Comparison Between Experiment and Simulation for the Fission Chamber Used in Fast Neutron Detection

A fission chamber coated with two layers of ²³⁸U fissile materials has been developed for the measurements of fast neutrons. The developed fission chamber can operate in the pulse mode, the mean square voltage mode, and the current mode to perform the flux measurement over a large dynamic range. The pulse mode of the fission chamber has been tested with a ²⁵²Cf neutron source by measuring the detection efficiency. To evaluate both the mean square voltage mode and the current mode, the pulse amplitudes from the fission chamber in different gas pressures have been measured with the ²⁵²Cf source. Then, the pulse amplitudes from the fission chamber have also simulated with the Geant4 Monte Carlo software tool. The simulation can explain measured results, detection efficiency is highest(4.30±0.7)×10^-7 when gas pressure is 2.64×10⁵ Pa and energy spectrum of fission fragments is clearly, so the fission chamber can work in different modes.