A Simulation Study and Its Experimental Validation for the Detection of Neutrons with a Continuous Energy Spectrum by Using a MICROMEGAS Detector

A MICROMEGAS (MICRO Mesh GASeous) detector is developed to monitor neutrons with a continuous energy spectra generated by bombarding protons on a thick Be target at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Sciences (KIRAMS). Two different neutron spectra are produced by protons of 20 and 40 MeV, and are detected by using the MICROMEGAS detector with a boron converter. Boron carbides (B4C) are deposited on the cathode of the detector and are used as a neutron-to-charged particle converter. alpha particles and Li-7 nuclei produced by the B-10(n,alpha)Li-7 reaction are detected by using the MICROMEGAS detector. Monte Carlo simulations for the detector system are performed to compare the experimental data with the simulation results. For measuring the energies of the alpha particles and the Li-7 nuclei, we vary the geometry of detector in both the simulations and the experiments to fully stop the alpha particles and the Li-7 nuclei in the detector. The changes of the positions of the alpha and the Li-7 peaks observed in the distribution of the deposited energy for different detector geometries agree more or less with those from the simulation results. The neutron conversion efficiency of the detector is studied.