Neutral particle analysis on ITER: present status and prospects

Abstract

This paper presents the physical basis for measuring the neutral particle fluxes emitted by ITER plasma and describes the instrumentation for that developed in Ioffe Institute (St. Petersburg, Russia). Possible mechanisms of the neutralization of the hydrogen and helium ions in the thermal and supra-thermal energy ranges are considered. Numerical simulation results of the neutral fluxes produced by the neutralization processes of the bulk thermal deuterium and tritium ions, the knock-on deuterium and tritium ions and the confined alpha particles are presented.Presented ITER NPA system consists of low energy neutral particle analyzer (LENPA) and high energy neutral particle analyzer (HENPA). The analyzers provide the measurements in the thermal (10–200keV) and supra-thermal (0.1–4MeV) ranges .Calculation of the counting rates in the analyzer energy channels shows that NPA system will be able to measure D/T ratio both in ITER plasma core (r<0.4a) by measuring the neutralized knock-on deuterons and tritons and in plasma medium region (r>0.4a) by measuring of the neutralized thermal deuterons and tritons. The possibility of measuring a flux of the neutralized confined alphas is also discussed in the paper.