The Normal Conducting RF Cavity for MICE +

1. The Normal Conducting RF Cavity for MICE+ D. Li, A. DeMello, S. Virostek, M. Zisman; D. Summers# Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A #University of Mississippi, Oxford, MS 38677, U.S.A. Abstract The international Muon Ionization Cooling Experiment (MICE) is a demonstration experiment of muon ionization cooling. MICE cooling channel requires normal conducting and low frequency RF cavities to compensate for muon beams’ longitudinal energy lost in the MICE cooling channel. The MICE cooling channel has eight 201-MHz normal conducting RF cavities with the conventional beam irises terminate by large and thin beryllium windows. The cavity design is based on a successful prototype cavity for the US MuCool program. The first five MICE RF cavities are complete. Low power measurements of the first five cavities have been conducted. The measurements agree well with theoretical predictions. RF Cavity and Coupling Coil (RFCC) Module International MICE Spectrometer Solenoid 1 42-cm Spectrometer Solenoid 2 Liquid Hydrogen Absorber and Focusing Coil (AFC) Module Layout of the International Muon Ionization Cooling Experiment at Rutherford Appleton Laboratory, UK measure ~ 10% of transverse emittance reduction of muon beams The RFCC Module Cavity design parameters Frequency: 201.25 MHz Shunt impedance (VT2/P): ~ 22 MΩ/m Quality factor (Q0): ~ 53,500 Be window diameter and thickness: 42-cm and 0.38-mm Peak RF power dissipation: 4.6 MW for ~ 16+ MV/m Cavity measurements The first five cavities (one spare) have been measured, the cavity body frequency (equivalent to cavity with flat windows on irises) variations are within ±400 kHz as predicted (based on fabrication techniques and theoretical studies). The measured frequencies are: SC coupling Coil Curved thin Be window Eight 201-MHz cavities for the MICE cooling channel, two pairs of 4-cavity in each RFCC module, cavity gradient will be operated at 8 MV/m, limited by available RF power. • Cavity fabrication • Spinning of half cavity shells using • 6-mm copper sheets • E-beam welding to join the cavity • Port extruding • Brazing of water cooling lines • Cleaning and electro-polishing (EP) Summary MICE RF cavity fabrication has been progressing well, next five cavities will be ready soon. Preliminary cavity measurements agree well with designs. Other auxiliary cavity components are either in final design phase or production. Four 201-MHz NC cavities + This work was supported by the Office of Science, U.S. Department of Energy (DOE) under DOE Contract No. DE-AC02-05CH11231