Potential of non-conventional superconductors for particle accelerator cavities

Superconducting RadioFrequency (SRF) cavities have been developed for modern particle accelerator projects in the world. These cavities are mainly made of bulk niobium operated in superfluid or normal fluid helium. Due to the price increase in niobium material as well as helium, superconductors beyond the niobium are investigated for more sustainable accelerators. In this paper, we consider the most fundamental loss mechanism of microwaves inside various superconductors caused by thermally excited quasi-particles in the Meissner state.