Status of the NICA cryogenics at JINR.

NICA (Nuclotron-based Ion Collider fAcility), presently in construction at JINR, is aimed to provide collider experiments with heavy ions up to uranium. In this project, a superconducting magnet system, which consists of 3 accelerator rings with total length of about 1 km and “cold” mass of 290 tons, will be cooled to operating temperature of 4.5 K by forced liquid helium flow. The main goals in this are increasing of the total refrigerator capacity from 4000 W to 8000 W at 4.5 K, creating a new distribution system of liquid helium, and ensuring the shortest possible cool-down time. These goals will be achieved by the use of an additional 1000 l/hour helium liquefier and “satellite” refrigerators located in close proximity to the accelerator rings. An important feature of the NICA cryogenic system is cryostatting of the accelerators by means of two-phase helium what provides high thermodynamic efficiency of cooling processes.

NICA（Nuclotron-based Ion Collider fAcility，基于Nuclotron的离子对撞机设施）目前正在联合核子研究所（JINR）进行建造，旨在为重离子（最高至铀离子）的对撞实验提供实验条件。本项目的超导磁体系统包含3台加速环，总长度约1千米，冷质量（cold mass）为290吨，将通过强制液氦流冷却至4.5K的工作温度。本项目的核心目标包括：将总制冷机在4.5K工况下的制冷容量从4000W提升至8000W，搭建全新的液氦分配系统，并尽可能缩短冷却耗时。上述目标将通过新增一台1000升/小时的氦液化装置，以及紧贴加速环布置的卫星式制冷机（satellite refrigerators）来实现。NICA低温系统的一项重要特性是借助两相氦（two-phase helium）对加速器进行低温恒温包覆，该方式可有效提升冷却过程的热力学效率。