High frequency response of thick REBCO coated conductors in the framework of the FCC study

Abstract

A thorough microwave response study of high temperature superconductors, considered as an alternative beam screen coating, has become integral in the design decisions for CERN’s future research infrastructure. Here, we present the surface resistance $R_s$ of various ${\text{REBa}}_2{\text{Cu}}_3{\text{O}}_{7-x}$ (RE = rare earth) coated conductors available in large scale as a function of magnetic field in a broad temperature range measured by a Hakki–Coleman type resonator with resonant frequency $\nu \approx 8\text{GHz}$. Analysis of the high frequency dissipation supported by DC transport characterization reveals the vortex dynamics in thick ${\text{REBa}}_2{\text{Cu}}_3{\text{O}}_{7-x}$ films. Determined microscopic vortex parameters span over a wide range of magnitudes and reflect the relevance of the superconducting layer’s microstructure. We demonstrate that the depinning frequencies ${\nu }_0$ surpass $\nu$, which confirms the operation in high performing, low dissipation pinning regime at measurement conditions. Surface impedance extrapolation to FCC-hh conditions points towards a significant outperformance of copper by coated conductors in terms of surface resistance. The surface resistance margins would open up potential ways for a more efficient frontier circular collider.