Comparison between Tomography and Langmuir Probe Data in PANTA (original) (raw)
Related papers
Computational technique for plasma parameters determination using Langmuir probe data
Plasma Physics Reports, 2011
In the present work, we consider a new numerical method for processing the experimental infor mation on the electron energy distribution function obtained with a Langmuir probe in a low pressure plasma. This method offers the possibility to establish the temperature and concentration of the electrons for different forms of the distribution function. Some specific difficulties of the previous methods used to do such estimations are surpassed using the method proposed in this work.
Magnetic Field Dependence of Plasma Properties Observed with Tomography in PANTA
Plasma and Fusion Research, 2020
The magnetic field dependence of a linear argon plasma is examined with a tomography system in PANTA. It is found that a plateau region exists around a particular region of magnetic field (∼600 G), below and above which the plasma changes the properties of emission and its fluctuations. A model is proposed to explain the observed dependence, and the comparison demonstrates that the dependence should be ascribed to the change in the Lamor motion inside the plasma production source using helicon wave and the plasma transport after the production.
Ion Source Plasma Parameters Measurement using Langmuir Probe
2019
In this work, we present the experimental results of plasma parameters using a Freeman type ion source, such as electron number density ne, plasma electron temperature Te, floating potential Vf, and plasma potential VS. The measurements of these basic parameters of pure Ar plasma were done with a cylindrical Langmuir probe situated perpendicular to a relatively weak magnetic field, B = 20 mT and were performed under constant low Ar pressure 4.6 × 10 mbar. Different methods were implemented to calculate the electron and ion densities. We have concluded that some of these methods are subjected to significant inaccuracy, mainly due to the uncertainty of the plasma potential location. However, It has been recognized that the plasma ion density ni = 1.46 × 10 m found in this experiment using the ion current saturation part is the most reliable among the other values found, using the standard procedures from the electron retardation region (classic Langmuir method) and the electron satura...
Plasma parameters measurements by means of Langmuir probe
Radiation Effects and Defects in Solids, 2008
The Langmuir probe (LP) diagnostics is a powerful method for the evaluation of the plasma resistivity curve (I-V curve) and the characterization of the following plasma parameters: electron temperature, electron density, ion density, and plasma potential. In presence of a stable plasma it is possible to extrapolate the electron energy distribution function of the plasma electron population. Because of the long acquisition time (in the order of hundreds of msec or more), this method is suitable for cw plasmas in thermal equilibrium for which the physical properties vary in a time scale longer than the acquisition time. At INFN-LNS the LP diagnostics has been used in order to characterize the TRasco Intense Proton Source plasma, and the low temperature -high density plasmas of a plasma reactor designed for complex molecules dissociation. In the first case, it has been possible to evaluate the plasma properties for different magnetic field profiles and for several operating conditions. In the second case, the LP has permitted to characterize the plasma properties of the plasma reactor at different microwave powers and gas pressures, with the aim to find the optimal experimental conditions in terms of rate of molecules dissociation and of plasma stability and reliability. These series of measurements are here reported, together with measurements of the plasma reactor parameters. Finally, some considerations about the possibility to extend the LP diagnostics to the non-equilibrium plasmas in pulsed mode, as the plasmas obtained by means of laser ablation of solid targets, are given; the design of a possible experimental set-up is outlined.
Advances in Space Research, 2016
The electron density of the topside ionosphere and the plasmasphere contributes essentially to the overall Total Electron Content (TEC) budget affecting Global Navigation Satellite Systems (GNSS) signals. The plasmasphere can cause half or even more of the GNSS range error budget due to ionospheric propagation errors. This paper presents a comparative study of different plasmasphere and topside ionosphere data aiming at establishing an appropriate database for plasmasphere modelling. We analyze electron density profiles along the geomagnetic field lines derived from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite / Radio Plasma Imager (RPI) records of remote plasma sounding with radio waves. We compare these RPI profiles with 2D reconstructions of the topside ionosphere and plasmasphere electron density derived from GNSS based TEC measurements onboard the Challenging Minisatellite Payload (CHAMP) satellite. Most of the coincidences between IMAGE profiles and CHAMP reconstructions are detected in the region with L-shell between 2 and 5. In general the CHAMP reconstructed electron densities are below the IMAGE profile densities, with median of the CHAMP minus IMAGE residuals around-588. Additionally, a comparison is made with electron densities derived from passive radio wave RPI measurements onboard the IMAGE satellite. Over the available 2001-2005 period of IMAGE measurements, the considered combined data from the active and passive RPI operations cover the region within a latitude range of 60°N, all longitudes, and an L-shell ranging from 1.2 to 15. In the coincidence regions (mainly), we check the agreement between available active and passive RPI data. The comparison shows that the measurements are well correlated, with a median residual of 52. The RMS and STD values of the relative residuals are around 22% and 21% resp. In summary, the results encourage the application of IMAGE RPI data for plasmasphere and plasmapause modeling.
Tomographic Measurements of Plasma Temperature Fields
Beiträge aus der Plasmaphysik, 1984
The paper presents a mathematical description of tomographic algorithms for experimental data reduction. In a numerical experiment, problems of selection of optimum parameters of a measuring system to attain a prescribed accuracy of the emission coefficient reconstruction were investigated.
Deduction of central plasma parameters from line‐of‐sight averaged
A method is presented to deduce central ion temperature and toroidal rotation velocity from line-of-sight averaged x-ray spectra from hot plasmas. The analysis is based on atomic data for the processes that give rise to x-ray spectral lines. Combined with measured electron temperature and density profiles a synthetic spectrum is calculated. The fit of this synthetic spectrum to the observed one gives a new level of accuracy to line-of-sight integrated observations in a considerably extended range of ion temperatures and toroidal rotation velocities. The choice of model for radial profiles for ion temperature and toroidal rotation velocity is shown not to be critical. The concentration of the emitting impurity is deduced from the total line intensity, making use of the absolute calibration of the detector sensitivity. The effective plasma charge ZeE is derived from the absolute level of the continuum radiation. These measurements are based on atomic data for x-ray line and continuum radiation and measured electron temperature and density profiles. The results for ion temperature and toroidal rotation velocity obtained by this analysis are compared with those from visible charge exchange spectroscopy. The observed visible lines are shifted in wavelength, and their width is reduced, due to the velocity dependence of the cross section for the charge transfer from the neutral beam particles to the observed impurities. The theoretically predicted magnitude of these effects is verified. When the results from visible charge exchange spectroscopy are corrected for the cross-section effects, excellent agreement of central ion temperature and rotation velocity with the results of this new analysis is obtained. 6732
Deduction of central plasma parameters from line‐of‐sight averaged spectroscopic observations
Journal of Applied Physics, 1991
A method is presented to deduce central ion temperature and toroidal rotation velocity from line‐of‐sight averaged x‐ray spectra from hot plasmas. The analysis is based on atomic data for the processes that give rise to x‐ray spectral lines. Combined with measured electron temperature and density profiles a synthetic spectrum is calculated. The fit of this synthetic spectrum to the observed one gives a new level of accuracy to line‐of‐sight integrated observations in a considerably extended range of ion temperatures and toroidal rotation velocities. The choice of model for radial profiles for ion temperature and toroidal rotation velocity is shown not to be critical. The concentration of the emitting impurity is deduced from the total line intensity, making use of the absolute calibration of the detector sensitivity. The effective plasma charge Zeff is derived from the absolute level of the continuum radiation. These measurements are based on atomic data for x‐ray line and continuum radiation and measured electron temperature and density profiles. The results for ion temperature and toroidal rotation velocity obtained by this analysis are compared with those from visible charge exchange spectroscopy. The observed visible lines are shifted in wavelength, and their width is reduced, due to the velocity dependence of the cross section for the charge transfer from the neutral beam particles to the observed impurities. The theoretically predicted magnitude of these effects is verified. When the results from visible charge exchange spectroscopy are corrected for the cross‐section effects, excellent agreement of central ion temperature and rotation velocity with the results of this new analysis is obtained.
IEEE Transactions on Plasma Science, 2000
The determination of the plasma potential V pl of unmagnetized plasmas by using the floating potential of emissive Langmuir probes operated in the strong emission regime is investigated. The experiments evidence that, for most cases, the electron thermionic emission is orders of magnitude larger than the plasma thermal electron current. The temperature-dependent floating potentials of negatively biased V p < V pl emissive probes are in agreement with the predictions of a simple phenomenological model that considers, in addition to the plasma electrons, an additional electron group that contributes to the probe current. The latter would be constituted by a fraction of the repelled electron thermionic current, which might return back to the probe with a different energy spectrum. Its origin would be a plasma potential well formed in the plasma sheath around the probe, acting as a virtual cathode or by collisions and electron thermalization processes. These results suggest that, for probe bias voltages close to the plasma potential V p ∼ V pl , two electron populations coexist, i.e., the electrons from the plasma with temperature T e and a large group of returned thermionic electrons. These results question the theoretical possibility of measuring the electron temperature by using emissive probes biased to potentials V p V pl .
Comment on determination of electron temperature from Langmuir probe data in tokamak edge plasma
Czechoslovak Journal of Physics, 1990
Langmuir probe measurements of electron temperature in a plasma in the limiter shadow of a tokamak are presented together with a method of probe data analysis which takes into account the iniIuence of the ion current vs voltage dependence in the determination of electron temperature, The method is based on the transformation of a single into a double probe characteristic. Values of the electron temperature calculated using this method are compared with the values estimated from single probe characteristic data.