Delta波荡器传导冷却的热分析与实验研究

Thermal analysis and experimental study on the conduction cooled cryostat for the Delta undulator

波荡器是同步辐射光源中产生X射线的关键设备,低温型Delta波荡器可明显提高镨铁硼永磁铁的峰值场强和内禀矫顽力,进而有效抵抗辐照环境下的磁场退化。为了使永磁阵列进入液氮温区,提出了磁铁干式传导冷却方案,设计了干式低温恒温器结构,利用数值模拟完成了热力学分析优化,并搭建实验台进行了降温测试。结果表明,Delta波荡器可通过单台小型低温制冷机传导冷却进入低温状态,并突破常压饱和液氮温度,最低达到40 K,四个梁的最大温差约1 K,达到温度均匀性要求,并将磁场强度提高20%以上。低温型Delta波荡器模组达到设计指标,验证了波荡器干式传导冷却方案的可行性,对低温型波荡器的研发设计具有重要意义。

The undulator is the key facility to generate X ray in the synchrotron radiation light source. When the Delta undulator is cooled to a low temperature, the magnet field peak can be increased dramatically. Meanwhile, the intrinsic coercivity can be strengthened quite much, which means more endurance to the radiation environment. In this paper, the concept of magnet conduction cooling was proposed and the liquid free cryostat was designed. In addition, the structure was optimized by thermal analysis, which depends on the numerical simulation. The entire temperature field of the cryogenic Delta undulator was calculated. At last, the cryogenic Delta undulator prototype was assembled and tested. The results show that the temperature of the magnets is about 40 K, which is lower than the temperature of the saturated liquid nitrogen at the atmospheric pressure. Also, the temperature uniformity of the magnet beam is good with the temperature difference of 1 K. At this low temperature, the magnet field peak is increased by 20 percent than that at room temperature. The cryogenic Delta permanent undulator module achieves the designed parameters, which proves the feasibility of the conduction cooled principle and has a great significance to the research and development of cryogenic permanent magnet undulators.