The performance regulation optimization and engineering application of a domestic helium liquefier

Abstract

<p indent="0mm">The superconducting magnets and the superconducting cavities are the key devices of large-scale scientific facilities, such as the HL-LHC in the CERN, the ITER, the EAST, the CiADS, and so on. A stable and reliable cold source such as the liquid helium (–269°C) is required to keep the superconducting magnets and the superconducting cavities working. Therefore, a helium liquefier or a helium refrigerator working at <sc>4.5 K</sc> is necessary for them. Research on high-field-strength superconducting dipole magnets used in future high-energy particle colliders is developed in the Institute of High Energy Physics of the Chinese Academy of Sciences. High-field-strength superconducting dipole magnets have large thermal loads and long test durations, which need large amount of liquid helium for their performance tests. Therefore, the long-term operating economy, stability, and reliability of the refrigeration system are highly required. The engineering application of using a helium liquefier for producing liquid helium to cool down superconducting dipole magnets has not been realized in China yet. Meanwhile, the price of the imported helium liquefiers is usually too high and the supply cycles are too long. Fortunately, a domestic helium liquefier has been developed by the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences. This paper will realize the engineering application of the domestic helium liquefier applied to the superconducting dipole magnet test platform for the first time. In order to meet the test requirements of high-field-strength superconducting dipole magnets, a performance regulation and optimization of the first domestic helium liquefier is studied. It realizes the optimal control of the cold-box cooling process and the Dewar cooling process, saves the power consumption of the compressor by 12.3% and 25.2% respectively, and significantly improves the economy of the helium liquefier. After the commissioning of the liquefier, the helium liquefier realizes the automatic control adjustment function to adapt to variable loads in different operating conditions. And the specific energy consumption of the helium liquefier under each load state is analyzed. Without considering the consumption of liquid nitrogen, the minimum specific energy consumption of the helium liquefier is <sc>2.4 kW h/L</sc> when the liquefier works with the full load. Through control optimization and experimental testing, the helium liquefier successfully realizes the joint operation with the user-end superconducting dipole magnet test platform, and passed the long-term operation reliability test. At present, the helium liquefier has run stably for more than two months, produced more than <sc>35000 L</sc> of liquid helium, promoting the first domestic accelerator high-field superconducting dipole magnet to achieve a breakthrough in the new index of the magnetic field strength of <sc>12.47 T.</sc> It’s the first time for the domestic helium liquefier applying to the superconducting dipole magnet test platform, and this engineering application can be further promoted in future.