Advanced radiation physics for microdosimetry and low-level gamma-ray spectrometry

许多人因职业或因诊断和治疗疾病而每天暴露于电离辐射。重要的是，我们能够准确地量化辐射剂量（单位质量的沉积能量）。特别是对于混合辐射场，如中子加伽马射线，准确的剂量测量是具有挑战性的。由于辐射效应发生在细胞或亚细胞水平上，因此组织的微米体积的辐射剂量是主要信息。辐射物理学的这一领域是微剂量学，它是量化辐射剂量和分析辐射质量的最佳方法。为了解决标准微剂量测定技术的基本局限性，Discovery研究的目标是开发先进的辐射探测器和信号处理系统。我们最近成功开发了THick气体电子倍增器（THGEM）探测器，这是一种新型的气体探测器，与标准设备相比具有许多优点。基于这一开创性的工作，我们建议开发一个位置敏感探测器，可以准确地收集空间剂量分布。 本研究的第二个目的是改进低水平放射性测量技术。特别是，我们的目标是开发一个先进的伽玛射线探测系统的陨石放射性测量。石陨石的放射性是了解其近期宇宙射线暴露历史的重要信息。通过测量陨石发射的伽马射线，可以量化放射性。不幸的是，陨石中的放射性水平极低，因此当使用常规检测技术时，陨石信号被掩埋在背景辐射信号之下。为了在保留陨石信号的同时剔除背景辐射信号，我们将开发一种先进的多探测器数字符合探测系统。 这项发现研究的成果将使辐射物理学家能够准确地测量空间微剂量分布，陨石科学家能够可靠地确定陨石放射性。

Many people are exposed daily to ionizing radiation occupationally or as a result of diagnosis and treatment of disease. It is important that we are able to quantify radiation dose (deposited energy per mass) accurately. Particularly for mixed radiation fields such as neutrons plus gamma-rays, accurate dose measurements are challenging. As radiation effects take place at the cellular or sub-cellular level, radiation dose for a micrometric volume of tissue is the primary information. This area of radiation physics is microdosimetry, which has been the best way to quantify radiation dose and analyze radiation quality. To address the fundamental limitations of the standard microdosimetric techniques, the goal of this Discovery research is to develop advanced radiation detectors and signal processing systems. We recently successfully developed the THick Gas Electron Multiplier (THGEM) detector, a new type of a gaseous detector which offers many advantages over the standard device. Founded on this pioneering work, we propose to develop a position sensitive detector which can collect spatial dose distributions accurately. The second objective of our research is to improve the low-level radioactivity measurement technique. Particularly, we aim to develop an advanced gamma-ray detection system for meteorite radioactivity measurements. Radioactivity of stone meteorites is vital information for understanding their recent cosmic-ray exposure history. By measuring gamma-rays emitted from a meteorite, the radioactivity can be quantified. Unfortunately, the radioactivity level in meteorites is extremely low, so meteorite signals are buried under the background radiation signals when normal detection techniques are employed. To reject the background radiation signals while keeping the signals from meteorites, we will develop an advanced digital coincidence detection system using multiple detectors. The outcomes of this Discovery research will enable radiation physicists to measure spatial microdosimetric distributions accurately and meteorite scientists to determine meteorite radioactivity reliably.