ANALYSIS AND OPTIMIZATION OF A FISSION CHAMBER DETECTOR USING MCNP4C AND SRIM MONTE CARLO CODES

In this study, a general theoretical model to foresee and calculate the current-voltage characteristics in a plateau zone and the associated efficiency of the neutron detector (sensitivity) is presented. This study is to complete the previous studies in this field. The model also considers electric field distortion resulting from the charge collection effect. The characteristics curve is obtained as a function of fission rate, chamber geometry, and filling gas pressure. The output current at the saturation domain is calculated. The applied voltages about two phenomena, recombination and avalanche, for working the chamber in an ionization zone are an important part of the calculation. In developing the theoretical model, the MCNP code for fission rate, the SRIM code for electron-ion pair and GEANT4 for gamma sensitivity calculations were used.