Optimum multilayer coating of superconducting particle accelerator cavities and effects of thickness dependent material properties of thin films

Abstract

We revisit the field limit of a superconductor-insulator-superconductor multilayer structure for particle accelerator cavities (B ML), taking into account thickness (d)-dependent critical temperature, normal resistivity, and normal density of states seen in many thin films. Resultant d-dependent thermodynamic critical field and penetration depth lead to the appearance of a peak in B ML(d) which has been missed in the previous studies. The procedure shown in this note would be useful to evaluate B ML based on properties of one's own films.