Observation of nonthermal electron tails in an rf excited argon magnetoplasma

Nonthermal beamlike electron tails have been observed in an argon magnetoplasma excited by rf without electron beam injecting. The plasma is highly ionized (∼100%) with central density ∼1014 cm−3, and is based on the excitation of helicon waves. Nonthermal electron tails are observed at the beginning of the plasma pulse and last for about 1 msec. There is a maximum in the electron energy distribution at 30–80 eV and a minimum at 20–30 eV. The mechanism responsible for driving this beamlike tail is not yet known.