摘要：
在第四代反应堆中，核石墨作为慢化体和反射体材料服役于高温和高通量的快中子辐照环境中。快中子辐照会在核石墨中产生大量的弗伦克尔缺陷对。这些缺陷经过湮灭、扩散、最终形成更大的缺陷团簇，从而改变核石墨的微观结构，进而改变核石墨的宏观性能。因此，研究核石墨在高温辐照条件下的缺陷演化行为和机理对提高反应堆安全性具有重要意义。本研究采用30 MeV的107Ag5+离子在420℃下辐照IG-110核石墨来模拟核石墨在快中子辐照过程中的缺陷演化行为。通过微区拉曼光谱对IG-110核石墨截面结构进行表征，并对比不同深度处的拉曼光谱特征参数和辐照损伤剂量之间的关系，研究IG-110核石墨微观结构随辐照损伤剂量（Displacements Per Atom,DPA）的演化行为。研究结果表明，随着注量的增加，核石墨拉曼光谱的特征参数D峰高度与G峰高度比值（ID/IG）、G峰半高宽（Full Width at Half Maximum of the G peak,FWHM（G））以及G峰的偏移量都显著增加。与58Ni5+辐照样品相比，相同辐照损伤剂量下，107Ag5+辐照的石墨拉曼光谱的ID/IG和FWHM（G）更大。相同的FWHM（G）下，107Ag5+辐照的石墨拉曼光谱的ID/IG比58Ni5+辐照样品大。这些结果说明更重的重离子辐照会在核石墨中引起更高速率的缺陷积累，从而更快地导致石墨晶粒尺寸变小，并促进纳米晶化进程。
作者：
Ye, Yan-Xi;Zhao, Xiu-Liang;Wang, Xiao-Dong;Feng, Song;Wei, Qi-an;...
期刊：
Journal of Instrumentation,2024年19(5) ISSN：1748-0221
通讯作者：
He, SJ
作者机构：
[Wei, Qi-an; Ye, Yan-Xi; Tian, Jin; Feng, Song; He, San-Jun; Wang, Xiao-Dong; He, SJ; Zhao, Xiu-Liang] Univ South China, Sch Nucl Sci & Technol, 28 Changsheng West Rd, Hengyang, Peoples R China.
通讯机构：
[He, SJ ] U;Univ South China, Sch Nucl Sci & Technol, 28 Changsheng West Rd, Hengyang, Peoples R China.
关键词：
Detector modelling and simulations II (electric fields;charge transport;multiplication and induction;pulse formation;electron emission;etc);Electron multipliers (gas);Gaseous detectors
摘要：
As one of the main detectors for monitoring neutron flux rate in a nuclear reactor, the fission chamber (FC) suffers from issues such as low sensitivity, limited counting rate dynamic range, and system mode switching is cumbersome. This study utilizes the advantages of gas electron multipliers (GEM), which are easy to fabricate in large areas and have high counting rates, to design a novel fission chamber. By conducting Monte Carlo simulations on parameters such as the thickness of the 235 U coating, the drift distance, and the operating electric field strength, a wide -range fission chamber design that combines high sensitivity and a counting rate range based on GEM has been obtained. The simulation results demonstrated that using a GEM detector to build a fission chamber can significantly improve sensitivity and extend the counting rate range. Subsequently we built a proof -of -concept GEMbased fission chamber and tested it with a 55 Fe low -energy X-ray source and an Am -Be neutron source. The results showed that the proof -of -concept detector had a good signal-to-noise ratio and energy linearity, as well as clear discrimination between alpha background and neutron pulse amplitudes.
作者机构：
[廖峰; 贺三军; 张双; 罗万; 刘丽艳; 赵修良] School of Nuclear Science and Technology, University of South China, Hengyang;421001, China;[廖峰; 贺三军; 张双; 罗万; 刘丽艳; 赵修良] 421001, China
关键词：
碳离子治疗;三维电离室阵列;三维剂量验证
摘要：
为快速准确地实现碳离子治疗计划的三维剂量验证,采用有机玻璃PMMA(聚甲基丙烯酸甲酯)为电离室室壁和水等效模体,设计了一种三维电离室阵列,并通过Geant4软件对三维电离室阵列的结构设计进行了深入研究与验证.首先通过模拟不同能量碳离子束在水和PM M A模体中沉积的剂量分布,计算了PM M A模体的水等效厚度系数;然后研究了三维电离室阵列中电离腔室间的距离及信号导线对其剂量测量准确度的影响;最后模拟并验证了碳离子束在三维电离室阵列中沉积的剂量分布.结果表明:PM M A模体的水等效厚度系数为1.151;相邻电离腔室间的信号串扰主要来源于前侧的电离腔室,且串扰程度与电离腔室间距呈反比,间距为1 mm时串扰程度占电离腔室内剂量的3％,间距为30 m m时串扰影响可完全消除;信号导线对后侧电离腔室内剂量的干扰影响约为1％.将碳离子束在三维电离室阵列中沉积的剂量分布与PM M A模体中的剂量分布进行对比,碳离子束的射程具有良好的一致性,偏差为0.5 mm.
作者机构：
[罗万; 赵修良] School of Nuclear Science and Technology, University of South China, Hengyang, 421000, China;[刘雅兰; 杨大伟; 姜仕林] Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China
摘要：
<jats:p xml:lang="en"><sec>ALETHEIA (a liquid hElium time projection cHambEr In dark matter) project is an originally creative dark matter experiment aiming to search for low-mass (100 MeV/c<sup>2</sup>–10 GeV/c<sup>2</sup>) WIMPs. While there have existed more than ten experiments doing research on low-mass WIMPs, the ALETHEIA is supposed to grow up to be a leading project worldwide due to many unique advantages, including but are not limited to extremely low intrinsic backgrounds, easy purification , and strong potential capability of signal/background discrimination. Owing to the project’s original creativity, there has existed no direct experience of building such a detector yet; consequently, we have to launch a set of R&D programs from scratch, including the TPB coating process conveyed in this paper.</sec><sec>An incident particle that hits a liquid helium detector would generate 80-nm-long scintillation. There are currently no commercially available photon detectors capable of efficiently detecting the scintillation light and a wavelength converter must be used to convert the 80-nm-long scintillator into visible light. Silicon photomultipliers (SiPMs) can then be implemented to detect the 450-nm-wavelength light. The TPB (Tetraphenyl Butadiene, 1, 1,4, 4-tetraphenyl-1, 3-butadiene) is widely used for realizing the conversion. Although in thedark matter experiment using argon pulse-shape discrimination (DEAP) , 2.3-μm-thick TPB is successfully coated on the inner wall of the sphere with a radius of 85 cm, we cannot mimic the whole process in our experiment directly out of the two following reasons: (a) our detector shape is cylindrical, not spherical, and (b) the diameter of the current detector prototype is only 10 cm, while the one of the DEAP detectors is as large as 1.7-meter. Consequently, we must design and build an appropriate coating apparatus suitable for our detector. Owing to the existence of necessary auxiliary parts (such as cables for heating and temperature sensors), on which some vapored TPB molecules would be deposited when the coating is in progress. As a result, a blind spot on the inner wall always exists that cannot be fully coated; the blind spot area will affect the visible light yield of 80-nm-long scintillation. To solve the problem, we split the coating process into two steps: coating the curved surface and one base together in the first step and coating another base in the second step. In this way, the cylindrical detector's whole inner wall (the curved surface and the two bases) will be coated. Another key technology is to design an appropriate source sphere containing TPB powder. There are 20 holes evenly distributed on the surface of the sphere. After the TPB powder is heated andevaporated into the gas, the TPB molecules should move slowly enough to ensure that they scatter from each other long enough within the source before randomly finding a hole to escape. As a result, the TPB molecules come out of the source in an isotropic way then adhere to the inner surfaces of a cylindrical detector (diameter and height are both 10 cm) with nearly the same thickness. The TPB coating thickness on the inner wall is in a range between 1.50 and 3.02 μm, which corresponds to the thinnest and thickest TPB plate, respectively. The variation mainly comes from the different distances from the coating place to the source, which lies at the center of the PTFE cylinder. The thickness difference will not bother us because the conversion efficiency for 80-nm-long scintillation is almost the same as that for the TPB thickness in a range from 0.7 to 3.7 μm.</sec><sec>In addition to introducing the ALETHEIA project briefly at the beginning, we mainly address several aspects of TPB coating: coating principle, source design, coating process, coating thickness monitoring, and the comparison of thickness among coating plates from three independent methods. The whole process addressed in this paper is expected to provide a valuable reference for other experiments with similar requirements.</sec></jats:p>
通讯机构：
School of Nuclear Science & Technology, University of South China, Hengyang, Hunan, China
关键词：
光致发光;食盐;辐射事故;剂量
摘要：
基于光致发光个人剂量监测系统In Light200,对1～100 m Gy辐照剂量范围内的食盐进行光致发光测量,分析了其光致发光信号的线性响应以及信号的稳定性;探究了不同自然光照时间和不同储存时间对食盐光致发光信号的影响。实验结果表明:食盐在1～100 m Gy辐照剂量范围内具有良好的线性响应和信号稳定性;信号在10 min的自然光照时间后降低到本底水平;信号在30 d的储存时间内几乎无衰减;食盐可用作辐射事故中验证重建的剂量材料。
