Bochum 2002 – scientific programme
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P: Plasmaphysik
P 21: Poster: Grundprobleme, Theorie, Plasmatechnologie, Astrophysikalische Plasmen
P 21.7: Poster
Monday, March 18, 2002, 17:40–18:40, HZO Foyer
On the theory of anomalous electron heating in helicon-produced plasmas due to excitation of an ion-sound parametric instability — •Yurii M. Aliev1 and Michael Krämer2 — 1Lebedev Physical Institute (RAS), 119991 Moscow, Russia — 2Experimentalphysik II, Ruhr-Universität Bochum, D-44780
We present a kinetic theory of the ion-sound parametric instability of a magnetized collisionless plasma in a helicon pump field which may explain the anomalous RF power absorption in helicon-sustained discharges. The treatment generalizes Silin’s kinetic parametric theory /1/ in that the pump frequency ω0 is comparable to the ion-sound frequency. For moderate magnetic fields ( ω0 ≥ 2ωLH; ωLH: lower-hybrid frequency) the growth rate of the instability has a maximum when the helicon pump decays dissipatively into two ion-sound waves. For stronger fields the instability is non-resonant so that only one ion-sound wave is excited /2/. Induced scattering of ion-sound waves from ions is considered as stabilizing mechanism. The resulting level of the ion-sound turbulence is used to estimate an effective collision frequency due to electron scattering from the ion-sound fluctuations. For typical helicon sources, this frequency is much larger than the binary collision frequencies in agreement with /2/. However, the origin of the present ion-sound instability is essentially different.
/1/ V. P. Silin, Sov. Phys. JETP 24, 1242 (1967), /2/ A. I. Akhiezer, V. S. Mikhailenko and K. N. Stepanov, Phys. Lett. A 245, 117 (1998)
(Supported by the DFG, Russian-German Contract 146 RUS 590.)