1. Spectrometer Solenoid Update Steve Virostek Lawrence Berkeley National Lab MICE Video Conference 114 September 18, 2008

2. Issues with Magnet #1 Frozen N 2 in cold mass helium lines prevented proper operation (mainly procedural, partially design issue) Inadequate thermal connection between 1 st stage of cold heads and cold mass radiation shield Venting of cold mass during quench is not sufficient due to crowding of vent line with instrumentation wires Mechanical issues: magnet alignment in vacuum vessel, support stand height, iron shield support pads, support stand offset No provision for direct cooldown of cold mass radiation shield (i.e. long cooldown time)

3. Design Solutions Solutions developed during visit to Wang NMR by M. Zisman, S. Virostek and M. Green on 9/12/08 Helium line blockage: increase liquid line , eliminate horizontal runs and traps in line, improve procedure Radiation shield connection: increase thermal conduction with thick 1100 Al flexible straps Cold mass venting: add an additional vent line to the cold mass with no wires Mechanical issues: realign magnet #1 during reassembly (also corrects support stand height), modify end support to clear iron shield mount pad (magnet #1 and #2) Radiation shield cooldown: incorporate LN reservoir to allow direct cooldown of shield

4. Original Design Modified Design Cold head Condenser Cold mass shell Coils Liquid He line Trap Larger diameter No trap Liquid He Line Modification A written cooldown procedure will be generated to ensure that all N 2 is purged from the system prior to introducing liquid helium

5. Venting and Shield Connection Improved radiation shield connection Cold head 1 st stage Radiation shield Additional vent line

6. Iron Shield Mount Interference Vacuum vessel Support braces Iron shield lower mounting pad Original Design Modified Design New braces Note: modification only affects supports at patch panel end of Magnet #1 and AFC end of Magnet #2

7. Support Stand Offset Nominal position of the support stands in the axial direction is centered on the magnet outer vacuum vessel For various reasons, the stands will likely be offset on both magnets (in different directions by different amounts of 100 to 150 mm) The offsets will directly impact the interface between the magnets and the floor Effect on floor mounting scheme needs to be assessed Also, as originally assembled, AFC end of Magnet #1 is approximately 20 mm higher than nominal value Height variation will likely be corrected during reassembly

8. The spectrometer solenoid cryostat is designed to ASME code but lacks weld certifications and pressure tests; a pressure vessel safety note has been developed at LBNL The LN reservoir being added to the radiation shield may present some safety issues, but its use is optional It now appears that each magnet will require three cryocoolers to operate; two additional units will need to be procured A compressor charging kit is required to adapt the cryocooler compressors to 50 Hz operation. LBNL will procure the kit and deliver it with the magnets Other Issues

9. Schedule The plan to move forward involves completing Magnet #2 first with all proposed design changes Upon shipping of Magnet #2 (now first unit), Magnet #1 would be opened, and the cryostat removed for modification (add vent line, reconfigure liquid He line) The current goal for completing the first unit (Magnet #2) including cooldown and test is early November The reassembly and completion of Magnet #1 should follow by approximately two months