Thomson scattering measurements of electron temperature and density in an electron cyclotron resonance plasma

Electron temperature T_e and density n_e in the source region of an electron cyclotron resonance discharge have been measured by incoherent Thomson scattering of the beam from a 0.5 J yttrium aluminum garnet laser. This is the first experiment in which this technique, routinely used on fusion plasmas, has been applied to a processing plasma. Measurements were made in an argon discharge at pressures from 0.3 to 2 mTorr and microwave powers from 250 to 1000 W. Velocity distributions were measured both parallel and perpendicular to the magnetic field and a slight anisotropy of electron temperature was observed for low-pressure discharges. Temperatures in the range of 1-5 eV and densities in the range of 2-10×10¹⁷ m ^-3 were measured. T_e and n_e were found to strongly depend on pressure but only weakly on the input power and discharge magnetic field. No deviations from a Maxwellian velocity distribution were observed.