Construction of a Positron Lifetime Spectrometer with beta^+-gamma coincidence for in-situ studies of lattice Defect

构建用于晶格缺陷原位研究的β^-γ符合的正电子寿命谱仪

基本信息

批准号：
05555167
负责人：
SHIRAI Yasuharu
金额：
$ 2.37万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05555167/
关键词：
Positron Annihilation Lattice Defects Metals Intermetallics 金属間化合物高温熱平衡測定

项目摘要

Positron lifetime spectrometry has been successfully applied to the studies of atomicscale defects in solids. The conventional positron source in the lifetime measurements is ^<22>Na. The positron emission is accompanied by a suitable start signal, the 1.28MeV photon from de-excitation of the resulting ^<22>Ne nucleus. The positron source is usually prepared by evaporating a few microcuries of aqueous ^<22>NaCl onto a thin metal or plastic foil (typically 1 mg cm^<-2>) and covering it with the same foil. The source is then sandwiched by two identical pieces of sample material.However, it is quite difficult or almost impossible to carry ont lifetime measurements at high temperatures or under high pressures with the sandwich configulation. We, therefore, constructed a new positron lifetime spectrometer adopting the beta^+-gamma coincidence technique which uses positrons themselves for supplying the start signal. Positrons give a start signal to the coincidence circuit when they pass a positron detector, which consists of a thin plastic scintillator connected with a light guide to a fast photomultiplier. The positrons passed through the start detector are guided and implanted into a sample marterial. The whole apparatus is desk-top. The time resolution of the whole system is about 300ps (FWHM) as yet, which is worse than that of the conventional gamma-gamma coincidence method but is better than any former beta^+-gamma coincidence lifetime spectrometers in the world.

正电子寿命光谱法已成功地应用于固体中原子尺度缺陷的研究。寿命测量中的常规正电子源为 ^<22> na。正电子发射伴随着合适的启动信号，即产生 ^<22> ne核的1.28mev光子。正电子源通常是通过蒸发几个微泡的水性 ^<22> nacl上的薄金属或塑料箔（通常为1 mg cm ^<-2>），并用相同的箔纸覆盖它。然后将源用两种相同的样品材料夹住。但是，在高温下或具有三明治配置的高压下或在高压下进行寿命的测量是非常困难或几乎不可能的。因此，我们构建了一种新的正电子寿命光谱仪，该光谱仪采用了β+ - 伽马巧合技术，该技术使用正电子本身来提供起始信号。正电子通过时，正电子探测器由薄塑料闪烁器组成，该塑料闪光灯与快速光电倍增器相连。通过起始探测器的正电子被引导并植入样品中。整个设备都是桌面。整个系统的时间分辨率迄今为止约为300PS（FWHM），这比常规的伽玛 - 伽马巧合方法要差，但比世界上任何以前的beta^+ - 伽玛偶然寿命光谱仪都要好。