrophysics Data System (ADS)

    Rezac, Filip; Safarik, Jakub; Macura, Lukas; Rozhon, Jan; Gresak, Erik

    2017-05-01

    The paper deals with a speech quality monitoring system using probes placed on the individual network nodes operating VoIP services. Information on speech quality is measured periodically and the results are then stored on the central server which provides visualization in a form of graph respecting a topology of the probes. Article provides overall description of the technology and algorithms used in the speech quality monitoring system and results achieved in this applied research are verified in real operation. Contribution of the work lies in a proposal of the new multi-agent system enabling speech quality monitoring and in own implementation and its verification in Czech academic network.

  13. Influence of heat treatment in air, and subsequent hydrothermal treatment in the liquid phase or water treatment in the liquid phase on a mixed Langmuir-Blodgett film of merocyanine dye-arachidic acid- n-octadecane ternary system

    NASA Astrophysics Data System (ADS)

    Hirano, Yoshiaki; Maio, Ari; Fukuda, Akira; Kitahama, Yasutaka; Ozaki, Yukihiro

    2010-07-01

    We have investigated the influence of heat treatment in air (HT), and subsequent hydrothermal treatment in the liquid phase (HTTL) or water treatment in the liquid phase (WTL) on the H-aggregate of mixed Langmuir-Blodgett (LB) films of merocyanine dye (MS 18)-arachidic acid (C 20)- n-octadecane (AL 18) ternary system by means of polarized visible and IR absorption spectroscopy. The MS 18 monomer is obtained from the first application of HT to the H-aggregate, and the monomer rapidly changes into the J-aggregate upon subsequent HTTL. This demonstrates variation via the monomer for reorganization of the MS 18 chromophore from H- to J-aggregates induced by directly performing HTTL to the H-aggregate in our previous study. While the number of gauche conformers in the MS 18 hydrocarbon chain increases by initial HT, the hydrocarbon chain adopts an all- trans conformation after subsequent HTTL. In addition, the degree of orientation of the MS 18 hydrocarbon chain after HT also approximates to that before HT. The C 20 hexagonal packing after HT turns to orthorhombic one with subsequent HTTL, and the orientation disorder of C 20 hydrocarbon chain caused by HT is renovated as well. The structural changes in the MS 18 and C 20 hydrocarbon chains resulting from latter HTTL arise from the hydrophobic effect in the presence of warm water. Moreover, it has been verified that the AL 18 evaporation strongly relates to the dissociation of H-aggregate, but is not responsible for the variation from the monomer to J-aggregate. Comparing the results obtained upon application of HT/HTTL and HT/WTL, it has been concluded that both large relative permittivity and thermal energy inherent in warm water are quite essential in inducing the rapid reconstitution of MS 18 aggregation state from the monomer to J-aggregate. These also promote the restoration of conformation and orientation changes in the MS 18 hydrocarbon chain, and the modification of subcell packing and orientation disorder in

  14. Examination system utilizing ionizing radiation and a flexible, miniature radiation detector probe

    DOEpatents

    Majewski, Stanislaw; Kross, Brian J.; Zorn, Carl J.; Majewski, Lukasz A.

    1996-01-01

    An optimized examination system and method based on the Reverse Geometry X-Ray.RTM. (RGX.RTM.) radiography technique are presented. The examination system comprises a radiation source, at least one flexible, miniature radiation detector probe positioned in appropriate proximity to the object to be examined and to the radiation source with the object located between the source and the probe, a photodetector device attachable to an end of the miniature radiation probe, and a control unit integrated with a display device connected to the photodetector device. The miniature radiation detector probe comprises a scintillation element, a flexible light guide having a first end optically coupled to the scintillation element and having a second end attachable to the photodetector device, and an opaque, environmentally-resistant sheath surrounding the flexible light guide. The probe may be portable and insertable, or may be fixed in place within the object to be examined. An enclosed, flexible, liquid light guide is also presented, which comprises a thin-walled flexible tube, a liquid, preferably mineral oil, contained within the tube, a scintillation element located at a first end of the tube, closures located at both ends of the tube, and an opaque, environmentally-resistant sheath surrounding the flexible tube. The examination system and method have applications in non-destructive material testing for voids, cracks, and corrosion, and may be used in areas containing hazardous materials. In addition, the system and method have applications for medical and dental imaging.

  15. Examination system utilizing ionizing radiation and a flexible, miniature radiation detector probe

    SciTech Connect

    Majewski, S.; Kross, B.J.; Zorn, C.J.; Majewski, L.A.

    1996-10-22

    An optimized examination system and method based on the Reverse Geometry X-Ray{trademark} (RGX{trademark}) radiography technique are presented. The examination system comprises a radiation source, at least one flexible, miniature radiation detector probe positioned in appropriate proximity to the object to be examined and to the radiation source with the object located between the source and the probe, a photodetector device attachable to an end of the miniature radiation probe, and a control unit integrated with a display device connected to the photodetector device. The miniature radiation detector probe comprises a scintillation element, a flexible light guide having a first end optically coupled to the scintillation element and having a second end attachable to the photodetector device, and an opaque, environmentally-resistant sheath surrounding the flexible light guide. The probe may be portable and insertable, or may be fixed in place within the object to be examined. An enclosed, flexible, liquid light guide is also presented, which comprises a thin-walled flexible tube, a liquid, preferably mineral oil, contained within the tube, a scintillation element located at a first end of the tube, closures located at both ends of the tube, and an opaque, environmentally-resistant sheath surrounding the flexible tube. The examination system and method have applications in non-destructive material testing for voids, cracks, and corrosion, and may be used in areas containing hazardous materials. In addition, the system and method have applications for medical and dental imaging. 5 figs.

  16. Examination system utilizing ionizing radiation and a flexible, miniature radiation detector probe

    DOEpatents

    Majewski, S.; Kross, B.J.; Zorn, C.J.; Majewski, L.A.

    1996-10-22

    An optimized examination system and method based on the Reverse Geometry X-Ray{trademark} (RGX{trademark}) radiography technique are presented. The examination system comprises a radiation source, at least one flexible, miniature radiation detector probe positioned in appropriate proximity to the object to be examined and to the radiation source with the object located between the source and the probe, a photodetector device attachable to an end of the miniature radiation probe, and a control unit integrated with a display device connected to the photodetector device. The miniature radiation detector probe comprises a scintillation element, a flexible light guide having a first end optically coupled to the scintillation element and having a second end attachable to the photodetector device, and an opaque, environmentally-resistant sheath surrounding the flexible light guide. The probe may be portable and insertable, or may be fixed in place within the object to be examined. An enclosed, flexible, liquid light guide is also presented, which comprises a thin-walled flexible tube, a liquid, preferably mineral oil, contained within the tube, a scintillation element located at a first end of the tube, closures located at both ends of the tube, and an opaque, environmentally-resistant sheath surrounding the flexible tube. The examination system and method have applications in non-destructive material testing for voids, cracks, and corrosion, and may be used in areas containing hazardous materials. In addition, the system and method have applications for medical and dental imaging. 5 figs.

  17. Spacecraft-level verification of the Van Allen Probes' RF communication system

    NASA Astrophysics Data System (ADS)

    Crowne, M. J.; Srinivasan, D.; Royster, D.; Weaver, G.; Matlin, D.; Mosavi, N.

    This paper presents the verification process, lessons learned, and selected test results of the radio frequency (RF) communication system of the Van Allen Probes, formerly known as the Radiation Belt Storm Probes (RBSP). The Van Allen Probes mission is investigating the doughnut-shaped regions of space known as the Van Allen radiation belts where the Sun interacts with charged particles trapped in Earth's magnetic field. Understanding this dynamic area that surrounds our planet is important to improving our ability to design spacecraft and missions for reliability and astronaut safety. The Van Allen Probes mission features two nearly identical spacecraft designed, built, and operated by the Johns Hopkins University Applied Physics Laboratory (JHU/APL) for the National Aeronautics and Space Administration (NASA). The RF communication system features the JHU/APL Frontier Radio. The Frontier Radio is a software-defined radio (SDR) designed for spaceborne communications, navigation, radio science, and sensor applications. This mission marks the first spaceflight usage of the Frontier Radio. RF ground support equipment (RF GSE) was developed using a ground station receiver similar to what will be used in flight and whose capabilities provided clarity into RF system performance that was previously not obtained until compatibility testing with the ground segments. The Van Allen Probes underwent EMC, acoustic, vibration, and thermal vacuum testing at the environmental test facilities at APL. During this time the RF communication system was rigorously tested to ensure optimal performance, including system-level testing down to threshold power levels. Compatibility tests were performed with the JHU/APL Satellite Communication Facility (SCF), the Universal Space Network (USN), and the Tracking and Data Relay Satellite System (TDRSS). Successful completion of this program as described in this paper validated the design of the system and demonstrated that it will be able to me

  18. Towards optimum sample-probe-spectrometer system design by adjusting receiving fiber end face position and probe-membrane sample separation.

    PubMed

    Ma, Jianjun; Bock, Wojtek; Wang, Zhiyuan; Hao, Wenhui

    2005-11-14

    A two-fiber probe interrogated by a spectrometer for the measurement of fluorescence emitted from a thin layer of membrane is investigated. For a specific spectrometer, an optimum fiber probe design exists to maximize the sample-probe-spectrometer system performance. In this paper, for the first time, we report that by separating the front end faces of the receiving and illuminating fibers, spectrum resolution and fluorescence collection capability may be simultaneously enhanced. Theoretical and experimental results reveal that such an optimized system collects more emitted rays with incident angles that fall within the full acceptance angle of the slit. The relative collection efficiency increases to 63% when the membrane is positioned very close to the probe tip. By adjusting positions of the receiving fiber and the membrane sample to an optimized combination, we also prove that the optimum performance of spectrometer can be achieved.

  19. Tribology of Langmuir-Blodgett Films

    DTIC Science & Technology

    1992-03-01

    the 1970" s . used a three-term model . The frictional force and hence the friction coefficient were modeled as the sum of three terms: adhesion between...N/A N/A 4. TITLE (and Subtitle) S . TyPE OF REPORT & PERIOD COVERED Tribology of Langmuir-Blodgett Films Interim Technical Report 6. PERFORMING ORO...AOORESS 12. REPORT OATE U. S . Army Research Office March 1992 Post Office Box 12211 I. NUMREROF PAGES R~~Arrh Tr npl= n D, ift’ n 25 14. MONITORING

  20. Probing the Conductance of the σ-System of Bipyridine Using Destructive Interference.

    PubMed

    Borges, Anders; Fung, E-Dean; Ng, Fay; Venkataraman, Latha; Solomon, Gemma C

    2016-12-01

    Guidelines to predict trends in the electrical conductance of molecules have been developed for the π-system of conjugated systems. Little is known, however, about the conductance of the underlying σ-systems because the π-system usually dominates the transport. Here we study a family of bipyridine-based molecules using STM-break junction experiments and density functional theory transport calculations. We use different lengths and substitution patterns to probe the role of both the σ-system and the π-system in controlling conductance. By exploiting the destructive interference feature found in the π-system of the meta-coupled six-membered aromatic rings, we show that the conductance of the σ-system of a meta-coupled molecule can be probed directly and can even exceed that of its para-coupled analog. These results add to the understanding of the conductance through the chemically hidden σ-electrons.

  1. Tethered Chains in Poor Solvent Conditions: An Experimental Study Involving Langmuir Diblock Copolymer Monolayers

    SciTech Connect

    Kent, M.S.; Lee, L.T.; Majewski, J.; Satija, S.; Smith, G.S.

    1998-10-13

    We have employed Langmuir monolayer of highly asymmetric polydimethylsiloxane- polystyrene (PDMS-PS) diblock copolymers on dioctyl phthalate (DOP) at temperatures ranging from 22 "C to -35 `C as a model system for tethered chains in poor solvent conditions. The thicknesses of the tethered PS layers extending into the DOP subphase, measured by neutron reflection, decrease with decreasing temperature (T) over this entire r~ge. However, the v~iation with T becomes weak below -20 "C. At the ]owest T, the layer thicknesses are contracted 55 % -75 `% of their values at the theta condition (T8 = 22 "C), but are still quite swollen compared to the fully collapsed, nonsolvent limit. The contraction of the layer with decreasing T is determined as a function of surface density and molecular weight. These data are compared to universal scaling forms. The PS segments are depleted from the air surface over the entire T range, the thickness of the depletion layer increasing slightly with decreasing T. The free energy of the surface layer is probed by surface tension measurements. Negative surface pressures are observed at low coverages for both PDMS-PS and PDMS monolayer, indicating metastability toward lateral phase separation. Evidence for a trruisition from a dispersed phase to a condensed phase with decreasing T was observed in the reflectivity at very low PDMS-PS coverage.

  2. Measuring system with a dual needle probe for testing the parameters of heat-insulating materials

    NASA Astrophysics Data System (ADS)

    Chudzik, Stanislaw

    2011-07-01

    The paper presents a prototype of a measurement system with a hot probe based on a transient line heat source method, designed for testing the thermal parameters of heat insulation materials. The proposition is to use an auxiliary thermometer (dual needle probe) and a trained artificial neural network to determine the parameters of thermal insulation materials. The data extracted from the simulation of a nonstationary two-dimensional heat conduction model inside a sample of material with a dual needle probe trained the artificial neural network (ANN). The significant heat capacity of the needle probe is taken into account in the model. To solve the system of partial differential equations describing the model, the finite element method (FEM) was applied. The ANN is used to estimate the coefficients of the inverse heat conduction problem for a solid. The network determines the values of the effective thermal conductivity and effective thermal diffusivity on the basis of the temperature increases of the hot probe and the auxiliary thermometer. All calculations, such as FEM, and training and testing processes of the ANN, were carried out in the Matlab environment. The results of the experiment are also presented. The proposed measurement system for testing the parameters is suitable for temporary measurements in a building site or factory.

  3. A lidar system for remote probing of the lower atmosphere

    NASA Technical Reports Server (NTRS)

    Craig, C. D.; Bartz, R.; Olsson, L. E.; Hewson, E. W.

    1974-01-01

    The development and characteristics of a lidar system for atmospheric measurements are discussed. The lidar system employs a Q-switched ruby laser that radiates an intense pulse of light into the atmosphere to illuminate aerosol particles in the laser beam. Light backscattered from the particles is received by a Cassegrain telescope equipped with a sensitive photomultiplier tube. The output signal of the photomultiplier tube is displayed on an oscilloscope and recorded on polaroid film.

  4. Development of coaxial ultrasonic probe for fatty liver diagnostic system using ultrasonic velocity change

    NASA Astrophysics Data System (ADS)

    Hori, Makoto; Yokota, Daiki; Aotani, Yuhei; Kumagai, Yuta; Wada, Kenji; Matsunaka, Toshiyuki; Morikawa, Hiroyasu; Horinaka, Hiromichi

    2017-07-01

    A diagnostic system for fatty liver at an early stage is needed because fatty liver is linked to metabolic syndrome. We have already proposed a fatty liver diagnosis method based on the temperature coefficient of ultrasonic velocity. In this study, we fabricated a coaxial ultrasonic probe by integrating two kinds of transducers for warming and signal detection. The diagnosis system equipped with the coaxial probe was applied to tissue-mimicking phantoms including the fat area. The fat content rates corresponding to the set rates of the phantoms were estimated by the ultrasonic velocity-change method.

  5. Automated measurement system employing eddy currents to adjust probe position and determine metal hardness

    DOEpatents

    Prince, J.M.; Dodson, M.G.; Lechelt, W.M.

    1989-07-18

    A system for measuring the hardness of cartridge cases employs an eddy current probe for inducing and sensing eddy currents in each cartridge case. A first component of the sensed signal is utilized in a closed loop system for accurately positioning the probe relative to the cartridge case both in the lift off direction and in the tangential direction, and a second component of the sensed signal is employed as a measure of the hardness. The positioning and measurement are carried out under closed loop microprocessor control facilitating hardness testing on a production line basis. 14 figs.

  6. Automated measurement system employing eddy currents to adjust probe position and determine metal hardness

    DOEpatents

    Prince, James M.; Dodson, Michael G.; Lechelt, Wayne M.

    1989-01-01

    A system for measuring the hardness of cartridge cases employs an eddy current probe for inducing and sensing eddy currents in each cartridge case. A first component of the sensed signal is utilized in a closed loop system for accurately positioning the probe relative to the cartridge case both in the lift off direction and in the tangential direction, and a second component of the sensed signal is employed as a measure of the hardness. The positioning and measurement are carried out under closed loop microprocessor control facilitating hardness testing on a production line basis.

  7. Sensitivity improvement of optical fiber acoustic probe for all-optical photoacoustic imaging system

    NASA Astrophysics Data System (ADS)

    Seki, Atsushi; Iwai, Katsumasa; Katagiri, Takashi; Matsuura, Yuji

    2017-07-01

    An acoustic probe based on a Fabry-Perot interferometer composed of a polymer film attached to the end of an optical fiber was designed and fabricated for an endoscopic, all-optical photoacoustic imaging system. The finesse of the interferometer was improved by forming a half-mirror at the end of the fiber and a partial reflection mirror on the outer surface of the polymer film. A photoacoustic imaging system was constructed by combining the fiber-optic acoustic probe with a bundle of hollow optical fibers used for the excitation of the photoacoustic wave, and an image of blood capillaries in a fish ovarian membrane was successfully obtained.

  8. Probing other solar systems with current and future adaptive optics

    SciTech Connect

    Macintosh, B; Marois, C; Phillion, D; Poyneer, L; Graham, J; Zuckerman, B; Gavel, D; Veran, J; Wilhelmsen-Evans, J; Mellis, C

    2008-09-08

    Over the past decade, the study of extrasolar planets through indirect techniques--primarily Doppler measurements--has revolutionized our understanding of other solar systems. The next major step in this field will be the direct detection and characterization, via imaging and spectroscopy, of the planets themselves. To achieve this, we must separate the light from the faint planet from the extensive glare of its parent star. We pursued this goal using the current generation of adaptive optics (AO) systems on large ground-based telescopes, using infrared imaging to search for the thermal emission from young planets and developing image processing techniques to distinguish planets from telescope-induced artifacts. Our new Angular Differential Imaging (ADI) technique, which uses the sidereal rotation of the Earth and telescope, is now standard for ground-based high-contrast imaging. Although no young planets were found in our surveys, we placed the strongest limits yet on giant planets in wide orbits (>30 AU) around young stars and characterized planetary companion candidates. The imaging of planetary companions on solar-system-like scales (5-30 AU) will require a new generation of advanced AO systems that are an order of magnitude more powerful than the LLNL-built Keck AO system. We worked to develop and test the key technologies needed for these systems, including a spatially-filtered wavefront sensor, efficient and accurate wavefront reconstruction algorithms, and precision AO wavefront control at the sub-nm level. LLNL has now been selected by the Gemini Observatory to lead the construction of the Gemini Planet Imager, a $24M instrument that will be the most advanced AO system in the world.

  9. PERFORMACE OF MULTI-PROBE CORROSION MONITORING SYSTEMS AT THE HANFORD SITE

    SciTech Connect

    CAROTHERS KD; BOOMER KD; ANDA VS; DAHL MM; EDGEMON GL

    2010-01-14

    Between 2007 and 2009, several different multi-probe corrosion monitoring systems were designed and installed in high-level nuclear waste tanks at the U.S. Department of Energy's Hanford Site in WaShington State. The probe systems are being monitored to ensure waste tanks operate in regions that minimize localized corrosion (i.e., pitting) and stress corrosion cracking. The corrosion monitoring systems have been installed in wastes with different chemistry types. An ongoing effort during the same time period has generated non-radioactive simulants that are tested in the laboratory to establish baseline corrosion monitoring system performance and characterize data to allow interpretation of readings from the multiple corrosion monitoring systems. Data collection from these monitoring systems has reached the point where the results allow comparison with the laboratory testing. This paper presents analytical results from the corrosion monitoring system development program.

  10. Probe Scanning Support System by a Parallel Mechanism for Robotic Echography

    NASA Astrophysics Data System (ADS)

    Aoki, Yusuke; Kaneko, Kenta; Oyamada, Masami; Takachi, Yuuki; Masuda, Kohji

    We propose a probe scanning support system based on force/visual servoing control for robotic echography. First, we have designed and formulated its inverse kinematics the construction of mechanism. Next, we have developed a scanning method of the ultrasound probe on body surface to construct visual servo system based on acquired echogram by the standalone medical robot to move the ultrasound probe on patient abdomen in three-dimension. The visual servo system detects local change of brightness in time series echogram, which is stabilized the position of the probe by conventional force servo system in the robot, to compensate not only periodical respiration motion but also body motion. Then we integrated control method of the visual servo with the force servo as a hybrid control in both of position and force. To confirm the ability to apply for actual abdomen, we experimented the total system to follow the gallbladder as a moving target to keep its position in the echogram by minimizing variation of reaction force on abdomen. As the result, the system has a potential to be applied to automatic detection of human internal organ.

  11. Serum albumin in 2D: a Langmuir monolayer approach.

    PubMed

    Crawford, Nicholas F; Leblanc, Roger M

    2014-05-01

    Understanding of protein interaction at the molecular level raises certain difficulties which is the reason a model membrane system such as the Langmuir monolayer technique was developed. Ubiquitous proteins such as serum albumin comprise 50% of human blood plasma protein content and are involved in many biological functions. The important nature of this class of protein demands that it be studied in detail while modifying the experimental conditions in two dimensions to observe it in all types of environments. While different from bulk colloidal solution work, the two dimensional approach allows for the observation of the interaction between molecules and subphase at the air-water interface. Compiled in this review are studies which highlight the characterization of this protein using various surroundings and also observing the types of interactions it would have when at the biomembrane interface. Free-energy changes between molecules, packing status of the bulk analyte at the interface as well as phase transitions as the monolayer forms a more organized or aggregated state are just some of the characteristics which are observed through the Langmuir technique. This unique methodology demonstrates the chemical behavior and physical behavior of this protein at the phase boundary throughout the compression of the monolayer. © 2013 Elsevier B.V. All rights reserved.

  12. An applied science perspective of Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Roberts, G. G.

    1985-11-01

    Langmuir-Blodgett (LB) films are prepared by transferring floating organic monolayers onto solid substrates. A combination of innovative chemistry and a carefully engineered instrument (a Langmuir trough) can result in high quality monomolecular assemblies displaying a high degree of structural order. The technique was first reported about fifty years ago and since then, LB films have been widely used as model systems in fundamental research. However, it is only during the past decade that the extensive applied potential has been recognised. Their precise thickness, coupled with the degree of control over the molecular architecture, has now firmly established a role for these layers in thin film technology.Following a historical introduction, this review describes the preparation and characterization of LB films and summarizes their importance in basic science. Particular emphasis is then placed on their potential applications, especially in fields related to electronics. The article concludes with a summary of the possible future role of ordered monomolecular films in the general field of molecular electronics.

  13. Growth of calcium oxalate monohydrate at phospholipid Langmuir monolayers

    NASA Astrophysics Data System (ADS)

    Whipps, Scott; Khan, Saeed R.; Jeffrey O'Palko, F.; Backov, Rénal; Talham, Daniel R.

    1998-08-01

    Calcium oxalate monohydrate crystals have been nucleated from metastable solutions at Langmuir monolayers of the phospholipids dipalmitoylphosphatidylglycerol (DPPG), dipalmitoylphosphatidylserine and dipalmitoylphosphatidylcholine and the fatty acid arachidic acid. The phospholipid monolayers were used as model systems for domains of pure lipid in cellular media as part of investigations of their potential role in the nucleation of calcium oxalate in the urinary tract. Crystal formation was monitored at the air/water interface using Brewster angle microscopy and in transferred films using SEM and TEM. For each Langmuir monolayer, it was observed that nucleation is heterogeneous and is selective with respect to the orientation and morphology of the precipitated crystals with up to 90% of crystals growing with the ( 1 0 1¯) face oriented towards the monolayer interface. The selectivity is attributed to calcium binding at the lipid monolayer favoring formation of the calcium-rich ( 1 0 1¯) face. The behavior at each monolayer was similar, although a higher rate of crystal formation was observed at the anionic DPPG interface.

  14. Electron probe microanalysis in the ternary Gd B C system

    NASA Astrophysics Data System (ADS)

    Ruiz, Domingo; Garland, Maria Teresa; Saillard, Jean-Yves; Halet, Jean-François; Bohn, Marcel; Bauer, Josef

    2002-09-01

    EPMA exploration of the Gd-B-C system in the region "Gd-GdB 2-GdBC" and in the neighborhood of the recently described Gd 4B 3C 4 compound led to the identification of 9 new ternary phases, which allows to clear up the phase diagram of this ternary system. A structural description of the bonding between the non-metal atoms in most of the identified compounds is proposed, on the basis of simple electron counting rules and using the planar repeat units or the finite linear anions which have been shown to exist in the structurally characterized rare-earth borocarbide compounds.

  15. Probing infinity in bounded two-dimensional electrostatic systems

    NASA Astrophysics Data System (ADS)

    Abutalib, M.; Batle, J.; Ooi, C. H. Raymond

    2016-07-01

    The total electrostatic energy of systems of identical particles of equal charge is studied in configurations bounded in space, but divergent in the number of charges. This approach shall guide us to unveil a non-linear, functional form specifying the divergent nature of system energy. We consider fractals to be physical entities, with charges located in their vertices or nodes. This description is interesting since features, such as the corresponding fractal dimension, can characterize the total energy EN. Finally, at local length scales, we describe how energy diverges at charge accumulation points in the fractal, that is, almost everywhere by definition.

  16. Phase behaviour in binary mixed Langmuir Blodgett monolayers of triglycerides

    NASA Astrophysics Data System (ADS)

    Zdravkova, Aneliya N.; van der Eerden, J. P. J. M.

    2007-09-01

    Binary mixed monolayers of the triglycerides (TAGs)-tripalmitin (PPP), tristearin (SSS) and triarachidin (AAA) at the air-water interface are investigated with the Langmuir method. Langmuir-Blodgett (LB) layers obtained by deposition on mica are investigated by Atomic Force Microscopy. Combining Langmuir and AFM results the relation between the phase behaviour of binary mixed TAGs and their chain length is established. TAG mixtures form monolayers with molecules in trident conformation at the air-water interface, like pure TAGs. The area Acond=63 Å 2 and the pressure πcond=8-10 mN/m that separate "gas" and "condensed" film structures are the same for all mixtures and pure systems. In the π- A isotherms the sharpness of the transition from "gas" to "condensed" phase decreases with the average chain length for all systems. Using AFM data the monolayer thicknesses for mixtures and pure systems is found to be linearly dependent on the average chain length of the TAG molecules. A linear relation between film thickness and applied AFM force is established. The corresponding coefficient K˜ is higher for mixed monolayers ( K˜=0.08±0.01 nN) than for pure systems ( K˜=0.07±0.01 nN). AFM images show phase separation in the systems PPP-SSS and PPP-AAA. The solubility of the shorter PPP molecules in the "long" (SSS- and AAA-rich) phase is significant. For the mixture SSS-AAA, phase separation is not observed. In that mixture the monolayer thickness varies linearly with composition, supporting the conclusion that SSS and AAA mix almost ideally. The main driving force for phase separation is the difference in the alkyl chain length. Indeed PPP-AAA (length difference 4 C atoms) shows the most clear phase separation. The relatively weak phase separation in PPP-SSS and the absence of phase separation in SSS-AAA show that the influence of chain length difference decreases with increasing average chain length. In air PPP-SSS and PPP-AAA mixed monolayers are unstable and

  17. Multiphoton microscopy system with a compact fiber-based femtosecond-pulse laser and handheld probe.

    PubMed

    Liu, Gangjun; Kieu, Khanh; Wise, Frank W; Chen, Zhongping

    2011-01-01

    We report on the development of a compact multiphoton microscopy (MPM) system that integrates a compact and robust fiber laser with a miniature probe. The all normal dispersion fiber femtosecond laser has a central wavelength of 1.06 μm, pulse width of 125 fs and average power of more than 1 W. A double cladding photonic crystal fiber was used to deliver the excitation beam and to collect the two-photon signal. The hand-held probe included galvanometer-based mirror scanners, relay lenses and a focusing lens. The packaged probe had a diameter of 16 mm. Second harmonic generation (SHG) images and two-photon excited fluorescence (TPEF) images of biological tissues were demonstrated using the system.

  18. Quasiperiodic behavior in beam-driven strong Langmuir turbulence

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Newman, D. L.

    1989-01-01

    The evolution of unmagnetized beam-driven strong Langmuir turbulence is studied in two dimensions by numerically integrating the Zakharov equations for systems pumped by monochromatic and broadband negative-damping drivers with nonzero central wavenumber. Long-time statistically steady states are reached for which the dependence of the evolution on the driver wavenumber, growth rate, and bandwidth is examined in detail. For monochromatic drivers, a quasiperiodic cycle is found to develop if the driver wavenumber is sufficiently large. The characteristic frequency of the quasiperiodic cycle and the average system energy are both approximately proportional to the growth rate. Broadening of the driver in wavenumber tends to degrade the system-wide coherence of the cycle, but its main features appear to survive on the scale of the coherence length of the driver.

  19. Using Approximate Bayesian Computation to Probe Multiple Transiting Planet Systems

    NASA Astrophysics Data System (ADS)

    Morehead, Robert C.

    2015-08-01

    The large number of multiple transiting planet systems (MTPS) uncovered with Kepler suggest a population of well-aligned planetary systems. Previously, the distribution of transit duration ratios in MTPSs has been used to place constraints on the distributions of mutual orbital inclinations and orbital eccentricities in these systems. However, degeneracies with the underlying number of planets in these systems pose added challenges and make explicit likelihood functions intractable. Approximate Bayesian computation (ABC) offers an intriguing path forward. In its simplest form, ABC proposes from a prior on the population parameters to produce synthetic datasets via a physically-motivated model. Samples are accepted or rejected based on how close they come to reproducing the actual observed dataset to some tolerance. The accepted samples then form a robust and useful approximation of the true posterior distribution of the underlying population parameters. We will demonstrate the utility of ABC in exoplanet populations by presenting new constraints on the mutual inclination and eccentricity distributions in the Kepler MTPSs. We will also introduce Simple-ABC, a new open-source Python package designed for ease of use and rapid specification of general models, suitable for use in a wide variety of applications in both exoplanet science and astrophysics as a whole.

  20. Probing quantum frustrated systems via factorization of the ground state.

    PubMed

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2010-05-21

    The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physical problems such as stochastic gene expression and the stability of long-period modulated structures.

  1. Photons probing dynamics in few-body systems

    NASA Astrophysics Data System (ADS)

    Scholten, O.; Korchin, A. Yu.

    2002-09-01

    In this presentation the use of photons is emphasized to test the dynamics in few-body systems and three different examples are shown. First, the momentum dependence of the Drell-Hearn-Gerasimov integral which is related to the polarized photo-absorbtion cross section; second, proton-proton bremsstrahlung where the photon is sensitive to off-shell effects in the proces; and third, radiative capture of proton on deuterium.

  2. Development of the STPX Spheromak System

    NASA Astrophysics Data System (ADS)

    Williams, R. L.; Clark, J.; Weatherford, C. A.

    2015-11-01

    The progress made in starting up the STPX Spheromak system, which is now installed at the Florida A&M University, is reviewed. Experimental, computational and theoretical activities are underway. The control system for firing the magnetized coaxial plasma gun and for collecting data from the diagnostic probes, based on LabView, is being tested and adapted. Preliminary results of testing the installed magnetic field probes, Langmuir triple probes, cylindrical ion probes, and optical diagnostics will be discussed. Progress in modeling this spheromak using simulation codes, such as NIMROD, will be discussed. Progress in investigating the use of algebraic topology to describe this spheromak will be reported.

  3. Quantum trajectories for systems probed by fields in multimode Fock and Schrodinger cat states

    NASA Astrophysics Data System (ADS)

    Combes, Joshua; Baragiola, Ben Q.; Branczyk, Agata M.; Cook, Robert L.; Gough, John E.; James, Matthew R.; Nurdin, Hendra I.

    2012-02-01

    Using Gardiner and Collet's input-output theory we derive system and output field master equations for an arbitrary quantum system probed by a field in a non-classical state of light. Specifically the field states we study are arbitrary combinations (superpositions and / or mixtures) of continuous-mode Fock states or continuous mode-coherent states. We also unravel the master equations for the system state to get the conditional evolution (the stochastic master equation) for homodyne and photon counting measurements.

  4. Complications with flush-mounted probe analysis beyond sheath-expansion

    NASA Astrophysics Data System (ADS)

    Kuang, A. Q.; Labombard, B.; Brunner, D.

    2016-10-01

    In a reactor relevant divertor, the heat-flux onto the target plate would be too large and traditional proud Langmuir probes will melt. By making the probes flush with the surface of the target plate they become nearly as robust as the divertor plates themselves. However, without a theoretically rigorous derivation of the sheath thickness, sheath expansion has been a primary concern for the interpretation of flush mounted probe data. Following the installation of a flush-mounted Langmuir probe system at Alcator C-Mod (toroidally-elongated and field-aligned to give it a `rail' geometry) that effectively mitigates the effects of sheath expansion down to incident field line angles of 0.5 degree, further complications have arisen that cannot be explained by sheath-expansion. The `rail' probes systematically measure lower densities and higher temperatures but have the same pressure. The evolution of the scrape-off layer profiles measured on the divertor target plate from sheath-limited to detached regimes is also different. These are indicative of important physics, perhaps unique to conditions in a vertical-target plate divertor with small field-line attack angles, that affects the I-V characteristics and is not currently included in probe data analyses. Controlled experiments performed at Alcator C-Mod mapped out this discrepancy and the results will be presented. Supported by USDoE Awards DE-FC02-99ER54512.

  5. Probing disorders of the nervous system using reprogramming approaches

    PubMed Central

    Ichida, Justin K; Kiskinis, Evangelos

    2015-01-01

    The groundbreaking technologies of induced pluripotency and lineage conversion have generated a genuine opportunity to address fundamental aspects of the diseases that affect the nervous system. These approaches have granted us unrestricted access to the brain and spinal cord of patients and have allowed for the study of disease in the context of human cells, expressing physiological levels of proteins and under each patient's unique genetic constellation. Along with this unprecedented opportunity have come significant challenges, particularly in relation to patient variability, experimental design and data interpretation. Nevertheless, significant progress has been achieved over the past few years both in our ability to create the various neural subtypes that comprise the nervous system and in our efforts to develop cellular models of disease that recapitulate clinical findings identified in patients. In this Review, we present tables listing the various human neural cell types that can be generated and the neurological disease modeling studies that have been reported, describe the current state of the field, highlight important breakthroughs and discuss the next steps and future challenges. PMID:25925386

  6. Tainted blood: Probing safety practices in the Danish blood system.

    PubMed

    Deleuran, Ida; Sheikh, Zainab Afshan; Hoeyer, Klaus

    2015-09-01

    The existing literature on donor screening in transfusion medicine tends to distinguish between social concerns about discrimination and medical concerns about safety. In this article, we argue that the bifurcation into social and medical concerns is problematic. We build our case on a qualitative study of the historical rise and current workings of safety practices in the Danish blood system. Here, we identify a strong focus on contamination in order to avoid 'tainted blood', at the expense of working with risks that could be avoided through enhanced blood monitoring practices. Of further significance to this focus are the social dynamics found at the heart of safety practices aimed at avoiding contamination. We argue that such dynamics need more attention, in order to achieve good health outcomes in transfusion medicine. Thus, we conclude that, to ensure continuously safe blood systems, we need to move beyond the bifurcation of the social and medical aspects of blood supply as two separate issues and approach social dynamics as key medical safety questions. © The Author(s) 2014.

  7. Probing Potential Energy Surface Exploration Strategies for Complex Systems.

    PubMed

    N'Tsouaglo, Gawonou Kokou; Béland, Laurent Karim; Joly, Jean-François; Brommer, Peter; Mousseau, Normand; Pochet, Pascal

    2015-04-14

    The efficiency of minimum-energy configuration searching algorithms is closely linked to the energy landscape structure of complex systems, yet these algorithms often include a number of steps of which the effect is not always clear. Decoupling these steps and their impacts can allow us to better understand both their role and the nature of complex energy landscape. Here, we consider a family of minimum-energy algorithms based, directly or indirectly, on the well-known Bell-Evans-Polanyi (BEP) principle. Comparing trajectories generated with BEP-based algorithms to kinetically correct off-lattice kinetic Monte Carlo schemes allow us to confirm that the BEP principle does not hold for complex systems since forward and reverse energy barriers are completely uncorrelated. As would be expected, following the lowest available energy barrier leads to rapid trapping. This is why BEP-based methods require also a direct handling of visited basins or barriers. Comparing the efficiency of these methods with a thermodynamical handling of low-energy barriers, we show that most of the efficiency of the BEP-like methods lie first and foremost in the basin management rather than in the BEP-like step.

  8. Unmanned Multiple Exploratory Probe System (MEPS) for Mars observation. Volume 1: Trade analysis and design

    NASA Technical Reports Server (NTRS)

    Adams, Daniel E.; Crumbly, Christopher M.; Delp, Steve E.; Guidry, Michelle A.; Lisano, Michael E.; Packard, James D.; Striepe, Scott A.

    1988-01-01

    This report presents the unmanned Multiple Exploratory Probe Systems (MEPS), a space vehicle designed to observe the planet Mars in preparation for manned missions. The options considered for each major element are presented as a trade analysis, and the final vehicle design is defined.

  9. TANK 241-AN-102 MULTI-PROBE CORROSION MONITORING SYSTEM PROJECT LESSONS LEARNED

    SciTech Connect

    TAYLOR T; HAGENSEN A; KIRCH NW

    2008-07-07

    During 2007 and 2008, a new Multi-Probe Corrosion Monitoring System (MPCMS) was designed and fabricated for use in double-shell tank 241-AN-102. The system was successfully installed in the tank on May 1, 2008. The 241-AN-102 MPCMS consists of one 'fixed' in-tank probe containing primary and secondary reference electrodes, tank material electrodes, Electrical Resistance (ER) sensors, and stressed and unstressed corrosion coupons. In addition to the fixed probe, the 241-AN-102 MPCMS also contains four standalone coupon racks, or 'removable' probes. Each rack contains stressed and unstressed coupons made of American Society of Testing and Materials A537 CL1 steel, heat-treated to closely match the chemical and mechanical characteristics of the 241-AN-102 tank wall. These coupon racks can be removed periodically to facilitate examination of the attached coupons for corrosion damage. Along the way to successful system deployment and operation, the system design, fabrication, and testing activities presented a number of challenges. This document discusses these challenges and lessons learned, which when applied to future efforts, should improve overall project efficiency.

  10. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    SciTech Connect

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  11. Chapman Conference Probes Water Vapor in the Climate System

    NASA Astrophysics Data System (ADS)

    Elliott, William P.; Gaffen, Dian J.

    About 125 scientists from 11 countries met in Jekyll Island, Ga., in October to discuss the unique role that water vapor plays in the climate system. Water vapor links the surface and atmospheric branches of the global hydrologic cycle. Its horizontal and vertical fluxes are key to the energy cycle, and its radiative effects are the major factor in the atmospheric greenhouse effect. Theoretical calculations indicate that global climate is highly sensitive to small changes in humidity at all levels in the atmosphere, but observations to test this hypothesis are lacking. Because few high-quality humidity observations exist, especially in the upper troposphere, researchers are uncertain of the nature and strength of climate feedback mechanisms involving water vapor and its distribution and long-term changes. Consequently, water vapor is not well treated in global climate models and requires more attention.

  12. Fragmentation in isotopic and isobaric systems as probe of density dependence of nuclear symmetry energy

    NASA Astrophysics Data System (ADS)

    Kaur, Mandeep; Gautam, Sakshi; Puri, Rajeev K.

    2016-11-01

    We probe the density-dependent behavior of symmetry energy using the yield of various fragments in central collisions of various isotopic and isobaric colliding pairs. We calculate the yields of free nucleons, light charged particles and intermediate mass fragments in neutron-rich colliding systems as well as the ratio of relative yields of above fragments and free nucleons. Our findings reveal that the ratio of relative yield of light charged particles poses better candidate to probe the density dependence of nuclear symmetry energy.

  13. Quantum and classical dynamics of Langmuir wave packets.

    PubMed

    Haas, F; Shukla, P K

    2009-06-01

    The quantum Zakharov system in three spatial dimensions and an associated Lagrangian description, as well as its basic conservation laws, are derived. In the adiabatic and semiclassical cases, the quantum Zakharov system reduces to a quantum modified vector nonlinear Schrödinger (NLS) equation for the envelope electric field. The Lagrangian structure for the resulting vector NLS equation is used to investigate the time dependence of the Gaussian-shaped localized solutions, via the Rayleigh-Ritz variational method. The formal classical limit is considered in detail. The quantum corrections are shown to prevent the collapse of localized Langmuir envelope fields, in both two and three spatial dimensions. Moreover, the quantum terms can produce an oscillatory behavior of the width of the approximate Gaussian solutions. The variational method is shown to preserve the essential conservation laws of the quantum modified vector NLS equation. The possibility of laboratory tests in the next generation intense laser-solid plasma compression experiment is discussed.

  14. Nondestructive measurements of complex tensor permittivity of anisotropic materials using a waveguide probe system

    SciTech Connect

    Chang, C.W.; Chen, K.M.; Qian, J.

    1996-07-01

    A nondestructive measurement of electromagnetic (EM) properties of anisotropic materials using an open-ended waveguide probe has been conducted. Two coupled electric field integral equations (EFIEs) for the aperture electric field are derived and solved numerically by employing the method of moments (MoM). After the determination of the aperture electric field, the reflection coefficient of the incident wave can be expressed in terms of the EM parameters of the material. Then, the EM parameters of the material layer can be inversely determined if the reflection coefficient of the incident wave is experimentally measured. A series of experiments has been conducted using the waveguide probe system constructed at MSU electromagnetics laboratory. The inverse results of the EM properties of various materials are presented. Finally, the effects of material parameters on the probe input admittance that cause problems in the measurement are analyzed.

  15. Nanoelectrical probing with multiprobe SPM Systems compatible with scanning electron microscopes

    NASA Astrophysics Data System (ADS)

    Lewis, Aaron; Ignatov, Andrey; Taha, Hesham; Zhinoviev, Oleg; Komissar, Anatoly; Krol, Alexander; Lewis, David

    2011-03-01

    A scanning electron microscope compatible platform that permits multiprobe atomic force microscopy based nanoelectrical characterization will be described. To achieve such multiple parameter nanocharacterization with scanning electron microscope compatibility involves a number of innovations both in instrument and probe design. This presentation will focus on how these advances were achieved and the results obtained with such instrumentation on electrical nano-characterization and electrical nano-manipulation. The advances include: 1. Specialized scanners; 2. An ultrasensitive feedback mechanism based on tuning forks with no optical feedback interference that can induce carriers in semiconductor devices; and 3. Unique probes compatible with multiprobe geometries in which the probe tips can be brought into physical contact with one another. Experiments will be described with such systems that will include multiprobe electrical measurements with metal and glass coated coaxial nanowires of platinum. This combination of scanning electron microscopes integrated with multiprobe instrumentation allows for important applications not available today in the field of semiconductor processing technology.

  16. Langmuir films containing ibuprofen and phospholipids

    NASA Astrophysics Data System (ADS)

    Geraldo, Vananélia P. N.; Pavinatto, Felippe J.; Nobre, Thatyane M.; Caseli, Luciano; Oliveira, Osvaldo N.

    2013-02-01

    This study shows the incorporation of ibuprofen, an anti-inflammatory drug, in Langmuir monolayers as cell membrane models. Significant effects were observed for dipalmitoyl phosphatidyl choline (DPPC) monolayers with relevant changes in the elasticity of the monolayer. Dipalmitoyl phosphatidyl glycerol (DPPG) monolayers were affected by small concentrations of ibuprofen, from 1 to 5 mol%. For both types of monolayer, ibuprofen could penetrate into the hydrophobic part of the monolayer, which was confirmed with polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). Brewster angle microscopy (BAM) images showed that ibuprofen prevents the formation of large domains of DPPC. The pharmacological action should occur primarily with penetration of ibuprofen via electrically neutral phospholipid headgroups of the membrane.

  17. Stable Ordering in Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Takamoto, Dawn Y.; Aydil, Eray; Zasadzinski, Joseph A.; Ivanova, Ani T.; Schwartz, Daniel K.; Yang, Tinglu; Cremer, Paul S.

    2001-08-01

    Defects in the layering of Langmuir-Blodgett (LB) films can be eliminated by depositing from the appropriate monolayer phase at the air-water interface. LB films deposited from the hexagonal phase of cadmium arachidate (CdA2) at pH 7 spontaneously transform into the bulk soap structure, a centrosymmetric bilayer with an orthorhombic herringbone packing. A large wavelength folding mechanism accelerates the conversion between the two structures, leading to a disruption of the desired layering. At pH > 8.5, though it is more difficult to draw LB films, almost perfect layering is obtained due to the inability to convert from the as-deposited structure to the equilibrium one.

  18. Coherency properties of strong Langmuir turbulence

    SciTech Connect

    Rose, H.A.; DuBois, D.F.; Russell, D. )

    1989-01-01

    Strongly correlated Langmuir wave collapse has been observed in two dimensional simulations of Zakharov's model in a regime characterized by strong ion sound wave damping and an external drive frequency, {omega}{sub 0}, close to but less than the plasma frequency, ({omega}{sub p} {minus} {omega}{sub 0})/{omega}{sub 0} > {epsilon} with {epsilon} {approx equal} 0.005. Caviton-caviton interactions induce temporal correlations between different collapse sites on a time scale the order of a collapse cycle, and on a longer time scale site locations migrate possibly leading to strong spatial correlations. Certain features of ionospheric incoherent scatter radar (ISR) spectra are consistent with such correlations. 6 refs.

  19. Probing the Structure-Function Relationships of Microbial Systems

    SciTech Connect

    Plomp, M; Leighton, T J; Holman, H; Malkin, A J

    2005-11-03

    The elucidation of microbial surface architecture and function is critical to determining mechanisms of pathogenesis, immune response, physicochemical properties, environmental resistance and development of countermeasures against bioterrorist agents. We have utilized high-resolution in vitro AFM for studies of structure, assembly, function and environmental dynamics of several microbial systems including bacteria and bacterial spores. Lateral resolutions of {approx}2.0 nm were achieved on pathogens, in vitro. We have demonstrated, using various species of Bacillus and Clostridium bacterial spores, that in vitro AFM can address spatially explicit spore coat protein interactions, structural dynamics in response to environmental changes, and the life cycle of pathogens at near-molecular resolution under physiological conditions. We found that strikingly different species-dependent crystalline structures of the spore coat appear to be a consequence of nucleation and crystallization mechanisms that regulate the assembly of the outer spore coat, and we proposed a unifying mechanism for outer spore coat self-assembly. Furthermore, we revealed molecular-scale transformations of the spore coat during the germination process, which include profound, previously unrecognized changes of the spore coat. We will present data on the direct visualization of stress-induced environmental response of metal-resistant Arthrobacter oxydans bacteria to Cr (VI) exposure, resulting in the formation of a supramolecular crystalline hexagonal structure on the cell surface. At higher Cr (VI) concentrations the formation of microbial extracellular polymers, which cover microbial colony was observed. High-resolution visualization of stress-induced structures on bacterial surfaces builds a foundation for real time in vitro molecular scale studies of structural dynamics of metal-resistant bacteria in response to environmental stimuli. In the case of the bacterium Chlamedia trachomatis, we were

  20. Simple solutions for relativistic generalizations of the Child-Langmuir law and the Langmuir-Blodgett law

    SciTech Connect

    Zhang Yongpeng; Liu Guozhi; Yang Zhanfeng; Shao Hao; Xiao Renzhen; Xing Qingzi; Zhong Huaqiang; Lin Yuzheng

    2009-04-15

    In this paper, the Child-Langmuir law and Langmuir-Blodgett law are generalized to the relativistic regime by a simple method. Two classical laws suitable for the nonrelativistic regime are modified to simple approximate expressions applicable for calculating the space-charge-limited currents of one-dimensional steady-state planar diodes and coaxial diodes under the relativistic regime. The simple approximate expressions, extending the Child-Langmuir law and Langmuir-Blodgett law to fit the full range of voltage, have small relative errors less than 1% for one-dimensional planar diodes and less than 5% for coaxial diodes.

  1. Polyoxometalate monolayers in Langmuir-Blodgett films.

    PubMed

    Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; Mingotaud, Christophe; Ravaine, Serge; Romualdo-Torres, Gemma; Delhaès, Pierre

    2005-06-20

    Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB film occur very quickly and are reversible. 2) The preparation of LB films based on magnetic polyoxometalates, such as the Keggin anions, [CoW12O40]6- and [SiMn(OH2)W11O39]6-, or containing magnetic clusters of increasing nuclearities such as [Co4(H2O)2(PW9O34)2]10- and [Co4(H2O)2(P2W15O62)2]16- based on a Co4O16 ferromagnetic cluster, and the polyoxometalates [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16- and [Ni9(OH)3-(H2O)6(HPO4)2(PW9O34)3]16- based on a nonanuclear M9O36 cluster. 3) The preparation of LB films of the giant heteropolyoxomolybdate, [Na3(NH4)12][Mo57Fe6(NO)6O174(OH)3-(H2O)24]76 H2O.

  2. Polarized control of probe absorption in a single-layer graphene nanostructure system

    NASA Astrophysics Data System (ADS)

    Jamshidnejad, M.; Vaezzadeh, Majid; Rahimpour Soleimani, H.; Asadpour, Seyyed Hossein

    2016-02-01

    In this paper, we investigated the behaviors of the absorptive-dispersive properties of weak probe light based on quantum coherence and interference in a Landau-quantized graphene nanostructure driven by coherent pumping fields. The linear dynamical properties of the grapheme are discussed with reference to the density matrix method and the perturbation theory. It is found that under certain conditions and by an appropriate selection of the parameters of the medium, the absorption, dispersion and group index of the weak probe light can be controlled. Moreover, the superluminal light propagation in the system is accompanied by amplification to make sure that the probe field is amplified as it passes through the system via adjusting the corresponding controllable parameters such as the intensity, the detuning and the relative phase of the applied fields. Moreover, it is observed that the probe amplification can be obtained in the presence or absence of population inversion by properly choosing the system’s parameters. We hope that these results may have useful application in future quantum communicational systems and networks.

  3. Precise Wireless Triggering System for Anemometers with Long-Baseline Acoustic Probes

    NASA Astrophysics Data System (ADS)

    Wakatsuki, Naoto; Kinjo, Shin; Takarada, Jun; Mizutani, Koichi

    2010-07-01

    A wireless triggering system for acoustic anemometers using an acoustic probe with a long baseline is investigated. Acoustic probes for measuring micrometeorologic parameters, such as temperature and wind velocity, are used as noncontact and nondestructive methods. The acoustic probe with a long baseline was previously proposed by the authors and investigated to form a sensing grid system for micrometeorologic measurement. The authors have also partially investigated a wireless sensing grid using a wireless local-area network (LAN). However, because of the synchronization problem between sensor nodes, the trigger line has been left wired. In this paper, the problem of synchronization is solved by investigating a wireless triggering system using frequency modulated (FM) radio waves. The primitive triggering system of FM radio waves has some instability on time synchronization depending on such the communication environment as signal-to-noise ratio (SNR). To overcome the influence of the instability, a cross-correlation method is adopted to the triggering system. As a result, the time synchronization errors of the trigger system were reduced by up to one tenth. In addition, not only the instability problem but also other larger errors are compensated by the proposed system in an experimental wind velocity measurement.

  4. Using phospholipid Langmuir and Langmuir-Blodgett films as matrix for urease immobilization.

    PubMed

    Caseli, Luciano; Crespilho, Frank N; Nobre, Thatyane M; Zaniquelli, Maria Elisabete D; Zucolotto, Valtencir; Oliveira, Osvaldo N

    2008-03-01

    The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many biotechnological applications. In this paper, we used the Langmuir-Blodgett (LB) technique to obtain controlled architectures of urease immobilized in solid supports, whose physicochemical properties were investigated in detail. Urease molecules were adsorbed at the air-water interface and incorporated into Langmuir monolayers of the phospholipid dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation of urease made DPPG monolayers more flexible and caused the reduction of the equilibrium and dynamic elasticity of the film. Urease and DPPG-urease mixed monolayers could be transferred onto solid substrates, forming LB films. A close packing arrangement of urease was obtained, especially in the mixed LB films, which was inferred with nanogravimetry and electrochemistry measurements. From the blocking effect of the LB films deposited onto indium tin oxide (ITO) substrates, the electrochemical properties of the LB films pointed to a charge transport controlled by the lipid architecture.

  5. Investigating the momentum balance of a plasma pinch: An air-side stereoscopic imaging system for locating probes

    SciTech Connect

    Sears, Jason Intrator, T. P.; Feng, Y.; Swan, H. O.; Klarenbeek, J.; Gao, K.

    2014-10-01

    The momentum balance of a plasma pinch in the Reconnection Scaling Experiment (RSX) is examined in three dimensions using several repositionable, insertable probes. A new camera-based system described here triangulates the locations of the probe tips so that their measurements are spatially registered. The optical system locates probes to within ±1.5 mm of their absolute 3D position in the vessel and to within ±0.7 mm relative to other probes, on the order of the electron inertial length (1–2 mm)

  6. Non-linear Langmuir waves in a warm quantum plasma

    SciTech Connect

    Dubinov, Alexander E. Kitaev, Ilya N.

    2014-10-15

    A non-linear differential equation describing the Langmuir waves in a warm quantum electron-ion plasma has been derived. Its numerical solutions of the equation show that ordinary electronic oscillations, similar to the classical oscillations, occur along with small-scale quantum Langmuir oscillations induced by the Bohm quantum force.

  7. Using Weighted Least Squares Regression for Obtaining Langmuir Sorption Constants

    USDA-ARS?s Scientific Manuscript database

    One of the most commonly used models for describing phosphorus (P) sorption to soils is the Langmuir model. To obtain model parameters, the Langmuir model is fit to measured sorption data using least squares regression. Least squares regression is based on several assumptions including normally dist...

  8. Thermal conductance of nanoscale Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Ziade, Elbara; Goni, Miguel; Sato, Toshiyuki; Czubarow, Pawel; Schmidt, Aaron J.

    2015-11-01

    Thermal transport across organic-inorganic interfaces is fundamental to understanding heat transfer in polymer-based composites, microelectronics, and energy conversion systems. We used the Langmuir-Blodgett (LB) technique to deposit nanometer-thick films of poly(vinyl acetate) (PVAc) on silicon and gold substrates in two distinct states: Liquid condensed (Lc) and Liquid expanded (Le). We used frequency domain thermoreflectance to measure the thermal conductivity of the PVAc film and its thermal interface conductance to the substrate. We found that PVAc films prepared through the LB process have a higher thermal conductivity when compared to bulk. We measured the thermal interface conductance between PVAc and gold to be approximately 90 MW/m2 K for both the Le and Lc states, and the thermal interface conductance between PVAc and silicon to be approximately 70 MW/m2 K for both the Le and Lc states.

  9. Two-Dimensional Axisymmetric Child-Langmuir Scaling Law

    NASA Astrophysics Data System (ADS)

    Ragan-Kelley, Benjamin; Verboncoeur, John

    2007-11-01

    The classical one-dimensional Child-Langmuir law has been extended to two dimensions by numerical simulation in planar geometries [1]. By considering an axisymmetric cylindrical system with emission radius r, outer radius R > r, and gap length L, we further examine the space charge limit in two dimensions. The ratio of the observed current density limit JCL2 to the theoretical one-dimensional value JCL1 is found to be a monotonically decreasing function of the ratio of emission area (r^2) to gap separation (L). This result is in agreement with the planar results, where the emission area is proportional to the cathode width (r) [1]. The simulations were run in the particle in cell code, OOPIC [2]. [1] J. W. Luginsland, Y. Y. Lau, and R. M. Gilgenbach, Phys. Rev. Lett. 77, 4668 (1996). [2] J. P. Verboncoeur, A. B. Langdon, and N. T. Gladd, Comp. Phys. Comm. 87, 199 (1995).

  10. Boronate-based fluorescent probes: imaging hydrogen peroxide in living systems.

    PubMed

    Lin, Vivian S; Dickinson, Bryan C; Chang, Christopher J

    2013-01-01

    Hydrogen peroxide, a reactive oxygen species with unique chemical properties, is produced endogenously in living systems as a destructive oxidant to ward off pathogens or as a finely tuned second messenger in dynamic cellular signaling pathways. In order to understand the complex roles that hydrogen peroxide can play in biological systems, new tools to monitor hydrogen peroxide in its native settings, with high selectivity and sensitivity, are needed. Knowledge of organic synthetic reactivity provides the foundation for the molecular design of selective, functional hydrogen peroxide probes. A palette of fluorescent and luminescent probes that react chemoselectively with hydrogen peroxide has been developed, utilizing a boronate oxidation trigger. These indicators offer a variety of colors and in cellulo characteristics and have been used to examine hydrogen peroxide in a number of experimental setups, including in vitro fluorometry, confocal fluorescence microscopy, and flow cytometry. In this chapter, we provide an overview of the chemical features of these probes and information on their behavior to help researchers select the optimal probe and application. Copyright © 2013 Elsevier Inc. All rights reserved.

  11. Systemic deterrence of aphid probing and feeding by novel β-damascone analogues.

    PubMed

    Gabryś, Beata; Dancewicz, Katarzyna; Gliszczyńska, Anna; Kordan, Bożena; Wawrzeńczyk, Czesław

    β-Damascone appeared a weak attractant close to not active to Myzus persicae, but modifications of its structure caused the avoidance of treated leaves by aphids during settling and reluctance to probe in simple choice- and no-choice experiments in previous studies. Here, the electrical penetration graph (EPG) technique, which allows monitoring of aphid probing within plant tissues, was applied to explore the biological background and localisation in plant tissues of the deterrent activities of β-damascone and its analogues. Activity of β-damascone and β-damascone-derived compounds depended on their substituents, which was manifested in the variation in the potency of the behavioural effect and differences in aphid probing phases that were affected. β-Damascone appeared a behaviourally inactive compound. The moderately active β-damascone ester affected aphid activities only during the phloem phase. The highly active deterrents-dihydro-β-damascol, β-damascone acetate, δ-bromo-γ-lactone, and unsaturated γ-lactone-affected pre-phloem and phloem aphid probing activities. The most effective structural modification that evoked the strongest negative response from M. persicae was the transformation of β-damascone into δ-bromo-γ-lactone. The behavioural effect of this transformation was demonstrated in frequent interruption of probing in peripheral tissues, which caused repeated failures in finding sieve elements, and reduction in the ingestion time during the phloem phase in favour of watery salivation. The inhibition of aphid probing at both the pre-phloem and phloem levels reveals the passage of the compounds studied through the plant surface and their distribution within plant tissues in a systemic way, which may reduce the risk of the transmission of non-persistent and persistent viruses.

  12. Advanced development of particle-beam-probe diagnostic systems. Technical progress report, 1 July 1980-30 April 1981

    SciTech Connect

    Hickok, R.L.; Jennings, W.C.; Woo, J.T.; Connor, K.A.

    1981-05-01

    The heavy ion beam probe system on the RENTOR tokamak has been reinstalled with considerably improved performance. The heavy neutral beam probe system on the ALEX baseball facility has demonstrated the capability of measuring space potential in minimum-B geometry. A large amount of data were obtained from the highly successful TMX beam probe system and are presently being analyzed. Technological improvements were made on both the RENTOR and ALEX diagnostic systems, new ion sources and extraction configurations were investigated, and the superiority of off-line processing techniques for beam probe data has been demonstrated. The development of high energy probing beams for application to major confinement experiments has been initiated and cross-over sweep systems to improve spatial resolution, differential pumping, and reduce energy requirements have been designed.

  13. Development of dual-probe atomic force microscopy system using optical beam deflection sensors with obliquely incident laser beams.

    PubMed

    Tsunemi, Eika; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2011-03-01

    We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The deflection of each cantilever is measured by the optical beam deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.

  14. Development of dual-probe atomic force microscopy system using optical beam deflection sensors with obliquely incident laser beams

    NASA Astrophysics Data System (ADS)

    Tsunemi, Eika; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2011-03-01

    We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The deflection of each cantilever is measured by the optical beam deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.

  15. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    SciTech Connect

    Kalinin, Sergei V; Rodriguez, Brian J; Jesse, Stephen; Karapetian, Edgar; Mirman, B; Eliseev, E. A.; Morozovska, A. N.

    2007-01-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  16. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Kalinin, Sergei V.; Rodriguez, Brian J.; Jesse, Stephen; Karapetian, Edgar; Mirman, Boris; Eliseev, Eugene A.; Morozovska, Anna N.

    2007-08-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  17. Landau damping of Langmuir twisted waves with kappa distributed electrons

    SciTech Connect

    Arshad, Kashif Aman-ur-Rehman; Mahmood, Shahzad

    2015-11-15

    The kinetic theory of Landau damping of Langmuir twisted modes is investigated in the presence of orbital angular momentum of the helical (twisted) electric field in plasmas with kappa distributed electrons. The perturbed distribution function and helical electric field are considered to be decomposed by Laguerre-Gaussian mode function defined in cylindrical geometry. The Vlasov-Poisson equation is obtained and solved analytically to obtain the weak damping rates of the Langmuir twisted waves in a nonthermal plasma. The strong damping effects of the Langmuir twisted waves at wavelengths approaching Debye length are also obtained by using an exact numerical method and are illustrated graphically. The damping rates of the planar Langmuir waves are found to be larger than the twisted Langmuir waves in plasmas which shows opposite behavior as depicted in Fig. 3 by J. T. Mendoça [Phys. Plasmas 19, 112113 (2012)].

  18. Langmuir wave in a dusty plasma with nonextensive electrons

    NASA Astrophysics Data System (ADS)

    Gong, B.; Dong, X. Y.

    2017-04-01

    The effect of the dust charge perturbation on Langmuir waves in a dusty plasma with nonextensive electrons and Maxwellian ions is investigated within the fluid theory framework, where the sink term of electrons in the continuity equation is considered. The dispersion of Langmuir waves shows that the dust charge relaxation introduces an additional source of dissipation in Langmuir waves. The damping rate of Langmuir oscillation caused by the dust charge fluctuations is bigger than the one with Maxwellian electrons when the nonextensively distributed electrons have a suprathermal tail. On the contrary, the excess of low energy electrons for nonextensively distributed electrons can lower the damping rate of Langmuir oscillation. These differences are mainly due to the modification of the unperturbed electron attachment frequency by the nonextensively distributed electrons. Our results may be of wide relevance to space and interstellar plasmas.

  19. Theory for low-frequency modulated Langmuir wave packets

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Robinson, P. A.

    1992-01-01

    Langmuir wave packets with low frequency modulations (or beats) observed in the Jovian foreshock are argued to be direct evidence for the Langmuir wave decay L yields L-prime + S. In this decay, 'pump' Langmuir waves L, driven by an electron beam, produce backscattered product Langmuir waves L-prime and ion sound waves S. The L and L-prime waves beat at the frequency and wavevector of the S waves, thereby modulating the wave packets. Beam speeds calculated using the modulated Jovian wave packets (1) are reasonable, at 4-10 times the electron thermal speed, (2) are consistent with theoretical limits on the decay process, and (3) decrease with increasing foreshock depth, as expected theoretically. These results strongly support the theory. The modulation depth of some wave packets suggests saturation by the decay L yields L-prime + S. Applications to modulated Langmuir packets in the Venusian and terrestrial foreshocks and in a type III radio source are proposed.

  20. Micromachined Silicon Stimulating Probes with CMOS Circuitry for Use in the Central Nervous System

    NASA Astrophysics Data System (ADS)

    Tanghe, Steven John

    1992-01-01

    Electrical stimulation in the central nervous system is a valuable technique for studying neural systems and is a key element in the development of prostheses for deafness and other disorders. This thesis presents a family of multielectrode probe structures, fulfilling the need for chronic multipoint stimulation tools essential for interfacing to the highly complex neural networks in the brain. These probes are batch-fabricated on silicon wafers, employing photoengraving techniques to precisely control the electrode site and array geometries and to allow the integration of on-chip CMOS circuitry for signal multiplexing and stimulus current generation. Silicon micromachining is used to define the probe shapes, which have typical shank dimensions of 3 mm in length by 100 mu m in width by 15 μm in thickness. Each shank supports up to eight planar iridium oxide electrode sites capable of delivering charge densities in excess of 3 mC/cm^2 during current pulse stimulation. Three active probe circuits have been designed with varied complexity and capability. All three can deliver biphasic stimulus currents through 16 sites using only 5 external leads, and they are all compatible with the same external control system. The most complex design interprets site addresses and stimulus current amplitudes from 16-bit words shifted into the probe at 4 MHz. Sixteen on-chip, biphasic, 8-bit digital-to-analog converters deliver analog stimulus currents in the range of +/- 254 muA to any combination of electrode sites. These DACs exhibit full-scale internal linearity to better than +/-1/2 LSB and can be calibrated by varying the positive power supply voltage. The entire probe circuit dissipates only 80 muW from +/-5 V supplies when not delivering stimulus currents, it includes several safety features, and is testable from the input pads. Test results from the fabricated circuits indicate that they all function properly at clocking frequencies as high as 10 MHz, meeting or exceeding

  1. Recognition- and reactivity-based fluorescent probes for studying transition metal signaling in living systems.

    PubMed

    Aron, Allegra T; Ramos-Torres, Karla M; Cotruvo, Joseph A; Chang, Christopher J

    2015-08-18

    Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed "recognition" and "reactivity". Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give three recent

  2. Recognition- and Reactivity-Based Fluorescent Probes for Studying Transition Metal Signaling in Living Systems

    PubMed Central

    2015-01-01

    Conspectus Metals are essential for life, playing critical roles in all aspects of the central dogma of biology (e.g., the transcription and translation of nucleic acids and synthesis of proteins). Redox-inactive alkali, alkaline earth, and transition metals such as sodium, potassium, calcium, and zinc are widely recognized as dynamic signals, whereas redox-active transition metals such as copper and iron are traditionally thought of as sequestered by protein ligands, including as static enzyme cofactors, in part because of their potential to trigger oxidative stress and damage via Fenton chemistry. Metals in biology can be broadly categorized into two pools: static and labile. In the former, proteins and other macromolecules tightly bind metals; in the latter, metals are bound relatively weakly to cellular ligands, including proteins and low molecular weight ligands. Fluorescent probes can be useful tools for studying the roles of transition metals in their labile forms. Probes for imaging transition metal dynamics in living systems must meet several stringent criteria. In addition to exhibiting desirable photophysical properties and biocompatibility, they must be selective and show a fluorescence turn-on response to the metal of interest. To meet this challenge, we have pursued two general strategies for metal detection, termed “recognition” and “reactivity”. Our design of transition metal probes makes use of a recognition-based approach for copper and nickel and a reactivity-based approach for cobalt and iron. This Account summarizes progress in our laboratory on both the development and application of fluorescent probes to identify and study the signaling roles of transition metals in biology. In conjunction with complementary methods for direct metal detection and genetic and/or pharmacological manipulations, fluorescent probes for transition metals have helped reveal a number of principles underlying transition metal dynamics. In this Account, we give

  3. Comparative Analysis and Approximations of Space -Charge Formation in Langmuir Electrodes Including Temperature Effects.

    NASA Astrophysics Data System (ADS)

    Valdeblànquez, Eder

    2001-10-01

    Eder Valdeblànquez,Universidad del Zulia,Apartado 4011-A 526,Maracaibo,Venezuela. ABSTRACT: In this paper by space charge effect in Langmuir probes are compared for different kind of symmetries; plane, cylindrical and spherical. A detailed analysis is performed here including temperature effects, and therefore kinetic theory is used instead of fluid equations as other authors. The strongly non-linear equations obtained here have been solved first by numerical analysis and later by approximations using Bessel functions. The accuracy of each approximaton is also discussed. Space Charge effects are important in plane geometries than in the case of cylindrical or spherical symmetries.

  4. Detection of bovine trichomoniasis with a specific DNA probe and PCR amplification system.

    PubMed

    Ho, M S; Conrad, P A; Conrad, P J; LeFebvre, R B; Perez, E; BonDurant, R H

    1994-01-01

    Trichomoniasis is a widespread, economically important venereal disease of cattle which causes infertility and abortion. Effective control of trichomoniasis has been impeded by the insensitivity of traditional diagnostic procedures, which require the isolation and cultivation of the parasite, Tritrichomonas foetus, from infected cattle. We developed a 0.85-kb T. foetus DNA probe by identifying conserved sequences in DNAs from T. foetus that were isolated from cattle in California, Idaho, Nevada, and Costa Rica. The probe hybridized specifically to DNAs of T. foetus isolates from different geographic areas but not to DNA preparations of Trichomonas vaginalis, bovine cells, or a variety of bacteria from cattle. The probe detected DNA from a minimum of 10(5) T. foetus organisms. To improve sensitivity, a partial sequence of the probe was used to identify oligonucleotide primers (TF1 and TF2) which could be used to amplify a 162-bp product from T. foetus DNAs by PCR. A chemiluminescent internal T. foetus sequence probe was hybridized to Southern blots of the amplification product. This system detected as few as one T. foetus organism in culture media or 10 parasites in samples containing bovine preputial smegma. Analysis of 52 clinical samples showed that 47 (90.4%) of the 52 samples were correctly identified, with no false-positive reactions. In comparison, the traditional cultivation method detected 44 (84.6%) of the 52 samples from T. foetus-infected and uninfected bulls. These results indicate that the PCR-based amplification system could be a useful alternative method for the diagnosis of bovine trichomoniasis.

  5. Development of a Computer Control System for Heavy Ion Beam Probes

    NASA Astrophysics Data System (ADS)

    Andersen, J. K.; Roberts, S. L.; Westervelt, E. R.; Schoch, P. M.; Schatz, J. G.

    1996-11-01

    Enhanced computer control of heavy ion beam probes would increase the reproducability of experimental conditions by automation and feedback control of some system parameters. Also, operation from a remote site would then be feasible. Computer control has been implemented on a variety of Rensselaer heavy ion beam probe systems. However, no system to date has allowed complete remote operation. This has been primarily due to the limitations of the user interface. The next generation of HIBP control systems software is being created with National Instruments' graphical language, LabVIEW. The virtual instruments allow detailed monitoring and control of the injected beam conditions. The control and monitoring of the ion beam, including filament current and Pierce, focusing, quadrupole lens, and sweep electrodes' voltages has been tested on RPI's vertical test stand. A feedback routine to focus the beam using the quadrupole lens is currently being developed. When this capability is available, it will be implemented on a heavy ion beam probe diagnostic operating on a magnetic confinement device.

  6. A multi-probe thermophoretic soot sampling system for high-pressure diffusion flames

    SciTech Connect

    Vargas, Alex M.; Gülder, Ömer L.

    2016-05-15

    Optical diagnostics and physical probing of the soot processes in high pressure combustion pose challenges that are not faced in atmospheric flames. One of the preferred methods of studying soot in atmospheric flames is in situ thermophoretic sampling followed by transmission electron microscopy imaging and analysis for soot sizing and morphology. The application of this method of sampling to high pressures has been held back by various operational and mechanical problems. In this work, we describe a rotating disk multi-probe thermophoretic soot sampling system, driven by a microstepping stepper motor, fitted into a high-pressure chamber capable of producing sooting laminar diffusion flames up to 100 atm. Innovative aspects of the sampling system design include an easy and precise control of the sampling time down to 2.6 ms, avoidance of the drawbacks of the pneumatic drivers used in conventional thermophoretic sampling systems, and the capability to collect ten consecutive samples in a single experimental run. Proof of principle experiments were performed using this system in a laminar diffusion flame of methane, and primary soot diameter distributions at various pressures up to 10 atm were determined. High-speed images of the flame during thermophoretic sampling were recorded to assess the influence of probe intrusion on the flow field of the flame.

  7. High repetition pump-and-probe photoemission spectroscopy based on a compact fiber laser system.

    PubMed

    Ishida, Y; Otsu, T; Ozawa, A; Yaji, K; Tani, S; Shin, S; Kobayashi, Y

    2016-12-01

    The paper describes a time-resolved photoemission (TRPES) apparatus equipped with a Yb-doped fiber laser system delivering 1.2-eV pump and 5.9-eV probe pulses at the repetition rate of 95 MHz. Time and energy resolutions are 11.3 meV and ∼310 fs, respectively, the latter is estimated by performing TRPES on a highly oriented pyrolytic graphite (HOPG). The high repetition rate is suited for achieving high signal-to-noise ratio in TRPES spectra, thereby facilitating investigations of ultrafast electronic dynamics in the low pump fluence (p) region. TRPES of polycrystalline bismuth (Bi) at p as low as 30 nJ/mm(2) is demonstrated. The laser source is compact and is docked to an existing TRPES apparatus based on a 250-kHz Ti:sapphire laser system. The 95-MHz system is less prone to space-charge broadening effects compared to the 250-kHz system, which we explicitly show in a systematic probe-power dependency of the Fermi cutoff of polycrystalline gold. We also describe that the TRPES response of an oriented Bi(111)/HOPG sample is useful for fine-tuning the spatial overlap of the pump and probe beams even when p is as low as 30 nJ/mm(2).

  8. High repetition pump-and-probe photoemission spectroscopy based on a compact fiber laser system

    NASA Astrophysics Data System (ADS)

    Ishida, Y.; Otsu, T.; Ozawa, A.; Yaji, K.; Tani, S.; Shin, S.; Kobayashi, Y.

    2016-12-01

    The paper describes a time-resolved photoemission (TRPES) apparatus equipped with a Yb-doped fiber laser system delivering 1.2-eV pump and 5.9-eV probe pulses at the repetition rate of 95 MHz. Time and energy resolutions are 11.3 meV and ˜310 fs, respectively, the latter is estimated by performing TRPES on a highly oriented pyrolytic graphite (HOPG). The high repetition rate is suited for achieving high signal-to-noise ratio in TRPES spectra, thereby facilitating investigations of ultrafast electronic dynamics in the low pump fluence (p) region. TRPES of polycrystalline bismuth (Bi) at p as low as 30 nJ/mm2 is demonstrated. The laser source is compact and is docked to an existing TRPES apparatus based on a 250-kHz Ti:sapphire laser system. The 95-MHz system is less prone to space-charge broadening effects compared to the 250-kHz system, which we explicitly show in a systematic probe-power dependency of the Fermi cutoff of polycrystalline gold. We also describe that the TRPES response of an oriented Bi(111)/HOPG sample is useful for fine-tuning the spatial overlap of the pump and probe beams even when p is as low as 30 nJ/mm2.

  9. A servomechanism for a micro-electro-mechanical-system-based scanning-probe data storage device

    NASA Astrophysics Data System (ADS)

    Pantazi, A.; Lantz, M. A.; Cherubini, G.; Pozidis, H.; Eleftheriou, E.

    2004-10-01

    Micro-electro-mechanical-system (MEMS)-based scanning-probe data storage devices are emerging as potential ultra-high-density, low-access-time, and low-power alternatives to conventional data storage. One implementation of probe-based storage uses thermomechanical means to store and retrieve information in thin polymer films. One of the challenges in building such devices is the extreme accuracy and the short latency required in the navigation of the probes over the polymer medium. This paper focuses on the design and characterization of a servomechanism to achieve such accurate positioning in a probe-based storage prototype. In our device, the polymer medium is positioned on a MEMS scanner with x/y-motion capabilities of about 100 µm. The device also includes thermal position sensors that provide x/y-position information to the servo controller. Based on a discrete state-space model of the scanner dynamics, a controller is designed using the linear quadratic Gaussian approach with state estimation. The random seek performance of this approach is evaluated and compared with that of the conventional proportional, integrator, and derivative (PID) approach. The results demonstrate the superiority of the state-space approach, which achieves seek times of about 4 ms in a ± 50 µm range. Finally, the experimental results show that closed-loop track following using the thermal position-sensor signals is feasible and yields a position-error standard deviation of approximately 2 nm.

  10. Electronic nose system combined with membrane interface probe for detection of VOCs in water

    NASA Astrophysics Data System (ADS)

    Cho, Junghwan; Howard, Zachary; Kurup, Pradeep

    2011-09-01

    This paper describes a novel electronic nose system combined with a membrane interface probe (MIP) for detecting volatile organic compounds (VOCs) in water. The MIP is an in situ tool that allows the detection of certain VOCs in the soil via a pushed or driven probe. The MIP was combined with a sensor array consisting of four different tin-oxide gas sensors known as an electronic nose (e-nose). The designed e-nose system was calibrated in aqueous media spiked with benzene, toluene, ethylbenzene, and p-xylene (BTEX) at concentrations of 100, 250, and 500 ppm. Since the experiment was conducted utilizing five repetitions for each analyte, a data set of 60 measurements was prepared for principal components analysis (PCA). The results of the PCA showed that two principal components contain more than 99% variance information and each VOC is separable and detectable by the e-nose.

  11. Investigation of outer planet atmospheres using the pioneer entry probe radio system

    NASA Technical Reports Server (NTRS)

    Croft, T. A.

    1974-01-01

    The requirements for a telecommunication link which will relay information from a space probe to a carrier spacecraft during space exploration missions are examined. Specific experiments are described and the relative value of the proposed techniques are evaluated. Radio science methods as related to telecommunications systems are discussed. Operational implications of the various approaches to scientific measurement by telemetry of tracking radios are analyzed. Emphasis is placed on a conceptual description of the physics rather than the mathematical development.

  12. Hand-held probe based optical imaging system towards breast cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Ge, Jiajia; Jayachandran, Bhavani; Regalado, Steven; Zhu, Banghe; Godavarty, Anuradha

    2007-02-01

    Near-infrared (NIR) optical imaging is an emerging noninvasive modality for breast cancer diagnosis. However, the currently available optical imaging systems towards tomography studies are limited either by instrument portability, patient comfort, or flexibility to image any given tissue volume. Herein, a hand-held based optical imaging system is developed such that it can possibly overcome some of the above limitations. The unique features of the hand-held optical probe are: (i) to perform simultaneous multiple point illumination and detection, thus decreasing the total imaging time and improving the overall signal strength; (ii) to adapt to the contour of tissue surface, thus decreasing the leakage of excitation and emission signal at contact surface; and (iii) to obtain trans-illumination measurements apart from reflectance measurements, thus improving the depth information. The increased detected signal strength as well as total interrogated tissue volume is demonstrated by simulation studies (i.e. forward model) over a 5×10×10 cc slab phantom. The appropriate number and layout of the source and detection points on the probe head is determined and the hand-held optical probe is developed. A frequency-domain ICCD (intensified charge coupled device) detection system, which allows simultaneous multiple points detection, is developed and coupled to the hand-held probe in order to perform fluorescence-enhanced optical imaging of tissue phantoms. In the future, imaging of homogenous liquid phantoms will be used for the assessment of this hand-held system, followed by extensive imaging studies on different phantoms types under various experimental conditions.

  13. The cervical cancer detection system based on an endoscopic rotary probe

    NASA Astrophysics Data System (ADS)

    Yang, Yanshuang; Hou, Qiang; Zhao, Huijuan; Qin, Zhuanping; Gao, Feng

    2012-03-01

    To acquire the optical diffuse tomographic image of the cervix, a novel endoscopic rotary probe is designed and the frequency domain measurement system is developed. The finite element method and Gauss-Newton method are proposed to reconstruct the image of the phantom. In the optical diffuse tomographic imaging of the cervix, an endoscopic probe is needed and the detection of light at different separation to the irradiation spot is necessary. To simplify the system, only two optical fibers are adopted for light irradiation and collection, respectively. Two small stepper motors are employed to control the rotation of the incident fiber and the detection fiber, respectively. For one position of source fiber, the position of the detection fiber is changed from -61.875° to -50.625° and 50.625° to 61.875° to the source fiber, respectively. Then, the position of the source fiber is changed to another preconcerted position, which deviates the precious source position in an angle of 11.25°, and the detection fiber rotates within the above angles. To acquire the efficient irradiation and collection of the light, a gradient-index (GRIN) lens is connected at the head of the optical fiber. The other end of the GRIN lens is cut to 45°. With this design, light from optical fiber is reflected to the cervix wall, which is perpendicular to the optical fiber or vice versa. Considering the cervical size, the external diameter of the endoscopic probe is made to 20mm. A frequency domain (FD) near-infrared diffuse system is developed aiming at the detection of early cervical cancer, which modulates the light intensity in radio frequency and measures the amplitude attenuation and the phase delay of the diffused light using heterodyne detection. Phantom experiment results demonstrate that the endoscopic rotary scan probe and the system perform well in the endoscopic measurement.

  14. Properties of Langmuir monolayers from semifluorinated alkanes

    NASA Astrophysics Data System (ADS)

    Broniatowski, M.; Macho, I. Sandez; Miñones, J.; Dynarowicz-Łątka, P.

    2005-06-01

    The aim of this study was to characterize several semifluorinated alkanes (SFA), of the general formula F(CF 2) m(CH 2) nH (in short F mH n), containing 25 carbon atoms in total (pentacosanes) differing in the m/ n ratio, as Langmuir monolayers at the free water surface. The following compounds have been studied: F6H19, F8H17, F10H15 and F12H13. Surface pressure ( π) and electric surface potential (Δ V) isotherms were recorded in addition to quantitative Brewster angle microscopy results. The negative sign of Δ V evidenced for the orientation of all the investigated semifluorinated pentacosanes, regardless the length of the hydrogenated segment, with their perfluorinated parts directed towards the air. As inferred from apparent dipole moment values and relative reflectivity results, the fluorinated pentacosanes with shorter perfluorinated fragment (F6H19 and F8H17) were found to be vertically oriented at the air/water interface, while those with longer perfluorinated moiety (F10H15 and F12H13) remain titled even in the vicinity of the film collapse.

  15. Probe tip heating assembly

    SciTech Connect

    Schmitz, Roger William; Oh, Yunje

    2016-10-25

    A heating assembly configured for use in mechanical testing at a scale of microns or less. The heating assembly includes a probe tip assembly configured for coupling with a transducer of the mechanical testing system. The probe tip assembly includes a probe tip heater system having a heating element, a probe tip coupled with the probe tip heater system, and a heater socket assembly. The heater socket assembly, in one example, includes a yoke and a heater interface that form a socket within the heater socket assembly. The probe tip heater system, coupled with the probe tip, is slidably received and clamped within the socket.

  16. Upgrade of a commercial four-probe scanning tunneling microscopy system

    NASA Astrophysics Data System (ADS)

    Ma, Ruisong; Huan, Qing; Wu, Liangmei; Yan, Jiahao; Zou, Qiang; Wang, Aiwei; Bobisch, Christian A.; Bao, Lihong; Gao, Hong-Jun

    2017-06-01

    Upgrade of a commercial ultra-high vacuum four-probe scanning tunneling microscopy system for atomic resolution capability and thermal stability is reported. To improve the mechanical and thermal performance of the system, we introduced extra vibration isolation, magnetic damping, and double thermal shielding, and we redesigned the scanning structure and thermal links. The success of the upgrade is characterized by its atomically resolved imaging, steady cooling down cycles with high efficiency, and standard transport measurement capability. Our design may provide a feasible way for the upgrade of similar commercial systems.

  17. Upgrade of a commercial four-probe scanning tunneling microscopy system.

    PubMed

    Ma, Ruisong; Huan, Qing; Wu, Liangmei; Yan, Jiahao; Zou, Qiang; Wang, Aiwei; Bobisch, Christian A; Bao, Lihong; Gao, Hong-Jun

    2017-06-01

    Upgrade of a commercial ultra-high vacuum four-probe scanning tunneling microscopy system for atomic resolution capability and thermal stability is reported. To improve the mechanical and thermal performance of the system, we introduced extra vibration isolation, magnetic damping, and double thermal shielding, and we redesigned the scanning structure and thermal links. The success of the upgrade is characterized by its atomically resolved imaging, steady cooling down cycles with high efficiency, and standard transport measurement capability. Our design may provide a feasible way for the upgrade of similar commercial systems.

  18. Laboratory measurements of the generation and evolution of Langmuir circulations

    NASA Astrophysics Data System (ADS)

    Melville, W. Kendall; Shear, Robert; Veron, Fabrice

    1998-06-01

    We present laboratory measurements of the generation and evolution of Langmuir circulations as an instability of a wind-driven surface shear layer. The shear layer, which is generated by an accelerating wind starting from rest above a quiescent water surface, both accelerates and deepens monotonically until the inception of the Langmuir circulations. The Langmuir circulations closely follow the initial growth of the wind waves and rapidly lead to vertical mixing of the horizontal momentum and a deceleration of the surface layer. Prior to the appearance of the Langmuir circulations, the depth of the shear layer scales with (vt)1/2 (v is the kinematic viscosity and t is time), in accordance with molecular rather than turbulent transport. For final wind speeds in the range 3 to 5 m s[minus sign]1, the wavenumber of the most unstable Langmuir circulation normalized by the surface wavenumber, k*lc, is 0.68±0.24, at a reciprocal Langmuir number, La[minus sign]1, of 52±21. The observations are compared with available theoretical results, although none are directly applicable to the conditions of the experiments. The implications of this work for the generation and evolution of Langmuir circulations in the ocean and other natural water bodies are discussed.

  19. Sensor probes and phantoms for advanced transcranial magnetic stimulation system developments

    NASA Astrophysics Data System (ADS)

    Meng, Qinglei; Patel, Prashil; Trivedi, Sudhir; Du, Xiaoming; Hong, Elliot; Choa, Fow-Sen

    2015-05-01

    Transcranial magnetic stimulation (TMS) has become one of the most widely used noninvasive method for brain tissue stimulation and has been used as a treatment tool for various neurological and psychiatric disorders including migraine, stroke, Parkinson's disease, dystonia, tinnitus and depression. In the process of developing advanced TMS deep brain stimulation tools, we need first to develop field measurement devices like sensory probes and brain phantoms, which can be used to calibrate the TMS systems. Currently there are commercially available DC magnetic or electric filed measurement sensors, but there is no instrument to measure transient fields. In our study, we used a commercial figure-8 shaped TMS coil to generate transient magnetic field and followed induced field and current. The coil was driven by power amplified signal from a pulse generator with tunable pulse rate, amplitude, and duration. In order to obtain a 3D plot of induced vector electric field, many types of probes were designed to detect single component of electric-field vectors along x, y and z axis in the space around TMS coil. We found that resistor probes has an optimized signal-to-noise ratio (SNR) near 3k ohm but it signal output is too weak compared with other techniques. We also found that inductor probes can have very high output for Curl E measurement, but it is not the E-field distribution we are interested in. Probes with electrical wire wrapped around iron coil can directly measure induced E-field with high sensitivity, which matched computer simulation results.

  20. Measuring the inboard side scrape-off layer of DIII-D plasmas using Swing-Probes

    NASA Astrophysics Data System (ADS)

    Tsui, Cedric

    The scrape-off layer (SOL) plasma of a tokamak often has a complicated spatial dependence. The temperatures, densities and flow speeds can vary significantly on the same magnetic flux tube at different poloidal locations. To fully understand the plasma variation, we must make active measurements along the full length of the flux tubes by expanding our diagnostic capability to include the critically under-diagnosed inboard side. To accomplish this, a new pair of in-situ reciprocating Mach probes called Swing-Probes have been developed and deployed on the DIII D centerpost. This design is unique in that the probe swings vertically through the SOL plasma, taking measurements along a 180° arc with a 20 cm radius. Two electrodes maintain a Mach-pair orientation throughout the swing and provide measurements of saturation current, electron temperature, and parallel flow speeds. The probes can handle very high heat fluxes and have taken measurements up to the Last Closed Flux Surface (LCFS) in high-powered H-Mode at 10 MW. The Swing-Probe temperature and density measurements have been verified against the floor Langmuir probes, the core Thomson scattering and the divertor Thomson scattering systems in DIII-D for conditions where poloidal variation are expected to be small. Measurements have been taken across a wide range of plasma conditions and provide informative relationships between the plasma parameters at the entrance of the inner divertor and the crown of the plasma. The low-turbulence plasmas on the inboard scrape-off layer make it possible to clearly quantify the sheath-expansion around Langmuir probes. An I-V fitter has been developed which can account for sheath-expansion in a theoretically consistent way, improving the reliability of Langmuir probe data analysis. In an inner-wall limited experiment in DIII-D requested by ITER, the Swing-Probes made the first Langmuir probe measurements of an enhanced heat flux feature just outside the LCFS. These measurements

  1. Low cost FPGA based data acquisition system for a gamma imaging probe

    NASA Astrophysics Data System (ADS)

    Fysikopoulos, E.; Georgiou, M.; Loudos, G.; Matsopoulos, G.

    2013-11-01

    We present the development of a low cost field programmable gate arrays (FPGA) based data acquisition system for a gamma imaging probe proposed for sentinel lymph node (SLN) mapping. Radioguided surgery using a gamma probe is an established practice and has been widely introduced in SLN biopsies. For such applications, imaging systems require compact readout electronics and flexibility. Embedded systems implemented in the FPGA technology offer new possibilities in data acquisition for nuclear medicine imagers. FPGAs are inexpensive compared to application specific integrated circuits (ASICs), usually used for the readout electronics of dedicated gamma cameras and their size is rather small. In this study, cost effective analog to digital converters (ADCs) were used and signal processing algorithms were implemented in the FPGA to extract the energy and position information. The analog front-end electronics were carefully designed taking into account the low sampling rate of the ADCs. The reference gamma probe has a small field of view (2.5 cm × 2.5 cm) and is based on the R8900U-00-C12 position sensitive photomultiplier tube (PSPMT) coupled to a pixellated CsI(Na) scintillator with 1 mm × 1 mm × 5 mm crystal element size. Measurements were carried out using a general purpose collimator and 99mTc sources emitted at 140 keV. Performance parameters for the imaging gamma probe were compared with those obtained when data were acquired using the standard NIM (Nuclear Instrumentation Modules) electronics and found to be in very good agreement, which demonstrates the efficiency of the proposed implementation.

  2. Development of an Integrated Data Acquisition System for a Small Flight Probe

    NASA Technical Reports Server (NTRS)

    Swanson, Gregory T.; Empey, Daniel M.; Skokova, Kristina A.; Venkatapathy, Ethiraj

    2012-01-01

    In support of the SPRITE concept, an integrated data acquisition system has been developed and fabricated for preliminary testing. The data acquisition system has been designed to condition traditional thermal protection system sensors, store their data to an on-board memory card, and in parallel, telemeter to an external system. In the fall of 2010, this system was integrated into a 14 in. diameter, 45 degree sphere cone probe instrumented with thermal protection system sensors. This system was then tested at the NASA Ames Research Center Aerodynamic Heating Facility's arc jet at approximately 170 W/sq. cm. The first test in December 2010 highlighted hardware design issues that were redesigned and implemented leading to a successful test in February 2011.

  3. Probing nanofriction and Aubry-type signatures in a finite self-organized system

    NASA Astrophysics Data System (ADS)

    Kiethe, J.; Nigmatullin, R.; Kalincev, D.; Schmirander, T.; Mehlstäubler, T. E.

    2017-05-01

    Friction in ordered atomistic layers plays a central role in various nanoscale systems ranging from nanomachines to biological systems. It governs transport properties, wear and dissipation. Defects and incommensurate lattice constants markedly change these properties. Recently, experimental systems have become accessible to probe the dynamics of nanofriction. Here, we present a model system consisting of laser-cooled ions in which nanofriction and transport processes in self-organized systems with back action can be studied with atomic resolution. We show that in a system with local defects resulting in incommensurate layers, there is a transition from sticking to sliding with Aubry-type signatures. We demonstrate spectroscopic measurements of the soft vibrational mode driving this transition and a measurement of the order parameter. We show numerically that both exhibit critical scaling near the transition point. Our studies demonstrate a simple, well-controlled system in which friction in self-organized structures can be studied from classical- to quantum-regimes.

  4. Extended geometric method: a simple approach to derive adsorption rate constants of Langmuir-Freundlich kinetics.

    PubMed

    Azizian, Saeid; Haerifar, Monireh; Basiri-Parsa, Jalal

    2007-08-01

    A new and simple equation has been presented here for calculation of adsorption and desorption rate constants of Langmuir-Freundlich kinetic equation. The derivation of new equation is on the basis of extension and correction to the geometric method which has been presented by Kuan et al. [Kuan, W.-H., Lo, S.-L., Chang, C.M., Wang, M.K., 2000. A geometric approach to determine adsorption and desorption kinetic constants. Chemosphere 41, 1741-1747] for the kinetics of adsorption/desorption in aqueous solutions. The correction is to consider that the concentration of solute is not constant and changes as adsorption proceeds. The extension is that we applied Langmuir-Freundlich kinetic model instead of Langmuir kinetic model to consider the heterogeneity and therefore it is more applicable to the real systems. For solving Langmuir-Freundlich kinetic model, some geometric methods and also Taylor expansion were used and finally a simple and novel equation was derived (Eq. (20)) for calculation of adsorption rate constant. This new method was named "extended geometric method". The input data of the obtained equation can be simply derived from initial data of adsorption kinetics. Finally the adsorption of methyl orange onto granular activated carbon was carried out at dynamic and equilibrium conditions and the capabilities of extended geometric method were examined by the experimental data.

  5. Initial Results in Power System Identification from Injected Probing Signals Using a Subspace Method

    SciTech Connect

    Zhou, Ning; Pierre, John W.; Hauer, John F.

    2006-08-01

    In this paper, the authors use the Numerical algorithm for Subspace State Space System IDentification (N4SID) to extract dynamic parameters from phasor measurements collected on the western North American Power Grid. The data were obtained during tests on June 7, 2000, and they represent wide area response to several kinds of probing signals including Low-Level Pseudo-Random Noise (LLPRN) and Single-Mode Square Wave (SMSW) injected at the Celilo terminal of the Pacific HVDC In-tertie (PDCI). An identified model is validated using a cross vali-dation method. Also, the obtained electromechanical modes are compared with the results from Prony analysis of a ringdown and with signal analysis of ambient data measured under similar op-erating conditions. The consistent results show that methods in this class can be highly effective even when the probing signal is small.

  6. Advanced surface-enhanced Raman gene probe systems and methods thereof

    DOEpatents

    Vo-Dinh, Tuan

    2001-01-01

    The subject invention is a series of methods and systems for using the Surface-Enhanced Raman (SER)-labeled Gene Probe for hybridization, detection and identification of SER-labeled hybridized target oligonucleotide material comprising the steps of immobilizing SER-labeled hybridized target oligonucleotide material on a support means, wherein the SER-labeled hybridized target oligonucleotide material comprise a SER label attached either to a target oligonucleotide of unknown sequence or to a gene probe of known sequence complementary to the target oligonucleotide sequence, the SER label is unique for the target oligonucleotide strands of a particular sequence wherein the SER-labeled oligonucleotide is hybridized to its complementary oligonucleotide strand, then the support means having the SER-labeled hybridized target oligonucleotide material adsorbed thereon is SERS activated with a SERS activating means, then the support means is analyzed.

  7. Use of the MATRIXx Integrated Toolkit on the Microwave Anisotropy Probe Attitude Control System

    NASA Technical Reports Server (NTRS)

    Ward, David K.; Andrews, Stephen F.; McComas, David C.; ODonnell, James R., Jr.

    1999-01-01

    Recent advances in analytical software tools allow the analysis, simulation, flight code, and documentation of an algorithm to be generated from a single source, all within one integrated analytical design package. NASA's Microwave Anisotropy Probe project has used one such package, Integrated Systems' MATRIXx suite, in the design of the spacecraft's Attitude Control System. The project's experience with the linear analysis, simulation, code generation, and documentation tools will be presented and compared with more traditional development tools. In particular, the quality of the flight software generated will be examined in detail. Finally, lessons learned on each of the tools will be shared.

  8. Propulsion System and Mission Design of AMSAT P5-A Mars Probe

    NASA Astrophysics Data System (ADS)

    Peukert, M.; Riehle, M.

    2002-01-01

    The ham radio operators group AMSAT is currently preparing studies about the feasibility of developing a low cost mission to mars. The probe, called P5-A shall be mainly based on the design of the amateur radio satellite P3-D, launched in November 2000 atop Ariane 507. The satellite design team of AMSAT is lead by the German subsidiary of this international organisation and is supported by ASTRIUM in Lampolshausen, Germany. The support of ASTRIUM may encompass the delivery of major propulsion system components like the bi-propellant Apogee Engine, as already done for former AMSAT projects. Further on propulsion system experts from ASTRIUM have offered support to AMSAT during the design process and during critical satellite operations (e.g. fuelling on launch site). The present paper describes the mission design and the general layout of the P5-A mars probe with strong emphasise on the propulsion system. Probe Design Communication and development of the corresponding techniques is the main field of activities of the amateur radio operators. Thus the main payload of the probe will be an extensive and sophisticated communication equipment. Other organisations even have shown interest to use this mars probe as data relay for their own missions. To save costs, the design of the recently developed satellite P3-D shall be used as far as possible. One side of the hexagonal shaped structure of the satellite will be occupied by a dish antenna to establish from mars orbit a high data download rate of 50,000 bits/sec at the frequency of 10.5 GHz. As counterpart on ground the 20 m Cassegrain-reflector of Bochum University will be used. Due to the fixed antenna the probe has to be 3- axis stabilised. Therefore the use of magnetic wheels in conjunction with thrusters is foreseen. The paper will describe the propulsion system layout and design. For impulsive manoeuvres the ASTRIUM built 400N Apogee Engine is foreseen. For interplanetary corrections or thrust phases the use of an

  9. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems

    NASA Astrophysics Data System (ADS)

    Miccoli, I.; Edler, F.; Pfnür, H.; Tegenkamp, C.

    2015-06-01

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  10. The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems.

    PubMed

    Miccoli, I; Edler, F; Pfnür, H; Tegenkamp, C

    2015-06-10

    The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

  11. Active probing of plasma edge turbulence and feedback studies on the Texas Experimental Tokamak (TEXT)

    SciTech Connect

    Uckan, T.; Richards, B.; Bengtson, R.D.

    1993-08-01

    A novel experiment is under way on the Texas Experimental Tokamak (TEXT) to actively modify the turbulence at the plasma edge by launching waves using electrostatic probes in the shadow of the limiter. The experiments are carried out with a wave launching system consisting of two Langmuir probes, which are about 1.8 cm apart in the poloidal direction, with respect to the magnetic field. These probes are operated in the electron side of the (I,V) characteristic. The probe tips are fed separately by independent ac power supplies. Measurements indicate that the wave, launched with a typical frequency image of 15--50 kHz from the edge of the machine top, is received by sensing probes located halfway around the torus. The detected signal strength depends on the frequency of the wave, the plasma current, and the phasing of the applied ac signal between the launching probes. Modifications to the spectra of the density and potential fluctuations are observed. These experiments have been extended to control of the edge plasma fluctuation level using feedback to explore its effects on confinement. When the launcher is driven by the floating potential of the fluctuating plasma at the location of the launching probes, then the fluctuations are suppressed or excited, depending on the phasing between the probe tips, both locally and at the downstream sensing probes. The fluctuation-induced particle flux also varies with the feedback phasing.

  12. Parametric decay of wide band Langmuir wave spectra

    NASA Astrophysics Data System (ADS)

    Kono, Mitsuo; Pécseli, Hans L.

    2016-12-01

    Previous results obtained for modulational instability of a Langmuir wave spectrum are extended to account also for the Langmuir wave decay. The general model is tested by considering first the parametric decay of single-mode Langmuir waves, and also two-wave models, where several combinations are considered: one wave is modulationally unstable, another decay unstable and one where both waves are unstable with respect to decay. For the general case with continuous wave spectra it is found that distribution of the Langmuir wave energy over a wide wavenumber band reduces the decay rate when the correlation length for the spectrum becomes comparable to the wavelength of the most unstable sound wave among the possible decay products.

  13. Experimental signatures of localization in Langmuir wave turbulence

    SciTech Connect

    Rose, H.A.; DuBois, D.F.; Russell, D.; Bezzerides, B.

    1988-01-01

    Features in certain laser-plasma and ionospheric experiments are identified with the basic properties of Langmuir wave turbulence. Also, a model of caviton nucleation is presented which leads to certain novel scaling predictions. 12 refs., 19 figs.

  14. Langmuir oscillations in a nonthermal nonextensive electron-positron plasma

    NASA Astrophysics Data System (ADS)

    El-Taibany, W. F.; Zedan, N. A.

    2017-02-01

    The high-frequency Langmuir-type oscillations in a pure pair plasma are studied using Vlasov-Poisson's equations in the presence of hybrid nonthermal nonextensive distributed species. The characteristics of the Langmuir oscillations, Landau damping, and growing unstable modes in a nonthermal nonextensive electron-positron (EP) plasma are remarkably modified. It is found that the phase velocity of the Langmuir waves increases by decreasing (increasing) the value of nonextensive (nonthermal) parameter, q ( α). In particular, depending on the degree of nonthermality and nonextensivity, both damping and growing oscillations are predicted in the proposed EP plasma. It is seen that the Langmuir waves suffer from Landau damping in two different q regions. Furthermore, the mechanism that leads to unstable modes is established in the context of the nonthermal nonextensive formalism, yet the damping mechanism is the same developed by Landau. The present study is useful in the regions where such mixed distributions in space or laboratory plasmas exist.

  15. Electron acceleration by parametrically excited Langmuir waves. [in ionospheric modification

    NASA Technical Reports Server (NTRS)

    Fejer, J. A.; Graham, K. N.

    1974-01-01

    Simple physical arguments are used to estimate the downward-going energetic electron flux due to parametrically excited Langmuir waves in ionospheric modification experiments. The acceleration mechanism is a single velocity reversal as seen in the frame of the Langmuir wave. The flux is sufficient to produce the observed ionospheric airglow if focusing-type instabilities are invoked to produce moderate local enhancements of the pump field.

  16. Probing vacuum-induced coherence via magneto-optical rotation in molecular systems

    NASA Astrophysics Data System (ADS)

    Kumar, Pardeep; Deb, Bimalendu; Dasgupta, Shubhrangshu

    2016-05-01

    Vacuum-induced coherence (VIC) arises due to the quantum interference between the spontaneous emission pathways from the degenerate excited states to a common ground state. The stringent requirement for the VIC to occur is the nonorthogonality of the transition dipole matrix elements. Unlike atoms, molecules are the promising systems for exploration of VIC, as it is possible to identify the non-orthogonal transitions due to the coupling of the rotation of molecular axis with molecular electronic angular momentum. Usually, the possible signatures of VIC are obtained by manipulating the absorption of the probe field. In this paper, we show how the dispersion of the probe field can be manipulated to obtain a measurable signature of VIC. Precisely speaking, we explore a way to probe VIC in molecules by observing its influence on magneto-optical rotation (MOR). We show that VIC in the presence of a control laser and a magnetic field can lead to large enhancement in the rotation of the plane of polarization of a linearly polarized weak laser with vanishing circular dichroism. This effect can be realized in cold molecular gases. Such a large MOR angle may be used as a tool for optical magnetometry to detect weak magnetic field with large measurement sensitivity.

  17. Through-wafer optical probe characterization for microelectromechanical systems positional state monitoring and feedback control

    NASA Astrophysics Data System (ADS)

    Dawson, Jeremy M.; Chen, Jingdong; Brown, Kolin S.; Famouri, Parviz F.; Hornak, Lawrence A.

    2000-12-01

    Implementation of closed-loop microelectromechanical system (MEMS) control enables mechanical microsystems to adapt to the demands of the environment that they are actuating, opening a broad range of new opportunities for future MEMS applications. Integrated optical microsystems have the potential to enable continuous in situ optical interrogation of MEMS microstructure position fully decoupled from the means of mechanical actuation that is necessary for realization of feedback control. We present the results of initial research evaluating through-wafer optical microprobes for surface micromachined MEMS integrated optical position monitoring. Results from the through-wafer free-space optical probe of a lateral comb resonator fabricated using the multiuser MEMS process service (MUMPS) indicate significant positional information content with an achievable return probe signal dynamic range of up to 80% arising from film transmission contrast. Static and dynamic deflection analysis and experimental results indicate a through-wafer probe positional signal sensitivity of 40 mV/micrometers for the present setup or 10% signal change per micrometer. A simulation of the application of nonlinear sliding control is presented illustrating position control of the lateral comb resonator structure given the availability of positional state information.

  18. Novel HDD-type SNDM ferroelectric data storage system aimed at high-speed data transfer with single probe operation.

    PubMed

    Hiranaga, Yoshiomi; Uda, Tomoya; Kurihashi, Yuichi; Tanaka, Kenkou; Cho, Yasuo

    2007-12-01

    In this study, several read/write tests were conducted using a novel ferroelectric data storage test system equipped with a spindle motor, targeted at high-speed data transfer using a single probe head. A periodically inverted signal can be read out correctly with a bit rate of 100 kbps using this test system, and 10 Mbps data transfer is also possible during writing operations. The effect of a dc-offset voltage applied to the writing waveform with high-speed probe scanning is discussed. In addition, a novel noncontact probe height control technique was adopted to solve the problem of tip abrasion.

  19. Phase Diagram of Fatty Acid Langmuir Monolayers from Rheological Measurements.

    PubMed

    Tajuelo, J; Guzmán, E; Ortega, F; Rubio, R G; Rubio, M A

    2017-05-02

    Langmuir monolayers of fatty acids and alcohols are two-dimensional systems with a rich equilibrium phase diagram. We have explored the temperature and surface-pressure-dependent shear response of monolayers formed by fatty acids of different chain lengths and a fatty alcohol. This has been accomplished with an interfacial shear rheometer utilizing magnetic tweezers and equipped with a refined temperature control and acquisition system. Our rheological results have allowed us to draw a phase diagram from the viscoelastic properties of these 2-D systems and show new phenomena that strongly depend on temperature: the existence of a maximum in viscosity at the L2' phase, the behavior of the elastic modulus to the storage modulus ratio at the L2 phase, and the increase or decrease in viscosity at the L2-LS phase transition. In addition, we unambiguously show that the LS phase displays a counterintuitive behavior in which the loss modulus increases with temperature. We demonstrate, through isothermal surface pressure sweeps and isobaric temperature sweeps, that the exponential dependence of the loss modulus on temperature at the LS phase appears for all hydrophobic tail lengths studied and for both acid and alcohol head groups.

  20. The Design and Evaluation of Transmit and Receive Antennas for an Ionospheric Communications Probe System: A. Multiband Dipole Antenna

    DTIC Science & Technology

    1992-12-01

    RECEIVE ANTENNAS FOR AN IONOSPHERIC COMMUNICATIONS PROBE SYSTEM: A. MULTIBAND DIPOLE ANTENNA by Sotirios Georgios Perros December, 1992 Thesis Advisor...PROBE SYSTEM: A. MULTIBANDDIPOLE ANTENNA 12 PERSONAL AUTHOR(S) PERROS , Sotirios Georgios 13a TYPE OF REPORT 13b TIME COVERED 14 DATE OF REPORT (Year...Sotirios Georgios Perros By Lieutenant, Hellenic Navy Dist! ibution I B.S., Hellenic Naval Academy, 1984 Availabiity des Avail i•,(lior Submitted in