The Radio-thermoluminescence of CaSO4:Sm and Its Use in Dosimetry

The general properties of the thermoluminescence of CaSO4:Sm have been investigated. The luminescent emission lies in the region 4,000 - 6,200 A with narrow bands at 5,600 and 5,900 A. The glow curve has the main peak at 400 deg C and a smaller one at 95 deg C. The fading of the thermoluminescence signal in the former peak is negligible at temperatures up to 200 deg C. The light yield of the 400 deg C emission is 0.3 % at small exposures and increases to 1.5 % at 10,000 R. Saturation occurs at about 30,000 R. The variation of the sensitivity is interpreted as being caused by a generation of new traps. It is concluded that CaSO4:Sm provides a good basis for gamma dosimetry at high temperatures. It can be used up to somewhat above 200 deg C without corrections for the influence of the irradiation temperature. It may be used up to 300 deg C if the exposure times are restricted and corrections are applied. Because of the high readout temperature needed, the emission of incandescent light is a severe background component. The system described cannot be used for the determination of exposures less than about one roentgen