Cryomodule tests of four Tesla-like cavities in the Superconducting RF Test Facility at KEK

Abstract

A 6-m cryomodule including four Tesla-like cavities was developed, and was tested in the Superconducting RF Test Facility phase-I at KEK. The performance as a total superconducting cavity system was checked in the cryomodule tests at 2 K with high rf power. One of the four cavities achieved a stable pulsed operation at 32 MV/m, which is higher than the operating accelerating gradient in the ILC. The maximum accelerating gradient (E_{acc,max⁡}) obtained in the vertical cw tests was maintained or slightly improved in the cryomodule tests operating in a pulse mode. Compensation of the Lorentz force detuning at 31 MV/m was successfully demonstrated by a piezo tuner and predetuning.