The development of gas-sealed type position-sensitive counter utilizing peculiar electron-avalanche mode

本研究为利用特殊电子雪崩模式开发气封式位置敏感计数器作了基础研究。我们的研究成果如下：(1)高压比例计数器在有限比例区域（RLP）的工作机理和性能。(a)对特征X射线产生的光晕效应进行了详细的分析，充分解释了这种效应导致的比例计数器响应。首先发现，在RLP中，光晕事件的气体放大程度大于光峰事件。从实际的角度来看，这一事实是有帮助的，因为一个简单的脉冲高度选择能够排除已知会降低位置分辨率的光晕事件。研究结果发表在《中国科学》杂志第11号文章上。(1) (b)通过带电粒子加速器实验验证了位置敏感比例计数器（PSPC）的可行性。结果表明，PSPC具有较高的能量（位置）分辨能力，能够在pxie中分析待研究的微量元素。(文章编号：(2) (c)在7-atm Ar+30% CH_4中，由于原初电子云的结构变化，雪崩模式发生了突变。(文章编号：(3) (d)在KEK光子工厂测试了PSPC对10-60 KeV高能光子束的性能。在20-keVX射线和35-keVX射线中分别获得了122mum （fwhm）和140mum （fwhm）的较好位置分辨率。第(4)条给出了部分结果。(e)最近，我们用6兆电子伏质子束轰击多个目标，利用配备PSPC的晶体光谱仪进行了高分辨率x射线测量。结果发现了异常峰结构，清楚地显示了原子体系的多体效应。正在进行详细的分析，尽快发表论文。在本研究项目中，我们完成了新改进的PSPC、去除氧气和水的气体净化系统、改变计数气体和混合比的气体混合系统的构建。气体系统与无油涡轮分子泵相结合。对于氩气，在PSPC中密封得到了较好的性能。而对于Xe气体，需要对气体系统特别是气体净化系统的性能进行改进。少

In this research, we have made basic studies for the development of gas-sealed type position-sensitive counter utilizing peculiar electron-avalanche mode. Our achievements are as follows :(1) Operational mechanism and performance of high-preessure proportional counter in the region of limited proportionality (RLP) (a) Detailed analysis was performed for the halo effect due to characteristic X rays, and the response of proportional counter caused by this effect was fully explained. It was first found that, in RLP,the degree of gas amplification for the halo events is greater than that for the photo-peak events. From the practical view-point, this fact helps since a simple pulseheight selection is able to exclude the halo events which is known to deteriorate position resolution. The results are published in the article No. (1). (b) The feasibility of our position-sensitive proportional counter (PSPC) was examined in charged-particle accelerator experiment. The result showed that high-ene … More rgy (position) resolving power of the PSPC enables to analyze trace elements to be studied in PIXE.(the article No.(2)) (c) It was confimed that the sudden change of avalanche mode due to strutural change of primary-electron cloud exists in 7-atm Ar+30% CH_4. (the article No.(3)) (d) The performance of the PSPC for 10-60 KeV high-energy photon beams was tested in KEK Photon Factory. Fairly good position resolitions of 122mum (fwhm) for 20-keVX rays and 140mum for 35-keVX rays were obtained. A part of the results is given in the article No.(4). (e) Recently, high-resolution X-ray measurement using crystal spectrometer equipped with our PSPC was made by bombarding several targets with 6-MeV proton beams. The results reveled anomalous peak structures which clearly show many-body effect of atomic system. The elaborate analysis is being proceeded to publish paper as soon as possible.(2) Further improvement In this research project, we have completed to construct a newly improved PSPC,gas purification system to remove oxygen and water, and a gas mixing system to vary counting gases and mixing ratio. The gas systems are combined with oil-free turbo molecular pump. For Ar gas, relatively good performance was obtained when the gas is sealed in the PSPC.For Xe gas, however, it is needed to improve gas system especially the performance of the gas-purification system. Less