A ceramic GEM-based neutron beam monitor for China Spallation Neutron Source

Abstract With the development of the new generation of high-flux pulsed neutron facilities, it is necessary that the neutron beam monitors have the characteristics of wavelength resolution and long- term stability, as well as high counting rates and two-dimensional(2D) spatial resolution. In this paper, a novel neutron beam monitor was developed using a single ceramic GEM(Gas Electron Multiplier) at China Spallation Neutron Source(CSNS). Its validation of the wavelength spectra measurement was verified via comparisons with measurements made with an ORDELA 4562N monitor. In addition, it was demonstrated that this neutron beam monitor was able to measure the beam profile of total and sliced wavelengths. The maximum counting rate was about 1.5 MHz by using an X-ray source. The RSD (the relative standard deviation) of instability fluctuations was approximately 0.5% during continuous operations of 40 h. The results show that the ceramic GEM-based neutron beam monitor can satisfy the demands of the high-flux neutrons measurement, and it has been regarded as a standard solution to the neutron beam monitor at CSNS.