Design and study of a high-current 5-cell superconducting rf cavity

The Advanced Photon Source(APS) at Argonne National Laboratory is considering the development of a superconducting linac-based fourth-generation hard X-ray source to meet future scientific needs of the hard X-ray user community.This work specifically focuses on the design of an optimized 5-cell superconducting radio-frequency structure well suited for a high-energy,high-beam-current energy recovery linac.The cavity design parameters are based on the APS storage ring nominal 7 GeV and 100 mA beam operation.A high-current 5-cell cw superconducting cavity operating at 1.4 GHz has been designed.In order to achieve a high current,the accelerating cavity shape has been optimized and large end-cell beam pipes have been adopted.The beam break-up threshold of the cavity has been estimated using the code TDBBU,which predicts a high threshold beam current for a 7 GeV energy recovery linac model.A copper prototype cavity has been fabricated that uses half-cell modules,initially assembled by clamping the cells together.