Fabrication of a GEM-based gas detector for thermal neutron measurement

Abstract

GEM (gas electron multiplier) has been studied in many application areas. One of the interesting application areas is the measurement of thermal neutrons. A thin-film neutron converter, B-10, which is widely used as a neutron converter, was installed in the GEM-based gas chamber, and the charged ions that were generated from the neutron interactions with the converter could be measured. The optimum thickness of B-10 film to measure thermal neutrons was obtained with a Monte-Carlo calculation. However, when pure B-10 is coated as a thin film, it peels off very easily. We employed a new method to make a stable B-10 film. The B-10 was evaporated to make a film with a structure of segmented rectangles, which reduced the tension on the film. Neutrons could be measured successfully with the GEM-based gas detector equipped with the B-10 film.