Measurement, Control and Minimization of Thermal Shift in Superconducting Devices

Abstract

Superconducting (SC) magnetic and SC radiofrequency (SRF) devices designed for use in particle accelerators present challenging alignment problems. These devices are assembled and aligned at room temperature but operate at 2-4 K with thermal offsets being large relative to the desired alignment tolerances. Unique solutions have been developed for controlling and minimizing the thermal shift including utilization of materials that expand under cooling to compensate for contraction and kinematic couplings. Measurement of the thermal shift within SC devices is performed using both optical telescope and laser instruments, typically through a parallel plate vacuum glass window. This paper presents techniques developed at Argonne National Laboratory for measuring, controlling and minimizing thermal shift in SC devices at both the Advanced Photon Source (APS) and the Argonne Tandem Linear Accelerator System (ATLAS). BACKGROUND Argonne National Laboratory has pioneered the development of particle accelerator technology for more than 50 years. Today, Argonne’s two main facilities with SC devices in use are the APS, a synchrotron light source, and ATLAS, the world’s first SC accelerator for heavy ions. In addition to supporting these facilities Argonne also supports SC accelerator technology development for other labs. The devices include SC magnetic undulators (SCUs) developed at the APS and SRF accelerating structures developed at ATLAS.