Author: Naisson, P.
Paper Title Page
MOP061 State of the Art of Niobium Machining for SRF Applications 210
  • P. Naisson, S. Atieh, K. Scibor, P. Trubacova
    CERN, Geneva, Switzerland
  • F. Dumont, D. Fabre, F. Valiorgue
    ENISE, Saint Etienne, France
  Niobium is a demanding material to be machined. Its low hardness, high melting temperature and abrasivity leads to poor cutting condition, and surface quality and shape accuracy could be difficult to achieve, especially for complex shapes such as HOM antennas. Recent CERN developements concerning DQW crab cavity for HL-LHC project had implied extensive research program to better understand and master the machining of this material. In this frame, the present article will introduce actual state of the art machining condition used at CERN and their consequences about the surface roughness, shape accuracy and taking into account the tool wear in order to maintain this level of quality. Morevoer, advance machning solution, such as cryogenic cooling could be used.  
poster icon Poster MOP061 [2.921 MB]  
DOI • reference for this paper ※  
About • paper received ※ 30 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
Nb/Cu Coatings Characterization in HiPIMS With Biased Substrate and Application of a Positive Pulse  
  • F. Avino, S. Calatroni, D. Fonnesu, A. Grudiev, P. Naisson, H. Neupert, A.T. Perez Fontenla, T. Richard, G.J. Rosaz, A. Sublet, M. Taborelli
    CERN, Geneva, Switzerland
  In this work, we present results on the characterization of Nb on Cu films obtained in High Power Impulse Magnetron Sputtering (HiPIMS) with a negatively biased substrate, or with a positive pulse after the main negative one [1]. This allows to accelerate the Nb+ atoms towards substrates with small grazing angles of incidence to obtain a dense and defect-free Nb film. Samples reproducing the shape of a 1.3 GHz SRF cavity are coated by varying the timing of the substrate bias with respect to the main HiPIMS. The Nb film residual stress and estimations of the amount of trapped discharge gas (Kr) are also presented. The effect of applying a positive pulse after the main HIPIMS pulse on Nb/Cu samples coated in Ar is further explored. Crystallites size characterization is obtained with X-Ray Diffraction. First SRF properties by measurement of the critical temperature are provided. Preliminary results of Nb/Cu coatings of Cu samples reproducing the real geometry of the Wide Open Waveguide Crab cavity [2] are presented.
[1] F Avino et al., Plasma Sources Sci. Technol., vol. 28 pp. 01LT03, 2019.
[2] A. Grudiev, Proceedings of SRF 2015.
slides icon Slides THFUB3 [5.369 MB]  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)