Mechanism of the Helicon Plasma Production
Shogo Isayama1*, Shunjiro Shinohara2, Tohru Hada3, Shih-Hung Chen1
1Physics, National Central University (NCU), Taoyuan, Taiwan
2Division of Advanced Mechanical Systems Engineering, Institute of Engineering,Tokyo University of Agriculture and Technology, Tokyo, Japan
3Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Japan
* Presenter:Shogo Isayama
Helicon plasma is one of the Radio Frequency (RF) plasma sources that can generate high-density (number density 10^19 m^-3) and low-temperature (electron temperature from a few eV to several eV) plasmas by utilizing the helicon wave, i.e., the electromagnetic whistler wave in a bounded geometry. The helicon plasma is thought to be useful for various applications including plasma processing, nuclear fusion, and electric thrusters. On the other hand, there remain many unsolved physical issues regarding how an efficient production of the helicon plasma is realized in laboratory experiments.

The helicon plasma production involves various processes such as the wave excitation (the RF antenna - plasma coupling), the wave propagation (dispersion relation), collisional or non-collisional wave damping and plasma heating, ionization and recombination of neutral particles, and spatial diffusion of the plasma. Besides these fundamental physical issues, the effects of neutral dynamics on the plasma transport and the variation of maximum plasma density are shown to be significant by experimental as well as theoretical studies.

We have constructed a self-consistent fluid model of the helicon plasma production that includes all the essential physical processes mentioned above: the wave excitation, the electron heating via collisional dissipation of excited waves, the diffusion of charged particles, and the neutral dynamics. Numerical results obtained by our model show a good agreement with experimental data, and furthermore, our model reproduces some distinct features observed in the helicon discharge. Our present model can serve as a framework to answer the fundamental question, ‘How the helicon plasma is generated?’. We believe that a deep understanding of the helicon plasma production will enable us to improve the helicon source both in terms of the production efficiency and the maximum plasma density.

Keywords: RF plasma, Helicon plasma, Helicon wave, Fluid simulation