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LPC meeting summary 20-03-2023 - final |
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Main purpose of the meeting: Dedicated to discussing the 2023 LHC start-up schedule, the special, ion and pp reference runs as well as feedback from the LHCC.
Introduction (Filip Moortgat)
Approaching first beams in the LHC and restart of operations
DSO test is done
Caverns to be closed on Wednesday noon
First beams expected on week-end earliest
Note after the meeting: now obsolete following an incident with B1H crystal collimator. Currently first beams are expected on Wednesday 29th.
Starting collecting request from experiments during startup
Asked to obtain more information regarding the justification of the 5h fill at low mu for ATLAS
Silvia Franchino responded that this is a new run with new measurements
Filip asked to have more detailed feedback
Silvia said this will be done
ALICE 0 field is expected to be done this at 75 bunches ramp-up fills
Niels noted that LHCb is not interested in splashes
450 GeV fills is limited to 3 or 4 bunches, at very most 12 bunches
Currently planned for 6,7,9, and 18 April
Stable Beams filler-fills may happen, but depend on requests
First collisions with no Stable Beams will be on Wednesday 5 April
Note after the meeting: new schedule is being drafted.
Jorg commented that this year it would be preferred to run with crossing angle at 450 GeV because possibly it should be possible to cross-check the difference between ATLAS/CMS already at 450 GeV
Can ATLAS/CMS determine the beam spot if the LHC runs with crossing angles?
Pileup would be low, so the question if this can be done within the allotted time
Gianni Masetti from CMS commented that it seems ok for beam spot determination
ATLAS will look into it.
If we stay below the 12 bunches, Roman Pot can be inserted without BBA
Discussion has started on ramp-up fills
Merged one step (300+600) into a single step of around 400
Plan to use 36b trains for 400b
Could do the first two steps at 400b with 36b trains and then last step to move to 8b4e (7x8b4e + 2x36b) for last fill?
Then move to 8b4e structures
Intensity per bunch will be kept at 1.4 x 1011 ppb until ~1200 bunches
There will be a dedicated MPP meeting on Friday March 24th
Witold asked when the 3/12b fills would happen
Jorg responded the schedule is still under discussion. The first step is close to a week-end, the last week of April.
400b could be before scrubbing, depending on schedule
Federico Alessio asked if there are many items expected for LHC commissioning during the intensity ramp-up
Jorg answered not much expected extra commissioning after the recommissioning period
INDIVs are always present for LHCb and ATLAS/CMS
Optics are ready for the very high beta* runs
Will be discussed in a special Run3 WG meeting on Friday 24th
Ion energy was decided to go for the higher value (6.8 Z TeV, i.e. 5.36 TeV)
This choice may be reconsidered in case the crystal collimation would not perform as expected
Reyes also had calculated first estimates for the pp reference runs parameters
beta* is to be checked because not sure if we can use the same optics as the standard pp ramp-up
Stephane Fartouk commented that b*=3.5 should be ok aperture wise and it can be produced easily for IP1 and 5
Jorg commented we may need to redistribute the points. He also commented that in ALICE there is no squeeze, standard optics at 10 m, LHCb has the same beta as IP1 and 5.
Regarding the pp reference run, it is expected to use the same trains and filling scheme as for the other fills, we can just go for 36b trains (no need for hybrid)
ALICE commented that they will take data at higher interaction rate so it would be better to have more bunches to not increase peak mu
Pileup can go up to ~6.6 for emittance of 2.5 with 1.8e11 ppb
Given the crossing angle in ALICE, Stephane asked what polarity ALICE would like to take data
Sarah answered +,+
Witold asked if it is possible to have lower intensity but larger emittance
Jorg will pass the question to the injectors
Slvia asked if 1.8e11 ppb is a given
Jorg commented we will get whatever we reach at end of the year, with the declared aim of reaching 1.8e11 ppb
Filip discussed some LHCC recommendations
Current end date of Run 3 is now established to 17 November 2025
Still under discussion, but LHCC recommended to keep end date open
Stable Beams time should be maximized
This message is to both LHC and experiments, so extra runs shall be discussed and checked
75 fb^-1 in IP1 and 5 is already a very challenging goal for 2023
No changes for the schedule in 2024, same end date of 28 October as for original scheduler
Not yet decided on the ion run flavors
Maciej asked if the high beta* commissioning can be anticipated as early as possible
Jorg commented he does not know if the squeeze is already prepared. Stephane will check. Maybe there will be something soon, but currently there is nothing foreseen.
Can always be added but this is at the cost of Stable Beams.
Could it fit in a spare slot?
It’s not only optics, but also crystal collimation. So once we are prepared we can discuss further.
Early emittance scan with VdM optics could be foreseen
Witold asked how far could we be allowed to scan?
Jorg answered the usual limits (whatever that means)
Gianni Masetti (CMS)
CMS interested in O(20) splashes per side
CMS expects to be able to provide beam spot position few hours after the run
Sarah Portebouef (ALICE)
Regarding the feedback on ZDC acceptance, Jorg said the response is not necessary within 2 weeks, the value can be changed later on
Silvia Franchino (ATLAS)
Need to have VdM validation earlier than few days before VdM in order to prepare
If it’s not done in Stable Beams then likely the magnet non-linearities scan be done earlier. Ok to go for +/- 3 sigmas, but not with 50 bunches.
No problem to have +/-2.5 sigma per beams regarding second question on slide 2
Message about non-factorization effects on slide 3 will be transmitted to the injector experts
Regarding the TCL6 collimation position (slide 5)
Roderik Bruce responded that if we go to 3mm it is unclear how much we would gain (maybe 25%). Discussion ongoing. Roderik also believes that we cannot get a factor 10 by simply opening the TCL6 to 2mm
Doing the third bullet point o slide 6 (validation after 90m b* ru) after a special runs does not seem plausible to Mario Deile as experts will be tired and people are the same.
Regarding slide 7 in which AFP would lose entirely acceptance with the inversion of the triple polarity, Stephane Fartouk commented that there should not be conclusions at this point, as the optics will still be developed. Maciej asked for newer optics and Stephane will provide a new version with more protons going thru AFP. The current optics are a first attempt.
Maybe in 1 or 2 months with certified optics
Maciej stressed that optics needs to take into account AFP acceptance
Niels Tuning (LHCb)
LHCb would prefer Vdm in week 38. Discussion is ongoing and a proposal will be put forward.
AoB
Witold asked for clarifications regarding the recovery from the high beta after TS1, that should be half a day. The schedule for the very high beta* is not yet finalized.
BSRT calibration fills will happen. David responded that they do see the wire scanners in their analysis, but then they would do a longer scan without the wire scanners. CMS is still interested in participating in the fill.