Minutes of the ICE section
87th meeting on Wednesday 07/08/2013 (08:40-10:30, 6/2-004)
ICE members: Adrian Oeftiger (AO), Andrea Passarelli (AP), Benoit Salvant (BS), Carlo Zannini (CZ), Danilo Banfi (DB), Daria Astapovych (DA), Elias Metral (EM), Elena Wildner (EW), Frank Schmidt (FS), Giovanni Iadarola (GI), Giovanni Rumolo (GR), Javier Barranco (JB), Jean-Luc Nougaret (JLN), Kevin Shing Bruce Li (KL), Nicolo Biancacci (NB), Nicolas Mounet (NM), Olav Ejner Berrig (OB), Serena Persichelli (SP), Sergio Rioja Fuentelsaz (SRF), Tatiana Pieloni (TP), Werner Herr (WH), Xavier Buffat (XB).
Present/Excused: AO, AP, BS, CZ, DB, DA, EM, EW, FS, GI, GR, JB, JLN, KL, NB, NM, OB, SP, SRF, TP, WH, XB, Guido Sterbini, Hannes Bartosik, Michael Bodendorfer, Fritz Caspers, Raymond Wasef.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous 86th meeting + Actions
- Comment from TP: "Crab cavities are being implemented into sixtrack" => Actually this is not correct, crab crossing of rigid beam has been implemented, crab cavities were already in, implemented by RogelioT and RamaC in the past.
- A formula (from EM, discussed in http://emetral.web.cern.ch/emetral/ICEsection/2013/2013-07-03/EffectOfTransvImpedOnLumiMeas_EM_26-06-13.pdf ) has been checked and corrected by a factor 2^-(1/4) after checks from NM and MikhailZ (many thanks!) => Updated slides are here: http://emetral.web.cern.ch/emetral/ICEsection/2013/2013-08-07/EffectOfTransvImpedOnLumiMeas_v2_EM_07-08-13.pdf.
3) General infos
- No particular comment from anyone.
- Paulina will be with us for ~ 2 weeks, working with Delphine => In case we need to scan some documents, etc.
- Eirini Koukovini Platia got a 2nd prize (ex-equo) for her work on collective effects for the CLIC damping rings, under the supervision of Giovanni Rumolo => This is the 1st prize of the Low Emittance Rings workshop (Oxford, 08-10/07/2013). Congratulations!
- The Review of LIU SPS High Bandwidth Feedback System took place as foreseen (on 30/07/13) => http://indico.cern.ch/conferenceTimeTable.py?confId=260522#20130730.
- Comment from TP: 2 students from EPFL interested in doing a TP (Practical work) in accelerator physics. 1 day/week (14 days total). Send few lines with proposal to TP and she'll send all to Prof. Rivkin and students.
- SL meeting (added after this meeting):
- There will be no tolerance for thefts. Hence, in case of transport of CERN equipment the proper documents should be prepared in order to avoid troubles in case of checks.
- News from LHC (added after this meeting):
- The Helium collectors in the triplet area will not be installed.
- LS1 progress: the percentage of non-conform interconnections is approximately 30% (expected 15%). More manpower is going to be organized to keep the schedule. No delay is expected for that activity. The refurbishment of the DFBs might take longer than expected, this might imply some delays. One splice with an interconnect resistance of 116 mOhm was identified in Sector 7-8. This could have caused a problem at 3.5 TeV in case of a quench...
- Coffee discussion after the meeting on the standard model Lagrangian... => http://www.quantumdiaries.org/2011/06/26/cern-mug-summarizes-standard-model-but-is-off-by-a-factor-of-2/.
4) Brief reports of the 4 WGs (by the WG leader or replacement) => Plan, activities, deadlines, issues, etc.:
a) BB (TP):
- Daresbury: J. Qiang and K. Ohmi working on benchmark of noise studies and reproducing BB observations of bunch shortening while going into collision if one bunch was transversaly blown up due to instability. Preparing also settings for a "full" benchmark of Sixtrack (now with Frequency Map Analysis) and Lifetrack (with crab cavities multipolar errors in September). Other studies on-going to prepare for collaborations meeting.
- VdM study with MADX including dynamic beta for W. Kozanecki writing up LHC note T. Pieloni. And going to second step: evaluating the effects of non-Gaussian distributions. M. Schubiger EPFL student working with beam-beam team over summer to create a code to numerically evaluate in self-consistent way the bb orbit effect during VdM scan for any distribution (single IP VdM). Important tool for after LS1 evaluations. A talk is foreseen at the LBOC in the next future.
- DA studies by D. Banfi on-going : 4 optics, only BB 4D 5 slides, 6D, with and without multipolar errors, tune scan intensity scan. Reduced DA confirmed for 10 cm beta* now trying to identify the cause of such degradation (phase space modification, switch on off different multipoles to find the impacts, etc). Change in tune can improve from 3 to 4 sigma but not enough FMA analysis also on-going with J. Barranco. Presentation of results at HL-LHC Task Leader meeting.
- X. Buffat soon presentation on COMBI developments, results of benchmark versus head-tail and matrix formalism developed to reproduce multibunch impedance modes for bunch trains structures and beam-beam.
- On-going work on analysis of LHC instabilities: D. Banfi, X. Buffat and T. Pieloni.
b) SC (FS): Nothing reported but here is a summary of the SC meeting which took place on 18/07/13:
- FS gave a report about the outcome of his visit at GSI: MICROMAP Benchmarking (with MAD-X) and 2D Resonance Analysis (Qx + 2 Qy).
- VincenzoF gave a talk on several PTC-ORBIT issues for PSB simulations:
1) It is not clear if ORBIT actually knows about acceleration from PTC,
2) The longitudinal phase space does not seem to be OK in the presence of a double RF,
3) In some cases there seems to be a shift by PI,
4) The aperture dependent emittance spikes are yet unexplained,
5) It was also mentioned that identical tracking runs provide different results and there was some obscure explanation related to MPI noise.
=> FS will look at this in detail with VincenzoF and MichelM at CERN after summer: FS proposes to first look at this in full detail before we ask for help.
- RaymondW and HarryR are working hard to identify where the PTC-ORBIT code produces the crashes and in this effort we also address the issue of "MPI noise" which most certainly is related to some real bug.
- Issue to resurrect AlexanderM's account with the old account name and all the data files that he had left there.
c) EC (GR): slides.
- GR took over (as of 04/07/13) the leadership of the Ecloud WG, replacing FZ (many thanks to FZ for the past work!) => New site: http://indico.cern.ch/categoryDisplay.py?categId=5020.
- GR reminded the structure and plans.
- EM => All the machines (projects) should/will be discussed there (but of course a priority will/should be put depending on the criticallity, time scale etc). GR discussed the different activities in the 1st meeting (http://indico.cern.ch/getFile.py/access?contribId=0&resId=1&materialId=slides&confId=263082):
- PS => Systematic comparison between meas. and simulations; mitigation measures (experimental and simulations); full characterization of the e-cloud in the machine (different chambers, combined function magnets); input for more measurement techniques to be developed (e-cloud monitors in magnets and/or synchrotron phase shift).
- Short term: write up of the LIU-PS TDR.
- Long term simulation plan: develop a PyECLOUD-HEADTAIL combined code to study the instabilities.
- SPS => Simulations and characterisation of all types of chambers (pending quadrupoles); measurements both with the e-cloud monitors and the pressure gauges + all beam based measurements (comparison between observations with standard and BCMS 25ns beam - impact of transverse emittance and train structure on e-cloud); studies for a scrubbing beam both in simulations and MDs with lower e-cloud threshold than the 25ns beam; general studies on the high bandwidth damper module in HEADTAIL to damp e-cloud instability; more detailed HEADTAIL simulations with Q20 to assess the tolerable amount of e-cloud in the machine.
- LHC => Preparation of the future 25ns runs of LHC; analysis of the existing data and forecast of what will be needed in future operation; dedicated simulation campaigns to fit machine data and describe/explain the evolution of the SEY until now; further extension of the PyECLOUD code to include more options (2-beam cases => ALICE 800mm tube and triplets; beams displaced from the center of the chamber); HEADTAIL simulations to determine instability thresholds, determine e-cloud tune footprints, study the effect of octupoles on e-cloud instabilities; tackle open questions: efficiency/speed of scrubbing - behaviour of e-cloud with energy in the different parts of the machine.
- Other ecloud studies
- Use of nonlinearities in the transverse plane to create islands to improve scrubbing efficiency (CedricH).
- Distribution of the synchrotron radiation around the LHC, important to define the distribution of seeds above a certain energy (HumbertoMC)
- Impact of the dipole edges? (GianniI)
- HL-LHC studies (OctavioD’s note already published) => Different filling patterns; Doublet beams; Scrubbing scenarios.
- CLIC damping rings.
- 2 meetings took place already to discuss the LHC (Update on LHC observations in LSS and simulation studies => OctavioD) and the PS (chambers => SergioRF. Talk also given the PS LIU meeting yesterday). A 3rd talk is already planned on 09/09/13 to disucss the LHC triplets (GianniI).
d) IMP (BS): slides.
- Several progresses in the general understanding: mode matching for transverse impedance (NicoloB); way to disentangle direct space charge from CST simulations with low beta (CarloZ); benchmark of resonance parameters obtained from eigenmode and wakefield simulations (BerengereL).
- Reminder on some deadlines:
- Beam induced heating for HL-LHC for end of Summer,
- HL-LHC impedance model for November.
- TDR chapter written by MauroM to be completed and given to SimoneG by mid-August.
- Lot of activities for LHC: wire meas. on new RF fingers design and TCTP (OlavB, JosephK et al.); geometric impedance of the current LHC collimators (MikhailZ et al.) => Good hope to explain part of the factor 2 between beam-based measurements and predictions; LTEX review for ALFA and TOTEM took place as foreseen (no showstopper); MKI8D, which had a very different behaviour from the others, was found to have a serious manufacturing issue (90 degrees twist of the contacts from one end to the other); etc.
- For the SPS, a practical solution for the wirescanner has not been found yet.
- Etc.
5) Status of the work for the internal review on the LHC performance limitations during run I (on 25-26/09/2013) => All the speakers
- Ongoing (~ as planned) and no major issues found. Some questions already answered.
=> To be continued with HIGH PRIORITY. We will discuss this item during all the next ICE meetings until the review.
- The next ICE meeting will be devoted to a finalization of the programme and speakers before I put them on indico.
- During the ICE meetings after, we will discuss with (first) slides for all the talks, to start to share the info altogether and these slides will be filled meetings after meetings.
6) Actions to be taken for the next meeting
- Old actions.
7) Miscellaneous
- Deadlines and important dates for ICE.
- The next (88th) meeting will take place on 14/08/2013 => Agenda:
1) Status of the work for the internal review on the LHC performance limitations during run I (on 25-26/09/2013) => All the speakers
2) Finalization of the review programme and speakers (before being put on indico)
- See preliminary agendas for the next meetings.
- See List of Actions.
Minutes by E. Metral, 08/08/2013.