Fluctuation in a Helicon plasma with additional immersed antenna

Res. Sch. of Phys. Sci. & Eng., Australian Nat. Univ., Canberra, ACT, Australia
IEEE Transactions on Plasma Science (Impact Factor: 1.1). 05/2005; 33(2):360 - 361. DOI: 10.1109/TPS.2005.845133
Source: IEEE Xplore


Fluctuations in the floating potential are measured in a cylindrical magnetised plasma, as the phase between a "primary" Helicon antenna and a "secondary" immersed antenna is varied. The two antennas are powered by separate radio frequency (RF) generators of 13.56 MHz controlled by a single oscillator and phase shifter. The Helicon antenna is separated from the plasma by a glass tube, while the immersed copper antenna is in direct contact with the plasma. The image presented here shows floating potential fluctuations of ∼100 Hz where the amplitude of the fluctuations vary dramatically with the phase between the two RF generators.

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Available from: Åshild Fredriksen, Oct 16, 2012
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    ABSTRACT: An analytical model is developed of an asymmetric electrode system immersed in a plasma, consisting of two dc-grounded electrodes, where the smaller one is biased at 13.56 MHz. The model is compared with a set of experiments performed in a high density low pressure plasma source an electron cyclotron resonance source where a second electrode is immersed into the plasma and powered by radio frequency. Excellent agreement is obtained between the analytical model and the experimental results. It is found that the time average plasma potential and the direct current dc flowing in the system during steady state are strongly dependent on both the rf voltage or power and the area ratio between the larger and smaller electrodes. For area ratios larger than 80, the dc current is large and the plasma potential is constant with respect to the applied rf voltage. For area ratios smaller than 80 but larger than unity, the plasma potential increases linearly with the applied rf voltage, and the dc current is reduced compared to the large area ratio case. © 2005 American Institute of Physics.
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