9th International Workshop on Thin Films and New Ideas for Pushing the Limits of RF Superconductivity

Material engineering of ALD- deposited multilayer to improve the superconducting performances of RF cavities under intense RF fields.

Mar 17, 2021, 10:15 AM

20m

Virtual Edition

SIS structures for SRF SIS structures for SRF

Speaker

Yasmine KALBOUSSI (IRFU/DACM CEA Saclay)

Description

We are exploring an original approach to improve the performance of bulk Niobium RF cavities through surface engineering with ALD superconducting multilayer capable of screening efficiently the magnetic fields and therefore inhibiting vortices penetration in Niobium SRF cavities [1].
As a first step for the multilayer, we aim at replacing the deleterious niobium native oxide by a clean interface between an insulator synthesized by ALD (Al2O3, Y2O3 and MgO) and the Niobium metal. To that end, I will present the results obtained on both flat niobium samples and 1.3 GHz elliptical cavities. Our study shows that ALD deposited films are in fact a good diffusion barrier, resist to thermal treatments and reduce significantly the presence of the niobium native oxide on the surface. Low SEY material such as TiN was also deposited on top of the insulator film to reduce multipacting phenomena. RF test on ALD coated cavities shows already a slight improvement of the superconducting performances.
In parallel we started synthesizing superconducting NbTiN alloys by ALD. I will present preliminary results on the superconducting properties of NbTiN films grown on AlN by ALD with various compositions on Nb substrates.
[1] A.Gurevich,”Enhancement of RF breakdown field of SC by multilayer coating”.Appl. Phys.Lett, 2006.