Photon dose mixed in monoenergetic neutron calibration fields using 7Li(p,n)7Be reaction

The ambient dose equivalents H*(10) of photons mixed in the 144, 250 and 565 keV monoenergetic neutron fields were evaluated using measurements from an NaI(Tl) detector and calculations done using the MCNP-ANT code. It was found that H*(10) of the photons produced in the target assembly dominates the dose, particularly near the target. The H*(10) of the photons produced in other materials in the field increases with the increase in distance from the target and could not be neglected at a large distance from the target. The ratios of the H*(10) of the mixed photons to that of the monoenergetic neutrons for 144, 250 and 565 keV neutron fields, were evaluated to be below 5.5, 6.9 and 1.5 %, respectively. The ratios were calculated at calibration points between 100 and 500 cm from the target.