Author: Scibor, K.
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.  
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About • paper received ※ 30 June 2019       paper accepted ※ 01 July 2019       issue date ※ 14 August 2019  
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Electrodeposition of Copper Applied to the Manufacture of Seamless SRF Cavities  
  • G.J. Rosaz, S. Atieh, S. Calatroni, L.M.A. Ferreira, E. Garcia-Tabares Valdivieso, C. Garion, L. Lain-Amador, A.T. Perez Fontenla, K. Scibor, M. Taborelli, C. Yin Vallgren
    CERN, Geneva, Switzerland
  Nb thin film SRF cavities have demonstrated for many years their strong potential as being an alternative to bulk Nb cavities [1]. However most of the defects observed in the Nb layers originate from defects inherited from the substrate itself [2]. Two routes are used to manufacture Cu cavities. The first one consists of forming the half-cells independently by either spinning or electro-hydroforming. The latter are then joined together and to the cut-offs by electron-beam welding. The second one is a seamless process in which the cell is entirely spun around a mandrel and then electron-beam welded to the cut-offs. Both approaches require welding, leading to potential formation of porosities. We propose an innovative route, inspired from a technology used to form small diameter vacuum chambers [3]. The cavity is formed by electrodeposition of Cu on a sacrificial mandrel whose surface state will determine the inner cavity’s surface quality. The strength of the process relies on the total absence of welding. We present the values obtained for Young Modulus, Ultimate Tensile Stress, roughness and RRR on dedicated samples. We will then discuss the fabrication route of a real cavity.
[1] C. Benvenuti et al., IEEE transactions on applied superconductivity, vol. 9, No. 2, June 1999.
[2] G. Rosaz et al., FCC week 2018
[3] L. Lain Amador et al., JVSTA, vol. 36, pp. 021601, 2018.
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