Analytical Description of the d(14)+Be Neutron Beam Source at the Essen Fast Neutron Therapy Facility

Monte Carlo simulation of accelerated ions is a standard method in radiation protection. Such simulations have been used to calculate photon and neutron production in a beryllium target of the Essen d(14)+Be Fast Neutron Therapy Facility. In the deuteron case the predominant part of the neutrons is produced by breakup of the input particle, a decay that is not foreseen in standard versions of Monte Carlo codes. Thus, the calculation yields results that are different from measured ones. For simulations of the neutron beam at such facilities, an input description containing the spectral and geometric properties of the neutron and eventually photon beams produced in the target is needed. For the Essen neutron beam, such a description has been obtained by comparison of MCNPX simulations with published data and measurements at a static beam geometry having no background radiation. The validation of the neutron beam input description was obtained by comparing measured and calculated dose distributions in a water phantom using a standard collimator at the treatment gantry.