Investigation of HiPIMS-Coated S(I)S Structures for SRF Cavities

International audienceThe sustainable next generation particle accelerators require innovative solutions to overcome the current technological challenges set by existing bulk niobium superconducting radio-frequency (SRF) cavities. Thin film-based multilayer structures in the form of superconductor-insulator-superconductor (SIS) may be the long-sought-after breakthrough for higher performance SRF cavities by enhancing both accelerating gradients and quality factors. In order to understand better the underlying mechanisms of SIS structures to be coated onto (S)RF cavities, we study various material properties with the resultant superconducting properties of high-power im-pulse magnetron sputtering (HiPIMS)-coated S(I)S structures of Nb-(AlN)-NbN with different thicknesses which are designed to be coated mainly on OFHC copper (Cu) samples for more efficient SRF cavities. This contribution presents materials properties of the aforementioned HiPIMS-coated S(I)S structures as well as the superconducting and RF behaviours of these multilayers which are assessed comparatively via DC and AC magnetization techniques

Synthesis of Nb and Alternative Superconducting Film to Nb for SRF Cavity as Single Layer

International audienceThe production of superconducting coatings for radio frequency (RF) cavities has been developed over several decades. It is widely accepted that for any further improvement in cavity RF performance, innovation is needed and one may have to turn to other forms of Nb and other superconducting materials. The potential benefits of using materials other than Nb would be a higher Tc and a potentially higher critical field Hc. This could lead to potentially significant cryogenic cost reductions if the cavity operation temperature is 4.2 K or higher. We report on optimising deposition parameters and the effect of substrate treatment prior to deposition, on successful synthesis of Nb and A15 superconducting thin film. The materials characterization is determined using scanning electron microscopy SEM, energy dispersive spectroscopy EDS, glancing X-ray diffraction GXRD, atomic force microscopy AFM and Rutherford backscattering RBS. The DC superconducting properties have been tested using Vibrating Sample Magnetometer VSM and Magnetic Field Penetration MPF. This work involves a team of 8 research groups in 7 different countries and is part of the H2020 ARIES collaboration

Main highlights of ARIES WP15 collaboration

International audienceAn international collaboration of research teams from CEA (France), CERN (Switzerland), INFN/LNL (Italy), HZB and USI (Germany), IEE (Slovakia), RTU (Latvia) and STFC/DL (UK), are working together on better understanding of how to improve the properties of superconducting thin films (ScTF) for RF cavities. The collaboration has been formed as WP15 in the H2020 ARIES project funded by EC. The systematic study of ScTF covers: Cu substrate polishing with different techniques (EP, SUBU, EP+SUBU, tumbling, laser), Nb, NbN, Nb₃Sn and SIS film deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application of all obtained knowledge on polishing, deposition and characterisation, Laser post deposition treatments, DC magnetisation characterisation, application to the QPR samples for testing the films at RF conditions. The preparation, deposition and characterisation of each sample involves 3-5 partners enhancing the capability of each other and resulting in a more complete analysis of each film. The talk will give an overview of the collaborative research and will be an introduction to the detailed talks given by the team members