Neutron spectrometer based on a gas electron multiplier (GEM) detector for fusion reactors

Neutron spectrometry is an important diagnostic method that will be used to determine the deuterium to tritium density ratio and the ion temperature in the core plasma of fusion reactors. In the case of ITER, the following spectrometric techniques are foreseen: Thin-foil Proton Recoil (TPR), diamond and time-of-flight detectors. The TPR spectrometer design for ITER includes a system of silicon detectors for the detection of protons resulting from the conversion of neutrons in a polyethylene converter. This arrangement has its drawbacks, one of which is limited resistance of silicon to radiation damage. Therefore, we propose using a Gas Electron Multiplier (GEM) type gas detector, which should have better resistance than silicon-based detectors. The concept and operating principle of a TPR neutron spectrometer based on GEM technology, so-called NS-GEM and intended for future fusion plasma spectrometry applications, is presented. The geometry of the detector and its feasibility study based on numerical calculations are discussed. In particular, the first results of experiments with a NS-GEM demonstrator on the IGN-14 neutron generator are shown.