Author: Proslier, Th.
Paper Title Page
SUPCAV013 Multipacting Analysis of the Quadripolar Resonator (QPR) at HZB 42
 
  • S. Bira, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • Y. Kalboussi
    CEA-IRFU, Gif-sur-Yvette, France
  • S. Keckert, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  • Th. Proslier
    CEA-DRF-IRFU, France
 
  Multipacting (MP) is a resonating electron discharge, often plaguing radio-frequency (RF) structures, produced by the synchronization of emitted electrons with the RF fields and the electron multiplication at the impact point with the surface structure. The electron multiplication can take place only if the secondary emission yield (SEY, i.e. the number of electrons emitted due to the impact of one incoming electron), , is higher than 1. The SEY value depends strongly on the material and the surface contamination. Multipacting simulations are crucial in high-frenquency (HF) vacuum structures to localize and potentially improve the geometry. In this work, multipacting simulations were carried out on the geometry of the Quadrupole Resonator (QPR) in operation at HZB using the Spark 3D module in Microwave Studio suite (CST). These simulations helped to understand a particular behavior observed during the QPR tests, and furthermore made it possible to suggest enhancement ways in order to limit this phenomenon and facilitate its operation.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2021-SUPCAV013  
About • Received ※ 09 July 2021 — Revised ※ 09 July 2021 — Accepted ※ 09 April 2022 — Issue date ※ 07 May 2022
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FROFDV07
Material Engineering of ALD- Deposited Multilayer to Improve the Superconducting Performances of RF Cavities Under Intense RF Fields  
 
  • Y. Kalboussi
    CEA, DES-ISAS-DM2S, Université Paris-Saclay, Gif-sur-Yvette, France
  • C.Z. Antoine, B. Delatte
    CEA-IRFU, Gif-sur-Yvette, France
  • S. Bira, D. Longuevergne
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • D. Dragoe
    ICMMO, Orsay, France
  • J. Leroy
    CEA/DRF/IRAMIS/SIS2M, Gif sur Yvette, France
  • Th. Proslier
    CEA-DRF-IRFU, France
  • S. Tusseau-Nenez
    Ecole Polytechnique, Palaiseau, France
 
  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 cavities. 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 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 Nbiobium.  
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