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用 1.15GeV的氩离子在室温下对二氧化硅玻璃样品进行了辐照 ,并通过正电子寿命测量技术研究了辐照后材料微观结构的变化。结果表明 ,在未辐照二氧化硅玻璃中有近 81%的正电子是以正电子素的形式湮灭的 ;根据o -Ps的撞击湮灭寿命确定出未辐照样品的自由体积分布在0 .0 2— 0 .13nm3的区域里 ,平均自由体积半径约为 2 .5nm。辐照后材料的自由体积分布函数变窄 ,峰位下移 ,显示样品经辐照后有密度增大的现象。随着剂量的增大 ,第二正电子寿命成分的强度逐渐增加 ,而相应于o -Ps的寿命成分的强度逐渐减小 ,这被认为是由于辐照产生的电离电子在自由体积中漫游 ,使正电子与这些漫游电子发生湮灭的几率增大 ,从而减小了正电子素的形成几率。
The silica glass samples were irradiated with 1.15GeV argon ions at room temperature, and the microstructural changes of the irradiated materials were studied by positron lifetime measurement. The results showed that nearly 81% of the positrons in the unirradiated silica glass were annihilated as positron; the free volume distribution of the unirradiated sample was determined to be zero according to the impact annihilation lifetimes of the o -Ps. In the region of 0 2- 0.13 nm3, the mean free volume radius is about 2.5 nm. After irradiation, the free volume distribution function of the material becomes narrower and the peak position moves downward, indicating the phenomenon that the density of the sample increases after being irradiated. As the dosage increases, the strength of the second positron lifetime component gradually increases and the intensity of the life component corresponding to the o -Ps gradually decreases, which is presumed to be due to ionizing electrons generated by irradiation roaming in the free volume, The positron and annihilation of these roaming electrons increases the probability of thereby reducing the probability of the formation of positron.