The generation of plasma by helicon waves has been investigated in the
Small Heliac Experimental Apparatus [Nucl. Fusion 25, 1485 (1985)]. E
vidence for wave-particle interaction in both argon and helium is pres
ented iri the form of observations of the electron distribution functi
on. A high energy bump-on-tail feature is shown to coincide with the w
ave phase velocity and with an energy corresponding to a large ionizat
ion cross section. It is shown that the bump-on-tail feature may be re
lated to the ionization capability of helicon waves and may be a resul
t of some form of radio frequency current drive.