21st Patras Workshop on Axions, WIMPs and WISPs

Superconducting Thin Film Development for RF Cavities in Axion Dark Matter Searches

Not scheduled

12m

University of Western Australia

Student/ECR Presentation

Speaker

Ethan Han (Swinburne University of Technology)

Description

Superconducting RF cavities operating in magnetic fields are a promising technology for next generation axion dark matter searches, where ultra high quality factors are required to maximise detection sensitivity. Achieving these performance levels requires low loss superconducting surface coatings that retain their properties under strong magnetic fields and cryogenic conditions. A key challenge is the development of reliable fabrication routes and a consistent evaluation framework for superconducting coatings across multiple material platforms.
This work develops and compares multiple thin film deposition approaches for superconducting cavity applications. Pulsed DC reactive magnetron sputtered NbTiN thin films are used as a mature experimental platform, while REBCO based thin films are pursued in parallel as a higher performance candidate system.
NbTiN is deposited using pulsed DC reactive magnetron sputtering, while REBCO is fabricated using a combination of RF and DC magnetron sputtering. The sputtering parameter space is systematically explored to identify stable deposition windows, with emphasis on optimising deposition conditions to improve film quality and superconducting performance.
A multi modal characterisation strategy is employed, combining X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), optical profilometry, and four point probe measurements. Together, these techniques establish a framework linking deposition conditions to structural, compositional, electrical, and morphological properties, enabling systematic process optimisation.
Final evaluation is performed through cryogenic measurements in a dilution refrigerator. Superconducting behaviour is confirmed around 5 K for NbTiN, with high magnetic field measurements to be completed prior to presentation.
Overall, this work establishes a fabrication and evaluation methodology for superconducting coatings intended for RF cavities operating in strong magnetic fields. By developing scalable deposition processes across both NbTiN thin films and REBCO based coated conductor systems, this work supports the advancement of low loss superconducting cavity technologies for future axion dark matter detection experiments.