MEASUREMENT OF NEUTRON KERMA FACTORS IN C AND O - NEUTRON ENERGY-RANGE OF 20 MEV TO 70 MEV

Kerma factors for oxygen and carbon have been measured in nearly monoe nergetic neutron beams of energies between 34 MeV and 66 MeV. The kerm a was determined experimentally with low pressure proportional counter s (PC) by measuring the absorbed doses to the gases. Recently calculat ed gas-to-wall absorbed dose conversion factors, r(m,g), were used to deduce the doses in the PC wall materials. The kerma in oxygen was obt ained from the difference of the kerma determined with ZrO2 and Zr wal led PCs, that in carbon was determined with graphite-walled PCs. The n eutron fluences were measured with a proton recoil telescope, the spec tral fluences with an NE213 scintillation detector by applying pulse s hape and time-of-flight techniques. The kerma factors of carbon from t he present measurements were compared with values of previous works wh ich were analysed anew using the improved r(m,g) values.