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Open Access Publications from the University of California

AC Losses in the MICE Channel Magnets -- Is This a Curse or a Blessing?


This report discusses the AC losses in the MICE channel magnets during magnet charging and discharging. This report talks about the three types of AC losses in the MICE magnets; the hysteretic AC loss in the superconductor, the coupling AC loss in the superconductor and the eddy current AC loss in the magnet mandrel and support structure. AC losses increase the heat load at 4 K. The added heat load increases the temperature of the second stage of the cooler. In addition, AC loss contributes to the temperature rise between the second stage cold head and the high field point of the magnet, which is usually close to the magnet hot spot. These are the curses of AC loss in the MICE magnet that can limit the rate at which the magnet can be charge or discharged. If one is willing to allow some of the helium that is around the magnet to boil away during a magnet charge or discharge, AC losses can become a blessing. The boil off helium from the AC losses can be used to cool the upper end of the HTS leads and the surrounding shield. The AC losses are presented for all three types of MICE magnets. The AC loss temperature drops within the coupling magnet are presented as an example of how both the curse and blessing of the AC losses can be combined.

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