GAS-TO-WALL ABSORBED DOSE CONVERSION FACTORS FROM 25 TO 250 MEV NEUTRON ENERGY

Gas-to-wall absorbed dose conversion factors r(m,g) were calculated wi th Bragg-Gray cavity theory for the 25 to 250 MeV neutron energy range . Calculations of r(m,g) were made for propane-based tissue-equivalent gas and walls of C, O, Mg, Al, Si, Fe, Zr, AlN, Al2O3, Zr, ZrO2, and A-150 plastic. Charged particle production in the wall materials was c alculated with nuclear model codes. Mass stopping powers were taken fr om recent tabulations. Above 70 MeV neutron energy the r(m,g) values w ere found to be nearly constant and to approach the wall-to-gas mass s topping power ratio of minimum ionising particles. Slight energy depen dencies were found in r(m,g) below 70 MeV. Uncertainties in r(m,g) are estimated to be less than five per cent below 100 MeV neutron energy and are primarily from the uncertainties of the stopping power data.