10 W@4.5 K GM/J-T Refrigerator Key Technology Research

Small-sized helium refrigerator can provide liquid helium cooling capacity for superconducting equipment,which promotes the development of superconducting research.The laboratory is developing a superconducting magnet for a compact synchrotron,requiring a 10 W@4.5 K GM/J-T refrigerator for cooling.This paper takes the 10 W@4.5 K research device（research device）based on the GM/J-T refrigerator as the research object for the preliminary research of key technologies of the GM/J-T refrigerator.Referring to the pre-cooling cycle mode of the GM/J-T refrigerator and other pre-cooling J-T helium cooler,the system parameters are designed and the research device is established,and the key component parameters and related process points are studied through the design,manufacture and test.The paper first designed the 10 W GM/J-T refrigerator,calculate the system cycle parameters and thermodynamic analysis.The results show that the GM/J-T refrigerator requires two two-stage GM cryocooler capacity at 10 W.Considering the research cost,experimental efficiency of the GM/J-T refrigerator,and the complexity of design and operation,a research device was designed for the preliminary research of the key technologies of the GM/J-T refrigerator.The research device adopts improved system flow chart and pre-cooling stage,which uses cold helium pre-cooling stage instead of GM cryocooler pre-cooling.It is conducive to speed up the system pre-cooling cooling rate and improve the efficiency of experimental research.The calculation model of the parameters of pre-cooling stage and the flow of helium mass is calculated.The COP and cycle performance of the research device and the GM/J-T refrigerator system compare the results,which are similar.Later,the heat exchanger,pre-cooling stage,liquid helium tank are designed and calculated according to the cycle parameters of the research device,and the research device is completed in the system insulation design and measurement system design.The calculation results of the system show that the theoretical heat leakage in the pre-cooling stage of 4.5 K is 1.201 W,and the main loop of 4.5 K is less than 0.4336 W.Considering the heat leakage,the theoretical cooling capacity is 10.16 W,which meets the design requirements of 10 W.Process and assemble the research device according to the relevant design,and improve the research device.Based on the research device,the experimental platform with cold capacity test and system cycle parameter test is built.The static heat leakage experiment of the research device is completed.The experimental results show that the static heat leakage of pre-cooling stage of 4.5 K is 1.187 W,which is consistent with the theoretical calculation results.The experimental platform is further built for cooling experiments,which tested the performance of the system.The test results showed that the cooling effect is good,the relationship between different valve front pressure,valve opening and main loop flow rate was obtained,and the key components of the system operated well.