Minutes of the ICE section
44th meeting on Wednesday 23/11/2011 (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), 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, TP, WH, XB, Alexey Burov, Chandrashekhara Bhat, Frank Zimmermann, Hannes Bartosik, Haryo Sumowidagdo, Octavio Dominguez, Tatiana Rijoff.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous 43rd meeting + Actions
- None.
3) General infos
- AP forum scheduled at 11:00 in this room: FACET status and plans by U. Wienands (SLAC).
- SL meeting (03/11/2011):
- 03/11/2011 => The staff association is going to make a proposal for a new Saved Leave Scheme. According to this proposal staff members could renounce to up 10% of their salary and two years before the official retirement age they could decide either to get back the money (an interest rate of CVI+1% should be guaranteed) or to get additional leave. In that case the money would be used to hire new staff. Details in the presentation of M. Ludwig.
- Safety for LINAC4: A. Funken (presently detached to BE) will take over this task from S. Maury.
- LHC status report: end of proton run. Delivered more than 5.6 fb-1 to ATLAS/CMS and 1.2 fb-1 to LHCb. MD programme heavily affected by a cryogenics stop and by a failure of the SPS beam dump kicker. This has implied revisiting the MD schedule heavily.
- A first p-Pb test has taken place, injection, acceleration and re-synchronization at flat-top have been tested. Lifetime has been rather good although some blow-up has been observed (to be quantified).
- Results of the measurements performed on the IR2 aperture in view of running with b*=1 m. An unidentified (yet) bottleneck has been detected left of point 2 close to the TCTVB. Further measurements will be taken during the MD. Alignment checks have been requested.
- SL meeting (10/11/2011):
- Meeting with the BI people on the subject of the Beam beam wire compensator for LHC. R Steinhagen presented a cost estimate of 1.5 MCHF => Action1: To be followed up by FZ (and WH, as this is part of HL-LHC WP2 Task 2.5) to be sure that we can install something useful during LS1.
- IPAC2012 reminder: DEADLINE for abstract submission to me by Friday 25/11. Action 2: EM to upload all the ICE abstracts to the link provided by DelphineR by Friday 25/11.
- List of people authorized (by the BE department) to attend IPAC2012: Oliver Bruning; Frank Zimmermann; Helmut Burkhardt; Christian Carli; Roberto Corsini; Massimo Giovannozzi; Andrea Latina; Elias Metral; Yannis Papaphilippou; Adriana Rossi; Elena Wildner; Riccardo De Maria; Guido Sterbini => We have 2 persons from ICE: EW and EM. Action 3: ICE students to inform EM about their intention to apply for a grant.
- The 52th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2012, will be held in Beijing from September 17 to 21, 2012: http://hb2012.ihep.ac.cn => Action 4 (all ICE members): Who would like to attend HB2012?
- Sasha (AM from KEK) will arrive on 25/11/11 for 1 month => Everything was discussed with the space charge team and everything should be ready.
- Discussion between CERN (GR) and GSI to organise a 1-day workshop at CERN beginning of 2012 to review the present status of the understanding and modeling of beam instabilities as well as incoherent collective effects, with special emphasis on machines operating in space charge dominated regime (high brightness, low energy). The main goals of the workshop will be to identify the important collective effects that can be anticipated as issues or limiting factors in the upgrade of the CERN injectors (PSB, PS, SPS) as well as for the SIS18-100 in the framework of the FAIR project, propose the necessary studies and, where possible, look for solutions => Action 5: GR, EM, FS et al. to discuss the detailed programme (FS will go to GSI to discuss in detail the space charge collaboration and possible session in the above workshop).
- Thijs Wijnands has been nominated as Scientific Secretary of the CERN ALARA Committee for 2 years, starting on 01/11/2011.
- BS has been nominated new IEFC scientific secretary.
- To be added in the ICE list:
- Dobrin Kalchev.
- Haryo Sumowidagdo [sumowidagdo@gmail.com].
- Tatiana Rijoff
- Heating of ALFA detectors: Slides from Sune Jakobsen and Per Grafstrom => To be followed up by the impedance team (Action 6) => Interesting to note that the TOTEM Roman Pot had a similar behaviour, which is also very similar to the TDI: temperature increase after stable beams and for few hours before going down.
- Discussion with Vincent Baglin: X-rays TCTVB-VAMTF-TCDD TS5 Nov 2011 => The spring of the module located between TCTVB.4L2 and TCDD.4L2 is broken, probably as a consequence of beam irradiation. The consequent deformation of the RF fingers could explain in turn the reduction of aperture observed during IT2L aperture measurements. To be followed up by the impedance team (Action 6).
- HL-LHC 1st general meeting => Preparation meeting + workshop => See at the end of my web page (http://emetral.web.cern.ch/emetral/) + http://indico.cern.ch/conferenceDisplay.py?confId=150474.
- UA9 goniometer conceptual design => Meeting with Francesca Galluccio => To be followed up by the impedance team:
- Idea to install a UA9 goniometer first in the SPS in June 2012 (point 5) and then in the LHC (point 7) during LS1.
- Length of a LHC collimator, ~ 1.5 m.
- Diameters (for SPS and LHC) under discussions => Waiting for some drawings.
- New instrumentation for the PSB => Estimation of the impedance => To be followed up by the impedance team .
- Status of SPS MKDV impedance data analysis => JLN will make a status report on 18/01/2012.
- LHC power spectra analyses => See http://emetral.web.cern.ch/emetral/ICEsection/2011-11-23/TheoreticalPowerSpectraComparison_LHCbunchAt3point5GeV_v6.pdf.
- Room: I reserved this room for another 2 years (same time slot) => 3 conflicts:
- 11/01/12: JENDE Konrad between 10:00 and 10:30 => We will have to finish before 10:00.
- 01/02/12: GARAI Zsuzsanna between 09:00 and 10:30 => No meeting.
- 09/05/12: AUGIER Alexia between 08:30 to 10:30 => No meeting.
- Christmas party: What do we (ICE) do?
- HL-LHC task 2.4:
- Discussion with Wolfgang Hofle and Elena Chapochnikova on their participation.
- I met Deepa last week => Would like to contribute to IBS computations => Need maybe another lab to work on it to check results. Discussions with Michel Martini + Alessandro Vivoli, who are interested to join as well.
- I met RainerW and Olga => Impedance computations => Issue at the moment: heating => Compute the real part of the longitudinal impedance until ~ 4 GHz.
- Next step: EM to contact all the collaborators and discuss the possible subjects etc.
- XXIII Russian Particle Accelerator Conference (RuPAC 2012) will take place at the Peterhof, St. Petersburg, Russia from 24 to 28 September, 2012.
- LHC-CC1 crab cavity workshop last week at CERN: http://indico.cern.ch/conferenceDisplay.py?confId=149614.
- LIU event next Friday: https://indico.cern.ch/conferenceTimeTable.py?confId=160434#20111125 => Talk by GR.
- Evian workshop (https://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=155520) => Talks by NM, BS, GR.
4) 2011 ICE goals: where do we stand? (all the ICE members)
- Seems OK.
- BBLR in the SPS (FZ) => Terrible year for MD, cable pb etc. To be followed up.
5) LHC: current hot topics and suggestions for MDs in 2012 (all the ICE members)
- Hot topics these days: Heating here and there => Being followed up by the impedance team and equipments colleagues.
- LHC MDs: Many beam-beam studies already discussed/planned in the beam-beam team (WH et al.), impedance and related instabilities at injection with space charge and top energy without octupoles but with beam-beam etc. (NM et al. and beam-beam team), transverse emittance growth origins (as proposed by GR), flat beam collisions (as mentioned by FZ and WH), certainly 25 ns scrubbing run (ecloud team) etc. => Action 7 (all ICE members): Send the LHC MD requests to LSWG by Thursday 07/12 and they will be discussed at the LSWG meeting to be held on 08/12.
- Injectors MDs: GR will send a request by the end of the year or beginning of the next.
6) Status report on BBLR simulations (Tatiana Rijoff): pdf1 and pdf2
- Tatiana made a review of her simulations (with FZ) on beam-beam compensation with a wire.
- Tatiana reminded us with a previous study by Jean-Pierre Koutchouk (note: CERN-SL-2001-048-BI):
- Longitudinal position of the wire = 104.93 m after IP1 and IP5 (with beta* = 0.55 m, betax,y ~ 1740 m and betatron phase advance ~ 0.25 deg.).
- Transversal position = 9.5 sigmas.
- Due to some constraints (followed up by R. Steinhagen), only 1 position is possible at the moment: TCT before the IP at -145.84 m. Alternative longitudinal positions were studied, but the one from JPK (i.e. nominal) one is the BEST and Q5 is the worst. After additional tests the TCT position could maybe be OK.
- As concerns the transverse positions, 9.5 sigmas were studied but also 11 sigmas as suggested by Ralph Steinhagen to preserve the hierarchy of the collimators:
- Wire (DC) current calculation for 9.5 sigmas = 176.8 A (with some assumptions, nominal intensity, 32 LR).
- Wire (DC) current calculation for 11 sigmas = 237.0 A (quadratically scaled).
- Simulations done with bbtrack (Ulrich Dorda):
- Footprint analysis : 10000 particles tested , [0sigma; 6:5sigmas] initial distribution, 50.000 turns.
- Instabilities analysis : 902 particles tested, [0sigma; 10sigmas] initial distribution, 300.000 turns.
- Stability criterion.
- Central tunes (i.e. for small amplitudes) moved back to original value:
- In IP1: DeltaQx < 0 and DeltaQy > 0 (and both are inversely proportional to d^2 with d = wire y-distance).
- In IP5: Reversed signs and d = wire x-distance.
- Simulated square wire (1 mm side).
- Crossing angle: 2/3 of the nominal one. Motivation being to take a case which could be tested in an MD and to see the positive effect of the wire.
- Many footprints analyses.
- Many DA analyses.
- Conclusions and outlook => Wire compensation for the nominal LHC has been studied:
- The best compensation is achieved with a wire at optimum location at 11 sigmas.
- Wire at the 2nd modified TCT location also promises a good performance.
- Changing the point like wire with a squared wire with (side 1 mm) seems to gives better results.
- The results seem encouraging also changing the crossing angle to 2 / 3 of nominal value.
- Question from FS: Shouldn't we compare these simulations with the usual/reference tool SIXTRACK, as this tool is set up for massive simulations and was used successfully in the past. Our reference (without wires) simulations were obtained with SIXTRACK. Furthermore, a wire is already there for several years. Therefore it should be easy => To be followed-up: discussions should take place between TatianaR, FrankZ, FS and WH. In particular we should be ready to answer to at least 2 questions (as mentioned by WH):
- What about the PACMAN bunches?
- Why do this whereas we know we have 8.5 sigmas DA?
=> To be discussed and followed up with the beam-beam team.
- Reminder: This is a DC current. We would need AC to be able to compensate for any bunch (i.e. 25ns which does not seem realistic for the moment) and in addition there are other effects which will not be able to compensate.
- Definition of DA they used: when 1/2 of the number of particles is lost.
- Comment from AlexeyB: Increasing the wire radius by 3 would decrease the resistivity by 10 and we could then have a better cooling etc.
7) Actions to be taken for the next meeting
- Old actions.
- New actions =>
- Action1: BBLR installation to be followed up by TatianaR-FrankZ-FS-WH (as this is part of HL-LHC WP2 Task 2.5) to be sure that we can install something useful during LS1.
- Action 2 (reminder to all IPAC2012 primary authors): Upload all the ICE abstracts to the link provided by DelphineR by Friday 25/11.
- Action 3: ICE students to inform EM about their intention to apply for a grant for IPAC2012.
- Action 4 (all ICE members): Who would like to attend HB2012 (Beijing, September 17 to 21)?
- Action 5: GR, EM, FS et al. to discuss the detailed programme of the CERN-GSI workshop to be held at CERN in January 2012 (FS will also go for 1 day at GSI to discuss in more detail the space charge collaboration).
- Action 6: Impedance team to follow many equipments (UA9 goniometer, LHC RF fingers and many LHC equipments, new instrumentation in the PSB, etc.).
- Action 7 (all ICE members): Send the LHC MD requests to LSWG by Thursday 07/12 and they will be discussed at the LSWG meeting to be held on 08/12.
8) Miscellaneous
- The next (45th) meeting will take place on 07/12/2011 => Agenda:
1) The ELENA project and possible ICE studies (OB),
2) HL-LHC WP2 task 2.4 (EM),
3) HL-LHC WP2 task 2.5 (WH).
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 24/11/2011.