课程文献中心 更多>>

摘要： Radio-Photo Luminescence (RPL) glasses are used as passive dosimeters, having a wide range of applications in different radiation fields, where low to high doses are absorbed. This work presents an experimental characterisation of FD-7, a commercial RPL glass dosimeter, irradiated with X-rays at different doses ranging from 0.3 kGy to 0.5 MGy. Investigation over such a broad range allows to enhance the understanding of RPL response in different dose level, out of their normal range of application up to 0.5 kGy. The purpose of this research is to achieve additional information on the response of FD-7 RPL glass dosimeters at high doses, to further their use in extreme high dose environment, especially targeting MGy range. The findings will be beneficial for the European Laboratory for Nuclear Research (CERN), where these dosimeters are used in environments in which such doses can be reached. In this study, a customized set-up has been developed, allowing the investigation of various relevant quantities, need to be measured in real-time. For instance, Radiation Induced Attenuation and transmittance response during irradiation and their recovery after irradiation are measured. It also allows to perform post-irradiation passive measurements. Parametric studies have been performed to assess the dependence of these quantities on the total absorbed dose and on the dose rate (ranging between 1.75 Gy/s and 0.175 Gy/s). Their kinetics during irradiation and recovery after irradiation are studied. Additionally, RPL signal evolution during irradiation with total absorbed dose up to 5 KGy at 1.036 Gy/s dose rate has been measured and reported, including settling of RPL signal to a constant intensity after irradiation. The RPL signal is normally used alone to determine the total absorbed dose, this technique being extensively used and considered as reliable up to approximately 0.3 kGy. For higher doses, a combination of both RPL signal and transmitted light is used to determine th

摘要： Acoustic neutrino detection is a promising method to observe ultra high energy neutrinos. These neutrino with energies larger than 10 18 eV have a relatively low expected flux, thus a large instrumented volume is required. Current estimations give an instrumented volume of around O(100) km 3 using hydrophones as the detection modules. Measuring ultra high en- ergy neutrino would provide us with crucial information on extragalactic sources, the GZK cut-off, and also the CνB. In this work, an event detec- tion algorithm based on clique, a subspace clustering algorithm, was de- veloped. Furthermore, a first look at event reconstruction was taken. Ultra high energy neutrino events with energies of roughly 5 · 10 19 eV were ap- proximated by using their characteristic pancake shape. An instrumented volume of 4 km 3 was simulated. The study has shown that a hydrophone density of 400 per km 3 would provide the desired detection efficiency of near 100%. At these values a noise rate of 5 Hz can be suppressed using an amplitude criterion besides a causality one. A causality criterion alone suppresses a noise rate of 0.5-0.6 Hz. Furthermore, it was found that a con- figuration utilizing multiple detector blocks would maximize the effective volume of the detector. Moreover, the hydrophones should be designed for a sensitivity in the range of 0-15 kHz. The reconstruction algorithm tested did not provide the desired results, it is recommended to develop an algorithm specifically for acoustic neutrino detection. We found that design of the detector is a balancing act between detection efficiency, de- tector size, and noise suppression. Finally, this study demonstrates the possibility of using a clique based approach for event detection in ultra high energy neutrino detection. However, we recommend the develop- ment of noise suppression algorithms at the single waveform level, as sup- pression of a noise rate of 0.5-0.6 Hz or 5 Hz, depending on match criteria, is not enough based o

关键词： 晶态物质   残余应力   X射线衍射   实验教学  

摘要： 为了提升大型仪器设备实验教学的效果,以X射线衍射技术测量残余应力实验为例,以样品前处理过程、测量条件优化过程和实验数据后处理过程为课堂教学关键,提升学生的实验操作技能和对实验过程和效果的逻辑思维能力。根据对教学方式的改革创新,加强了老师和学生的互动交流,锻练了学生的实际操作能力,进一步加强了对X射线衍射测试残余应力基本原理的了解,教学效果明显。

关键词： 国家点火装置   利弗莫尔   聚变点火   净增益   NIF   实验室   劳伦斯  

摘要： 【美国《今日物理》网站2023年8月11日报道】美国劳伦斯·利弗莫尔国家实验室(LLNL)国家点火装置(NIF)在近期实验中再次实现聚变点火,且此次点火获得的能量净增益超过了2022年12月首次聚变点火。

关键词： 黑体辐射   瑞利-金斯公式   修正  

摘要： 以“瑞利-金斯公式”的提出与修正过程为主线,从黑体辐射分布函数的完备表达式被提出,到公式中的系数值被确定,再到这一系数值被金斯所修正,并最终以“瑞利-金斯公式”命名;尝试梳理并还原了这一时期相关物理学家的思考与贡献,基于物理学的发展历史,为中学物理教学提供具有参考意义的课程资源。

关键词： 印刷电路板(PCB)   缺陷检测系统   X射线图像   YOLOv7算法   多尺度融合   损失函数  

摘要： 针对PCB内部缺陷检测速度慢、精度低的问题,提出一种基于X射线图像的PCB缺陷检测系统。该系统算法对YOLOv7进行改进,在Neck区域设计一种高效的特征提取模块,优化Neck区域网络结构,降低模型复杂度。在多尺度特征融合模块引入ACmix注意力机制,增加不同尺度目标特征的权重。将SIoU作为边框损失函数,提高网络的定位能力。实验结果表明:所提系统算法在测试集上的平均准确度均值(mAP)达到了92.8%,比YOLOv7算法提高4.6%;检测速度提升25%,模型计算量降低29%,面对复杂场景具有较强的鲁棒性,能够满足实际工业检测的需求。

关键词： 全反射X射线荧光分析   TXRF   分析仪器  

摘要： 全反射X射线荧光分析技术(Total-Reflection X-Ray Fluorescence Analysis,TXRF),是一种多元素、高灵敏分析技术,具有样品需求量小、非破坏性、量化方法简单、检测限低、多元素同时分析等特点,适用于痕量元素快速分析,其技术与分析仪器广泛应用于环境、材料、生物、半导体材料等领域,近年来成了X射线荧光光谱学领域的研究热点之一。对全反射X射线荧光分析的技术背景、技术特点、全反射X射线荧光分析物理原理、全反射X射线荧光分析仪器关键部件的发展与新型产品进行了综述,对全反射X射线荧光分析仪器的国内外发展现状进行了梳理和总结,从关键部件、分析方法等方面出发对全反射X射线分析技术与仪器的新应用领域,新型X射线光管与新型SDD探测器的诞生对分析仪器性能的提升以及新定量分析方法对分析精度的影响进行了展望。