The role of a fast ion component on the heating of the plasma bulk

Abstract

Ion temperatures have been measured in the TJ-II stellarator using passive emission spectroscopy in parallel and perpendicular directions. A high-energy component was observed from the tails of the Hα line emission in both directions, suggesting a non-negligible population of suprathermal ions. The role of this fast ion energy component, which has been observed in both stellarator and tokamak plasmas when heated by electron cyclotron resonance heating in the additional heating of the plasma bulk is investigated by means of a simple model. The origin of such a fast component is discussed in terms of different mechanisms.