Determination of Kerma Factors for A-150 Plastic and Carbon for Neutron Energies Above 20 MeV

Kerma factors for carbon and A-150 tissue-equivalent plastic were measured in nearly monoenergetic neutron beams with energies of 26 and 38 MeV, respectively. The kerma was measured with low-pressure proportional counters (PC) with walls made of graphite and A-150 plastic material. Corrections had to be made, for significant fractions of low-energy neutrons which were present in the beams. The correction factors for kerma were determined from time-of-flight measurements using NE213 scintillation detectors and PCs. For the kerma factor weighted mean neutron energies of 26.3(29) and 37.8(25) MeV the kerma factors for carbon were determined to be 34.7(29) and 41.0(37) pGy cm2 and for A-150 plastic to be 75.2(51) and 78.4(53) pGy cm2.