Ion temperature in a 'cold' microwave-produced plasma

Observations have been made of the (parallel) ion velocity distribution function in a 'cold' microwave discharge under a variety of machine conditions. It is found that, contrary to common assumption, the ion temperature is not always close to room temperature but in fact can be several electron volts. The temperature is dependent upon neutral gas background pressure. Ion heating has been further accomplished by the application of r.f. electric fields, stochastic or sinusoidal, across a section of the plasma column.