[论文解读] High intensity proton beam impact at 440 GeV/c on Mo and Cu coated CfC/graphite and SiC/SiC absorbers for beam intercepting devices

Jorge Maestre, C. Bahamonde+15 more|arXiv (Cornell University)|Dec 9, 2021

Radiation Effects in Electronics参考文献 27被引用 5

一句话总结

本研究在CERN的HiRadMat设施中，对Mo-和Cu涂层的等静压石墨、CFC以及SiC/SiC吸收体材料在440 GeV/c高强度质子束撞击下的性能进行了评估，模拟了LHC束流排放系统的工作条件。关键结果表明，尽管涂层出现了熔化（Cu）或剥落（Mo）现象，基体材料仍保持结构完整，且通过轨道校正可有效管理束流冲击对阻抗的影响。

ABSTRACT

Beam Intercepting Devices (BIDs) are essential protection elements for the operation of the Large Hadron Collider (LHC) complex. The LHC internal beam dump (LHC Target Dump Injection or LHC TDI) is the main protection BID of the LHC injection system; its main function is to protect LHC equipment in the event of a malfunction of the injection kicker magnets during beam transfer from the SPS to the LHC. Several issues with the TDI were encountered during LHC operation, most of them due to outgassing from its core components induced by electron cloud effects, which led to limitations of the injector intensity and hence had an impact on LHC availability. The absorbing cores of the TDIs, and of beam intercepting devices in general, need to deal with high thermo-mechanical loads induced by the high intensity particle beams. In addition, devices such as the TDI - where the absorbing materials are installed close to the beam, are important contributors to the accelerator impedance budget. To reduce impedance, the absorbing materials that make up the core must be typically coated with high electrical conductivity metals. Beam impact testing of the coated absorbers is a crucial element of development work to ensure their correct operation. The behaviour of several metal-coated absorber materials was investigated when exposed to high intensity and high energy proton beams in the HiRadMat facility at CERN. Different coating configurations based on copper and molybdenum, and absorbing materials such as isostatic graphite, Carbon Fibre Composite (CfC) and Silicon Carbide reinforced with Silicon Carbide fibres (SiC-SiC), were tested in the facility to assess the TDI's performance and to extract information for other BIDs using these materials. In addition to beam impact tests and an extensive Post Irradiation Examination (PIE) campaign, extensive numerical simulations were carried out.

研究动机与目标

• 评估涂层束流吸收体材料在LHC类似束流冲击下的热机械性能与电磁性能。
• 识别石墨、CFC和SiC/SiC基体在高强度质子辐照后的材料退化机制。
• 评估束流诱导的表面损伤对加速器阻抗及运行安全的影响。
• 验证预测吸收体材料在束流冲击下热机械响应的数值模型。
• 支持下一代束流拦截装置（BIDs）的设计，以提升可靠性并降低阻抗。

提出的方法

• 在CERN的HiRadMat设施中，利用440 GeV/c质子束对Mo-和Cu涂层靶材进行束流冲击测试。
• 采用辐照后检测（PIE）方法，包括光学显微镜和扫描电镜（SEM），分析涂层与基体的损伤情况。
• 对束-物质相互作用、热响应及基体中的热-机械应力进行数值模拟。
• 通过谐振腔扰动技术，利用S21散射参数测量冲击前后表面的阻抗变化。
• 采用参考金属和清洁谐振腔对阻抗测量进行校准，以确保测量精度。
• 将实验结果与模拟预测进行关联，以验证模型并评估故障预测中的保守性。

实验结果

研究问题

• RQ1 Mo和Cu涂层在440 GeV/c质子束冲击下，其熔化、剥落和结合力表现如何？
• RQ2 高强度束流辐照后，石墨、CFC和SiC/SiC基体发生了何种类型的结构损伤？
• RQ3 束流冲击在多大程度上改变了涂层吸收体材料的表面电阻率和阻抗？
• RQ4 数值模拟在多大程度上准确预测了涂层吸收体材料在束流冲击下的热机械响应？
• RQ5 通过轨道校正或光阑调整等运行调控手段，能否有效缓解束流冲击引起的表面损伤？

主要发现

• 铜涂层在束流冲击区域表现出局部熔化，尤其在掠射和倾斜入射条件下，与热模拟预测结果一致。
• 石墨基体上的钼涂层未出现熔化，但显示点状脱落，可能由剥落引起，且无明显粘附力损失。
• 铜涂层CFC靶材出现沿纤维排列方向的脱落，纤维间伴有轻微熔化，表明损伤响应具有各向异性。
• SiC/SiC基体在深穿透和掠射冲击后出现表面损伤，包括基体脱粘、平行于顶面的纤维断裂以及界面脱粘。
• 辐照后阻抗测量显示，Mo-和Cu涂层石墨表面的S21散射参数出现畸变，表明表面电阻率发生变化。
• 尽管表面出现退化，但通过轨道校正或光阑位置调整等运行调控手段，整体阻抗性能可被恢复。