Ion temperature measurements in helicon plasmas

Summary form only given. Laser induced fluorescence measurements of the ion temperature in a helicon plasma indicate that the perpendicular ion temperature scales linearly with applied magnetic field. Finite gyroradius effects play a negligible role since at the lowest magnetic fields examined, the ion gyroradius remains much smaller than the chamber diameter. In a cylindrical device, Bohm diffusion across the axial magnetic field leads to a diffusion coefficient which depends inversely on the magnetic field strength. Assuming that the diffusion coefficient determines both the particle and energy confinement times, linear scaling of the ion temperature with magnetic field suggests that the ions are heated by collisions with the electrons. Measurements of the parallel and perpendicular ion temperatures and the electron density versus magnetic field in helicon source will be presented. Ongoing attempts to demonstrate ion cyclotron resonant heating in helicon plasmas will also be discussed and the latest results presented.