Minutes and Summary

Main purpose of the meeting: Machine commissioning plans and preparations for 2022 special runs.

1) Introduction (Brian Petersen)

- Heavy Ion running during Run 3: discussion on pros/cons of having 4 weeks of HI runs each year during Run 3, versus having no HI run in 2024 and an 8-week HI run in 2025.

Discussed with spokespeople of LHC expeeiments and DRC on Feb 9th and preference was to have 4 weeks of heavy Ion periods during each year of Run 3 will.

To be confirmed with accelerator management.

- crossing angle polarity in IP1:

crossing angle needs to be flipped regularly to even out radiation damage to IP1 triplet. Plan was to start with - polarity as Run 2 was mostly +.

Alternative could be to start with + in 2022/2023, which could avoid a flip in middle of 2025 to equalize dose. FASER needs YETS to change position in case of polarity flip;

currently set up for - polarity. Proposal to stick with original plan (- polarity in 2022). Also discussion in next LMC.

- as beam approaches, LPC meeting will become more regular. Please keep Monday 14:00 slot reserved.

Next meetings scheduled for March 14, April 4, April 25.

2) LHC start up plans (Jorg Wenninger)

- powering ests in full swing (all sectors except S23). Sectors 34, 45, 56 and 78 have reached 6.8 TeV + margin, 1 quench at FT in S56.

- 6 machine coordinators for LHC. Almost same team as in 2018. Coordinators will work in tandem from week 15. Morning meetings will start on Tuesday March 22nd.

Daily meetings will start in week 14.

- DSO tests (also experiments!) on March 25th. From then, machine and expts closed with exception of 3 day access in week 14 (access to be negotiated with machine coordination).

- week 15: start of beam

- week 24 or 25: first stable beams in 2022 (media event).

- bulk of machine checkouts in week 13, final tests end of week 14. 9 weeks of checkout foreseen.

Action: BIS inputs of experiments must provide beam permit (no interlock).

If you cannot provide this, please let OP know asap.

During phase of checkout, expect change of energy, beta*, beam modes, … Post mortem events. Accelerator mode will be switched by week 14 (tbd).

Draft schedule of commissioning activities: see google spreadsheet.

1 shifter only. Assume no

- ATLAS and CMS magnets expected to be on from day 1. For ALICE and LHCb: withc on durnig injection setup phase with nominal bumnch (week 4), then say one.

- splashes: 2 shifts of splashes foreseen in weeks 1-2 of commissioning. More can be negotiated.

- finding collisions:

Summary on slide 11.

Q (Trevor, ATLAS): collisions at 450 GeV

one as soon as possible, other one not too far from 13.6 TeV c

Q (Witold): collisions at 900 GeV: with crossing angle oft not?

A (Jorg): prefer with crossing angle. Overhead for no crossing angle would be 0.5-1 shift.

Q (Gianni, CMS): machine mode for first week of commissioning?

A (Jorg): From past experience: keep in “shutdown”.

Q (Gianni, CMS): first commissioning of beta* leveling even with low #bunches?

A(Jorg/Stephane): yes. PU per bunch crossing will be the same (< 60). No limit of cryo with low #bunches though, so we can go down in beta* rather fast.

3) Preparations for 2022 special runs (Ilias Efthymiopoulos)

Requests:

- 2022: VdM runs for lumi calibration (also for LHCf), high beta run (90-120m) for TOTEM (ATLAS/ALFA will participate)

- 2023: VdM runs for lumi calibration, very high beta run (3km, 6km) for TOTEM (ATLAS/ALFA will participate)

Overall strategy: develop optics compatible with ATS optics used for standard runs.

Status: VdM optics well advanced, high beta optics in the pipeline.

Summary:

Q (Witold): for VdM scans need to be able to move the beam in x-y by 2-3 (even 4) sigma per beam.

Can the new optics scan in the same range?

A (Ilias): the range is the same, see slide 7.

Q (Helmut): for high beta, there were already high beta run meetings in which we converged on the optics. Gave a full set of optics to OP.

A (Ilias): understood, but need to check if they are still compatible with Run 3 machine layout.

Q (Gianni): during the LHCf run, would like to do a VdM scan in IP5 (with no crossing angle). Is it possible to run without crossing angle in IP5 while having crossing angle in LHCf?

A (Ilias): probably yes, to be checked explicitly.

Q (Witold): to validate optics, will phase advance method be used, or K-modulation?

A (Jorg): assume K-modulation, but t to be discussed with OMC team.

Round table:

1) CMS (Gianni)

- splashes: ~ 10 per side, similar intensity as in pilot run.

- 900 GeV: same lumi as in October. At least 12 hours, preferable in 2 or more separated periods.

In October, large beam background (missing collimators?), still to be expected?

- luminometry request: emittance scan soon after

- 900 GeV special runs: recently discussing power of 900 GeV runs in benchmarking the combi/b*b simulations that are very important for vdm calibrations.

Comment (Jorg): indeed collimators will be in place this time, so less beam background.

Comment (David S): special emittance scans: doing the proposal during 1 initial run only.

2) PPS (Mario):

- new T2: assembly ongoing.

- Roman Pots: silicon strip tracking in

- diamond detectors: still under assembly; installation in short accesses in spring (1 day)

- movement systems and interlocks to be validated

3) ATLAS (Trevor)

ATLAS ready for cavern closure on March 24th.

Requests during the period of re-commissioning with beam: • In addition to parasitic splashes that will come during initial threading of the beams, would like to request 25-30 splashes per side, with an intensity as low as possible

Requesting at least two fills with collisions at 900 GeV

Horizontal muons for validation of Tile calorimeter calibration • Low intensity Stable Beams with few bunches. The collimators should be adjusted as to provide scraping muons with rate of ~few 100 Hz. Beam from one side at a time.

Loss maps: would like to understand the schedule for loss maps during commissioning

Non-linearity scans in preparation for Sep. 2022 vdM session:

Top priority: √s = 13.6 TeV, no collisions in IP1/5, vdM optics; ~2 h data-taking

2nd priority: √s = 900 GeV. 1-2 h data-taking

Validation of beam-beam corrections to vdM calibration • Goal: validate beam-beam simulations with COMBI & B*B used in vdM analysis • Requested by LLCMWG, approved by ATLAS EB. Similar Request from CMS • Beam conditions: multiple patterns of a few ten isolated bunches, X-angle = 0

Comment (Roderik): loss maps will be discussed in the next LHC background meeting.

Q (Brian) horizontal muons: is this with stable beams?

A (Trevor): yes. One beam per side at a time.

Comment (Witold): not sure that this was done in SB. To be confirmed.

Q (Maciej): alignment scheduled during MPP meetings or via email?

Will have same request as during pilots.

A (Jorg) : to be discussed with Roderik.

Q (Stephane): for 2023, is there interest to inject with 19m beta* (i.e. VdM optics-like)?

A (Witold): no, it’s too high. Cross section too low.

Q(Ilias): lot of gaps in lumi information from experiments during Run 2. Will this improve in Run 3?

A (David/ Witold): not in physics. Maybe during MD sessions. Is it Timber? To be clarified offline.

3) ALICE (F. Ronchetti)

Ready for 450 GeV collisions in May 10th then for Stable Beams in June

Start Up – Phase 1: Low-Rate Magnet Scan : slide 3

Start Up – Phase 2: Interaction Rate Ramp Up : slide 4

Start Up – Phase 3: 1 MHz Running Validations: slide 5

Start Up – Phase 4: 5 MHz Running Validations: slide 6

Q (Jorg): Can low rate magnet scan be moved by ~2 weeks?

A (Federico): needs to be one of the first things that we do, so cannot be moved too much.

To be negotiated.

Q (Stephane): can you review the luminosity goal based on the 0.5 MHz?

4) LHCb (F. Alessio)

Status: no VELO side installed; second VELO side is expected to arrive hours before cavern closure. So all commissioning will need to happen during beam commissioning.

Commissioning schedule on slide 3. Will need tight coordination with LHC.

450 GeV runs:

Request at least 3 Stable Beams fills well spaced in time (and during day time).