Performance of a neutron beam monitor with a GEM for the high-intensity total diffractometer at J-PARC

We are developing a neutron beam monitor with a gas electron multiplier (GEM) for the high-intensity total diffractometer at J-PARC. In order to analyze the basic characteristics of the GEM-based detector, a neutron irradiation test was carried out at J-PARC. The wavelength-spectrum distribution obtained from the test is consistent with the calculations, and the beam profiles agree with the simple Monte Carlo (MC) simulation. Therefore we found that as a neutron beam monitor, the GEM-based detector has good two-dimensional imaging ability.