Study of the Fast Ion Slowing–Down Process and ECRH Effects in Heliotron E

Abstract

In the Heliotron E device, combining a neutral beam injection (NBI) with an electron cyclotron resonance heating (ECRH) system, new physical issues are applied to the investigation of fast ion behavior. Especially, the slowing-down (deceleration and parallel diffusion) and the loss processes are studied experimentally through measurements of the temporal change of charge-exchange neutral particle energy spectra. As results, first, in the longer slowing-down time (τ s ∼200 ms) plasma realized by ECRH, discrepancies from the theoretical values are detected in the deceleration and the parallel diffusion processes, whose factors are 4∼6 for the former, 6∼13 for the latter. Second, the fast ion loss cone is reduced by the ECRH on the NBI plasma, of which cause is discussed associated with the modification of the radial electric field, E r .