两种LiF(Mg,Cu,P)热释光探测器γ射线响应特性比较研究

Comparison of response characteristics toγrays of TLD-2007C and TLD-SWB LiF(Mg,Cu,P)thermoluminescence detector

为保证剂量学测量结果的准确性,本文采用标准γ参考辐射场( 60 Co),对TLD-2007C和TLD-SWB两种LiF(Mg,Cu,P)片型热释光探测器进行照射,对其γ射线响应的一致性、线性度和重复性开展相关研究,比较了两种探测器在不同吸收剂量下的灵敏度和变异系数,并获得了其线性响应上限。实验结果表明:TLD-2007C和TLD-SWB探测器在吸收剂量为10 mGy时读数变异系数分别为3.5%和3.2%,重复性指标均在5%以内,线性响应上限分别在12~15 Gy和10~12 Gy之间,在线性响应范围内再次使用灵敏度基本不变,超过线性响应范围后,灵敏度均下降;再次使用时TLD-2007C探测器仍能保持超线性后的灵敏度,而TLD-SWB探测器灵敏度仍下降,为了恢复其原有的灵敏度,必须完成一次完整的退火周期。实验结果还表明,通过一致性筛选的探测器,后续使用过程中辐射剂量是否在线性范围内,响应的一致性均不会变差。

In this study, two kinds of LiF(Mg,Cu,P)thermoluminescence detector, namely the TLD-2007C and TLD-SWB TLDs, were irradiated in standard Gamma radiation field. The uniformity, repeatability and linearity of the response to γ rays were compared in order to ensure the measurements accuracy. The variation coefficient of their sensitivities under different absorbed doses were analyzed and the linear upper limit was obtained. The results indicated that the reading coefficient of variation of TLD-2007C and TLD-SWB was 3.5% and 3.2% respectively when the absorbed dose was 10 mGy,and the repeatability indicator was within 5%. The linear response upper limits of TLD-2007C and TLD-SWB were between 12 to 15 Gy and 10 to 12 Gy respectively. The sensitivity of TLDs changed little when reusing with radiation below the upper limit, but decreased for the radiation beyond the upper limit. If reused in radiation filed beyond the upper limit, the sensitivity of the TLD-2007C could maintain the new decreased level, while the sensitivity of the TLD-SWB continued decreasing. Completed integrated annealing cycle was necessary in order to recover its sensitivity. The results also indicated that the uniformity of the group of TLDs with consistency screening could remain well no matter their absorbed dose were beyond the upper limit.