Fading in thermoluminescent lithium fluoride after irradiation with gamma-ray doses up to 1000 rad

In a previous paper the fading in thermoluminescent lithium fluoride after irradiation with low doses (0·5 rad) was examined. The present paper describes an extension of the work to higher gamma-ray doses, involving measurements of fading at 10 and 1000 rad for three types of phosphor. An accelerated fading technique was used which was shown to agree with previous work at low doses. The results show that the fading is a monotonically decreasing function of time and amounts to 7 ± 2% over 100 days for all phosphors up to doses of 1000 rad, with the exception of Con-Rad N at 1000 rad. The lower fading of this latter phosphor is attributed to the increase in sensitivity at doses greater than 100 rad being due mainly to the creation of deep traps, thereby reducing the proportion of shallow traps. Examination of glow curves supports this hypothesis.