1. Magnet quench during a training run Successfully trained to peak currents and operationally tested Thermal performance requirements met 3D magnetic bore mapping to start soon ASSEMBLY AND TEST OF A MODIFIED SPECTROMETER SOLENOID FOR MICE * Abstract: The MICE superconducting spectrometer solenoids have been modified and rebuilt as a result of the testing done in 2008, 2009 and 2010. The number of two-stage cryocoolers was increased from three in 2009 to five in the modified magnet. The new shield for the spectrometer solenoid is fabricated primarily from 1100-O aluminum instead of 6061-T6 aluminum used in the former versions of the magnet. The thermal connection between the shield and the first-stage of the cold heads has been improved to reduce the temperature drop between the shield and the coolers. As a result of these changes, the first-stage cooler temperatures are below 45K, which resulted in an increase in the refrigeration generated by the cooler second stages. The quench protection system has been altered in order to provide additional protection to the magnet in the event of a lead failure between the magnet power supply and the magnet coils. The quality of the shield and cold mass MLI wrap has also been improved. Details of the modifications and final test and training results that demonstrate improved magnet performance are presented in this paper. S.P. Virostek, D. Li, H. Pan and S. Prestemon Lawrence Berkeley National Lab, Berkeley, CA 94720, USA R. Preece, STFC Rutherford Appleton Laboratory, Didcot, UK * This work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231. Paper ID: THPME048 Added two Cryomech PT-415 cryocoolers to increase the cooling capacity to 7.5 W at 4.2K Improved connection between the cooler first stages and the radiation shield using layered sheets of flexible copper Replaced most of original 6061-T6 aluminum shield material with higher conductivity 1100-O MAGNET AND SYSTEM IMPROVEMENTS INTRODUCTION The nominal coil currents for MICE operation range from 234 to 280 amps During the latest training runs, all five coils reached their performance targets The peak coil currents were held constant for 24 hours The first magnet has met all of the training current and cooling circuit system performance requirements Improved the quality of the cold mass and shield MLI – blankets custom cut using 3D CAD model Enhanced the thermal connection between the cold mass mandrel and the internally mounted passive quench protection diodes and resistors Incorporated an improved insulating vacuum pumping system and associated instrumentation Acceptance tests are complete for the first magnet, which remains at LHe temperature Preparations are under way for full 3D bore mapping, with and without the iron shield disk mounted on the end of the magnet A second, identical spectrometer solenoid with all of the same design changes is currently being assembled CURRENT STATUS & PLANS Spectrometer solenoid cold mass coil ass’y MICE consists of two spectrometer solenoid systems and a cooling channel. Muon ionization cooling occurs in three liquid hydrogen absorbers in the cooling channel, and the muons are reaccelerated by eight RF cavities. Scintillating fiber tracker detectors in the spectrometer solenoid bores are used to measure the incoming and outgoing emittance of the muons. Spectrometer Solenoid #1 Spectrometer Solenoid #2 Cooling Channel MAGNET TRAINING & TESTING TRAINING PROGRESSION FIRST MAGNET Integrated a much enhanced instrumentation, controls and data acquisition/logging system Reconfigured the power supply rack (5 supplies) to more closely resemble the operational system Added a new external quench detection system integrated with fast data acquisition capability to protect the coils and leads Center Coil Failed HTS lead Ice blockage Training Current Progression (all coils) 2 nd magnet progress The 2 nd magnet is in the final assembly stages, and training will begin in June Both magnets are to be shipped to the MICE hall at RAL later in the summer