- Action 1: FS will give some references about these observations or simulations (see text above) => Done on 20-07-10.
- Action 2: WH will make a detailed review of all the beam-beam predictions for the LHC (it is already foreseen for the 3rd meeting, i.e. not the next one but the one after) => Would be perfect to train everybody and try and understand what happens in the LHC in stable-beam conditions! => Postponed.
- Action 3 (everybody): At the next meeting (see point 4)), we will have a round table to present everybody and explain what the status of their activities (linked to our section) is: successes, issues and next steps. I would like everyone to prepare a short text which he could send me (either before the meeting or just after the meeting for the minutes), including links to all the web pages we should have in our ICE section web page. Note: For those who cannot come to the next meeting (or to a meeting where we have a round table), could you please send me the small text before the meeting and I will read it to the others? Many thanks in advance! => Still waiting for some contributions (on 23/07/10).
- No other actions than ones of 1st meeting.
- No other actions than ones of 1st meeting.
- Actions of 1st meeting.
- Action 4 (NM): Study the effect of the bunch length on the single-bunch and coupled-bunch tune shifts at 7 TeV/c in the LHC (with nominal parameters). In particular the case of a sigmaz = 6 cm (instead of the nominal 7.5 cm). A reasonable Qprime of ~ 2 should be assumed => Done on 15-09-10 for the coupled-bunch study.
- Action 5 (GR): What are the synchrotron periods at the 3 PSB instability timings? => Done on 15-09-10.
- Actions of 1st meeting (14-07-10) + 4th meeting (04-08-10).
- Action 6 (EM): Invite Christine Vollinger (BE/RF) to present the material characterization method and the ferrite's results at one of the next ICE meetings => Done and Christine agreed. Exact date for the presentation still need to be found.
- Action 7 (NM): Answer to Fritz Caspers' requests:
1) Plot of all (longitudinal and transverse) impedances for a graphite tube (L = 1 m, b = 2 mm) without and with copper (or Titanium) coating (5, 10 and 20 microm) at 7 TeV/c => 2 displays: Log (as usual) + Linear over 1 or 2 decades (=> several plots to cover all the interesting frequency range). We could also perhaps redo the same thing in the real case of flat chambers.
2) Computation of the associated tune shifts (single-bunch and coupled-bunch) at 7 TeV/c.
3) Same as 1) but for beta ≠ 1.
- Actions of previous meetings.
- Action 8 (BS): Perform HEADTAIL simulations to try and reproduce the losses observed in the LHC at 3.5 TeV/c during chromaticity measurements and see if this can be explained by a head-tail instability. => Done.
- Action 9 (BS): Organize "impedance meetings" with Carlo and Hugo (and other interested people) via webcast with our impedance colleagues from GSI and TU Darmstadt, every ~ 1-2 months => Started: the 1st meeting was organized on 14-09-10. => Done.
- No new actions.
- No new actions.
- Old actions.
- Action 10 (BS and NM): Perform HEADTAIL simulations to see if the single-bunch instability threshold, with the IR3MBC collimators, can be increased sufficiently above the ultimate intensity with Landau octupoles. => Done but still some studies to be done over more turns for the instability and to analyze in detail the emittance growth.
- Action 11 (CH): Update the comparison between the analytical formula (essentially the coasting-beam formula with peak values), MOSES and HEADTAIL, for the beta-beams studies. => Done.
- No new actions.
- Old actions.
- Action 12 (BS and NM): Try and answer to FritzC's comment (the longitudinal impedance is wrong as it does not allow for a voltage drop in DC which he believes we should have).
- Action 13 (GR and ecloud team): Redo simulations and perform MDs to check the effect of the transverse emittances on the ecloud build up.
- Old actions.
- Beam-beam tools needed, in increasing order of complexity (see 3rd ICE meeting, 28/07/2010):
- Action 14 (FS and beam-beam team): Possibility to make some tracking with SIXTRACK when betax* ≠ betay*, called flat beams. It is worth mentioning that 3 cases might be referred to as flat beams: betax* ≠ betay* (the case of interest here), epsx ≠ epsy and flat longitudinal distribution. In the case of betax* ≠ betay*, the output of MADX is fine (it is well computed) but the problem is then the data transfer between MADX and SIXTRACK => Not all the parameters (betas, sizes, intensities) are transferred. For the other two "flat" cases it should be fine. => Done (EmmanuelL) but to be redone as it seems there are some issues (see beam-beam meeting on 11/12/2013).
- Action 15 (FS and beam-beam team): 6D beam-beam lens (in fact it is 4D + time dependence) => We need this even if the strong beam is a single particle. There is a lens in SIXTRACK but it is not debugged. For instance it is not clear if the crossing angle is defined for the strong or the weak beam.
- Action 16 (FS and beam-beam team): Effect of the 6D beam-beam lens on the strong beam => Both the divergence effect of the strong beam and crab tilt.
- Old actions.
- Action 17 (All people responsible for an equipment during the 2010 ecloud MDs with 50 and 75 ns beams): Present a LHC equipment: How does it work? Where is it physically? Data saved? Resolution? Mode of operation? etc. => Done.
- Action 18 (FZ and ecloud team): Redo in the LHC the same analysis as the one done in the past in the SPS by DanielS (Constrain parameters by benchmarking multiple measurements, change distance between trains & use relative measurements to deduce deltamax and R and possibly Emax).
- Old actions.
- Action 19: All people responsible of a LHC equipment during ecloud MDs in the LHC in 2010 => Send to EM a contribution for a MD note by the end of March. EM to publish then the MD note.
- Old actions.
- Old actions.
- Action 20 (for HDWG): Effect of Q" on the head-tail instability of the LHC.
- Action 21 (for HDWG): Addition of 2 localized impedances (effect of the transverse betatron phase between the 2).
- Action 22 (Sandra Aumon and MD team): Optimize the working point and linear coupling on the long injection flat bottom to have minimum (no) transverse emittance growth and beam stability (as linear coupling was optimized in the past for the ~ nominal LHC beam!).
- Action 23 (Sandra Aumon and MD team): Try and redo the coherent tune shift measurements with the same bunch length at injection and top energy.
- Action 24 (Sandra Aumon): Remove the incoherent space charge contribution from the images. => After discussion between Sandra and EM, it seems that what Sandra did is OK as she evaluated the "total" impedance, i.e. dipolar + quadrupolar => Nothing to be done.
- Action 25 (EM): Answer to the question from Sandra Aumon => 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 on 24/02/2011 after discussion with him and 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. Reviewing this action, FritzC mentioned also some cavities with other impedance switching mechanisms (pin diode ON/OFF instead of relay gaps open/closed => To be looked at in some detail at some point).
- Old actions.
- Action 26 (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.
- Action 27 (EM): Identify the person who could/should attend the next CST user group meeting (deadline for abstracts submission is 31/03/2011).
- Old actions.
- Action 28 (BS): Check the frequency method to deduce the head-tail instability rise-time with the HEADTAIL simulations BS did in the past for the LHC head-tail instability observed last year.
- Old actions.
- Action 29 (HTWG): Check that idea from ElenaS to measure and simulate the case of batches of 72 bunches spaced symmetrically in the SPS to avoid ecloud and then put them closer and closer to see the effect on the coupled-bunch instabilities => May be with this method we could disentangle the contributions from impedance and ecloud. To be followed up.
- Action 30 (EM): To check what we can do for the visit from Vladimir Kornilov (GSI).
- Action 31 (impedance team): Discussions to insert a shield in the SPS, which is coated with carbon instead of coating the chamber itself (for the half of dipoles whose aperture is less a problem in the SPS) => Follow this activity as Mauro Taborelli will come with some questions at some point (after the proper choice of material/thickness etc. to avoid Eddy currents etc.) + Send to Mauro the formula for the power loss (=> Done. EM sent the formula, with explanations and a numerical example, on 30-03-11).
- Action 32 (OB): For the previous idea discussed in Action 31, check the maximum aperture we could remove in ~ half of the dipoles, to give a value to Mauro Taborelli.
- Action 33 (impedance team): BS presented an update on BPM impedance in the SPS at the last SPSU => Check why the resonance at ~ 2 GHz, above cut-off according to FritzC, has such a high Q, which would mean that the mode does not couple to boundaries etc (to be checked by changing the boundaries).
- Action 34 (impedance team): Try and answer to a request from ElenaS in ~ 1-2 months: Study the SPS BPM enameld flanges(all, i.e. ~ 200, SPS BPMs are electrically isolated by enamel flanges (one in each side) => We could also contact Yoshihiro Shobuda (shobuda@post.kek.jp), who developed a 3D analytical model for small gaps, to compare with our simulations.
- Action 35 (impedance team): The deadline (from Marc Timmins) for providing all the manufacturing drawings for the DS collimators to the main workshop is end of April. So the models will be frozen at the latest at that time.
- Action 36 (impedance team): Review of the impedances of tapers (IN and OUT).
- Action 37: All the ICE members (who want to present a paper to IPAC2011 and have someone to present the results there) to send the abstracts to Oliver Bruning and EM on Monday 4 April 2011 at the latest.
- Old actions.
- Old actions.
- Action 38: EM to make the follow up of the PS WS in SS68 where ferrite has been installed during the technical stop in week 13 without any recommendation from our team.
- Old actions.
- Action 39: FS to review in detail the SC and BB (HO) tune footprints.
- Old actions.
- Action 40: HD and OB to measure the (5) impedances of the new PS wire scanner, in May.
- Action 41: HD to follow up the LHC TDI, due to some hints that the impedance could be larger than predicted (factor 2-3?).
- Action 42: BS and NM to follow up the LHC DS collimators => Email from Nicolas Provot: "Dans le cadre du projet collimateur DS, 4 chambres vide pour une longueur totale d'environ 6m viendront s'inserer dans le LHC. Ces chambres seront munies d'un depot de cuivre de 0.5mm d'epaisseur, cela pose-t-il un quelquonque probleme d'impedance vis a vis du faisceau?".
- Action 43: Ecloud team to follow up the ecloud simulations and the recent heat loads measured in the LHC. Can we quantify the effect of the scrubbing run?
- Action 44: EM to follow up the power loss from the resistive wall measured by Laurent Tavian in different half cells.
- Action 45: EM and MG to follow up:
(1) Laslett tune shifts => Where are the poles? Estimations from Francesco Ruggiero (Eq. (8) of http://cdsweb.cern.ch/record/279204/files/p83.pdf): Expected incoherent tune shift to be ~ - 7E-4 in V and ~ + 7E-4 in H for 100 bunches with ~ 1.2E11 p/b (increases linearly with the number of bunches). This has to be compensated in the LHC.
(2) Use of octupoles (Landau or spool pieces) at injection? What is the current we could use for DA consideration and current stability?
- Action 46: HD to check with Jan Uythoven who mentioned some heating on the LHC injection kicker (MKI). To which level? Is it in agreement with our predictions? => To be followed-up and compared to predictions.
- Action 47 (NM): Prepare an update of the impedance model (and related instabilities) for several collimators' settings (to be sent by the collimation team), for the collimation review on TU 14/06 and WE 15/06. .
- Action 48 (impedance team): Do we know the electrical field at the surface of the primary collimators for the nominal LHC? There could be electron(-cloud) field emission for high field in the LHC (question from FrankZ to be answered).
=> Preliminary answer from NM on 31/05/2011: For the moment, one can compute the EM fields in a cylindrical collimator and in the frequency domain only. The generalization to the flat case and to the time domain is possible but will take some time (many other priorities).
- Action 49 (impedance team): Evaluate impedance vs. bunch length (to try and understand LHC's observations of heating/outgassing). The bunch spectrum was measured and it will be used to review the estimates.
- Action 50 (ecloud team): Study the stabilization of the fast ecloud instability at LHC injection with octupoles (instead of chroma): Which octupole's current would be needed?
- Action 51 (HDWG): Study with HEADTAIL the head-tail and TMCI instabilities of the LHC with a double harmonic RF (still without space charge first) => We will add a 2nd RF voltage from 800 MHz RF cavities equal to half of the RF voltage from the 400 MHz RF cavities and study both regimes of bunch lengthening and bunch shortening. Comment: Look also at an old paper from S. Myers which showed that the threshold goes down + recent IPAC11 paper from Y.H. Chin.
- Action 52: EM to compute the LCBI rise-time for the case considered by AlexeyB (or similar) using Sacherer's longitudinal formula => See May resistive-wall drive longitudinal coupled-bunch instability? (Alexey Burov).
- Action 53: Impedance team to check the impedance and the induced heating of the LHC BGI as some heating might have been observed.
- Action 54: Ecloud team to study the ecloud build-up in some LHC chambers with very large diameter (800 mm), after some observations made by the vacuum people.
- Action 55: Impedance team to compute the impedance for the PS dummy septum (for MTE) => Will/could be studied by Mauro Migliorati when he comes to CERN as PJA to work on PS impedance.
- Action 56: Impedance team to provide the current LHC longitudinal impedance model.
- Action 57: 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 58 (reminder to all IPAC2012 primary authors): Upload all the ICE abstracts to the link provided by DelphineR by Friday 25/11.
- Action 59: ICE students to inform EM about their intention to apply for a grant for IPAC2012.
- Action 60 (all ICE members): Who would like to attend HB2012 (Beijing, September 17 to 21)?
- Action 61: 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 62: Impedance team to follow many equipments (UA9 goniometer, LHC RF fingers and many LHC equipments, new instrumentation in the PSB, etc.).
- Action 63 (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.
- Action 64: BS-JLN-FritzC-EM to follow the VMTSA RF fingers closely at the beginning of 2012 with top priority.
- Action 65: BS-EM-FritzC to send a summary to the ALPHA team.
- Action 66 (Impedance team ): Develop impedance models for the PSB and PS => Some people (collaborators and new staff) will be able to work on these subjects soon...
- Action 67 (Impedance team): Installation or not of ferrites on the PS WS (question from William Andreazza)?
- Action 68 (Impedance team): Follow-up of the new tune PU for the PS (with Marek Gasior).
- Action 69 (Impedance team): Send a sample of the TT2-111R selected ferrite for the new TCTP to vacuum people (Vincent Baglin) to measure the outgassing properties of the ferrite as a function of temperature.
- Action 70 (Beam-beam team): Try and fully understand how the beam could be unstable (due to beam-beam) on FR 06/04/12 with the wrong LHCb procedure.
- Action 71 (Impedance team): Set up a common procedure for our RF heating estimates for sharp resonances.
- Action 72 (Impedance team => Maybe OB): Put some info on the impedance web page about all the materials we use in our impedance simulations (different types of ferrite etc.) => For everybody to be able to use the same data.