scholarly journals Estimation of probe measurements reliability in a supersonic flow of a four-component collisionless plasma

2021 ◽  
Vol 2021 (3) ◽  
pp. 57-69
Author(s):  
D.N. Lazuchenkov ◽  
◽  
N.M. Lazuchenkov ◽  
Keyword(s):  
Ionic Composition ◽  
Collisionless Plasma ◽  
Plasma Electron ◽  
Plasma Potential ◽  
Plasma Parameters ◽  
Probe Current ◽  
Bias Potential ◽  
Probe System ◽  
Parametric Studies ◽  
Probe Measurements

The aim of this work is to estimate the reliability of extracting the plasma electron density and temperature and ionic composition from the current-voltage (I-V) characteristic of an isolated probe system with cylindrical electrodes. An earlier proposed mathematical model of current collection by the probe system at positive bias potentials and an arbitrary ratio of the electrode areas is analyzed. The model is supplemented with a formula that determines, with an accuracy of several percent, the value of the bias potential at which the probe is under the plasma potential and the I-V characteristic splits into a transition and an electronic region. The analytical dependence of the bias potential on the plasma parameters and the ratio of the electrode areas made it possible to formalize the procedures for determining and assessing the reliability of the extracted plasma parameters using the regions of their strongest effect on the collected probe current. Parametric studies of the effect of the plasma parameters on the probe current were carried out for conditions close to measurements in the ionosphere. The paper demonstrates the feasibility of partitioning the sought-for plasma parameters into the regions of their strongest and weakest effect on the probe current in the range of the bias potentials considered. The problem of plasma parameter identification is formulated on the basis of a comparison of the probe current and the measured I-V characteristic in the L2 theoretical approximation. To each parameter there corresponds an objective function of its own, which differs in the domain of definition and the ratio of the electrode areas used in I-V characteristic measurements. Based on this formulation of the inverse problem in L2, estimates of the reliability of identification of the parameters of a plasma with two ion species are obtained depending on the errors of the model and probe measurements. The results obtained may be used in ionospheric plasma diagnostics.

scholarly journals Mathematical modeling of probe measurements in a supersonic flow of a four-component collisionless plasma

2020 ◽  
Vol 2020 (4) ◽  
pp. 97-109
Author(s):  
D.N. Lazuchenkov ◽  
◽  
N.M. Lazuchenkov ◽  
Keyword(s):  
Electrode Surface ◽  
Collisionless Plasma ◽  
Reference Electrode ◽  
Area Ratio ◽  
Ion Composition ◽  
Surface Area Ratio ◽  
Probe Current ◽  
Surface Areas ◽  
Probe System ◽  
Probe Measurements

The aim of this work is the development of a procedure for extracting the plasma electron density and temperature and ion composition from the current-voltage characteristic (C –V characteristic) of an isolated probe system of cylindrical electrodes. The plasma is four-component and consists of electrons, ions of two species with significantly different masses, and neutrals. The measuring probe and the reference electrode of the probe system may be made up of several cylinders. The electrodes of the probe system are placed transversely to a supersonic flow of a low-temperature collisionless plasma with a specified mass velocity. Using the familiar theoretical and experimental relationships for the ion and electron currents to a cylinder, a mathematical model of current collection is constructed for an isolated probe system at an arbitrary ratio of the electrode surface areas. The model includes the calculation of the equilibrium potential of the reference electrode as a function of the probe bias voltage. A procedure is developed for the identification of local plasma parameters using a priori information on the plasma properties and the experimental conditions. The effect of the electron density and temperature and the ion composition on the probe current of the isolated probe system at different ratios of the current-collecting electrode surface areas is studied. The ranges of the probe bias potentials and the values of the electrode surface area ratio that maximize and minimize the effect of the sought-for parameters on the probe current are determined. The quantitative restrictions on the bias potentials and the surface area ratio obtained in this study are used in the probe measurement procedure and in the objective function for comparing the theoretical approximation of the probe current with the measured I– characteristics. A numerical simulation of probe measurements under the ionospheric conditions was conducted to verify the efficiency of the procedure for extracting the local parameters of a four-component plasma from the electron branch of the I –V characteristic of an isolated probe system. The results obtained may be used in ionospheric plasma diagnostics onboard nanosatellites.

scholarly journals COMPARISON BETWEEN 2D TURBULENCE MODEL ESEL AND EXPERIMENTAL DATA FROM AUG AND COMPASS TOKAMAKS

2015 ◽  
Vol 55 (2) ◽  
pp. 128-135 ◽  
Author(s):  
Peter Ondac ◽  
Jan Horacek ◽  
Jakub Seidl ◽  
Petr Vondrácek ◽  
Hans Werner Müller ◽  
...  
Keyword(s):  
Turbulent Transport ◽  
Plasma Potential ◽  
Density Fluctuations ◽  
Tokamak Plasma ◽  
Plasma Parameters ◽  
Fluid Turbulence ◽  
Radial Profiles ◽  
Parallel Dynamics ◽  
Two Machines ◽  
Probe Measurements

<!-- p, li { white-space: pre-wrap; } --><p style="text-indent: 0px; margin: 0px;">In this article we have used the 2D fluid turbulence numerical model, ESEL, to simulate turbulent transport in edge tokamak plasma. Basic plasma parameters from the ASDEX Upgrade and COMPASS tokamaks are used as input for the model, and the output is compared with experimental observations obtained by reciprocating probe measurements from the two machines. Agreements were found in radial profiles of mean plasma potential and temperature, and in a level of density fluctuations. Disagreements, however, were found in the level of plasma potential and temperature fluctuations. This implicates a need for an extension of the ESEL model from 2D to 3D to fully resolve the parallel dynamics, and the coupling from the plasma to the sheath.</p>

scholarly journals Elevating the Precision of Plasma Probe Diagnostics by Elimination of Bare Probe Protective Shields’ Influence

2017 ◽  
Vol 1 (1) ◽  
Keyword(s):  
Measurement Errors ◽  
Plasma Electron ◽  
Physical Analysis ◽  
Bare Metal ◽  
Langmuir Probes ◽  
Plasma Parameters ◽  
Probe Diagnostics ◽  
Plasma Probe ◽  
Shield Length ◽  
Probe Measurements

Probe diagnostics of the low pressure inductive xenon plasma were conducted using classic cylindrical Langmuir probes with conventional protection of their circuits against radio frequency interferences by bare metal shields. The dimensions of their probetips were determined in the special experiment that provided negligible local plasma distortions. Accurate probe measurements were used to determine the spatial plasma parameter distributions in a gas discharge unit of an ion thruster model which helped to develop its ion-extracting grate. The subsequent analysis of probe measurements showed that in these experiments, the plasma electron energy distribution function (EEDF) was quite noticeably deviated from the Maxwell function depending on the main probe shield length that varied from maximum to zero. Use of an additional probe in the special position where its shield was rather long with zero shield length of the main probe showed that the additional shield lowered all plasma parameters. Comparison of both probes’ data identified the principled relationship between measurement errors and EEDF distortions caused by bare probe shield and this dependence was used to correct the initial probe measurements. Therefore plasma probe diagnostics became more precise due to the lowered influence of the bare probe protective shields. Its physical analysis based on previous authors’ works showed that this effect was caused by a shortcircuited double-probe phenomenon in the bare metal shields.

Design of a Wien Filter Type Heavy Ion Beam Probe System for the Measurement of Plasma Potential

1987 ◽  
Vol 26 (Part 1, No. 5) ◽  
pp. 755-759 ◽  
Author(s):  
Hideki Fujita ◽  
Keizô Adati ◽  
Ryuhei Kumazawa ◽  
Shoichi Okamura ◽  
Teruyuki Sato
Keyword(s):  
Ion Beam ◽  
Heavy Ion ◽  
Plasma Potential ◽  
Wien Filter ◽  
Probe System ◽  
Filter Type ◽  
Heavy Ion Beam ◽  
Heavy Ion Beam Probe

scholarly journals Effect of the gas puff location on the divertor plasma properties in COMPASS tokamak

2020 ◽  
Vol 1492 (1) ◽  
pp. 012003
Author(s):  
M Dimitrova ◽  
M Tomes ◽  
Tsv Popov ◽  
R Dejarnac ◽  
J Stockel ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Vacuum Chamber ◽  
Plasma Potential ◽  
Saturation Current ◽  
Langmuir Probes ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
Low Field ◽  
Saturation Current Density ◽  
Deuterium Gas

Abstract Langmuir probes are used to study the plasma parameters in the divertor during deuterium gas puff injection on the high- (HFS) or low-field sides (LFS). The probe data were processed to evaluate the plasma potential and the electron temperatures and densities. A difference was found in the plasma parameters depending on the gas puff location. In the case of a gas puff on the LFS, the plasma parameters changed vastly, mainly in the inner divertor – the plasma potential, the ion saturation-current density and the electron temperature dropped. After the gas puff, the electron temperature changed from 10-15 eV down to within the 5-9 eV range. As a result, the parallel heat-flux density decreased. At the same time, in the outer divertor the plasma parameters remained the same. We thus concluded that using a gas puff on the LFS will facilitate reaching a detachment regime by increasing the density of puffed neutrals. When the deuterium gas puff was on the HFS, the plasma parameters in the divertor region remained almost the same before and during the puff. The electron temperature decreased with just few eV as a result of the increased amount of gas in the vacuum chamber.

scholarly journals Optical Emission Spectroscopic Analysis of Plasma Parameters in Cadmium by Nd: YAG laser Technique

2021 ◽  
Vol 2114 (1) ◽  
pp. 012049
Author(s):  
Uday H. Tawfeeq ◽  
Ahmed K. Abbas ◽  
Kadhim A. Aadim
Keyword(s):  
Laser Pulse ◽  
Atmospheric Pressure ◽  
Spectroscopic Analysis ◽  
Debye Length ◽  
Optical Emission ◽  
Plasma Electron ◽  
Laser Technique ◽  
Plasma Parameters ◽  
Yag Laser ◽  
Emission Spectroscopic Analysis

Abstract In this work, optical emission spectroscopy (OES) was used to estimate the parameters of plasma electron temperature (Te), electron density (ne), plasma frequency (fp), Debye length (λD), and Debye number (ND). Understanding how an energy pulsed laser affects these variables is also important. Irradiation of pure cadmium using an Nd: YAG laser pulse with a wavelength(1064)nm and energy ranging from (200-600)millijoules, of frequency (6) Hz. The spectrum of laser-induced plasma was detected under atmospheric pressure. It was discovered that when the energy of the laser pulse rises, the intensity of the CdI and CdII lines increases.

scholarly journals Electric discharge during electrosurgery

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Alexey Shashurin ◽  
David Scott ◽  
Taisen Zhuang ◽  
Jerome Canady ◽  
Isak I. Beilis ◽  
...  
Keyword(s):  
Electric Discharge ◽  
Rayleigh Scattering ◽  
Positive Column ◽  
Plasma Electron ◽  
Atmospheric Plasma ◽  
Plasma Parameters ◽  
Breakdown Threshold ◽  
Half Wave ◽  
Electrical Conductivities ◽  
The Moment

Abstract Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 103 A/cm2. The plasma electron density and electrical conductivities in the channel were found be 1016 cm−3 and (1-2) Ohm−1cm−1, respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold.

scholarly journals Stimulated Brillouin backscattering of a ring-rippled laser beam in collisionless plasma

2015 ◽  
Vol 33 (3) ◽  
pp. 499-509 ◽  
Author(s):  
Gunjan Purohit ◽  
Priyanka Rawat
Keyword(s):  
Laser Beam ◽  
Narrow Range ◽  
Brillouin Scattering ◽  
Collisionless Plasma ◽  
Plasma Parameters ◽  
Ion Acoustic Wave ◽  
Coupled Equations ◽  
Ion Acoustic ◽  
Paraxial Ray ◽  
Stimulated Brillouin

AbstractThe effect of the propagation of a ring-rippled laser beam in the presence of relativistic and ponderomotive non-linearities on the excitation of ion-acoustic wave (IAW) and resulting stimulated Brillouin backscattering in collisionless plasma at relativistic powers is studied. To understand the nature of propagation of the ring ripple-like instability, a paraxial-ray approach has been invoked in which all the relevant parameters correspond to a narrow range around the irradiance maximum of the ring ripple. Modified coupled equations for growth of ring ripple in the plasma, generations of IAW and back-stimulated Brillouin scattering (SBS) are derived from fluid equations. These coupled equations are solved analytically and numerically to study the intensity of ring-rippled laser beam and excited IAW as well as back reflectivity of SBS in the plasma for various established laser and plasma parameters. It is found that the back reflectivity of SBS is enhanced due to the strong coupling between ring-rippled laser beam and the excited IAW. The results also show that the back reflectivity of SBS reduce for higher intensity of the laser beam.

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