Development of the DT ${\_}$GEM: A Gas Electron Multiplier Detector for Neutron Diagnostics in Controlled Thermonuclear Fusion

A new neutron flux monitor for fusion applications (DT _GEM) has been developed by means of a triple-GEM (Gas Electron Multiplier), a proton recoil converter and a low energy proton absorber. The design and the optimization for the detection of 14 MeV neutrons have been performed using MCNPX and FLUKA Monte Carlo Codes and the detector has been tested under 14 MeV neutron irradiation at the Frascati Neutron Generator (FNG). Polyethylene is used as a converter and an aluminum absorber sheet covers a triple 10 times 10 cm
²
GEM filled with an Ar/CO
₂
/CF
₄
gas mixture. The detector is read out with 64 pads (10 times 6 mm
²
) in a 4 times 16 matrix. The DT_ GEM design and the results of the first tests performed at FNG are presented and discussed in this paper. Excellent performances at high count rates in transient neutron flux, good efficiency, low sensitivity to gamma radiation and high voltage stability under irradiation make the DT_GEM a promising detector for neutron diagnostics in fusion.