Speaker
Description
The maximum accelerating gradient of niobium radio frequency cavities are currently reaching their theoretical limits. It can be enhanced by increasing the cavity’s peak surface magnetic field at which the magnetic field penetrating into the superconductor in the form of vortices. To delay the penetrating of vortices into the bulk Nb, SIS structure which is superconductor (S) and insulator (I) layers alternatively coated on bulk niobium has been proposed. Magnetic field at full flux penetration, Bp through a superconductor is a useful characteristic to test the high field performance of SIS structure. DC magnetic Hall probe technique has been developed at Jefferson Lab, which can measure Bp of a superconducting sample placed under parallel DC magnetic field. Using a field much smaller than the sample allows limitations such as edge effects to be significantly reduced. Bulk Pb and Nb samples have been tested for varying thickness to determine how the thickness affect to Bp measurements. The multilayers based NbTiN and AlN deposited on bulk Nb were used to test the proposed field enhancement.
