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.

AbstractThe 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.

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)

+ This work was supported by the Office of Science, U.S. Department of Energy (DOE) under DOE Contract No. DE-AC02-05CH11231

Cavity design parameters Frequency: 201.25 MHzShunt impedance (VT2/P): ~ 22 MΩ/mQuality factor (Q0): ~ 53,500Be window diameter and thickness: 42-cm and 0.38-mmPeak RF power dissipation: 4.6 MW for ~ 16+ MV/m

The RFCC Module

SC coupling Coil Curved thin Be window

Four 201-MHz NC cavities

Cavity measurementsThe first five cavities (one spare) have beenmeasured, 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:

SummaryMICE 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.

Frequency (MHz) Q

Cavity #1 201.084 44,400Cavity #2Cavity #3 201.247 44,600Cavity #4 200.740 44,600Cavity #5 201.707 44,200

SpectrometerSolenoid 1

SpectrometerSolenoid 2

RF Cavity and Coupling Coil (RFCC) Module

Layout of the International Muon Ionization Cooling Experiment at Rutherford Appleton Laboratory, UK

measure ~ 10% of transverse emittance reduction of muon beams

Liquid Hydrogen Absorber and Focusing Coil (AFC) Module

International MICE42-cm