A Monte Carlo study for the shielding of γ backgrounds induced by radionuclides for CDEX

The CDEX (China Dark matter EXperiment) Collaboration will carry out a direct search for WIMPs (Weakly Interacting Massive Particles) using an Ultra-Low Energy Threshold High Purity Germanium (ULE-HPGe) detector at the CJPL (China JinPing deep underground Laboratory). A complex shielding system was designed to reduce backgrounds and a detailed GEANT4 Monte Carlo simulation was performed to study the achievable reduction of γ rays induced by radionuclides and neutron backgrounds by D(γ,n)p reaction. Furthermore, the upper level of allowed radiopurity of shielding materials was estimated under the constraint of the expected goal. Compared with the radiopurity reported by other low-background rare-event experiments, it indicates that the shielding used in the CDEX can be made out of materials with obtainable radiopurity.     

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.     

屏蔽电磁波和红外的激光滤光片研制

为了研制具有高效电磁屏蔽功能的反红外、透1064nm激光的滤光片,基于金属薄膜诱导理论和多层薄膜的干涉原理,设计了诱导滤光膜的膜系结构,并讨论了金属Ag薄膜厚度误差对滤光片光谱性能的影响。采用离子束辅助沉积的方式制备膜系中的介质薄膜,采用离子束溅射方式制备了金属Ag薄膜;利用放大膜厚控制误差的方法,精确地监控薄层金属Ag膜的沉积厚度,同时避免了Ag膜被氧化。通过工艺实验,制备的滤光片在1064nm激光波长的透射率达到88%以上、中长波红外波段反射率达90%以上,对18～36GHz电磁波屏蔽效能达到23dB以上,具有良好的中长波红外及电磁波屏蔽功能。     

改进的屏蔽氢离子模型中量子修正△nl的推算

此文用等电子系列实验抛物线关系推算出了改进的屏蔽氢离子模型中量子修正△ｎｌ的值，从而提高了屏蔽氢离子模型计算离子能量的精度。     

激光防护技术的发展现状

为了对抗日趋严重的激光致盲威胁 ,世界各国加速发展激光防护技术 ,并已取得了相当大的进展。本文综述激光防护技术的发展现状     

焊缝区选择性腐蚀及其防护措施

焊缝区选择性腐蚀的类型,腐蚀机理,以及防护措施等进行了评述。     

Bi（2223）超导体的磁屏蔽效应

本文研究了Ｂｉ（２２２３）超导体屏蔽筒的磁屏蔽效应，从而得出了屏蔽效果与超导体的微观结构、临界电流密度、屏蔽空间大小有关，以及双筒套构的方法可进一步增强磁屏蔽效果的结论。     

井下恶劣环境冲击波发生器热管理的实验研究

页岩油开采系统面临井下恶劣环境,为了保证设备的长期稳定性,本文提出了一种外部热防护配合内部储热的井下冲击波发生器热管理系统。构建石蜡与泡沫铜的复合相变材料储热装置,并对多种热防护措施进行评估。结果表明,在100℃井下热环境中,外环境对于系统内部电子元件的影响较大;在仅使用空气作为隔热层的情况下,热辐射占比大于30%,而使用酚醛树脂可以有效提升热防护层的等效热阻;然而随着外部环境温度的提升,热防护层的效果逐渐降低。采用热防护结合内部相变储热的热管理方法,可将电子元件持续工作1.5 h时的节点温度控制在90℃以下。