Keywords: activation foils, absolute neutron dosimetry, In–115, Au–197, neutron detection, radiotherapy, radiation protection, gamma radiation, thermal neutron irradiation, low neutron fluence
Enhancement of absolute neutron dosimetry by activation technique
In this work, an activation technique was used for absolute neutron dosimetry. Induced gamma within two activation foils (115In and 197Au) was detected by (5 × 5) sodium iodide (NaI) crystal. Thermal neutron irradiation was performed using the thermal neutron irradiation facility at the National Institute for Standards (NIS). Two gamma lines of 416.9 keV and 411.8 keV from 115In and 198Au, respectively, were chosen for the estimation of the neutron fluence. Gamma lines of 416.8 keV and 1293.56 keV from 115In were used to assure the obtained values of neutron fluence. Absolute neutron dose was calculated utilising the measured neutron fluence. Estimated neutron dose was found to be 1.50 mSv/h. The calculated dose by activation technique was verified by neutron rem meter NM2. Enhancement of neutron fluence was performed by adding Perspex sheets behind the activation foils to produce multiple scattering on the foils, and hence resulting in increasing the capability of accurate estimation of low neutron fluence.