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P: Plasmaphysik

P 10: Theory and Plasma Diagnostic (Poster Session)

P 10.18: Poster

Wednesday, April 4, 2001, 12:30–15:00, AT2

LIF measurements of wave electric fields in a helicon discharge — •Christian Franck¹, Thomas Klinger¹, Earl Scime², and John Kline² — ¹Ernst-Moritz-Arndt Universität, Institut für Physik, 17489 Greifswald — ²West Virginia University, Department of Physics, USA

Recently, Skiff proposed a new method for determining the wavenumber of an electrostatic wave in collisionless plasmas by measuring the perturbed ion distribution function f₁ with laser induced fluorescence (LIF) [1]. His method has been succesfully applied to low frequency waves (f<100kHz). It is a challenging task to extend the method to higher frequencies and to apply it to a helicon plasma operating at typically f=13.56MHz. In the present paper, we report measurements, done with a dye laser based LIF system, on low (f<100kHz) and high (f=8MHz) frequency wave electric fields. Moreover, first measurements with a more compact diode laser based LIF system are presented. There have been numerous attempts to clarify the mechanism that is responsible for the efficient transfer from the helicon wave energy into the plasma. Unfortunately, no unambiguous verification has been presented. The results presented in this paper can be used to determine nonintrusively the wave electric fields in a helicon discharge (frequency, wavenumber and amplitude).

[1] F. Skiff and F. Anderegg, Phys.Rev.Lett. 59, 896 (1987)