The rotating cryogenic system is a device designed similar to the cooling system for the rotor of a superconducting generator. The experimental rotor has an inner vessel which is a copy of the winding space of an actual superconducting rotor, and a torque tube of comparable design. There is no superconducting field winding inside the inner vessel. This thesis describes the realization process of the experimental rotor especially including the application of cryogenic insulation techniques, and the evaluation of total heat leak into the inner vessel which leads to the study of the heat transfer characteristic of the rotating cryogenic system.
Maintaining high vacuum around the cryogenic system was the most essential preliminary condition for the insulation of the cryogenic system. Because the experimental rotor has to rotate at high speeds up to 1800 rpm, structural safety as well as the outgassing rate was very important. Such a joint technique as welding, brazing, soldering, and indium sealing methods were utilized properly. For the successful welding procedure of the vent tube and the torque tube parts of which the thickness of stainless steel tubes were 0.25 mm, an automatic welding system was constructed and welding was done at firsthand in the laboratory. Calibration of the carbon resistor cryogenic temperature sensors, and the design and manufacturing of the slip ring which was necessary for the delivery of electric signals from the stationary system to the rotating experimental rotor was also done by the author. Alignment of the shaft center point of the whole system to reduce vibration and prevent structural failure, and the validation of vacuum sealed parts at 300 K and 77 K was the most important but difficult jobs.
To examine the insulation performance of the experimental rotor, temperature was measured at each part of the system at various rotating speeds from 0 rpm to 600 rpm. Total heat leak into the inner vessel was calculated by measuring the boil-off rate of liquid helium. Conduction heat leak to the inner vessel was obtained by the temperature profile of the torque tube and the vent tube, and radiation heat leak was found by subtracting the conduction heat leak from the total heat leak. There seemed to be no rotational dependency of total heat leak at least up to 600 rpm
