Measurement of the energy response of LiF—, CaF₂— and CaSO₄—TL-dosimeters

Abstract

The most important materials used in thermoluminescence dosimetry (TLD) are LiF, CaF₂ and CaSO₄ with various dopants. LiF: Mg, Ti is almost tissue equivalent and therefore the most applied TLD-material in personnel and medical dosimetry. CaF₂: Dy offers the highest sensitivity of the above mentioned materials and is used in environmental and lowdose dosimetry. CaSO₄: Dy can easily be labor made and is the cheapest phosphor. As the effective atomic numbers of CaF₂ and CaSO₄ differ markedly from that of tissue material the response curve of both materials must be carefully determined in the energy range dominated by the photoeffect. The energy responses of these three listed phosphors were determined by means of a Bragg monochromator, filtered radiation from a gold target bombarded by electrons from a Van de Graaff accelerator, the radiation of a¹³⁷Cs-source (662 keV) and a⁶⁰Co-source (1.17, 1.33 MeV). The response-energy dependence of the three dosimeters shows maxima at 35 keV (LiF and CaF₂) and 40 keV (CaSO₄).