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, H vp . One method which can potentially increase H vp 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 H vp cannot be measured. If H vp 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 H vp 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, H vp 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.