Development of Superconducting Cavities for ILC

Aiming at construction of a future International Linear Collider (ILC), intensive R&D work to develop a superconducting (SC) cavity system consisting of a nine-cell cavity, a frequency tuner, an input coupler and two higher order mode couplers has been carried out at KEK. Approximately 30 nine-cell cavities were fabricated, and vertical tests to qualify high gradient performance were repeatedly carried out at the superconducting RF test facility (STF) in KEK. A maximum accelerating gradient higher than 35 MV/m, which is a target value for ILC, was achieved in approximately 90% of the latest 11 nine-cell cavities. Cryomodule tests with a high-power RF system at the STF were performed in three cryomodules including a total of 14 nine-cell cavities, and the stable pulsed operation at high gradients was successfully demonstrated. Remarkable progress in the technologies required for the SC cavity system in ILC has been made in the past several years.