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 limi t, dose response in a low dose range and sensitivity to scattered radi ation 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 irradia tion under a fluorescent lamp. However, this phosphor was highly sensi tive to indoor natural light. The light-induced increase of thermolumi nescence intensity was about 26.3 times as great as the background noi se for the naked one within 20 minutes after annealing, and optical fa ding approached 29.7% within 1 hour after irradiation for the one encl osed in a white plastic case. Mg2SiO4(Tb) had a linear response over t he low dose range from 10 mu Gy to 2000 mu Gy. The thermoluminescence response to scattered radiation was lower than that to primary one. Th e detection limit for diagnostic X ray measurement was 0.53 mu Gy in o ur laboratory.