ICE Min meeting

Minutes of the ICE section

2nd meeting on Tuesday 20/07/2010 (15:30-17:00, 6/2-004)

ICE members: Benoit Salvant (BS), Christian Hansen (CH), Carlo Zannini (CZ), Diego Quatraro (DQ), 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), Werner Herr (WH).

Present: BS, CH, CZ, HD, EB, EHM, EM, EW, FS, GR, JLN, KL, NB, NM, OB + Dobrin Kaltchev (from TRIUMF).

Excused: DQ, MCAP, WH.

1) Comments on the minutes of the 1st meeting + Actions

- No comment to the minutes except from WH for Action 2 (see below).

- Action 2 (WH) postponed as the top priority for the moment is to run the LHC machine.

- Action 1 (FS) => Done (see point 4))

- Action 3 (everybody) => Still waiting for some contributions.

2) Decisions on the ICE organization (room, time, etc).

- All the next ICE section meetings will take place on Wednesdays, every week, in room 6/2-004 (I reserved it until the end of 2011):

08:40 - 09:00 (20 min) => Closed part (only for the members of the ICE section) => General info, hot topics, etc.
09:00 - 10:30 (1h30 max) => Open part (with interested colleagues from other sections, groups etc.) => "Collective effects meetings" (replacing the "impedance meetings"), where "informal" presentations (in particular on impedances, space charge, coherent instabilities, ecloud and beam-beam) will be given and discussed in detail.

- When I will send the invitations each week, I will send only those to the 2nd part and I will send them also to the LIS and LCU members and members of the "impedance team". Please tell me if I should add other colleagues and feel free to forward the invitations to any interested person, depending on the subject.

- The CERN impedance web pages (as well as the ones for beam-beam etc.) should be maintained and linked to the ICE section web page.

3) General infos

- ABP organigram still under discussion and therefore not yet on the web.

- Web page still needed for the ICE section => In my personal web page for the moment (https://emetral.web.cern.ch/emetral/ => Section XIV)).

- Review of Proposed LHC Collimation Work in DS for 2012 (http://indico.cern.ch/conferenceDisplay.py?confId=100156) => Project approved. Reminder on the goals:

1) Review the overall priorities and the schedule defined in the LHC collimation project.

2) Review the work in the IR3 dispersion suppressors, proposed for 2012.

3) Take a decision on starting the work for a 2012 collimation upgrade in IR3:

a) Upgrade of DS.

b) Installation of vertical collimators into IR3 warm part.

- Reminder on holidays: On September 30th, all the days above 30 will be lost => Take them before!

- The high luminosity upgrade should be led by Luccio Rossi with Oliver Bruning acting as his deputy.

- Request from William Andreazza (BE/BI) for the PS wire scanner (new universal tank etc.) => They need some recommendations for the ferrite to be put (deadline: Beginning of August) => BS will follow this up.

- Concerning the LHC, it seems that the last fill was quite good (without the huge losses in stable-beam conditions, which could happen in the past) but the one before suffered from some huge beam loss => Picture of the last 2 LHC fills. The huge losses on B1 occurred when switching on the Xing angle (non closure).

- Reminder on the LHC procedure at top energy to put the beams into collisions (tbc):

- Ramp to 3.5 TeV/c and then put the octupoles to K3F=K3D=-6.

- Correct orbits, tunes, coupling and chromaticities.

- Squeeze to 7 m.

- Collimators IN to do a squeeze down to 3.5 m.

- Squeeze to 3.5 m.

- Put Xing angles => 2 knobs to put -100 microrad (half angle) at IP1 and +100 microrad at IP5. Reminder: the nominal full Xing angle at the IP is 285 microrad. Then correct the orbits again. One could imagine that some losses could appear during this process and that the quality of the orbit plays an important role.

- Collapse the separation bumps (of 2 mm) => There is a Sequence to Collapse + Introduce the values of the last Lumi scans. Then correct the orbits again. "Stable-beam" condition can be declared after this step or the following one if the luminosity is very poor.

- Lumi scans => Either automatically (applic from Simon Mathieu White) or manually. Since the last few fills this is done manually because some losses were observed after some lumi scans and because it seems to be faster (according to Mirko, OP, 19/07/10, as we start with a situation close to the optimum one). Once the luminosity has been maximized (using the BRANS) in H and V and in 1 and 5, physics can start! Reminder: The BRAN (Beam RAte of Neutrals) detector monitors the collision rates in the high luminosity interaction regions of LHC (ATLAS and CMS). This Argon gas ionization detector measures the forward neutral particles from collisions at the IP (http://accelconf.web.cern.ch/AccelConf/IPAC10/papers/mopec020.pdf).

- It seems that now the transverse dampers are ON during stable-beam operation and that the octupoles are removed (after discussin with W. Hofle, tbc). The transverse dampers are thus ON at injection and during the ramp (with injection tunes), switched OFF at top energy and switched ON again in stable beam with the collision tunes. The next step would be to have them ON also during the time needed to put the beams in collisions (but the tunes are changing during this time and it is more difficult).

4) Action 1 (FS)

- FS showed a nice example where a "Christmas tree" can be observed, considering only single-particle dynamics => Used a simple FODO cell + a sextupole + multipole components. The tunes were set to qx = 0.202 and qy = 0.31, and the study was performed in the horizontal plane with a negative detuning, meaning that when the amplitude is increased the tune decreases and therefore the particle approaches the 5th order resonance 0.2.

- Increasing the amplitude many lines appear and the lines also become thicker => SIXTRACK input: fort.2 and fort.3, Evolution of the (5,0) resonance (x Axis just amplitude steps => Last step = 10 mm), Lines spectrum (numbers in the legend are in mm).

- BS asked whether the observation made in the LHC could be of such a nature. Comment from EM (after the meeting): the Christmas tree observed in the LHC is linked to a coherent instability (from the whole beam).

5) Round table (everybody)

- BS, CH, CZ, DQ, HD, EB, EHM, EW, FS, GR, JLN, KL, MCAP, NB, NM, OB, WH.

- EW mentioned in particular that she got the following remark from the international advisory panel (IAP EUROnu): "... try to benchmark collective effects estimations and simulations against experimental scaling with heavy ions at GSI and BNL" => To be followed up.

- FS mentioned in particular his co-responsibility to organize possible experiments at the Tevatron at the end of run II in 2011.

- Dobrin Kaltchev (from TRIUMF) was also with us:

- No collaboration with CERN this year. New collaboration possible next year. This is due to a new project at TRIUMF, which was financed last month, called ELINAC.

- DK is doing BBU studies these days but he worked in the past on beam-beam (weak-strong) with SIXTRACK.

- We should send a request directly to Rick Baartman (TRUMF) for any future collaboration.

6) Actions to be taken for the next meeting

- No other actions than ones of 1st meeting.

7) Miscellaneous

- Links to useful web pages:

- Old RLC section on "R&D and LHC Collective Effects": LHC nominal perfomance and LHC upgrade.

- LIS and LCU sections.

- Low impedance hardware design and CERN Impedance Database.

- Ecloud.

- Beam-beam and beam-beam compensation.

- Optics database.