Superconducting Radiofrequency

The maximum accelerating gradient can be increased by using SIS coatings. By delaying the initial flux penetration to higher fields in the first superconducting layer, a greater accelerating gradient can be achieved. Magnetometry is a commercially available but consists of limitations, such as SQUID measurements apply a field over both superconducting layers, so the initial flux penetration through the sample cannot be measured. If SIS structures are to be investigated, a magnetic field must be applied from one plane of the sample, with no magnetic field on the opposing side to allow the initial flux penetration to be measured. A magnetic field penetration experiment has been developed at Daresbury laboratory, where a VTI has been created for a cryostat where the field penetration of a sample can be measured. The VTI has been designed to allow flat samples to be measured to reduce limitations such as edge effects by creating a DC magnetic field smaller than the sample. A small, parallel magnetic field is produced on the sample by the use of a ferrite yoke. The field is increased to determine when the vortices penetrate the sample by using 2 hall probes either side of the sample. The VTI will be placed in a Cu tube which is connected to the first stage of the cryostat by a Cu baffle and will be cooled with He gas.