Development and testing of secondary ion accelerator for ITER neutral particle diagnostic system

This paper presents the results of the development and testing of a secondary ion accelerator for the diagnostic complex of neutral particle analyzers at ITER. The accelerator is part of an analyzer designed to measure fluxes of neutral deuterium and tritium particles escaping from reactor plasma in a total range of 10–200 keV. The aim of the accelerator is to improve the signal/background ratio of the analyzer. It is especially important for the region with a relatively low energy of 10–50 keV. The accelerator has the function of converting atoms into secondary ions and accelerating them in an electrostatic field with a voltage of up to +100 kV. The accelerator is based on two high-voltage accelerating tubes. A special unit is built into the central electrode of the accelerator, which provides the replacement of stripping foils used for the conversion of the flux of neutral particles into a flux of secondary ions. The high-voltage tube assembly is encompassed by a sealed steel housing, in which electrical insulation is provided by a gas gap (nitrogen at 6 bar). The results of tests of the accelerator under ITER relevant conditions, namely, under high-intensity gamma irradiation and seismic loads, have shown its high reliability for use in the diagnostic complex of the fusion reactor.