Minutes of the ICE section
61st meeting on Wednesday 25/07/2012 (08:40-10:30, 6/2-004)
ICE members: Benoit Salvant (BS), Christian Hansen (CH), Carlo Zannini (CZ), Hugo Alistair Day (HD), Elena Benedetto (EB), Elias Metral (EM), Elena Wildner (EW), Frank Schmidt (FS), Giovanni Iadarola (GI), Giovanni Rumolo (GR), Jean-Luc Nougaret (JLN), Kevin Shing Bruce Li (KL), Nicolo Biancacci (NB), Nicolas Mounet (NM), Olav Ejner Berrig (OB), Serena Persichelli (SP), Tatiana Pieloni (TP), Werner Herr (WH), Xavier Buffat (XB).
Present/Excused: BS, CH, CZ, HD, EB, EM, EW, FS, GI, GR, JLN, KL, NB, NM, OB, SP, TP, WH, XB, Alessandro Vivoli, Alexander Molodozhentsev (from KEK), Alexej Grudiev, Alexey Burov (from FNAL), Andy Butterworth, Bettina Mikulec, Cedric Hernalsteens, Chandrashekhara Bhat (from FNAL), Christian Carli, Christine Vollinger, Daniel Valuch, Daniel Wollmann, Eirini Koukovini Platia, Elena Shaposhnikova, Fanouria Antoniou, Frank Zimmermann, Fritz Caspers, Gabriel Mueller, Gerad Tranquille, Gersende Prior, Giulia Papotti, Giuliano Franchetti (from GSI), Georges Trad, Hannes Bartosik, Harry Renshall, Haryo Sumowidagdo, Helmut Burkhardt, Humberto Maury Cuna, Javier Fernando Cardona, Ji Qiang (from LBNL), John Jowett, Kazuhito Ohmi (from KEK), Lajos Bojtar, Massimo Giovannozzi, Mathilde Favier, Michel Martini, Miriam Fiterrer, Octavio Dominguez Sanchez de la Blanca, Rama Calaga, Raymond Veness, Raymond Wasef, Riccardo de Maria, Roderik Bruce, Rogelio Tomas, Sandra Aumon, Simon White, Tatiana Libera Rijoff, Theodoros Argyropoulos, Tom Mertens, Uli Wienands (from SLAC), Valeri Lebedev (from FNAL), Vittorio Vaccaro (from Naples), Wolfgang Hofle, William Andreazza, Yannis Papaphilippou, Yuri Alexahin (from FNAL), Mauro Migliorati (from La Sapienza), Vincenzo Forte.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous meetings + Actions
3) General infos
- OB => Pb with the optics of the BT line, where they want to implement YASP. It is the worst line at CERN due to the recombination of the 4 rings and MADX is not done for that.
- SL meeting:
- LS1 has been shifted. The proton run will be extended until end of February and this seems to be related to the need for additional time for CMS and for CERN services.
- LMC:
- p-Pb run confirmed for 2013.
- LHC operation: When the machine is running for physics good production rates (0.5 fb-1 in 3 days).
- Tune footprint: a first version is available. Strong request by SteveM to improve speed and add additional features previously discussed at the LBOC.
- News from LHC:
- Sill instabilities at the end of the squeeze => Guidelines required (ongoing).
- CMAC on 16-17/08/12 => 3 talks from us:
- Impedance, instabilities and implications for the future (EM),
- Beam-beam effects in operation and MDs, projection for 7 TeV (WH),
- Status and prospects of the 25 ns studies (GR).
- LIU project:
- LIU MD day on 28/08/12 (BE Auditorium, 6/2-024) chaired by GR.
- HL-LHC project:
- Seems that the bunch length should not be decreased to ~ 4 cm and instead kept to ~ 7.5 cm => Much better for RF heating!
- Any proposal for an article for the BE department newsletter? EW will write something about the neutrino activities for the issue to be released in December.
4) Longitudinal impedance measurements in the PS: comparison between measurements, theory and simulations (Mauro Migliorati): pdf
- White noise to excite incoherent motion inside the bunch.
- Factor of 2 discussed in detail (also discussed in Laclare).
- Comparison with simulations with a parabolic distribution => Very good agreement.
- Analysis of the phase shift vs. intensity.
- Final value obtained: Im[Zl/p] = 18.4 +-2.2 Ohm, assuming a parabolic line density => Very close to the value obtained in the past (~ 20).
- Clear procedure established to monitor the BB impedance over the coming years.
- Impedance budget:
- Space charge,
- Ferrite loaded kickers,
- Connections between beam pipe and vacuum pumps (CST simulations) => 100 equipments,
- Resistive wall,
- Cavities (10-40-80 MHZ), resonant modes,
- Step transition (average 35*73 mm -> 73*73 mm).
- Bellows => 200 elements.
=> Summary of impedance budget (at the bunch cut-off frequency) given.
- The main contribution of the impedance is coming from the kickers.
- Reminder: 2 contributions from EM:
- 1 to restore the boundary conditions.
- A second linked to the discontinuity and which radiates (and we need to be above cut-off for the radiated field to be able to propagate).
- Total wake potentials of a 2.3 ns Gaussian bunch => Very good agreement.
- Question from AlexeyB about ratio between real and imaginary part => MauroM replied about 10%.
- Comment from FC: we should not neglect the bypasses in our analysis => To be checked.
5) Actions to be taken for the next meeting
- Old actions.
6) Miscellaneous
- Deadlines and important dates for ICE.
- The next (62th) meeting will take place on 01/08/2012 => Agenda:
1) Electron cloud instability (Alexey Burov).
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 25/07/2012.