Minutes of the ICE section
19th meeting on Wednesday 02/03/2010 (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), Ewen Hamish Maclean (EHM), Elias Metral (EM), Elena Wildner (EW), Frank Schmidt (FS), Giovanni Rumolo (GR), Jean-Luc Nougaret (JLN), Kevin Shing Bruce Li (KL), Maria Carmen Alabau Pons (MCAP), Nicolo Biancacci (NB), Nicolas Mounet (NM), Olav Ejner Berrig (OB), Tatiana Pieloni (TP), Werner Herr (WH).
Present/Excused: BS, CH, CZ, HD, EB, EHM, EM, EW, FS, GR, JLN, KL, MCAP, NB, NM, OB, TP, WH, Chandrashekhara Bhat (Fermilab), Giuliano Franchetti (GSI), Humberto Maury Cuna, Miriam Fitterer, Octavio Dominguez Sanchez de la Blanca, Rama Calaga, Vittorio Vaccaro (Naples)
1) Newcomers / visitors
- Giuliano Franchetti (GSI).
2) Comments on the minutes of the 18th meeting + Actions
- No particular comments.
- Action 25 (EM): Answer to the question from Sandra Aumon (previous meeting) => What is the effect of closing or opening the relay gaps on the PS 40 and 80 MHz RF cavities? EM sent an email to Erk Jensen after discussion with him and he is waiting for his data. According to what was discussed together, it seems that when the relay gaps are closed the impedance can be considered ~ 0 and when the relay gaps are open we expect some HOMs but not a huge broad-band impedance.
3) General infos
- No particular comment.
- SL meeting last week:
- Reminder for travel reimbursements: They must be requested within 6 months.
- News on the LHC:
- LHC 08:30 meeting on MO 28/02/11:
- New squeeze in place: 1.5 / 10 / 1.5 / 3.0 m.
- This year the crossing angle at top energy on LHCb has been increased by a factor 2.5 (was 100 microrad last year and is 250 microrad this year) with a beta* smaller (3.0 m now) which was said to make it very difficult to have a good orbit correction => This is now understood and comes from the wrong reference.
- Ralph Assmann mentioned that it takes a lot of time to make the collimation set-up due to the very small transverse emittances => We could/should do this with much larger transverse emittances to gain some time (~ 4 microm would be much better), as mentioned during the meeting.
- Hump on B2V still there!
- Email from Ralph Steinhagen on possible observations of head-tail instabilities: picture 1 and 2 (full).
- Observations made on SA 26/02 /11 with an ~ nominal bunch (LHCINDIV) at injection, with Q'x ~ Q'y ~ 4 and with the transverse damper (ADT) ON. The peak of the line changes only over few minutes, i.e. it is as if it is ~ constant, and it can be up to 20 dB (10 x) larger than the residual ADT noise floor. There are some errors on the absolute scale but these lines move in response to tune trims (red: before; blue: after) which confirms that they are not instrumental but actually being tune related.
- 3 questions from RalphS:
- 1) Why does it oscillate? What drives it? The damper is ON and it seems that it is an intra-bunch motion according to RalphS. It is however difficult to see with the HEADTAIL monitor as the oscillation is too small (~ 100 microm at most).
- 2) Does it have an impact on the emittance growth?
- 3) If yes, how to improve this? Can we use Landau octupoles?
- LBOC (TP): The plan is to ramp with a nominal bunch by the end of this week and during the week-end to go to munlti-bunch operation.
- Q" study of RogelioT => Possible talk to be given at one of the next ICE meetings.
- News from the 2nd Extended Engineering and Design Meeting for the LHC Collimation Upgrade => BS and HD:
- Part of the email from BS: Alessandro envisage de mettre des mchoires en graphite dans la machine (jusqu' 6 collimateurs, TCSG il me semble) si une solution nest pas trouve pour obtenir du CFC. RalphA a considr cette hypothse comme tant inacceptable si des tudes trs lourdes sur la rsistance mcanique et limpdance du graphite ne sont pas ralises. Le design du DS collimator sera fige dans 3 semaines, sans quon en ait fait de simulation... => Discussions avec Marc Timmins pour les dtails
=> Action1 (HD and Impedance team): Try and simulate, during the next 3 weeks, the impedances for (i) the Phase 1 LHC collimator (checking the results obtained in the past by Alexey Grudiev), (ii) the LHC collimator with integrated BPM, and (iii) the DS LHC collimator. The idea is to do this time domain for the single-bunch wake-fields but also in the frequency domain to have all the trapped modes important for coupled-bunch effects.
- Concerning absences from CERN of ~ 1-2 hours (from time to time!) in the morning or in the afternoon working hours, it is not a problem for me and it is not necessary to fill EDH BUT please inform me and/or Delphine to be sure that we can cover you in case of accidents etc.
- Laurent Deniau (TE/MSC) will join us (ABP/LCU) starting from 1st of May and he will take over the role of MAD-X custodian (replacing FS, after a transition period).
- CST user group meeting. CZ went there last year, who could/would like to go? Action2 (EM): Identify the person who could/should attend the next CST user group meeting.
- LHC MDs web site => Submit MD requests through the sharepoint website: http://www.cern.ch/lhc-md => To submit a request for LHC MD time please do as follows:
1) Fill out WORD template (available for download from "shared documents" part of web site).
2) Save file with unique name, for example replace "FORM v2" by your name.
3) Upload the file into the "Shared Documents / 2011 MD Requests" folder on the web. You must be member of the e-mail list "lhc-md-user" and log in into the sharepoint web site for submission.
- DEADLINE: Please submit your requests for 2011 by March 16th. We will then go through the collected requests and organize a meeting for discussion on a coherent MD proposal for 2011, before it is taken to LMC for further discussion and approval.
- Chairmen: R. Assmann and F. Zimmermann & Scientific secretary: G. Papotti.
- Reminder on the dates for the different beams:
- In the LHC injector chain: https://lhc-beam-operation-committee.web.cern.ch/lhc-beam-operation-committee/minutes/Meeting2-22_02_2011/DeadlinesLHCBeams2011.pdf.
4) BE-IT meetings and outcome (FS): ppt
- FS showed a nice plot revealing the number of running LSF jobs (from SLAP Linux Cluster, for tracking studies) vs. time (since January 2005).
- ICE lxbatch Group:
- Before discussing with Bernd Panzer-Steindel (IT/DI): 66 132 jobs in parallel.
- After discussing with him => For 6 weeks (starting ~ 1.5 weeks ago): Upgrade by a factor 5, i.e. 330 660 jobs in parallel.
- Reminder on queues:
- The shorter the queue the higher the priority!
- 200 max per user in 1nw & 2nw
- 1500 in 2nw und 5000 in 1nw total in parallel
- Comment by BS: In fact the queues depend also on the processors and it seems that nowadays it corresponds to less time in reality => I imagine it should be renamed...
- MESSAGE: In case of any problem etc. => Do not hesitate to contact FS or Bernd Panzer-Steindel (IT/DI).
- List of BE-IT Needs:
- Tools on lxplus (SLC5) => Excellent support by Steve Traylen (very pro-active)!
- All relevant Fortran compilers available on Lxplus/Windows/Mac
- New NAGLIB installed including special SMP routines
- Missing static libraries provided by Harry Renshall
- In general no service expertise left in IT!
- Harry Renshall & Eric McIntosh honorary members of our group!
- All trouble, demands, requests etc => BE-IT forum (every ~ 2 months)!
5) LHC BLM (Humberto Maury Cuna and Octavio Dominguez Sanchez de la Blanca): ppt
- Most use BLM device in the LHC = (short) ionization chamber > 4000.
6) LHC BBQ (TP and BS): ppt
- BBQ measurement = Base Band Q (i.e. tune) measurement.
- The full name is 3D-BBQ => 3D = Direct Diode Detection.
- Reminder: PLL = Phase Locked Loop.
- BE CAREFUL: The signal reflects the tune from the most intense bunches (it is a peak detection ) and not from the bunches which the largest oscillations!
- We cannot measure bunch by bunch tunes with this system => Therefore, the beam-beam team (in particular) which needs bunch by bunch tune measurements relies on the Schottky monitor for that.
- Discussion during the meeting about "Baseband" => Reminder from Wikipedia...: Baseband describes signals and systems whose range of frequencies is measured from close to 0 hertz to a cut-off frequency, a maximum bandwidth or highest signal frequency. Baseband can often be considered as a synonym to lowpass or non-modulated, and antonym to passband, bandpass, carrier-modulated or radio frequency (RF) signal => Simplest definition: a signal's baseband bandwidth is its bandwidth before modulation and multiplexing, or after demultiplexing and demodulation. Note that the fact that the BBQ operates in the low frequency range, it is more susceptible to EMC.
7) Look at the list of Actions => POSTPONED TO THE NEXT MEETING. Please have a look and we will discuss this item in 2 weeks
8) Reminder on the determination of the the Head-Tail instability rise time in time and frequency domain (EM): pdf => This was not discussed during the meeting (but could be if needed).
9) Actions to be taken for the next meeting
- Old actions.
- New actions:
- Action1 (HD and Impedance team): Try and simulate (and compare), during the next 3 weeks, the impedances for (i) the Phase 1 LHC collimator (checking the results obtained in the past by Alexey Grudiev), (ii) the LHC collimator with integrated BPM, and (iii) the DS LHC collimator. The idea is to do this time domain for the single-bunch wake-fields but also in the frequency domain to have all the trapped modes important for coupled-bunch effects.
- Action2 (EM): Identify the person who could/should attend the next CST user group meeting.
10) Miscellaneous
- No meeting next week.
- The next (20th) meeting will take place on 16/03/2011 => Agenda:
1) General wall impedance theory for 2D axisymmetric and flat multilayer structures (NM).
2) Look at the list of actions: List of Actions.
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 02/03/2011.
