Advanced mechanical characterisation of two phase CO2 cooling pipe connections for the CMS tracker upgrade.

欧洲核子研究中心（CERN）的紧凑型介子螺线管（CMS）实验选择了一种两相二氧化碳冷却系统，用于即将升级的探测器中心（跟踪器）。该系统需要由薄壁管道生产（为了减少入射辐射的吸收量），并将在高压（最大163巴）和低温（-35摄氏度）下运行。以往的薄壁冷却管和接头的力学性能已不能满足这些要求。该博士将研究新的薄壁冷却管材料和连接，以优化制造路线，从而促进该系统的设计和生产。研究问题/目标哪些材料具有合适的机械性能，可以制成所需尺寸和强度的薄壁冷却管？我们如何永久地连接这些管道材料？哪种连接机制（焊接、轨道焊接、激光焊接、钎焊）最适合各种不同的连接条件/位置？哪种设计和路线最适合可拆卸薄壁管连接？我们如何优化这个设计？长期低温高压条件对这些接头有什么影响？我们如何优化生产方法以达到所需的高可靠性？即将进行的方法/新工程对市售薄壁管材料的材料、制造路线和机械性能进行全面审查。分析提高这些材料“接合性”的技术，包括表面处理、涂层和冶金评估。永久薄壁pip连接机构的微力学性能评估，包括焊接、钎焊、轨道焊接和激光焊接。这将涉及使用基于实验室的研究以及同步加速器光束时间来研究联合失效机制和界面，以及生产方法的优化。可拆卸薄壁连接机构的设计、机械测试、表征和优化。开发和生产模拟服役条件的高压试验台。薄壁连接制造技术的评估和改进（代表所需的大生产率）。制作CMS跟踪器薄壁冷却系统的设计和构建所需的参考文档，并在此过程中为设计人员提供支持。相关的EPSRC研究领域：材料工程-金属和合金需要大量的冶金来理解和优化永久和可拆卸连接制造技术一系列不同的连接机制将被调查和评估作为这个项目的一部分。表面科学有效的界面连接机制是这一研究的基本组成部分。机械结构和系统的性能和检查将对CMS冷却系统中使用的薄壁冷却管连接的性能进行量化。工程设计项目的总体目标是生产生产两相CO2系统所需的设计工具集。在此过程中，设计工程师的支持也将是项目成功的基础。

The Compact Muon Solenoid (CMS) experiment at the European Organisation for Nuclear Research (CERN) has selected a 2-phase CO2 cooling system for an upcoming upgrade to the centre of their detector (the tracker). This system needs to be produced from thin walled pipes (in order to reduce the amount of absorption of the incident radiation) and will be operated at high pressures (163 bar max) and low temperatures (-35c). The mechanical performance of previous thin walled cooling pipes and connections is unable to meet these requirements. This PhD will investigate new thin walled cooling pipes materials and connections in order optimise manufacturing routes, and thereby facilitate the design and production of this system.Research questions/objectivesWhich materials have suitable mechanical properties to be formed into thin-walled cooling pipes of the required size and strength?How can we permanently join these pipe materials? And which joining mechanisms (soldering, orbital welding, laser welding, brazing) are most suited to a range of different joining conditions/locations?Which design and route is most suited for detachable thin walled pipe connections? And how can we optimise this design?What is the impact of long-term low temperature and high-pressure conditions on these joints?How can we optimise the production approaches in order to achieve the high reliability rates required?Approach/novel engineering to be undertakenA comprehensive review of materials, manufacturing routes and mechanical properties of commercially available thin walled pipe materials. Analysis of techniques to improve 'joinability' of these materials including surface treatment, coating and metallurgy assessment.Micromechanical performance assessment of permanent thin-walled pip joining mechanisms, including soldering, brazing, orbital welding and laser welding. This will involve the use of lab-based studies as well as synchrotron beamtime to study joint failure mechanisms and interfaces, as well as the optimisation of production methods.Design, mechanical testing, characterisation and optimisation of detachable thin-walled connection mechanisms.Development and production of a high-pressure test rig to simulate in-service conditions.Assessment and refinement of thin-walled connection manufacturing techniques (representative of the large production rates required).Production of the reference document required to design and build the CMS tracker thin-walled cooling system, and support to the designers during this process.Relevant EPSRC research areas:Materials engineering - metals and alloysA significant amount of metallurgy is required to understand and optimise permanent and detachable connectionsManufacturing technologiesA range of different joining mechanisms will be investigated and assessed as part of this project.Surface ScienceEffective interface joining mechanisms form a fundamental part of this investigation.Performance and inspection of mechanical structures and systemsQuantification of the performance of the thin walled cooling pipe connections for use within the CMS cooling system will be performed.Engineering DesignThe overall goal of the project is to produce the design toolset required to produce the 2 phase CO2 system. Support of the design Engineers during this process will also be fundamental to project success.