Lithium Fluoride Thermoluminescent Responses to Neutrons

Two different types of commercial lithium fluoride phosphors in powder form, Con-Rad type N and type 7, have been systematically studied according to their reactions with different neutron energies which range from thermal to 14 Mev. Special efforts have been made to investigate the half life of isothermal decay, the order of kinetics, frequency factor, trap depth, probability factor, and the dosimetry prospect. The study of kinetics of thermoluminescent decay is based on the first-order and second-order kinetics and also on the experiments of isothermal decay and the glow curve analysis from which the parameters such as the frequency factor, s; the trap depth, E; the probability factor, pi, are derived. Comparison is made with the work of other investigators who have derived methods to determine the values of E and s. The experimental results show that type N LiF has a relatively deep trap distribution, while type 7 LiF has a rather shallow trap distribution. This indicates that the order of kinetics for type NI LiF seems to be second order while that for type 7 LiF is most likely first order. Type NJ LiF has a cross section of 71 barns for thermal neutrons. Through the reaction Li6(n, ??) H3, type N LiF can be applied in thermal neutron dosimetry. Followqing Cameron´s mathematical model, a definite relationship betwieen neutron fluence and thermoluminescence response has been obtained. Type 7 LiF is a prospective material for fast neutron dosimetry.