Measurement of neutron kerma factors for carbon and A-150 plastic at neutron energies of 26.3 MeV and 37.8 MeV

Kerma factors for carbon and A-150 tissue equivalent plastic were determined in two nearly monoenergetic neutron beams. Kerma was measured with low pressure proportional counters (PCs) with walls made of graphite and A-150 plastic. The neutron fluence was measured with a proton recoil telescope. The corrections for the kerma contributions from low energy neutrons in the beams were determined by time-of-flight measurements with an NE213 scintillation detector and with the PCs. For neutron energies of (26.3+or-2.9) MeV and (37.8+or-2.5) MeV the kerma factors for carbon were (35.5+or-3.0) pGy cm 2 and (42.6+or-3.9) pGy cm 2 , respectively, and for A-150 they were (75.6+or-5.4) pGy cm 2 and (79.0=5.6) pGy cm 2 . At these energies the kerma factor ratio for ICRU muscle tissue to A-150 calculated on the basis of the new kerma factors, is 0.93.