Production of fast electrons in a prototype heliac by helicon waves

The generation of plasma by helicon waves has been investigated in the Small Heliac Experimental Apparatus [Nucl. Fusion 25, 1485 (1985)]. Evidence for wave–particle interaction in both argon and helium is presented in the form of observations of the electron distribution function. A high energy bump-on-tail feature is shown to coincide with the wave phase velocity and with an energy corresponding to a large ionization cross section. It is shown that the bump-on-tail feature may be related to the ionization capability of helicon waves and may be a result of some form of radio frequency current drive.