Evidence for a critical dose above which damage to carbonate ester bonds in PADC appear after gamma ray and ultra soft X-ray exposures
Evidence for a critical dose above which damage to carbonate ester bonds in PADC appear after gamma ray and ultra soft X-ray exposures
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DOI：
10.1016/j.radphyschem.2019.108628
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发表时间：
2020-05-01
影响因子：
2.9
通讯作者：
Yamauchi, Tomoya
中科院分区：
文献类型：
--
作者：
Kusumoto, Tamon;Okada, Shogo;Yamauchi, Tomoya
已经证实，聚（烯丙基二甘醇碳酸酯）（PADC）（其是公知的聚合物核径迹探测器CR-39）中的碳酸酯的密度在暴露于Co-60伽马射线和超软X射线（USX：能量为1.49 keV的K α（Al））期间开始降低到高于约60 kGy的临界剂量。在77 K和室温（RT）下暴露于Co-60 γ射线后，在60 kGy的临界剂量两侧观察到电子自旋共振（ESR）谱的显著差异，其中60 kGy是PADC中碳酸酯降解的阈值。也就是说，在该临界剂量以下和以上，PADC中的自由基类型彼此不同。还观察到PADC中碳酸酯的FT-IR光谱在γ射线和USX暴露的临界剂量以上的变化，而醚的FT-IR光谱随着吸收剂量的增加而线性下降。这些结果与以前用28 MeV电子束得到的结果是一致的。它们还表明，至少需要两次电子撞击才能破坏PADC中的碳酸酯。这些实验结果可以解释PADC中离子径迹的层状结构。此外，还从ESR和IR的结果中获得了一些鉴别生成自由基的线索。
It has been confirmed that the density of carbonate ester in poly(allyl diglycol carbonate) (PADC), which is a well-known polymeric nuclear track detector CR-39, begins decreasing above a critical dose of about 60 kGy during exposures to Co-60 gamma rays and Ultra Soft X-rays (USX: K alpha (Al) with energy 1.49 keV). After exposure to Co-60 gamma rays at 77 K and room temperature (RT), a significant difference in Electron Spin Resonance (ESR) spectra has been observed at both sides of a critical dose of 60 kGy, where is a threshold for the degradation of carbonate ester in PADC. Namely, the types of free radicals in PADC are different from each other below and above this critical dose. Changes in FT-IR spectra of carbonate ester in PADC above critical doses for gamma ray and USX exposures have also been observed, while that of ether decreases linearly with increasing absorbed dose. These results are well concordant with previous results obtained with 28 MeV electron beams. They also indicate that at least two hits of electrons are needed to destroy the carbonate ester in PADC. The layered structure of ion tracks in PADC can be explained thanks to these experimental results. Also, some clues for the identification of created radicals have been obtained from the results using both ESR and IR.