Wave-electron coupling in helicon source

Summary form only given. Helicon studies by Ellingboe et al. (1994), have shown that argon emission intensity is strongly modulated at the 13.56 MHz RF frequency, and that the peak emission propagated axially at a velocity corresponding to that of the helicon waves, and consistent with electrons trapped in the traveling wave. Electrons traveling at the phase velocity would have an energy of a few tens of eV, energetic enough to efficiently ionize the gas, as suggested by Chen. We have assembled a helicon source, consisting of solenoidal magnets and a Nagoya Type III antenna surrounding a 15 cm inner diameter Pyrex tube. At one end, the tube expands to a 30 cm diameter aluminum vessel surrounded by a picket fence array of permanent magnets. The antenna is driven by up to 3 kW at 13.56 MHz. This helicon source is being studied and optimized for possible application to a large area plasma source. We are initiating a study of the wave coupling to electrons using a calorimeter probe that measures the power density coupled into the plasma, to determine the heating efficiency. Swept Langmuir probes, and a gridded energy analyzer will measure the electron energy distribution function at various axial positions. B-dot probes will measure the wave amplitude, k/sub /spl par// and phase velocity vs axial position. We will compare our measurements with theoretical studies, that apply formalisms developed to study bucket trapping and heating of electrons by electron cyclotron waves.