Optical, wave measurements, and modeling of helicon plasmas for a wide range of magnetic fields

Abstract

Helicon waves are excited in a plasma wave facility by a half-turn double-helix antenna operating at 13.56 MHz for static magnetic fields ranging from 200 to 1000 G. A non-perturbing optical probe located outside the Pyrex™ plasma chamber is used to observe 443 nm Ar II emission that is spatially and temporally correlated with the helicon wave. The Ar II emission is measured along with wave magnetic and Langmuir probe density measurements at various axial and radial positions. 105 GHz interferometry is used to verify the bulk temperature corrected Langmuir probemeasurements. The measured peak Ar II emission phase velocity is compared to the measuredwavemagnetic field phase velocity and code predicted wave phase velocity for the transition and blue mode regimes. Very different properties of the optical emission peak phase and wavecharacteristics for the transition and helicon modes of operation are observed. Comparison of the experimental results with the ANTENAII code [Y. Mouzouris and J. E. Scharer, IEEE Trans. Plasma Sci. 24, 152 (1996)] is carried out for the wave field measurements for the two regimes of operation.