Slow wave ion heating in the HELIX helicon source

Ion temperature measurements have been made at multiple axial and radial locations in a helicon source for a range of magnetic field strengths and RF frequencies. The observed temperature gradient along the axis suggests limited thermal transport along the magnetic field. The radial profiles are flat near the axis and in some cases peak near the edge of the plasma. The ion temperature measurements combined with calculations of the perpendicular wave numbers for the slow wave or `Trivelpiece–Gould' mode are consistent with ion heating due to ion Landau damping of the slow wave at the edge of the plasma.