Cold Mass Issues in the MICE Coupling Magnet

Green, Michael A.¹ 

[1] Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

DOI  :  10.2172/1213559
RP-ID  :  LBNL--5628E
PID  :  OSTI ID: 1213559

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来源: SciTech Connect

【 摘 要 】

I have identified two potential issues in the design of the attachments to the MICE coupling magnet cold mass. One of these attachment issues may extend into the cold mass. Both issues came to light during the analysis of what happened to the spectrometer solenoids. We must not make the same mistakes that were made on the spectrometer solenoids. The two questions that result from the identified issues are; 1) Are the superconducting low temperature superconducting leads between the coupling coil and the lower end of the high temperature superconducting (LTS) leads robust enough not quench and burn out? In the spectrometer solenoid one part of the LTS lead was not robust enough to prevent quenching and a burn out of the LTS lead and ; 2) Will there be problems with the quench protection resistors and diodes when the magnet quenches as a result of an HTS lead burning out or a disconnect of the magnet from its power supply? The second question is very important because the coupling coil has a large stored energy and inductance. As result, when current flows through the diodes and the resistors, both can be over heated. We observed resistor overheating in spectrometer magnet 2. This heating probably happened when the HTS lead the LTS lead burned out during the tests of magnet 2A and 2B respectively. (See MICE Note 324.) The answer to the first question is simple and straightforward. This is the issue that is primarily dealt with in MICE Note 324. If the resistance across the coil sub-divisions is high enough, the whole magnet will turn normal through quench-back. Making the resistance across a coil sub-division high enough is not simple.