Characterisation of an accelerator-based neutron source for BNCT of explanted livers

An accelerator-based thermal neutron source for BNCT of the explanted liver was designed using the MCNP code. Neutrons are generated via (d,n) reactions by 7 MeV deuterons bombarding a beryllium target The therapy constraints were approached by simulating an irradiation cavity placed inside a graphite reflector parallelepiped containing a heavy-water moderator in turn enclosing the beryllium target The experimental verification was performed at the Laboratori Nazionali di Legnaro (Italy). The thermal and epithermal neutron flux was measured at various positions in the irradiation cavity by means of activation techniques employing bare and cadmium covered indium foils. Further measurements were performed with BF3 detectors. The fast neutron component of the dose equivalent and the energy spectrum above 100 keV were assessed by means of a recently developed technique employing variable threshold superheated drop detectors. The prompt gamma ray dose was measured with (LiF)-Li-7 TLDs.