• 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.

• J. Pasternak, L.J. Jenner, Y. Uchida
  Imperial College of Science and Technology, Department of Physics, London
• R.J. Barlow
  UMAN, Manchester
• K.M. Hock, B.D. Muratori
  Cockcroft Institute, Warrington, Cheshire
• D.J. Kelliher, S. Machida, C.R. Prior
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• Y. Kuno, A. Sato
  Osaka University, Osaka
• A. Kurup
  Fermilab, Batavia
• J.-B. Lagrange, Y. Mori
  KURRI, Osaka
• M. Lancaster
  UCL, London
• S.A. Martin
  FZJ, Jülich
• C. Ohmori
  KEK/JAEA, Ibaraki-Ken
• J. Pasternak
  STFC/RAL, Chilton, Didcot, Oxon
• S.L. Smith
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• H. Witte, T. Yokoi
  JAI, Oxford

The next generation of lepton flavour violation experiments will use high intensity and high quality muon beams. Such beams can be produced by sending a short proton pulse to the pion production target, capturing pions and performing RF phase rotation on the resulting muon beam in an FFAG ring, which was proposed for the PRISM project. A PRISM task force was created to address the accelerator and detector issues that need to be solved in order to realise the PRISM experiment. The parameters of the initial proton beam required and the PRISM experiment are reviewed. Alternative designs of the PRISM FFAG ring are presented and compared with the reference design. The ring injection/extraction system, matching with the solenoid channel and progress on the ring's main hardware systems like RF and kicker magnet are discussed. The activity on the simulation of a high sensitivity experiment and the impact on physics reach is described. The progress and future directions of the study are presented in this paper.

• M.Y. Yoshida, M. Aoki, Y. Kuno, A. Sato
  Osaka University, Osaka
• T. Nakamoto, T. Ogitsu, K. Tanaka, A. Yamamoto
  KEK, Ibaraki

An intense muon beam is mandatory for the next-generation experiments to search for lepton flavor violating processes in the muon sector. The COMET experiment, J-PARC ·10²¹, aims to search for muon to electron conversion with an unprecedented sensitivity.. The muon beam is produced from pion decays in a strong magnetic field generated by superconducting solenoid coils. The large-bore superconducting coils enclose the pion-production target to capture pions with a large solid angle. The magnetic field is designed to have a peak of 5T at the target. To avoid severe radiation from the target, thick shielding is inserted in the warm bore of the pion capture solenoid magnet. The proton beam is injected through the gap between the pion capture solenoid and the subsequent transport solenoid magnets. For this purpose, the bore of the pion capture solenoid has to be larger than 1 m. This paper describes the design of the pion capture solenoid magnet for the COMET experiment.