SOME CHARACTERISTICS OF MG2SIO4 (TB) PHOSPHOR FOR MEASURING DOSES FROM DIAGNOSTIC X-RAYS

The effect of light on the thermoluminescence response of Mg2SiO4(Tb) phosphor is described in detail, including light-induced increase and optical fading of thermoluminescence intensity, and its detection limit, dose response in a low dose range and sensitivity to scattered radiation during the measurement of diagnostic X rays. Thermoluminescence of Mg2SiO4(Tb) was scarcely affected in a dark environment, and there was a slight increase after annealing and a small decrease for irradiation under a fluorescent lamp. However, this phosphor was highly sensitive to indoor natural light. The light-induced increase of thermoluminescence intensity was about 26.3 times as great as the background noise for the naked one within 20 minutes after annealing, and optical fading approached 29.7% within 1 hour after irradiation for the one enclosed in a white plastic case. Mg2SiO4(Tb) had a linear response over the low dose range from 10 mu Gy to 2000 mu Gy. The thermoluminescence response to scattered radiation was lower than that to primary one. The detection limit for diagnostic X ray measurement was 0.53 mu Gy in our laboratory.