Compositional Principle in Fast Neutron Thermoluminescence Dosimetry

The principle consists in monitoring the selective phosphor response. The phosphor is one of the elements of the composite detector, the other being a fast neutron scintillator. The selectivity of the phosphor lies in the great difference between accumulation efficiencies of its various traps when passing from high energy photon irradiation to that of light photons, corresponding to the long wavelength band of activator absorption. The luminescence characteristics of SrS:Sm,Tb and CaCO3:Sm,Eu phosphors are presented. The glow curves are shown to have two main peaks: glow peak 1 at 130 oC and glow peak 2 with maximum in the 220-390 oC range. The peak 1 to peak 2 intensity ratio can reach 1000:1 for gamma irradiation and 1:100 for visible light irradiation. The accumulation and luminescence mechanism of selective phosphors is considered. The potential for fast neutron selective dosimetry in mixed fields is also discussed.