Neutron interaction data in carbon derived from measured and calculated ionisation yield spectra

The analysis of measured and calculated ionisation yield spectra for neutrons can be used for the investigation of dosimetric quantities and of basic interaction data for single elements. First results obtained with A-150 plastic (78% carbon by weight) and with graphite counters showed that measured carbon kerma factors for high energy neutrons are significantly lower than the calculated values. Measured and calculated ionisation yield spectra for carbon were analysed at 15 and 17 MeV neutron energy with special attention given to the (n,n'3α) reaction. The partial kerma factor for this process was evaluated from the experiments taking account of experimental artefacts (wall effects) and of the ionisation produced by charged particles originating in elastic scattering, inelastic scattering and in (n,α) reactions. The results show that the calculated partial kerma factors would have to be reduced by 30% at 15 MeV and by 50% at 17 MeV neutron energy in order to match the evaluated experimental partial kerma factors. (author)