Facility for the Characterization of Planar Multilayer Thin Film Superconductors

The maximum accelerating gradient of SRF cavities can be increased by raising the field of full flux penetration, Hvp. One method which can potentially increase Hvp is to use structures consisting of alternating layers of superconductors and insulators (SIS). Magnetometry is commercially available but consists of limitations, such as SQUID measurements which apply a field over both superconducting layers, so Hvp cannot be measured. If Hvp is to be measured for SIS coatings, a parallel, local magnetic field must be applied from one plane of the sample, with no field on the opposing plane. A field penetration experiment has been developed at Daresbury laboratory allowing Hvp to be measured using a local, parallel DC magnetic field. Using a field much smaller than the sample allows limitations such as edge effects to be significantly reduced. By increasing the field, Hvp can be found by using 2 hall probes, one either side of the sample. The experiment was designed to use a variable temperature insert (VTI) to run in a cryogen free environment, but has been running in a LHe bath for thermal stability. © Published under licence by IOP Publishing Ltd

Design, specifications, and first beam measurements of the compact linear accelerator for research and applications front end

The compact linear accelerator for research and applications (CLARA) is an ultrabright electron beam test facility being developed at STFC Daresbury Laboratory. The ultimate aim of CLARA is to test advanced free electron laser (FEL) schemes that can later be implemented on existing and future short-wavelength FELs. In addition, CLARA is a unique facility to provide a high-quality electron beam to test novel concepts and ideas in a wide range of disciplines and to function as a technology demonstrator for a future United Kingdom x-ray FEL facility. CLARA is being built in three phases; the first phase, or front end (FE), comprises an S-band rf photoinjector, a linac, and an S-bend merging with the existing versatile electron linear accelerator beam line; the second phase will complete the acceleration to full beam energy of 250 MeV and also incorporate a separate beam line for use of electrons at 250 MeV; and the third phase will include the FEL section. The CLARA FE was commissioned during 2018, and the facility was later made available for user experiments. Significant advancements have been made in developing high-level software and a simulation framework for start-to-end simulations. The high-level software has been successfully used for unmanned rf conditioning and for characterization of the electron beam. This paper describes the design of the CLARA FE, performance of technical systems, high-level software developments, preliminary results of measured beam parameters, and plans for improvements and upgrades. © 2020 authors. Published by the American Physical Society