Development Of A Cryogen-free Test Facility For Small Superconducting Magnets And Experiment

Nowadays, as we all know, the application of superconducting technologywhich was mainly represented by the application of superconducting magnet isbecoming more and more widely. In the field of high energy physics,superconducting insert devices such as undulator play an important role inSynchrotron Light Source. SSRF has already carried out the superconductingmagnets and superconducting undulator related research program.Based on the requirement of the research, the purpose of this thesis researchwork is aimed to develop a Cryogen-Free test facility for small superconductingmagnets, research the cooling process of “Dry” Magnets and its operation andquench characteristics. Here are the major significance of this thesis: first, to providepractical test facility for superconducting magnets, saving a lot of funds; second, totest and verify that dry magnets system, and accumulate of Cryocoolerconduction-cooled superconducting magnets engineering experience; third, toresearch on dry superconducting undulator experimental coil properties, provideexperimental basis for selection of cooling method of superconducting undulator.This research lays a solid foundation to the development of superconductingundulator. The research work in this thesis was supported by the National NaturalScience Foundation of China (NO:11275254) and also the frontier program in thearea of the knowledge innovation, CAS.The development of Cryogen-Free test facility for small superconductingmagnets was completed with many prominent characteristics such like Cryocoolerconduction-cooled superconducting magnets, easily-dismounting structure, nominalcurrent500A, a pair of multi-stage current leads real-time data collecting andrecording and humanized user interface. To some extent, our achievements reachedthe international advance level.Based on the experiment of superconducting undulator five–cycle preliminary coil, the result can be concluded as below:1）It takes12hours for the preliminary coil to drop from285K to4.2K.Thelowest balance temperature can be reached at about3.9K after30hours. Naturerecovering time needs30hours.2）Twice dropping rates had been found in cooling process, the first caused bythe Cryocooler, and the second caused by the superconducting transition.3）Zero resistance phenomenon of coil can be found at about8K. It takes15minutes to complete superconducting transition, and to complete heat ofsuperconducting transition conduction needs50minutes.4）Twice preliminary coil experiments had been completed in this research. Thefirst quench happened at38A, caused by huge Joule heat generation of HTS bottom.In the second experiment, the quench current reached261A, and quench at250Aafter running5minutes. At the end, it ran stably at230A more than30hours.5）By conduction-cooled,, critical current of preliminary coil is about260A,while immersed in helium, the current will reach at about310A, with a difference of50A.