Measurement of non-Maxwellian electron energy distributions in an inductively coupled plasma

The electron energy distribution function (EEDF) in an argon planar inductively coupled plasma was measured by the method of laser Thomson scattering. In a low-pressure discharge, a clear departure from a Maxwellian distribution function was observed; an unambiguous measurement of a non-Maxwellian distribution in a low-density glow discharge. The non-Maxwellian EEDF became Maxwellian in a higher pressure discharge. These observations were attributed to the lack of randomizing collisions in the low-pressure discharge and the increase in the number of these collisions at higher pressure.