1. MICE Spectrometer Solenoid Update Michael S. Zisman Center for Beam Physics Accelerator & Fusion Research Division Lawrence Berkeley National Laboratory MICO Meeting August 10, 2009

2. Spectrometer Solenoid Update - Zisman2 Introduction After a period of testing at the vendor, magnet 2 was warmed up last week and opened for inspection —magnet had developed open circuit during “training” o suspected to be failure of HTS lead –but, needed confirmation that it was not more serious Inspection and testing on August 4 confirmed that HTS lead had failed —lead temperature was too high for high-current operation o human error (mea culpa!) —visual inspection showed that HTS lead farthest from coolers had failed o not a surprise, as this was the warmest lead –pictures on next slide —electrical resistance tests on superconducting coil showed no changes compared with initial setup o pictures also indicate no damage to lower part of lead

3. August 10, 2009Spectrometer Solenoid Update - Zisman3 (Dirty) Pictures Pictures taken on August 4 show clear evidence for failure Top and bottom connections look pristine

4. August 10, 2009Spectrometer Solenoid Update - Zisman4 Plan Vendor will swap all HTS leads with those for magnet 1 —other leads will be retested to ensure they are unharmed —at least one replacement lead will be purchased LBNL will order one single-stage AL330 cooler —delivers ~170 W at 50 K (and costs $40K) —vendor will mount this near the HTS leads by extending the turret and the copper heat sink within —expected duration 2-3 months o cool-down and testing will follow Goals of initial tests —complete magnet training to 270 A —carry out power supply testing (ramp up and down) —determine whether magnet will operate cryogen-free with 4 coolers o determine shield temperature in this configuration

5. August 10, 2009Spectrometer Solenoid Update - Zisman5 Single Stage Cooler Option A concept for adding a fourth (single-stage) cooler to magnet 2 —should handle heat load from leads to make sure we can operate safely o will lower shield temperature somewhat, but no direct connection

6. August 10, 2009Spectrometer Solenoid Update - Zisman6 Future Options Possible outcomes of present testing program —magnet will operate (fully charged) cryogen-free with 4 coolers o declare victory and ship to Fermilab for measurements —magnet still requires cryogen top-up to operate (fully charged) properly o once a day? a week? a month? What do we do with magnet 1 in the meantime? —implement ideas to improve thermal connection between coolers and shield o use copper sheets rather than Al cylinder o use copper sheet on outside of shield to improve heat conductivity –thus lowering cold mass support intercept temperature —make preparations for using additional 2-stage cooler o either augmenting or in place of single-stage cooler –one or the other (or both) will likely solve both thermal problems o decision to do this will depend on outcome of present tests

7. August 10, 2009Spectrometer Solenoid Update - Zisman7 Possible Magnet 1 Modifications We could add a fourth 2-stage cooler as shown below Side view: Top view:

8. August 10, 2009Spectrometer Solenoid Update - Zisman8 Summary Present spectrometer solenoid (#2) has thermal problems —proposed fix will likely make the magnet usable o but not necessarily cryogen-free Preparing for improvements on magnet 1 that will hopefully meet its specifications —these are costly, but reasonably straightforward to implement before magnet is assembled Big question —what do we do with magnet 2 if it is commissioned but not cryogen-free? o fixing it properly would likely mean disassembly –big time delay plus risk of damage or assembly errors –costly (with money we do not really have) Review planned for late August to discuss options/plans