Commissioning of the CRAFT Cryogenic System 6 kW@4.5 K Helium Refrigerator Successfully Completed

Recently, significant progress has been made in the construction of the helium refrigeration system on the CRAFT magnet platform. The on-site commissioning and performance testing of the main body of the CRAFT cryogenic system 6 kW@4.5 K helium refrigerator have been successfully completed, with all indicators meeting the design acceptance requirements.

The commissioning work focused on systematic verification of the cold box refrigeration performance, liquefaction capacity, control system, safety interlocks, and the operating status of key cryogenic equipment. During the acceptance tests, the helium refrigerator completed 12 hours of continuous stable operation under design conditions, achieving a refrigeration capacity of 6 kW@4.5 K + 50 K@GHe. In addition to design conditions, the project team also conducted performance tests under helium liquefaction conditions, with parameters such as temperature, pressure, flow rate, heating power, and Dewar liquid level all maintained within their respective operating ranges. These results verified the refrigerator's refrigeration capacity and operational stability under complex load conditions, providing an important technical foundation for flexibly adjusting operating modes according to future superconducting load requirements. Building on the performance tests, the project team validated the safety functions of the helium refrigerator, simulating scenarios such as system restart after power outages or emergency shutdowns and vacuum system operation, further examining the coordinated control, safety protection, and fault recovery capabilities among the cold box and related subsystems, thereby ensuring the long-term continuous, stable, and reliable operation of the system.

The 6 kW@4.5 K helium refrigerator is a key core subsystem of the CRAFT cryogenic system. The successful commissioning of the main body's performance has comprehensively verified the refrigerator's overall performance under different operating modes such as large refrigeration capacity and liquefaction, as well as the coordinated operation capability of the cold box, compressor station, control system, and related auxiliary systems. This important milestone marks the transition of the CRAFT cryogenic system from the equipment construction and installation phase to the system commissioning and application operation phase. This system will provide reliable deep cryogenic conditions for the system commissioning, performance verification, and stable operation of superconducting magnets and related cryogenic experimental facilities, and will provide important foundational support for experimental research on large superconducting magnets, advanced cryogenic technologies, and related major scientific research equipment.

The success of this commissioning benefits from the team's collaborative efforts across multiple disciplines including cryogenic engineering and automatic control. It also lays a talent and technical foundation for undertaking larger-scale cryogenic system construction and operation tasks in the future, further validating the comprehensive technical capability of the Institute of Plasma Physics' large-science team in the integration, commissioning, and operational support of large-scale helium refrigeration equipment.

CRAFT cryogenic system compressor unit