ANL, Argonne
PKU/IHIP, Beijing
A simple technique based on an in-situ moveable germanium resistance thermometer is used to measure the quench location in a superconducting (SC) cavity in superfluid liquid helium. SRF cavities are very often limited in operating field level by thermal instability manifesting as a transient "quench" of the electromagnetic field. The field energy is transferred into the superfluid helium bath as a heat pulse and may be detected as a wave of phonons at a thermometer. The germanium thermometer technique was developed at Argonne three decades ago and used to measure time-of-flight of the second-sound to locate defects in split-ring resonators for the ATLAS SC linac at Argonne. The present goal is to extend and adapt the second-sound diagnostic technique in a simple, easy-to-use and cost effective way for use with cavities under development today. These include for example, the 9-cell, 1.3 GHz SC cavities, as well as, reduced beta superconducting cavities such as half-wave and quarter-wave structures.
AAI/ANL, Argonne
PKU/IHIP, Beijing
ANL, Argonne
We are considering the development of a fourth-generation hard x-ray source to meet future scientific needs of the hard x-ray user community. This work focuses on the design of an optimized 5-cell structure well-suited for a high-energy; high-beam current Energy Recovery Linac. The cavity design parameters are based on the Advanced Photon Source (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 high current, the cavity shape has been optimized and large end-cell beam pipes have been adopted. The beam break-up (BBU) threshold of the cavity has been estimated using the code TDBBU1 which indicates a high threshold for a 7-GeV Energy Recovery Linac model. A copper prototype cavity is being fabricated that uses half-cell modules, initially assembled by clamping the cells together. We will report on the cold-model measurements including the higher-order modes and will compare the measurements with the simulation results.
* Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.