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Construction of a desk-top-sized and mobile positron lifetime spectrometer with β^<+->γ coincidence and positron energy selection for in-situ studies of lattice defects

构建具有β^<+->γ符合和正电子能量选择的台式移动正电子寿命谱仪，用于晶格缺陷的原位研究

基本信息

批准号：
10555212
负责人：
SHIRAI Yasuharu
金额：
$ 7.74万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

The positron lifetime measurement is a non-destructive method for sensitively detecting and differentiating crystal lattice defects with size of nanometer order in materials. In the conventional positron lifetime measurement it is necessary to sandwich a positron source between two identical pieces of sample material, because all positrons emitted in all directions from the positron source have to annihilate with electrons in the sample material. It is therefore quite difficult to measure positron lifetime in the place where the sample exists, without cutting two pieces out of the sample material.We have constructed a new β^<+->γ coincidence lifetime spectrometer with positron energy selection in order to achieve in-situ measurement of positron lifetime. In the spectrometer a positron source is placed well apart from the sample. The positrons emitted from the positron source are selected in energy by a magnetic lens and only the positrons with a certain energy are led to an advanced photo diode. When the positron passes through the diode, it gives a start signal to the coincidence circuit. The positron that passed through the positron detector is again focused on the sample by a magnetic lens. The positron annihilates with an electron in the sample. The annihilation photon is detected to use as a stop signal. The new positron lifetime spectrometer with fast positron beam is desk-top-sized and can be easily carried.

正电子寿命测量是一种无损检测和鉴别材料中纳米级晶格缺陷的方法。在传统的正电子寿命测量中，必须将正电子源夹在两块相同的样品材料之间，因为从正电子源沿所有方向发射的所有正电子必须与样品材料中的电子湮灭。为了实现正电子寿命的原位测量，我们研制了一种新的具有正电子能量选择的β^<+->γ符合寿命谱仪。在光谱仪中，正电子源被放置在远离样品的地方。从正电子源发射的正电子在能量上被磁透镜选择，并且只有具有一定能量的正电子被引导到先进的光电二极管。当正电子通过二极管时，它给符合电路一个启动信号。通过正电子探测器的正电子再次被磁透镜聚焦在样品上。正电子与样品中的电子湮灭。检测湮灭光子以用作停止信号。新型快正电子束正电子寿命谱仪体积小巧，携带方便。