Development of neutron gaseous detector with GEM

We are developing new neutron gaseous detector with Gas Electron Multiplier (GEM) as a detector for material science using thermal (cold) neutron at strong pulsed sources. For detection of neutron, Boron is coated on the both surfaces of one GEM foil. In order to obtain higher efficiency, several GEM foils are stacked in a chamber. A prototype chamber was constructed with 100 mmtimes100 mm GEM foils and a beam test was performed at a research reactor in Japan. Results show the detection efficiency is 30% for 0.22 nm thermal neutron and the position resolution is around 0.5 mm. Uniform 2D position without distortion can be obtained. Diffraction pattern for a single crystal can be clearly observed.