Simulation and design of a fast neutron radiography detector based on MCP

A fast neutron detector, consisting of a high-density polyethylene sheet, a micro-channel plate, a phosphor screen, a reflection mirror and a CCD camera, is proposed for fast neutron radiography purpose. To optimize the design of the detector, a series of simulations are performed by using Geant4 code. Simulation results indicate that the maximum conversion efficiency of the high-density polyethylene is about 0.38% when its thickness is 2 mm. To ensure the spatial resolution of the detector, the distance between high-density polyethylene and micro-channel plate should be as small as possible. The gap between MCP and PS is selected as 2 mm with a bias voltage of −4 kV to balance the luminescence efficiency and the spatial resolution of the PS. With the optimized structure, the detection efficiency of the detector is calculated to be 0.14% and the spatial resolution is possibly better than 500 μm.