Berlin 2001 – scientific programme

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P: Plasmaphysik

P 11: Dusty Plasmas and Low Temperature Discharges (Poster Session)

P 11.8: Poster

Thursday, April 5, 2001, 12:30–15:00, AT2

Characterisation of a large helicon source with multipole magnetic confinement — •Michael Krämer, Bernd Clarenbach, Waldemar Kaiser, and Bernd Lorenz — Experimentalphysik II, Ruhr-Universität Bochum, D-44780 Bochum

First experimental results obtained on a large volume plasma produced by helicon wave coupling are presented. The device consists of a helicon source section connected with a large stainless steel chamber (d_ch = 60  cm, l_ch = 80  cm) which contains a magnetic multipole field configuration consisting of 10 rings of permanent magnets (distance = 8  cm, diameter = 54  cm). The discharge vessel is a quartz tube (d_p = 14.6  cm,  l_p = 110  cm) surrounded by 16 electromagnet coils producing a homogeneous magnetic field. The helicon plasma is produced via an m = 1 helical antenna driven by RF power pulses (τ_pulse = 2 − 3  ms,  f_pulse = 25 − 100  Hz, P_RF < 3  kW,   f_RF = 13.56   MHz). Such antennas reveal a pronounced axial asymmetry, so that, in case of proper magnetic field direction, the plasma is injected into the chamber where typical discharge densities n_e = O(10¹⁸  m⁻³) are achieved. Langmuir and energy analyzer probe diagnostics, 1 mm interferometry as well as emission spectroscopy were applied to measure the distribution of the plasma parameters in the chamber for different antenna positions in a wide range of magnetic field strengths (B₀ < 0.1  T) and argon gas pressures (p = 0.1 − 2  Pa).

This work was supported by the Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich 191 (Projekt A12)