Rotating machine applications with superconductors attract much interest in the industry. For maintaining the operating temperature of high-temperature superconductor (HTS) field poles, the sophisticated cooling system is required. A thermosyphon (TS) is one of the ways for this purpose. The cryo-mechanical system composition is relatively simple, lightweight and based on natural convection therefore not using any mechanical pump. It supplies the refrigerant from static condenser part to the rotating evaporator part by using a mechanical rotary joint. The operating temperature of the TS cooling system depends on the refrigerant. Considering the current HTS materials, the suitable refrigerant is neon, hydrogen. Nitrogen provides a higher operating temperature than the utilization of neon and hydrogen. In this study, we focused on and investigated the heat transfer capacity of TS using nitrogen as the refrigerant. The heat transfer performance with rotation was also studied. As a result of the experiment, the TS cooling system could maintain the evaporator temperature with rotating. Moreover, it could transfer the 90 W heat load with rotating.

Acknowledgements
This work is supported by JSPS KAKENHI Grant Number JP18J14409.
The work of K. Yamaguchi is supported by the Research Fellowship for Young Scientists (PD).

Keywords: thermosyphon, rotating machine, cryogenic