High-Z X-ray detectors for security imaging

用于安全成像的高 Z X 射线探测器

• 批准号: ST/F000073/1
• 负责人: Paul Sellin
• 金额: $ 40.94万
• 依托单位: University of Surrey
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FF000073%2F1
• 关键词: ray; detectors; security; imaging

The primary aim of this project is to transfer expertise and knowledge to DSTL Fort Halstead in the development and application of high-Z semiconductor X-ray detectors, which has been developed out of PPARC-funded research at the University of Surrey. The Surrey group, led by Dr Sellin, is one of the country's leading centres for high-Z semiconductor detector development, with particular expertise in the characterisation of wide bandgap detector materials, and the development of prototype X-ray and gamma ray detectors. This work has been focussed on CdZnTe/CdTe devices, for applications in ambient temperature hard X-ray imaging. The PPARC support for this work has come through two main sources; (1) PPARC CASE Studentship (2006 / 2009) 'Characterisation of High-Z materials and pixellated electronics for use as Hard X-ray imaging detectors', with CCLRC Rutherford Appleton Laboratory (Paul Seller) as the collaborating partner; (2) PIPSS award (2000-2003) 'Characterisation of CdZnTe pixel detectors based on Rockwell CMOS Readout', jointly with Leicester University Space Centre. This project developed one of the first prototype CdZnTe pixellated imaging detectors for future space science applications In this proposal we address a specific requirement from DSTL for X-ray imaging over the energy range 100 keV / 1 MeV keV. Of the various X-ray detectors available, semiconductor devices provide several advantages over scintillator-based detectors in terms of energy resolution, spatial resolution, and compactness. However silicon, which is the material of choice for charge particle detection, has an extremely low X-ray detection efficiency. As a result there has been considerable interest in high-Z compound semiconductor materials for use as high energy X-ray detectors, such as CdZnTe. For the particular security imaging application that DSTL require even CdZnTe is not sensitive enough for photon energies above ~200 keV. For this reason we propose to develop radiation detectors made from the very high-Z materials HgI2 and TlBr which combine an excellent photon detection efficiency with good spectroscopic performance. Based on our expertise with CdZnTe detectors, Surrey will develop and characterise a set of prototype HgI2 and TlBr detectors, which will be transferred to DSTL for use in their specific application. Although the spectroscopic performance of both HgI2 and TlBr has been proven in the laboratory these relatively new detector materials have not yet been transferred into the real application areas. There are potential problems due to poor charge transport (especially low hole mobility) in these materials which can degrade the spectroscopic performance in large active volume detectors. Consequently a range of instrumentation techniques must be adopted to minimise these deleterious effects, including the use of a Frisch grid electron structure and the use of digital pulse processing algorithms. This will require a combination of detector physics to achieve a fundamental understanding of the performance of the devices, the development of digital data acquisition and pulse processing techniques, and detector tests in realistic photon beams. By close co-operation between the two centres the data obtained from these series of tests will be used to optimise the performance of the detectors for DSTL's specific security-based applications. The final aim of the project is to commercialise this new detector technology through either direct exploitation within the MoD/DSTL or through some form of joint venture company or other licensing arrangement.

该项目的主要目的是向 DSTL 霍尔斯特德堡传授高 Z 半导体 X 射线探测器开发和应用方面的专业知识和知识，该探测器是由萨里大学 PPARC 资助的研究开发的。由塞林博士领导的萨里小组是美国领先的高阻抗半导体探测器开发中心之一，在宽带隙探测器材料的表征以及原型 X 射线和伽马射线探测器的开发方面拥有特别的专业知识。这项工作的重点是 CdZnTe/CdTe 器件，用于环境温度硬 X 射线成像。 PPARC 对这项工作的支持主要来自两个来源： (1) PPARC CASE 学生奖学金（2006 / 2009）“用作硬 X 射线成像探测器的高 Z 材料和像素化电子器件的表征”，以 CCLRC Rutherford Appleton 实验室（Paul Seller）为合作伙伴； (2) PIPSS 奖（2000-2003 年）“基于 Rockwell CMOS 读出的 CdZnTe 像素探测器的表征”，与莱斯特大学航天中心联合颁发。该项目为未来空间科学应用开发了第一批 CdZnTe 像素化成像探测器原型之一。在本提案中，我们满足了 DSTL 对能量范围 100 keV / 1 MeV keV 的 X 射线成像的具体要求。在各种可用的 X 射线探测器中，半导体器件在能量分辨率、空间分辨率和紧凑性方面比基于闪烁体的探测器具有多种优势。然而，作为带电粒子检测的首选材料，硅的 X 射线检测效率极低。因此，人们对用作高能 X 射线探测器的高 Z 化合物半导体材料（例如 CdZnTe）产生了相当大的兴趣。对于 DSTL 要求的特定安全成像应用，即使 CdZnTe 对于高于 ~200 keV 的光子能量也不够敏感。为此，我们建议开发由极高 Z 材料 HgI2 和 TlBr 制成的辐射探测器，它将出色的光子探测效率与良好的光谱性能结合起来。基于我们在 CdZnTe 探测器方面的专业知识，萨里将开发并表征一套原型 HgI2 和 TlBr 探测器，这些探测器将转移到 DSTL 以用于其特定应用。尽管 HgI2 和 TlBr 的光谱性能已在实验室得到证实，但这些相对较新的探测器材料尚未转移到实际应用领域。由于这些材料中的电荷传输差（特别是空穴迁移率低），存在潜在的问题，这可能会降低大活性体积探测器的光谱性能。因此，必须采用一系列仪器技术来最大限度地减少这些有害影响，包括使用弗里施栅极电子结构和数字脉冲处理算法。这将需要结合探测器物理学，以实现对设备性能的基本了解、数字数据采集和脉冲处理技术的开发以及真实光子束中的探测器测试。通过两个中心之间的密切合作，从这一系列测试中获得的数据将用于优化 DSTL 特定安全应用的探测器性能。该项目的最终目标是通过在 MoD/DSTL 内直接利用或通过某种形式的合资公司或其他许可安排，将这种新探测器技术商业化。