利用轫致辐射X射线进行正电子分析的研究

A New Method of Positron Analysis with Bremsstrahlung - induced X - ray

针对现有的正电子分析方法无法分析材料内部缺陷的缺点,提出了一种新的正电子分析方法——光致正电子分析。利用加速器打靶产生的轫致辐射X射线照射样品,通过光子在材料内部发生的电子对效应来产生正电子,然后测量511 keV湮没光子进行正电子分析。通过模拟计算定量研究了该方法用于正电子分析的灵敏度、屏蔽条件等问题;建立了一套实验系统,在该系统上成功实现了对511keV湮没光子能谱的精确测量,并在低碳钢样品的缺陷含量与测量结果之间得到了对应关系。

Current positron analysis technologies can not measure the defect inside samples because of the small range of positron produced from source outside. A new method of positron analysis, Photon Induced Positron A- nalysis （PIPA） is showed to solve the problem. When irradiating samples with Bremsstrahlung - induced X - ray based on LINAC, pair production takes place inside the material. Analyzing the annihilation photons helps reveal the information of micro - structure in the samples. Several issues of this method is studied quantitively by simulation with MCNP, like sensitivity and shielding parameters. As well, an experimental system is set up to measure the spectra shape of 511 keV γ precisely. With the analysis result of 511 keV full peak, the relationship between defect concentration and PIPA result is appreciable.