A sealed ceramic GEM neutron detector with the mixture gas Ne/CO2

Majority of the Gas Electron Multiplier (GEM) neutron detectors with 3He-free operate in gas-flow mode, which affects the performance of the detector by the change of environment and limits its portability by the external facilities. A sealed ceramic GEM neutron detector was developed and measured at China Spallation Neutron Source (CSNS). The detector was equipped with a 100 mm × 100 mm ceramic GEM and the working gas was Ne/CO2 (90/10). A voltage of only 350 V was required for the ceramic GEM. The beam profile and wavelength spectrum of BL20 were successfully reconstructed and confirmed. The spatial resolution of the detector was below 3.00 ± 0.01 mm (FWHM), and the detector exhibited good energy/wavelength selective neutron imaging ability. In addition, the counting rate of the detector fluctuated only 0.25% (RSD) during 678-hour  241Am irradiation test. The detector exhibited reliable and stable performance in sealed mode. This detector is an ideal candidate detector for beam monitors, very small angle scattering, neutron reflection and Bragg edge imaging in vacuum.