Influence of an external circuit on the plasma parameters in the channel of the radio-frequency accelerator with a closed electron drift

The axial distribution of the plasma potential, concentration and temperature of electrons in an RF capacitive plasma source with the geometry of an accelerator with a closed electron drift is experimentally investigated in this work. Two cases of the external electrical discharge circuit are considered. In the first case, the electrodes were closed by direct current, in the second, they were opened. It is shown that direct current closure of the electrodes leads to a significant increase in the plasma potential and electron concentration. In a number of cases, local maxima of temperature and plasma density are observed near the electrodes, which can be associated with the occurrence of azimuthal electron drift in crossed electric and magnetic fields.

Influence of an external circuit on the plasma parameters in the channel of the radio-frequency accelerator with a closed electron drift

The axial distribution of the plasma potential, concentration and temperature of electrons in an RF capacitive plasma source with the geometry of an accelerator with a closed electron drift is experimentally investigated in this work. Two cases of the external electrical discharge circuit are considered. In the first case, the electrodes were closed by direct current, in the second, they were opened. It is shown that direct current closure of the electrodes leads to a significant increase in the plasma potential and electron concentration. In a number of cases, local maxima of temperature and plasma density are observed near the electrodes, which can be associated with the occurrence of azimuthal electron drift in crossed electric and magnetic fields.

Influence of electron temperature on breaking of plasma oscillations

The influence of thermal motion of electrons on the processes of relativistic plasma oscillations is studied analytically and numerically. It is shown that if the temperature of electrons grows and exceeds a certain critical level, then the breaking effect vanishes due to transformation of plasma oscillations into travelling waves. Analytical conclusions are made in the framework of the theory of small perturbations based on Lagrangian variables. Numerical simulation of the transformation is performed using three different algorithms constructed on the basis of the method of finite differences in Eulerian variables. The analytical results are in good agreement with numerical experiments.

Диссоциативная рекомбинация молекулярных ионов Ne-=SUB=-2-=/SUB=--=SUP=-+-=/SUP=- с электронами. Заселение атомов конфигурации 2p-=SUP=-5-=/SUP=-4p в распадающейся плазме

The paper presents the results of the study of decaying neon plasma by the method of kinetic spectroscopy. Experimental conditions: neon pressure 0.2–152 Torr, electron density in the initial stage of decay [e] ≤ 5 × 1010 cm-3. The plasma was created by a pulsed barrier discharge with electrodes on the outer surface of a cylindrical glass tube. Discharge frequency 40–160 Hz. On the basis of a comparative analysis of the dependences of the intensities of spectral lines on the time and temperature of electrons in the afterglow, it was shown that in terms of the mechanisms of population, the levels of 2p54p are clearly divided into two groups. Lower levels: from 3p10 to 3p3 (Paschen notation) are associated with the dissociative recombination of molecular ions with electrons and, up to pressures of 0.6 Torr, the lines emitted by them behave identically to the lines of 2p53s ← 2p53p and 2p53p ← 2p53d transitions. The behavior of the upper levels (3p5, 3p2, 3p4, and 3p1) was more complex, and at low pressures, the populations of all 2p54p levels turned out to be related to the impact-radiation recombination of Ne + ions. Significant differences in the dependences of the relative populations of 3d and 4p levels on the neon pressure are discussed.

Измерение пространственных распределений температуры электронов в облаках полистироловых пеллетов, испаряющихся в плазме гелиотрона LHD

Two methods for measuring the spatial distribution of the temperature of electrons in a cloud near a polystyrene pellet that ablates in LHD heliotron plasma are described. The first method is based on measuring the ratio of the local emission-coefficient values at wavelengths of 486 ± 5 nm (the H _β line) and 630 ± 5 nm (continuum). The second (new) method is based on the measurement of radiation distributions of the H _β line in the direction along the magnetic field. Both the methods use an assumption about the partial local thermodynamic equilibrium in the cloud and show close results. It is shown for the first time that the temperature of cloud electrons increases from 0.8 eV in the immediate vicinity of the pellet surface to 6.0–7.0 eV at a distance of 6–8 mm from the pellet in the direction along the magnetic field, which agrees with the experimentally observed longitudinal distribution of the H _β radiation in the cloud.