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

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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.