Measured neutron carbon kerma factors from 14.1 MeV to 18 MeV

For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183+-0.015 10-8 cGy cm2 and 0.210+-0.016 10-8cGy cm2 at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297+-0.03 10-8cGy cm2 has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3α) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184+-0.019 10-8cGy cm2 in agreement with the present result