Investigations and Considerations of Oxygen Diffusion Profiles in Superconducting Mid-T RF Cavities Utilizing EXAFS Spectroscopy

TL;DR

This study analyzes oxygen diffusion in superconducting RF cavities using EXAFS spectroscopy, highlighting measurement challenges and confirming current models without contradicting previous findings.

Contribution

It provides a detailed experimental approach to measure oxygen profiles in SRF cavities and discusses the limitations and future directions of EXAFS spectroscopy in this context.

Findings

Measurement results are heavily affected by noise.

No deviations from existing models were observed.

The study suggests repeating experiments at PETRA III for better data.

Abstract

A screening of oxygen profiles in mid-T treated SRF cavities is crucial, in order to infer physical correlations between the microscopic cavity lattice and cavity performance - a problem concerning acceleration physicists for years. This thesis provides an analysis of oxygen diffusion profiles for three differently treated samples: Two mid-T baked and the third with the standard EuXFEL recipe. The measurement method utilizes EXAFS spectroscopy and was carried out at the DELTA facility in Dortmund. The result suffers heavily under noise, making the quantity of the result barely useable. Qualitatively, no deviations of current models regarding the profiles, could be proven, and no results of previous studies were contradicted. The experimental analysis is described in precision, interpretations of the possible are undertaken and theoretical considerations regarding error estimation and possible EXAFS simulations for future attempts are provided. A repetition at the PETRA III facility is indicated.