Response of 7LiF thermoluminescence dosemeters to clinical neutron beams with energies ranging from d(14)+Be to p(75)+Be

Thermoluminescence dosemeters have been proposed in the literature for application as combined neutron/photon dosemeters for fast neutron beams. We report the variation of the relative sensitivity (kU for neutrons compared with that for photons of 60Co) of 7LiF (TLD-700) as a function of different neutron energies and as a function of depth in a phantom. The neutron irradiations were performed at the neutron therapy facility of Louvain-la-Neuve using d(20) + Be, d(50) + Be, p(34) + Be, p(45) + Be, p(65) + Be and p(75) + Be neutron beams, and at the Gent facility using the d(14.5) + Be neutron beam, kU was found to increase with energy; for example, kU increased from 10.5% to 57% for the d(14.5) + Be and the p(65) + Be neutrons, respectively. This restricts the applicability of TLD-700 to the measurement of the γ component (DG) at low neutron energies. At high neutron energies, it allows measurement of the neutron dose (DN) since the γ component is small and kU is relatively important. Furthermore, since at these high neutron energies the γ component varies only slowly with depth and field size, these dosemeters allow an estimation of the total absorbed dose. (author)