Calcium Sulfate Activated by Lead and Manganese for Thermoluminescence Dosimetry

Abstract

CaSO₄ : Pb, Mn has been found to be free from the serious disadvantage of rapid fading possessed by CaSO₄ : Mn, the most sensitive thermoluminescence phosphor available so far. A study has been made on the effect of lead and manganese content on CaSO₄, and it is concluded that lead in CaSO₄ produces new traps for radiation energy, resulting in improvement of the properties of the phosphors for dosimetry. The optimum content of such activator additives was found to be 0.2 n14/7 of lead and 3 m% of manganese.
The improved phosphor thus obtained produces glow peaks at 160° and 190°C, and the energy yield of the thermoluminescence is about 4 %, which is twice that of CaSO₄ : Mn. The more significant properties of this phosphor from the viewpoint of application to radiation dosimetry include:
(1) Linear responce from 50μR to 10⁴R
(2) Minimum detectable dose of 50μR±25 % by experimental reader
(3) Fading rate of 5 % in a week