Dosimetric Characteristics of Natural Calcium Fluoride of Iran

Abstract

Thermoluminescent characteristics of nine batches of fluorite (natural CaF<inf>2</inf>) from seven mines in Iran were studied for radiation protection dosimetry, some preliminary results of which are presented and discussed. The initial thermal treatment was optimised for cleaning the natural dose at 500(C for 24 h. All the batches, except two, showed the same glow curve structures with three prominent peaks of different intensities at approximately 120, 180 and 270(C (� = 3(C.s-1). One batch from one mine showed a sensitivity about 8.7 times by peak area higher than that of TLD-100 (Harshaw) powder and about the same sensitivity as that of TLD-200, with a dose response linear up to 100 Gy. A thermal fading of 15% during the first day and 17% during a month reached negligible fading per month after a post-irradiation thermal treatment at 100(C for 20 min. The minimum measurable dose of this phosphor was determined to be 18 �Gy.mg-1.