Minutes and Summary
Main purpose of the meeting:
Update on Run 3 planning and first input for Run 4 ramp-up
Introduction (Brian Petersen):
- recap of oxygen run discussion in the September LHCC session. LHCC supported the proposal to study the possibility of an oxygen run during Run 3.
LHCC follows the LPC assessment that it should be a special run rather than taken out of the ion programme. LHCC suggests to consider scheduling this run in 2022 if possible.
Working group being set up by IEFC.
- Run-4 ramp-up scenario: LPC received request for input to a first reference scenario for the HL-LHC ramp-up (Run 4).
Questions include the following: Assume experiments will need time for detector commissioning? Optimize ramp-up for peak bunch luminosity or lower pile-up?
Steps needed in luminosity running points? Aim to achieve ultimate bunch luminosity (µ~200) quickly or rather nominal luminosity (µ~140)?
For feedback from experiments, see below.
- some clarification on Run 3 planning from Stephane:
Flat beams only likely if fourth year added to Run 3.
First Run 3 optics available for tests in 1-2 months from now.
No work yet on LHCb vertical crossing, will start this year.
LHC restart after Run 2 (Jorg Wenninger).
Single person will be on shift for the LHC. Support from SPS shift crew. Will be challenging.
Also PS and PSB island: reduction of night and weekend shift from 3 to 2. Possible impact on beam preparations in the injectors (esp. for MD).
First schedule for recommissioning is presented. Schedule is 6.5 TeV. Add ~ 6 weeks training for 7 TeV.
Machine hand over to OP in beginning of October 2020.
Fully in power and check out in December.
Commissioning with beam in March 2021.
9-10 weeks to get to early collisions (few bunches)
Questions to experiments:
1) Can you close the experiments for 1-2 days in Week 44 of 2020 for access safety system and DSO tests? [answer requested within a ~month, i.e. by the next LPC]
If not, schedule global tests in 2021?
2) Is there a need for “early” stable beams fill at 450 GeV? If yes, how many hours?
—> LHCb and ALICE expressed interested in this (e.g. during nights, few bunches per beam)
3) Is there a need for an early VdM scan? (could commission VdM cycle in parallel to the nominal cycle)
Could consider “light VdM scan” (like for HI).
LHC mode cleanup during LS2 (Jorg Wenninger)
Some of the LHC modes are outdated and have never/rarely been used. Will remove the outdated modes. Concerns accelerator modes, beam modes and RBAC related OMODE.
Values and mode names will remain (i.e. no code change is necessary — though cleanup of code in case some of the unused modes occur is welcome).
Access control to ATLAS and CMS magnets: currently non-standards tricks being used. Ongoing discussion to converge on better solution. Final proposal expected by next LPC.
Round of the experiments:
Input for Run 4 ramp-up scenario:
ATLAS expects to be able to perform the commissioning after LS3 in the shadow of the LHC ramp-up.
Will likely request few special calibration and alignment runs at certain luminosity points, but these should not exceed a few days.
For regular data taking, the ATLAS Phase-II upgrade is designed for pileup levels up to 200. There is no staged upgrade foreseen that would limit ATLAS running to lower pileup for any period after LS3.
ATLAS is therefore interested in achieving ultimate peak luminosity as soon as possible.
If there is a question of ramping either bunch pileup OR bunch number, with a comparable total luminosity, ATLAS prefers to ramp the number of bunches first, before ramping pileup.
Request from ATLAS:
ATLAS would like to see a prediction of the integrated luminosity projection vs year. During long shutdowns, it is foreseen to exchange certain detector components depending on the radiation dose (e.g. ITK IS after 2000 fb-1, HGTD inner ring after 1000 fb-1). This requires longterm planning.
Run 3 comments:
Luminous size region: all configurations ok, only small changes observed. Flat beams configuration slightly better since less PU density.
Outstanding issue: impact of flat beams on ARP still to be quantified
Mixed filling scheme: L1 can sustain level well above 30% 8b4e inserts
Outstanding issues: effect on HLT and effect of bunch-by-bunch PU variation on trigger still to be studied
welcome to new incoming run coordinator Federico Ronchetti.
No additional feedback from ALICE on Run 3 conditions.
ALICE would like to use early stable beams at 450 GeV.
Run 4 ramp-up scenario: no strong ALICE opinions. Commissioning will be in the shadow of other activities. No other preferences of requirements.
Input for Run-4 ramp-up scenario: CMS commissioning expected to be in shadow of LHC commissioning. No specific requests. Would be good to know ramp up plans (even draft) in advance.
CMS detector can deal with PU 200 from the start, but LHC and offline computing need to have the infrastructure in place than can handle the amount of data (need to foresee computing budget etc.).
CMS would like to request 1 year in advance the plans of the machine so they can plan accordingly.
Input for Run 4 ramp-up scenario:
in LS3 there will be a “phase1b” upgrade, mostly consolidation. Commissioning expected to go in shadow of LHC.
Data taking conditions in Run 4 similar to Run 3. At the beginning, few fills with well separated bunches (non 25ns filling schemes) will be necessary to complete the commissioning of the detector.
LHCb will want to take data at the same value of pile-up as in Run3, from the start of Run 4.
Run 3 commissioning:
Would like some fills at 450 GeV.