Design features of neutral particle diagnostic system for ITER

Abstract

The control of plasma fuel isotopic ratio (DT) has to ensure the best performance of the deuterium-tritium fusion reactor ITER. The diagnostic system, described in this paper, allows to measure this ratio using neutral particle analysis (NPA). The procurement of NPA diagnostics for ITER is delegated to the Russian Federation. This diagnostics is being developed in Ioffe Institute. It consists of two analyzers - LENPA (Low Energy Neutral Particle Analyzer) with 10-200 keV energy range and HENPA (High Energy Neutral Particle Analyzer) with 0.1-4.0 MeV energy range. Simultaneous operation of both analyzers gives the opportunity to measure DT fuel ratio in the central burning plasma and at the edge, as well. During the development, it was necessary to account for high levels of neutron and gamma radiation; presence of the vacuum atomic beam channel, connecting the analyzers with the ITER plasma chamber; strict requirements to reliability of separate parts and units and the limited space available for deployment of the diagnostics hardware at ITER. The technical solutions, which make it possible to conduct the measurements under such conditions and the complex design are described in the paper. The suggested technical solutions allow to: provide common vacuum channel for hydrogen atoms to reach the analyzers, safe with relation to thermal and mechanic loads; efficiently shield the analyzers from ITER stray magnetic field (up to 1 kGs); provide remote handling means for the NPA diagnostic complex, in particular, to connect/disconnect NPA vacuum beamline from ITER vessel; meet ITER radiation safety requirements and ensure fuel isotopic ratio measurements under high levels of neutron and gamma radiation.