Minutes and Summary
Main purpose of the meeting:
Discuss the remaining weeks of running, in particular the planned ion test.
Collect input from experiments for 2023
Introduction (Filip)
- The schedule for last two weeks was presented along with recent performance
- The vdM scan largely proceeded as scheduled thanks to very good machine performance
- The ATLAS crossing angle test was moved to the end of the IP2/8 fill
- During the IP1/5 fill, the LHCb scans and ATLAS length-scale calibration fills were repeated making the fill almost 24 hours long
- For the last two weeks the plan is to stay with current 36b train scheme
- There are still a few LHC OP tests planned to prepare for the 2023 run
- Push IP1/5 peak luminosity above 2e34 to find cryo limit
- ATLAS asked if it was necessary to push in both IPs. Matteo said probably not, but to be confirmed later and possibly it will depend on the results from the first IP
- Push bunch intensity to 1.6e11ppb in a special fill with fewer bunches
- BSRT calibration fill, if needed
- CMS confirmed this was useful during the meeting
- LHC confirmed strong request from machine side after the meeting
- ATLAS also confirmed the desire for this post meeting
- The ion test is scheduled to start at noon on Thursday, November 17
- Two stable beam fills are planned for the Friday
- Proposed to have head-on collisions in all experiments for the first hour of each fill and then level ATLAS and CMS for the remaining time of the fills
- The first fill with individual bunches should be 2-3 hours long, while the second fill with trains should be kept for longer (up to 8 hours)
- CMS RCs asked what accelerator mode would be used during ion test
- Matteo confirmed that this will be "ION Physics"
- Roderik noted that the ion bunch intensity has gone down and suggested to update the filling schemes to have a few more bunches while still staying below the setup beam limit of 3e11 charges per beam
Roundtable
ALICE (Federico Ronchetti):
- The vdM scans went smooth and were completed successfully
- The full programme was done with ITS and FIT detectors
- Detector commissioning was done in parallel, including for the ZDC
- During the other vdM scans, ALICE took combined data with all 15 detectors of ALICE 2
- To be used for diffractive physics
- Recorded 6.5/nb (390M min bias events)
- Realized that some massi files are missing from the LPC site
- Code has been fixed to handle this better
- Since the ALICE magnets draw 8MW they plan to turn them off if beams are off for 5 hours or more
LHCb (Federico Alessio):
- The vdM data was taken with good efficiency, but with a heavy load on experts
- The first scan was done with SMOG injection in the full vessel instead of SMOG2 cell due to miscommunication, hence the extra scan later
- Ghost charges were measured at four points during scans for other experiment
- It will take a while for data to be analyzed, but data looked ok
- Couldn't keep running 24/7 with SMOG due to expert availability and vacuum spikes
In the future will stop smog injection during VELO movement
- Witold asked when would a first estimate of ghost-charge could be available
Vladik: in about a month it should be possible to have a preliminary measurement
- Witold asked how confident the machine is in LDM measurements (action on LPC/Matteo)
- Plan to do a mu-scan up to pile-up of 7
- Critical to make measurements at different mu (so far was running at mu=1)
- Input to decide pile-up target for next year
- Plan for mu-scan presented - should be compatible with BLM thresholds
- Would like to schedule the start of fill during the morning which should be compatible with planning
- Test of emittance scan procedure in IP8 to be tested in the last week
- Aim to take stable condition data during the weekend after the ion test
- Might request another fill for magnet-off data - still to be confirmed
- Similarly, LHCb might want to change field polarity after the quench test (TBC)
- The LHC experts confirmed that the LHCb magnet should be on during the floating MD on November 22
ATLAS (Joerg Stelzer):
- vdM recap:
- Saw a difference in the LUCID response during the crossing angle test, so test was useful
- Had to repeat the LSC due to ATLAS SCT data missing in first attempt
- Otherwise scan worked as expected including the grid scan
- Feedback for 2023 was provided in form of several slides
- Aim to be able to level at mu=58 (2e34 at 2450b), but might be limited by CPU processing
- For ALFA have to repair the water-damaged station in YETS - on track so far
- Considering asking for one more hybrid fill in 2022 for detector response studies, but will confirm later
- Had several instances where Stable Beam flags was removed less than 30 seconds after an unplanned beam dump
- This causes HV to be interlocked as it is still ramping down
- Would like to avoid this as it is better to ramp down smoothly
- Currently nothing enforces a delay and it depends on machine operator
CMS (Andrea Massironi):
- No major problems during the vdM scan - completed it on schedule
- CMS is happy to keep running at the current mu=54
- For high-mu/lumi runs, CMS will need 1-2 days of warning
- CMS is happy to dedicate some time for the BSRT fill
- For the YETS, CMS repeated its request to move collision point in IP5 1.1mm outwards (horizontally) to have be better centered in the pixel detector
- This is needed to avoid asymmetric radiation of pixel detector
- Jorg asked what the minimum acceptable movement is. Gaelle answered 0.5-0.6mm
- The vacuum is concerned about the mechanical movement needed to move 0.6mm
- This is being followed up by Laza
- Would like to have a fill where CMS is leveled at mu=60
- This would exceed 2e34 if done with normal filling scheme
- Therefore either have to be done after actual cryo limit has been determined or with fewer bunches
- Alternatively, leveling at 2e34 (mu=57-58) should also be sufficient for CMS