Minutes of the ICE section
81st meeting on Wednesday 15/05/2013 (08:40-10:30, 6/2-004)
ICE members: 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: BS, CZ, DB, DA, EM, EW, FS, GI, GR, JB, JLN, KL, NB, NM, OB, SP, SRF, TP, WH, XB, Alexey Burov, Mauro Migliorati, Hannes Bartosik ,Georges Trad, Rogelio Tomas, Javier Barranco.
1) Newcomers / visitors
- None.
2) Comments on the minutes of the previous 80th meeting + Actions
- No comment.
3) General infos
- No particular comment from anybody.
- SL meetings:
- CHIS audit: after the actions taken there is a surplus. According to the experts this should be temporary.
-Report about the global infrastructure => The big roundabout, the small roundabout, the tram which should come soon, the traffic light (idea is that it goes automatically to red when the tram is coming), etc. The idea is to continue until Divonne but it seems that people don’t talk to each other and it is currently a mess. The work is foreseen between 2015 to 2017, and in 2017 the tram should reach Saint Genis.
- From LMC on 24/04:
- IP8 aperture. Bernhard will make a presentation at one of the next LMC. A vertical crossing at injection is possible provided the emittance is smaller than 3mm. Possible alternatives:
- Different optics for non-injected beam,
- Partial ramp of LHCb dipole,
- Rotation of the beam screen (unlikely).
- MPP Workshop summary:
- Some actions for LBOC. Ongoing discussions about the set-up for the LBOC during LS1.
- Proposal for a “Beam Induced Heating WG” to follow-up the issues related to beam induced heating during LS1 and operation.
- CMAC report => Some actions on ABP for electron cloud:
- Investigate the possibility of installing electron cloud diagnostics in the LHC to enhance the understanding of the scrubbing process with 25 nsec bunch spacings, the operational state of the machine during collisions at 6.5 TeV, and the effects of future mitigation methods on the SEY. Compare with “PyECLOUD” code predictions.
- Perform additional simulations for 25 ns bunch spacing of the dedicated scrubbing process at 450 GeV and parasitic scrubbing at 6.5 TeV to predict the operational state of the LHC after a few months into the 2015 run looking for acceptable vacuum condition and cryogenic heat load.
- Investigate the possibility to operate the LHC at 6.5 TeV with a combination of trains with 50 nsec bunch spacing interleaved with trains with 25 nsec bunch spacing to allow particle physics to proceed while 25 nsec scrubbing continues.
- Investigate the possibility to use bunch spacing shorter than 25 ns to enhance the scrubbing efficiency i.e. the 5 + 20 ns bunch pattern used in the SPS.
- Presentation by Steve on the European Strategy Document.
- LS1 progress:
- 70 % of the interconnections in Sector 56 have been opened, 32 splices accessible, resistance measured in 12 of them, analysis ongoing.
- Shunt soldered in 1 splice but clamp not installed yet.
- Sputnik (ping-pong ball) test did not revealed any buckled RF finger in Sector 56.
- Conclusions from the IPAC13 exercise => 118 papers from ABP (12 from BI, 1 from HDO, 17 from OP and 37 from RF):
- The number of papers was really too high => One should try in the future to decrease it to ~ 80 max (as we had in the past).
- Some people will have more than 10 posters to present => How can this be done correctly?
=> Action: One should try and publish more (in PRSTAB in particular). One could submit some publications at the beginning of the year and then publish condense versions at the conferences (to avoid the huge number of papers for IPAC13…).
- Accelerator consolidation day => Change of the date: 12/09/13.
- 2 actions for HL-LHC => Impedance and e-cloud teams.
- NM raised the question about the NEG properties at low temperature. Reminder: CZ is also doing some measurements of the EM properties of the NEG.
- Comment from GR => Ecloud studies are quite heavy and might take time.
- There will be a SL retreat next Tuesday.
4) Discussion about the review being organised for ~ mid September on the LHC performance limitations during run I (EM): docx
- Summary of the comments (during the meeting or by emails):
- Add also the beam-induced RF heating item.
- Check systematically if there are oscillations on the 2 beams (or not) when there are instabilities.
- Would be good that some OP people participate.
- Studies for the transverse damper: fill analysis of the injection damping to give the damping time for each fill and retrieving from the logging the damper settings of gain along the cycle one can reconstruct the history along the cycle.
- Keeping the review in that week of September seems fine.
- One could also review the status of the transverse emittance blow-up in the LHC and the depenedence with the different parameters: multi-bunch vs. single-bunch, 50 ns vs. 25 ns, bunch length, etc.?
- One should also study the LHC fills which had no pb at all and try and understand why.
- Might be good, as a short introduction, to review all the performance limitations (and not only those related to collective effects) to put things in perspective. How much luminosity was lost due to collective effects / instabilities last year? What can be predicted for the future? etc.
- Some discussions about UFOs?
- Reminder: We never ran with the nominal rms bunch length of 7.5 cm => Was ~ 9 cm in 2011 and ~ 10 cm in 2012 for beam induced RF heating reasons.
- Conclusions / propositions:
1) This review (for ~ mid September) should be devoted to the statistical data analysis (ONLY) of all the observations performed in 2012.
2) A second review could be organised at the end of the year (beginning of next year) about the existing theoretical / simulation models (integrating impedance, beam-beam, e-cloud in the presence of damper, octupoles, chromaticity, etc.) and their applications with realistic sets of machine parameters, to compare to measurements.
3) After these 2 steps, recommendations should be made for the LHC restart in 2015.
5) Actions to be taken for the next meeting
- Old actions.
- New actions:
- Action 1 (e-cloud team): Actions from the last CMAC (14-15/03/13: https://indico.cern.ch/conferenceDisplay.py?confId=235072).
6) Miscellaneous
- Deadlines and important dates for ICE.
- The next (82nd) meeting will take place on 22/05/2013 => Agenda:
1) Van der Meer Scans with offsets and beam-beam (TP et al.).
- See preliminary agendas for the next meetings.
- See List of Actions.
Minutes by E. Metral, 15/05/2013.