Effects of the electron distribution on the expansion of a collisionless plasma into a background of lower density

Мордвинов, А. В.; Томозов, В. М.; Файнштейн, В. Г.

doi:10.1007/bf00919520

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…7,8 Experiments carried out in thermionic discharges, 10,11 fireballs, 12 and laser produced plasmas [13][14][15][16][17] yield that the expansion velocities depend strongly on the electron energy distribution. [17][18][19][20][21] It is predicted that the occurrence of high energetic electrons results in enhanced ion acceleration. 10,22 In the present work, a one-dimensional particle-in-cell (PIC) simulation is presented.…”

Section: Introductionmentioning

confidence: 99%

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

et al. 2016

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The dynamics during plasma expansion are studied with the use of a versatile particle-in-cell simulation with a variable neutral gas density profile. The simulation is tailored to a radio frequency plasma expansion experiment [Schr€ oder et al., J. Phys. D: Appl. Phys. 47(5), 055207 (2014)]. The experiment has shown the existence of a propagating ion front. The ion front features a strong electric field and features a sharp plasma potential drop similar to a double layer. However, the presented results of a first principle simulation show that, in general, the ion front does not have to be entangled with an electric field. The propagating electric field reflects the downstream ions, which stream with velocities up to twice as high as that of the ion front propagation. The observed ion density peak forms due to the accumulation of the reflected ions. The simulation shows that the ion front formation strongly depends on the initial ion density profile and is subject to a wave-breaking phenomenon. Virtual diagnostics in the code allow for a direct comparison with experimental results. Using this technique, the plateau forming in the wake of the plasma front could be indirectly verified in the expansion experiment. Although the simulation considers profiles only in one spatial dimensional, its results are qualitatively in a very good agreement with the laboratory experiment. It can successfully reproduce findings obtained by independent numerical models and simulations. This indicates that the effects of magnetic field structures and tangential inhomogeneities are not essential for the general expansion dynamic. The presented simulation will be used for a detailed parameter study dealt with in Paper II [Schr€ oder et al., Phys. Plasma 23, 013512 (2016)] of this series. V

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Section: Introductionmentioning

confidence: 99%

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

et al. 2016

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“…[14][15][16] They yield that the expansion velocities depend strongly on the electron energy distribution. [16][17][18][19][20] In particular, the ion acceleration is expected to be enhanced by non-thermal electrons. 11,21 In this work, a particle-in-cell (PIC) simulation is used that has been tailored to a pulsed rf plasma expansion experiment.…”

Section: Introductionmentioning

confidence: 99%

Collisionless expansion of pulsed radio frequency plasmas. II. Parameter study

et al. 2016

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The plasma parameter dependencies of the dynamics during the expansion of plasma are studied with the use of a versatile particle-in-cell simulation tailored to a plasma expansion experiment [Schr€ oder et al., J. Phys. D: Appl. Phys. 47, 055207 (2014); Schr€ oder et al., Phys. Plasmas 23, 013511 (2016)]. The plasma expansion into a low-density ambient plasma features a propagating ion front that is preceding a density plateau. It has been shown that the front formation is entangled with a wave-breaking mechanism, i.e., an ion collapse [Sack and Schamel, Plasma Phys. Controlled Fusion 27, 717 (1985); Sack and Schamel, Phys. Lett. A 110, 206 (1985)], and the launch of an ion burst [Schr€ oder et al., Phys. Plasmas 23, 013511 (2016)]. The systematic parameter study presented in this paper focuses on the influence on this mechanism its effect on the maximum velocity of the ion front and burst. It is shown that, apart from the well known dependency of the front propagation on the ion sound velocity, it also depends sensitively on the density ratio between main and ambient plasma density. The maximum ion velocity depends further on the initial potential gradient, being mostly influenced by the plasma density ratio in the source and expansion regions. The results of the study are compared with independent numerical studies.

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“…the maximum expansion velocities vary on a scale from the electron thermal velocity υ e [1,2] down to the ion sound velocity c i [3][4][5]. Experiments carried out in thermionic discharges [7,8], fireballs [9], and laser produced plasmas [10][11][12] yield that the expansion velocities depend strongly on the electron energy distribution [12][13][14][15][16]. It is predicted that the occurrence of high energetic electrons results in enhanced ion acceleration [7,18].…”

Section: Introductionmentioning

confidence: 99%

Collisionless expansion of pulsed rf plasmas

Schröder¹,

Grulke²,

Klinger³

et al. 2014

J. Phys. D: Appl. Phys.

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This paper presents experimental results of the quasi isothermal expansion of a pulsed rf argon plasma (P rf ≈ 300W) into a vacuum like environment. A fast (τ open < 200µs) gas puffing system prevents significant ionization by energetic electron in the expansion region. Thus the expansion is dominantly determined by ion dynamics. The spatio temporal measurement of the ion saturation current indicates a preceding ion front entangled with a strong potential drop. This is in qualitatively good agreement with the predictions by Widner et al., and Crow et al.. Additionally, there is evidence for a supersonic ion population formed by acceleration of the background plasma by the bypassing ion front.

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Effects of the electron distribution on the expansion of a collisionless plasma into a background of lower density

Cited by 3 publications

References 2 publications

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

Collisionless expansion of pulsed radio frequency plasmas. I. Front formation

Collisionless expansion of pulsed radio frequency plasmas. II. Parameter study

Collisionless expansion of pulsed rf plasmas

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