Monte Carlo calculation of the compensation ability of ionization chambers in tritium measurements

Compensation for gamma-ray background is of great importance in tritium measurements with ionization chambers. Three kinds of ionization chamber systems are often used to cancel the gamma background: base to base model, coaxial model and differential model. Monte Carlo method is employed to evaluate the compensation ability of all the three models and the compensation character of each model is also specified in this paper. Ionization chambers are modeled with MCNP5 code and the absorbed dose is calculated. Results turn out that chambers arranged in coaxial model can compensate most gamma background from any direction and any distance but with complex structure. The compensation ability varies greatly with directions and distances for both base to base model and differential model.