3rd meeting

Europe/Zurich
30-6-017 (CERN)

30-6-017

CERN

Description
SPL cavities working group video conference meeting
Participants: CERN: E. Chiaveri, O. Capatina, M. Schuh, R. Calaga, T. Renaglia, S. Calatroni, W. Weingarten TRIUMF: R. Laxdal CEA Saclay: G. Devanz, S. Chel, J. Plouin Rostock University: H.W. Glock CNRS Orsay: G. Olry TU Darmstadt: W. Mueller Royal Holloway London: S. Molloy The proposed agenda was: • Approval /follow up of minutes of previous meeting • Beam tube damping estimations for SPL cavity, W. Weingarten (CERN) • First estimations of external Q-values for specific HOM damping schemes (2nd part), R. Calaga (BNL) • Towards the acquisition of niobium: Mechanical calculations , O. Capatina (CERN) • Discussion on conformity of designs for SPL cavity • AOB • Proposed visit CERN -> CEA Saclay • Date of next meeting and agenda topics Detailed discussions: • Approval /follow up of minutes of previous meeting o The minutes are approved • Beam tube damping estimations for SPL cavity, W. Weingarten (CERN) o Wolfgang W. presents his estimates of power deposited in the (highly resistive stainless steel) beam pipe by the strongest HOM modes as a function of Qext and for different choices of beam pipe diameters. The taper is chosen either SC or NC for comparison. Conclusions are in slide 16, suggesting that HOM antennas seem to be needed even with larger beam pipes. Guillaume D. comments that care should be taken when comparing with LEP which was CW. Wolfgang replies that his calculations include the 50 Hz repetition rate. • First estimations of external Q-values for specific HOM damping schemes (2nd part), R. Calaga (BNL) o Rama C. presented his estimates of Qext for HOM deposition in highly dissipative material in the transition section (I) or in the cutoff (II), as a function of cut-off diameter and tapering or enlargement, comparing also CEA and BNL design. (II) seems better but requires a notch for the fundamental mode. BNL design is slightly better at the higher frequencies. Guillaume is perplexed by the high Qext for low frequency HOM. • Towards the acquisition of niobium: Mechanical calculations , O. Capatina (CERN) o Ofelia C. showed her mechanical stress calculations for the reference CEA geometry in order to optimize niobium thickness for procurement. The choice seems to converge towards 3.5 mm initial thickness. A spinning test will be soon launched at CERN to confirm the estimated values for thickness reduction. Sergio comments that the calculations don’t consider buckling, Ofelia confirms that the stress is considered uniform. • Discussion on conformity of designs for SPL cavity o Juliette Plouin compares the reference CEA design with BNL design. The cavity design values are in her slide 1. BNL design has lower Ep/Eacc and Bp/Eacc, as a consequence the dissipated power is 10% larger. It is commented that the definitive estimate should also include the power dissipated by HOM
There are minutes attached to this event. Show them.
    • 17:00 17:10
      Approval /follow up of minutes of previous meeting 10m
      Speaker: Wolfgang Weingarten (CERN)
    • 17:10 17:30
      First estimations of external Q-values for specific HOM damping schemes (2nd part); retained from previous meeting 20m
      Speaker: Rama Buchi Rao Calaga
      Slides
    • 17:30 17:50
      Towards the acquisition of niobium: Mechanical calculations 20m
      Speaker: Ofelia Capatina (CERN)
      Slides
    • 17:50 18:10
      Beam tube damping estimations for SPL cavity 20m
      Speaker: Wolfgang Weingarten (CERN)
      Slides
    • 18:10 18:30
      beta = 1 cavity: new studies, related questions & comparison BNL-Saclay geometries 20m
      Speaker: Stephane Chel (Centre d'Etudes de Saclay (CEA-Saclay))