First studies of electron transport along small gas gaps of novel foil radiation converters for fast-neutron detectors
First studies of electron transport along small gas gaps of novel foil radiation converters for fast-neutron detectors
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DOI：
10.1088/1748-0221/8/01/p01016
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发表时间：
2012-10
影响因子：
1.3
通讯作者：
M. Cortesi;R. Zboray;R. Adams;V. Dangendorf;A. Breskin;S. Mayer;H. Hoedlmoser;H. Prasser
中科院分区：
文献类型：
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作者：
M. Cortesi;R. Zboray;R. Adams;V. Dangendorf;A. Breskin;S. Mayer;H. Hoedlmoser;H. Prasser
提出了用于扇束层析成像的新型高效快中子探测器。他们将气体介质中的多层聚合物转换器与厚气体电子倍增器（THGEM）结合在一起。转化器氢核上的中子诱导散射导致两个连续转化器之间逃逸的反冲质子产生气体电离。电子在均匀电场的作用下漂移，平行于转换器箔表面，朝向位置敏感的THGEM倍增元件。在这项工作中，我们讨论了一个系统研究的结果，电子传输在一个狭窄的间隙内，连续的转换器箔，影响检测器的性能，无论是在检测效率和定位特性。在6和10毫米宽的聚合物转换器中沿0.6毫米宽的气隙测量了电离电子的传输效率。计算机模拟提供了对观测的概念性理解。当漂移长度为6 mm时，电子沿着狭窄的气隙有效地传输，而扩散引起的损失最小；对少量keV光电子诱导的电离电子，平均收集效率可达95%。由于转换器箔的电气和机械缺陷，10毫米高度的转换器产生了相当低的效率。结果表明，对于2.5 MeV的中子，采用300片、6 mm高、0.4 mm厚、0.6 mm气隙的转换器，检测效率可达7%。
Novel high-efficiency fast-neutron detectors were suggested for fan-beam tomogra- phy applications. They combine multi-layer polymer converters in gas medium, coupled to thick gaseous electron multipliers (THGEM). Neutron-induced scattering on the converter's hydrogen nuclei results in gas ionization by the escaping recoil-protons between two successive converters. The electrons drift under the action of a homogeneous electric field, parallel to the converter-foil surfaces, towards a position-sensitive THGEM multiplying element. In this work we discuss the results of a systematic study of the electron transport inside a narrow gap between successive converter foils, which affects the performance of the detector, both in terms of detection efficiency and localization properties. The efficiency of transporting ioniza- tion electrons was measured along a 0.6 mm wide gas gap in 6 and 10 mm wide polymer con- verters. Computer simulations provided conceptual understanding of the observations. For drift lengths of 6 mm, electrons were efficiently transported along the narrow gas gap with minimal diffusion-induced losses; an average collection efficiency of 95% was achieved for ionization elec- trons induced by few keV photoelectrons. The 10 mm height converter yielded considerably lower efficiency due to electrical and mechanical flaws of the converter foils. The results indicate that detection efficiencies of 7% can be expected for 2.5 MeV neutrons with 300-foils converters, of 6 mm height, 0.4 mm thick foils and 0.6 mm gas gap.