Surface impedance measurements in superconductors in dc magnetic fields: challenges and relevance to particle physics experiments

TL;DR

This paper discusses the challenges and importance of surface impedance measurements in superconductors under dc magnetic fields, especially for particle physics and RF applications, highlighting new measurement needs and difficulties.

Contribution

It identifies the challenges in measuring surface impedance in superconductors in high dc magnetic fields and emphasizes their relevance to particle physics experiments and RF superconductivity.

Findings

Surface impedance in superconductors is difficult to measure accurately in high dc magnetic fields.

Such measurements are crucial for optimizing superconducting materials in particle physics and RF applications.

The paper highlights the need for new measurement techniques to address these challenges.

Abstract

Particle physics and radio-frequency (RF) superconductivity have driven each other on since the 1970s. The unique properties of superconductors (SC) have been the enabling keys for the realization of accelerators with always increased performances thanks to the realization of all-superconducting cavities. The use of increasingly pure superconducting coatings for accelerating cavities, with lower and lower RF losses, determined such high-quality factors that the need to operate at low temperatures (below the superconducting transition temperature Tc) was well paid for. Recently, with respect to the path followed by the high frequency superconductivity, a new field opened since SCs are being considered for GHz operation in high dc magnetic fields, and measurements (and optimization) of totally different quantities are needed. The possibility of successfully using SCs in high magnetic fields for these purposes is far from obvious and it depends on the outcome of accurate measurements of usually overlooked quantities.