Recoil Energy Effects in High Energy Particle Irradiation

碰撞级联产生的点缺陷团簇非常小，其性质的识别并不容易。名古屋大学高压电子显微镜实验室辐射危害控制区的建立，使高能电子对中子辐照的放射性样品的辐照成为可能，通过对电子辐照下缺陷的行为进行可靠的识别成为可能。聚变中子(RTNS-II)辐照样品的研究取得了进一步进展，裂变反应堆(JMTR)的受控辐照进行了温度循环辐照和多节可拆卸装置的辐照，获得了缺陷结构演变的连续过程的数据。裂变中子辐照和聚变中子辐照的直接比较首次成为可能。通过总结聚变和裂变中子辐照以及轻、重离子辐照的结果，阐明了碰撞级联直接产生缺陷的累积模式(辐照剂量Phi)：碰撞碰撞效应的非常早期阶段(Phi^2)，与辐照剂量成正比的简单阶段(Phi^1)，通过自由迁移间隙组织的反应而恢复的阶段(Phi^1；1/2&gt；)和缺陷几何重叠阶段(1-exp(-α))。将电子辐照实验得到的小间隙团簇容易运动的结果应用于中子辐照，解决了晶体取向依赖等悬而未决的问题。同时，利用电子辐照得到的点缺陷反应的涨落，解释了碰撞级联形成的小间隙团簇成功几率很小的原因。

Point defect clusters produced from collision cascades are very small and the identification of their nature was not easy. The establishment of radiation hazard control area on High Voltage Electron Microscopy Laboratory of Nagoya University has enabled to irradiate neutron irradiated radioactive samples with high energy electrons, and the reliable identification became possible from the behavior of each defects under electron irradiation.Further progress was made on the research of fusion neutron (RTNS-II) irradiated samples, and the controlled irradiation with a fission reactor (JMTR) proceeded to temperature-cycle irradiation and irradiations with multi-section removable rigs to obtain the data on the continuous progress of defect structure evolution. Direct comparison of fission neutron irradiation with those of fusion neutron irradiation became possible for the first time.Accumulation modes (irradiation dose phi) of defects produced directly from collision cascades were clarified from summing up the result of fusion and fission neutron irradiatoin and light and heavy ion irradiation : Very early stage by impact effect from collisions (phi^2), Simple stage proportional to irradiaton dose (phi^1), Stage with recovery by the reaction of freely migrating interstitials (phi^<1/2>), and Stage of geometrical overlap of defects (1-exp (-alphaphi) ).Applying the result of easy motion of small interstitial clusters obtained from electron irradiaton experiment to neutron irradiation, unsolved problems such as crystallographic orientation dependence were solved. Also, applying the fluctuation of point defect reactions obtained from electron irradiatoin, the origin of very small success probability of interstitial cluster growth from small interstitial clusters made by collision cascades was understood.