DEVELOPMENT OF ONE DIMENSIONAL ANGULAR CORRELATION OF POSITRON ANNIHILATION RADIATION MEASU REING WIDE MOMENTUM REGION FOR NON-DESTRUCTIVE INSPECTION OF NUCLEAR REACTOR PRESSURE VESSEL

确保核电反应堆的安全运行是最近的一个紧迫问题，因为第一代反应堆正在超过其最初设计的运行寿命。反应堆压力容器（RPV）用钢的中子辐照脆化是一个重要的问题，它被认为是由第一代反应堆压力容器用钢中Cu杂质（100.3%）在中子辐照下产生超细沉淀而引起的。然而，很少有人知道的辐射诱导的Cu沉淀或聚集，因为它是非常困难的，即使是通过当前的高分辨率透射电子显微镜（HR-TEM）观察到它们。本工作的目的是研制一种新型的正电子湮没辐射一维角关联（1D-ACAR）无损检测装置。我们的最终目标是建立一种利用该仪器分析超微粒子形成过程和结构的方法 关于我们 为了利用我们最近发现的Cu沉淀中的亲合诱导正电子约束效应，研究其它技术难以探测到的精细Cu沉淀，我们必须研制一种新的一维ACAR装置，它不仅能测量传导电子的动量分布，而且能测量芯电子的动量分布，具有很高的动量分辨率（~ 1x 10 ^<-3>mc）。因此，我们开发了一对具有高位置分辨率（102 mm），高计数率（宽有效面积：150 mm x 150 mm）和高时间分辨率的位置灵敏γ射线探测器。一个检测器安装在固定支架上，另一个检测器安装在可垂直移动的支架上。在下一步中，构建用于低温（15 K）测量的样品室和用于该室的支撑件。最后，建立了正电子湮没γ射线对符合测量的电气系统，并对新的1D-ACAR装置进行了性能评价。在高动量区观察到一个长尾巴，这导致高背景和差的位置分辨率。我们发现这是由闪烁光子在光导表面的反射引起的。为了消除这种影响，探测器现在正在改进光导几何形状和定时输出放大器的设置。少

Ensuring safe operation of nuclear power reactors is a recent urgent issue since the reactors of the first generation are going over their initially designed operating lifetimes. One of the most important problem is the embrittlement of the reactor pressure vessel (RPV) steels by neutron irradiation, which is considered to be caused by the ultrafine precipitation of Cu impurities contained in the RPV steels (〜O.3 %) of the first generation induced by neutron irradiation. However, little is known about the irradiation-induced Cu precipitates or aggregations because it is very difficult to observe them even by current high-resolution transmission electron microscopes (HR-TEM). The aim of this work is to develop a new type of one-dimensional angular correlation of positron annihilation radiation (1D-ACAR) apparatus for non-destructive inspection of the RPV steels. Our final goal is to establish the method, using the apparatus, to analyze the formation process and the structure of the ultr … More afine Cu precipitates, difficult to detect by other techniques, utilizing affinity-induced positron confinement in the Cu precipitate which we have recently found.For the above purpose, we have to develop a new 1D-ACAR apparatus which enables us to measure the momentum distribution of not only conduction electrons but also core electrons with high momentum resolution (〜1x10^<-3>mc). Thus, we developed a pair of position sensitive gamma-ray detectors with high position resolution (〜2 mm), high counting rate (wide effective area : 150 mm x 150 mm) and high time resolution. One detector was mounted on a fixed support, and the other detector was mounted on a support movable vertically. In the next step, the sample chamber for low temperature (〜15K) measurements and the support for the chamber were constructed. Finally, the electric system for the coincidence measurement of a pair of positron annihilation gamma-rays was set up.We performed a test measurement of the new 1D-ACAR apparatus for the evaluation of the performance. A long tail in the high momentum region was observed, which results in high background and poor position resolution. We found that this was caused by the reflection of the scintillation photons at the light-guide surfaces. To remove this effect, the detectors are now improving the setting of the light-guide geometry and the amplifiers for the timing outputs. Less