Thermoluminescent LiF:Cu,Mg,P for gamma ray dosimetry in mixed fast neutron-gamma radiation fields

In thermoluminescent dosimetry (TLD), the relative TL response, η(nγ), of fast neutrons to gamma rays usually lies between 0.05 to 0.3. Recently, several groups have reported on the development of a new TL material, LiF:Cu,Mg,P, with a gamma ray TL sensitivity ~20 times greater than LiF:Mg,Ti(TLD-100), Harshaw-Filtrol). We have measured the relative TL response of LiF:Cu,Mg,P to ²⁵²Cf fast neutrons (Ēn) = 2.5 MeV). Neutron dosimetry was carried out using the polycarbonate technique, and, for comparison purposes, the neutron irradiations were also carried out simultaneously on pairs of LiF:Mg,Ti(TLD-700, H/F) and CaF₂:Tm (TLD-300, H/F) dosemeters. The following results were obtained: (1) n(LiF:Cu,Mg,P) = 0.011 ± 0.01; (2) n(TLD-700)/n(LiF:Cu,Mg,P) ≃5:1; and (3) n(TLD-300)/n(LiF:Cu,Mg,P) ≃ 4:1. Estimation of the TL signal was carried out using computerised glow curve deconvolution (CGCD). These results establish LiF:Cu,Mg,P as the 'tissue-equivalent' TL material least sensitive to fast neutrons discovered to date and suggest that LiF:Cu,Mg,P can serve as an excellent discriminator for gamma ray dose measurement in fast neutron - gamma ray radiation fields.