• M.A. Green, A.J. DeMello, D. Li, F. Trillaud, S.P. Virostek, M.S. Zisman
  LBNL, Berkeley, California
• X.L. Guo, S.Y. Li, H. Pan, L. Wang, H. Wu, S.X. Zheng
  ICST, Harbin

Tests of the spectrometer solenoids have taught us some important lessons. The spectrometer magnet lessons learned fall into two broad categories that involve the two stages of the coolers that are used to cool the magnets. On the first spectrometer magnet, the problems were centered on the connection of the cooler 2nd-stage to the magnet cold mass. On the second spectrometer magnet, the problems were centered on the cooler 1st-stage temperature and the connections between leads, the cold mass support intercept, and the shields to the cooler first-stage. If the cooler 1st-stage temperature is too high, the refrigerator will not produce full 2nd stage cooling. If the 1st-stage temperature is too high, the temperature of the top of the HTS leads. As a result, more heat goes into the 4 K cold mass and the temperature margin of the top of the HTS leads is too small, which are in a magnetic field. The parameters that affect the magnet cooling are compared for the MICE coupling magnet and the spectrometer magnet.

• S.P. Virostek, M.A. Green, F. Trillaud, M.S. Zisman
  LBNL, Berkeley, California

The Muon Ionization Cooling Experiment (MICE), an international collaboration sited at Rutherford Appleton Laboratory (RAL) in the UK, will demonstrate ionization cooling in a section of a realistic cooling channel using a muon beam. A five-coil superconducting spectrometer solenoid magnet will provide a 4 tesla uniform field region at each end of the cooling channel. Scintillating fiber trackers within the 400 mm diameter magnet bore tubes measure the emittance of the beam as it enters and exits the cooling channel. Each of the identical 3 meter long magnets incorporates a three-coil spectrometer magnet section and a two-coil section that matches the solenoid uniform field into the MICE cooling channel. The cold mass, radiation shield and leads are kept cold by means of three two-stage cryocoolers and one single-stage cryocooler. After incorporating several design changes to improve the magnet cooling and reliability, the fabrication and acceptance testing of the spectrometer solenoids has been completed. The key features of the spectrometer solenoid magnets are presented along with the details of a finite element model used to predict the thermal performance of the magnets.

• S. Ishimoto, S. Suzuki
  KEK, Ibaraki
• M.A. Green
  LBNL, Berkeley, California
• Y. Kuno, M.Y. Yoshida
  Osaka University, Osaka
• W. Lau
  OXFORDphysics, Oxford, Oxon

Liquid hydrogen absorbers for the Muon Ionization Cooling Experiment (MICE) have been developed, and the first absorber has been tested at KEK. In the preliminary test at KEK we have successfully filled the absorber with ~2 liters of liquid hydrogen. The measured hydrogen condensation speed was 2.5 liters/day at 1.0 bar. No hydrogen leakage to vacuum was found between 300 K and 20 K. The MICE experiment includes three AFC (absorber focusing coil) modules, each containing a 21 liter liquid hydrogen absorber made of aluminum. The AFC module has safety windows to separate its vacuum from that of neighboring modules. Liquid hydrogen is supplied from a cryocooler with cooling power 1.5 W at 4.2 K. The first absorber will be assembled in the AFC module and installed in MICE at RAL.