Background

2

The magnetic performance of the cryogenic permanent magnet undulator (CPMU)

whose magnets work at the temperature of 50-150 K

can be enhanced by 30%-50% compared with that of the conventional in-vacuum undulator (IVU). As the magnetic characteristics of both the remanence and the intrinsic coercivity of NdFeB and PrFeB increase substantially with the decreasing of working temperature

the CPMU can gain higher peak field within shorter magnetic period under a given magnetic gap

which is of great significance to improve the brightness of the synchrotron radiation light source.

Purpose

2

This study aims to investigate the sources of the static heat loads of the CPMU and develop methods of evaluating and testing the heat loads.

Methods

2

The thermal conduction and the thermal radiation of the CPMU were analyzed theoretically. Two methods of analyzing the practical static heat loads of the CPMU were proposed

compared and tested by using the CPMU test device without magnet arrays.

Results

2

The method of analyzing the test heat loads that utilizes the measured temperatures of the girders and liquid nitrogen (LN

2

) tubes is better than the one that calculates the heat loads with the LN

2

flow rate and temperature rise in the tube.

Conclusion

2

The results were applied to the development of a full scale NdFeB based CPMU prototype.