Minutes and Summary

Main purpose of the meeting: Main topics of the meeting are near term schedule, schedule 2024/2025 and scenarios for the ramp-up fills.

 

Filip Moortgat (Introduction)

• Recent LHC activities

  • Many activities performed since Friday (see slide 3)

  • A test on the only remaining crystal collimator (B2H) was performed and has shown good performance (see slide 4)

  • Electrical incident happened in P4 and since Saturday 1 April night no beams are possible to inject/circulate. Expect beam conditions back on Tuesday evening (see slide 5). All in all, we can consider about 3 days lost. 

  • A previous incident affected the B1H crystal incident. The motor got stuck and the collimator remained in the beam line. An intervention took the collimator out; the plan is to re-install during TS1, as a decision driven by various arguments (see slide 6).

    • TS1 will likely be extended by 1-2 days (TBC and discussions ongoing).

• Impact of the incident is to be evaluated but the 2023 commissioning schedule is still evolving.

  • Operations can likely start again on Tuesday 4 April afternoon/evening

• Other incidents happened but did not affect operations

  • Fast discharge of CMS magnet

  • LHCb dipole tripped

• First 450 GeV Stable Beams will happen with 3b circulating and 2 colliding at each experiment. 

  • Unclear yet if it is possible to have it before Easter week-end, but currently scheduled for Thursday 6 April and LHC will try its best to provide so

  • Important to have feedback regarding luminous region by ATLAS/CMS

    • Michi Hofstettler underlined the importance of having both lumi and lumireg Massi’s files as they are both important for the debugging.

• Schedule for 2023 has been clarified, still in draft version and comments are welcome

  • Main changes: very high beta* scheduled for 18-21 July and VdM split in 2 parts, first for ATLAS/CMS on 26-27 June and LHCb/ALICE on a date in September.

• Regarding requests for startup from experiments (slide 10), main changes are:

  • 5h fill at very low mu with 64 isolated bunches planned in // to the VdM scan of ALICE/LHCb

  • Silvia Franchino commented that ATLAS is ok with this, but the VdM plan is still under discussion

• MPP+OP are discussing the ramp-up fills (slide 11) and the rules are being decided

  • Slide 12 contains the first (draft) filling schemes

  • They follow the rules from MPP+OP and provide 1 INDIV to LHCb and 1 INDIV to ATLAS/CMS. Filip asked if ALICE also wanted an INDIV. Sarah Porteboef says she will check with experts. 

  • Silvia commented that ATLAS would prefer to have two INDIVs, at the beginning.

    • The 12 bunches-train (non colliding) are also present for ATLAS/CMS.

  • Niels asked if the 400b is done before or after scrubbing. Jorg responded that they will decide close to when it will happen.

• Rende Steerenberg has prepared 2024 and 2025 schedules

  • See slide 13, comments are welcome.

 

Mario Deile (90 vs 120 m)

• Both options are possible, but need a pileup between 0.04 and 0.1

• Mario pointed to a BPM that would dump with too low intensity

  • Jorg says that given the few bunches this can be masked

• Emittance would be easier to handle at beta* of 120m, as at 90m blow up would be needed and operationally would be more complicated (unnecessarily)

  • Filip commented that Ilias is developing the optics and he is ok with both solutions. Filip then asked for confirmation that we will run at 120m and it seems now the accepted baseline.

• Filip also commented that Ilias has discovered an issue with ALFA during the 3/6 km run. Ilias is suggesting to do a a 3/3 km run. 

  • Filip asked Mario what TOTEM would prefer

  • Mario says it should be just feasible, but it is still to be understood

    • Physics justifications point to having a 6km in V run as well, but we will come back to it for a more definite decision

  • Stephane commented that one possibility would be to relax the strict phase advance constraint. Like that it would be possible to increase beta* while keeping the optics unchanged.

    • To be followed-up.

 

Silvia Franchino (ATLAS)

• Will there be non stable Beams collisions? 

  • Jorg commented that yes, but the program will be compressed as much as possible.

• Observed a shift of beam1 and beam2 by 4 and 2ns respectively

• ATLAS is interested in participating in the VDM cycle with nominal bunches

  • Preferred during daytime but ok tobe at night

  • Request to be informed if they move from the current slot (10th April afternoon)

• ATLAS also asked to clarify when magnetic non linearities scan be done

  • Proposed to do it on the 10th April

  • Jorg will look into it and see if it is possible and when, given that no collisions are asked for IP1 and 5 and that implies another cycle (which news to be slotted and adjusted).

    • Filip asked how long it would take to perform the scans. Witold responded around 3 hours from the time we started scanning. 

    • To be followed up. 

• More follow-up on forward detectors on slide 6

  • Still unclear if the 2mm opening on TCL6 can be agreed upon

  • Roderik confirmed that we can go in this direction and agree at the next Collimator Working Group

• A question regarding if preparation for high beta* is affected by the collimator incident was raised by Silvia

  • Roderik responded that the critical ones for the very high beta* are the crystals in the vertical and those are unaffected. The idea would be to run with standard collimation in the H and crystal in the V.

  • Filip asked if anything changes from collimation perspective if the very high beta* would become 3/3 (instead of 3/6). Roderik responded it doesn't change much.

 

Elena Dall’Occo (LHCb) 

• Problem with the LHCb spectrometer is fixed and can be powered on anytime

  • Requested to power on with positive (DOWN field) by default unless asked otherwise

• Stephane and Jorg will clarify the uncertainty on the convention regarding the internal crossing angle

  • This was clarified after the meeting and LHCb/LHC agreed on the convention

• Request for daytime (non holidays) Stable Beams is taken

  • Extra Stable Beams after Easter during daytime if cannot be done on Thursday

 

Gaelle Boudoul (CMS)

• CMS confirms the beam shifts seen by ATLAS

• Issues with the magnet is resolved and it was brought up to 3.8T after the splashes

  • No impact on splashes data taking

Sarah Portebouef (ALICE)

• ALICE needs a 5h access to replace a fiber that was damaged just before the end of the YETS

• No problem to move the VdM to September

• Slide 4 and slide 5 outline the various configurations for the ALICE magnet runs

  • Dates are tentative as they depend on the planning. The key point is when going from +/+ to -/- and vice versa, they will do low field data taking

    • Jorg commented low field but not zero as solenoid is critical for electron cloud

    • Sarah highlighted that 0/0 field to be done with 75b only, the other runs are with low field, but non-0

• There are no obvious signs of the impact of the TCLIA collimator with crossing angle at 100urad vs 56urad.

  • Roderik asked when the final analysis will be available to go ahead.

    • Sarah said that even though final analysis is still to be concluded, the conclusions from the slides are solid and can be taken as baseline.

• Sarah asked if once B1H is reinstalled, will there be a commissioning exercise like with B2H?

  • Jorg and Roderik commented that yes that would be necessary.

  • Roderik highlighted that the highest energy in PbPb can only be reached if all crystal collimators are in place and functioning.

    • This test in this sense is quite important and should be done as soon as the collimators are reinstalled

 

Next LPC meeting in two weeks (17 April)