Suprathermal ion studies in ECRH and NBI phases of the TJ-II stellarator

Abstract

The goal of this work is to study the empirical behaviour of suprathermal ions in the electron cyclotron resonance heating (ECRH) and neutral-beam injection (NBI) phases of the TJ-II stellarator. Our approach combines passive emission spectroscopy, which detects confined suprathermal ions with energies up to hundreds of electronvolts, and a luminescent probe operated as a multichannel fast-ion energy spectrometer using pulse height analysis, which detects suprathermal ions with energies ⩾1 keV that escape from the plasma. We will present data taken from density and power scans of TJ-II ECRH plasmas and the spatial and time response of suprathermal protons and impurities in both scenarios. The comparative behaviour between the suprathermal ions present in the plasma and those escaping ions may shed some light on the physical mechanisms responsible for the generation and confinement of these ions.