Experiment Of Cryogenic Mechanical Properties On Superconducting Materials And Key Technologies R&D Of Multi-field Prototype Test Facility

With the development of science equipments,large volume and high magnetic fields superconducting magnets were usually required.Magnetic field,temperature field,current field are often key parameters for the design and operation of superconductors and their structure.Under complicated multi-field,how to optimize the three key parameters are an important and basic issue for superconducting magnets and their application.Since superconducting magnet was usually operated under intense/variable electromagnetic field and cryogenic/variable temperature field,and the multi-field interaction may led easily to the nonlinear variation of superconductor's physical parameters.Currently,based on some tested physical parameters under single or simple field,the design of the superconducting magnet is always inadequate for its complicated operation.Therefore,under the ultra-variable environment of multi-fields,experimental characterization/detect method of cryogenic mechanical properties on superconducting materials,and R&D of their multi-field test facility are both necessary for high performance superconducting equipments.In this dissertation,a self-innovative variable low temperature system combined with mechanical loading apparatus is applied for experimental characterization of variable cryogenic dependence of mechanical properties on superconducting materials,meanwhile,some smart detect methods on strain and thermal expansion coefficient for variable cryogenic were developed.Furthermore,we also introduce independent R&D of 4.2K multi-field prototype test facility based on GM refrigeration and optimization of its key components,finally,test and analysis for commissioning of this system were also carried out.(1)The strain measurements and methods on superconductors under variable cryogenic were conducted.Based on the low temperature strain gauge and fiber Bragg grating(FBG),the study of embedding optical fiber Bragg grating for high temperature superconducting taps were developed.Some compensate methods on cryogenic temperature were introduced using strain gauge and FBG technology.Based on above two strain measurement methods,we report a comparative and tested study on deformations for superconductors under cryogenic.Then,some error analysis and methods or skills on reducing errors were also argued in detail.(2)The new method of stretch measuring of linear thermal expansion for several commercial superconducting wires was proposed using self-innovative variable low temperature system combined with mechanical loading apparatus.The cryogenic temperature dependence of the thermal expansion coefficient is measured by tensile method for Nb Ti/Cu,Nb3Sn/Cu,and Bi2212/Ag tapes.Based on the thermal expansions measured from room temperature to liquid nitrogen temperature,the thermal expansions at 4.2K are extrapolated for these composite wires and their filaments,which are compared well with the experiments using thermal methods in the existing literature.(3)We tested in detail mechanical behaviors of several commercial superconducting composites,which had been used widely for many HTS/LTS superconducting magnet engineering,under variable cryogenic field,and preliminarily basic data is also established base on tested mechanical parameters of some high/low temperature superconductors.Mechanical properties,such as the tensile strength,elongation at fracture,yield strength,and Young's modulus,were tested repeatedly for 41 commercial LTS/HTS materials with different size under variable cryogenic temperature(77K~RT).By aggregation and integration,a basic data base on mechanical parameters was developed.It will be very helpful for the optimal design and application of superconducting magnets.(4)The partial design and assembly,commissioning of multi-field prototype test facility and optimization of some key components were carried out.Based on assembled mechanical test system at 77K~RT in our lab,the development of 4.2K multi-field prototype test facility based on GM refrigeration and its sub-system function were further introduced.And for this 4.2K multi-field prototype,the innovative design and smart optimization of its crucial cryogenic temperature vacuum chamber and high current leads system were carried out in detail.Finally,some test and analysis for commissioning of this system were carried out in detail.The tested results show that some key functional indexes are according with our design requirements,which is very meaningful for the development our high performance zero boil-off 5T multi-field test facility project in future.