Neutron-beam depth-dose dosimetry and spectrometry in water phantom using SSNTDs and multigroup transport calculations

The aim of the work described is to investigate the production and energy transfer of charged particles generated by fast-neutron interactions with tissue-equivalent materials. For that purpose, two different approaches have been used: an experimental one using Solid State Nuclear Track Detectors (SSNTDs) and a theoretical one using multigroup transport calculations. For the experiments, the set-up of Hammersmith Hospital, London, was utilized which is currently used for neutron radiotherapy treatment. The polymeric SSNTDs (CR-39, LR-115 and Lexan) were mounted in different positions, both on and off the beam axis and at various depths, in a cubic water phantom. The track densities, produced in each type of detector through the interactions of neutrons with the constituents of both water and plastics themselves, were measured. Using a MORSE-H Monte Carlo code, in conjunction with a 46 group cross-section library, the energy-dependent and -independent neutron fluences were calculated at various positions within the above phantom. This was done by simulating all the important details of the experiment. From the neutron spectrum and the ''response functions'' taken from the same library, the numbers of (n,p), (n,α), and H and O elastic-scattering reactions as well as the dose delivered by each of charged particles were calculated. The two methods were compared and found to be in good mutual agreement. (author)