Monte Carlo simulation of exposure factor

In this paper, we simulate the exposure factor by a simple model of afree-air ionization chamber with the Monte Carlo programme Geant4.Special emphasis is placed on the discussion of the exposurefactor related to parameters of the chamber model. The reason for thevariation in exposure factor with incident ray energy is alsoanalysed in terms of reaction cross section for different types ofreactions. The obtained results indicate that our simulation isaccurate in the calculation of the exposure factor and can serve asa reference in designing air ionization chambers.