Minutes and Summary
Main purpose of the meeting:
Planning rest of 2022:
* VELO insertion test
* Ion test period
Introduction (Filip):
- Schedule for remaining weeks of 2022 run showed
- mu-scan is for ATLAS and CMS
- LHC delivered 2.5/fb in the last week and bunch intensity was pushed to 1.3x10^11 ppb
- During velo insertion, saw some small temperature increase, but did not scale with #bunches
- For the full velo insertion it is not proposed to run 300, 600 and 1200b fills with ~1 hour at each step
- TBC in LMC
- Mixed scheme test to happen in the next days
- Sstill using one 8b4 and three 48b trains
- pile-up to be kept at mu=52
- Received feedback from CMS on the vdM programme - to be included in the planning
- For the ion test with Pb, we foresee 36 hours of test
- Injection scheme similar to the one in 2017 (not final), but with 16_8_16_8
- ALICE asked if possible to use slip stacked bunches ramped? ALICE prefer trains for testing detector performance
- This might be possible if one can test slipstacking, but will not be optimal as one has to have 8b train
- One might go for collisions right after ramp at beta*=1.3m in IP1/5
- The difference in integrated luminosity between ATLAS and CMS was found to be partly due to missing Massi files
- Access planned for this Wednesday (October 12)
- To be seen if one needed next Wednesday
LHCB VELO insertion (Victor):
- Partial closure of VELO was done on October 6 to:
- Confirm detector alignment
- Monitor temperator and vacuum
- Also had dress-rehearsal on September 30
- The closing was already done using the automatic system
- The procedure worked smoothly
- Stopped at 4mm from nominal as some heating was seen
- Analysis of material interactions on going from large dataset
- See a bulging of RF foil at z=500mm of ~0.5mm or so
- Had seen similar effect in metrology data
- Should still have sufficient aperture (to be confirmed)
- Saw temperature and pressure increases, but not clear that these scale with beam intensity
- This was discussed in thee rMPP this morning
- Plan is to go 300, 600, 1200 bunches in ramp-up
- Hope to have results ready by Thursday, so can do ramp on Friday
- The VELO will likely not go during following first 2400b fills following the insertion tests
- Only a subset of fills will have the VELO inserted
Round table:
CMS:
- Happy to run at mu=52, but can also deal with mu=54
- CMS pile-up is higher because the lumi reported by CMS is now a high in CMS than ATLAS and the system is leveling on ATLAS
- CMS luminosity calibration was changed by <1% after the vdM scan programme during the LHCf run
ALICE:
- Doing high rate scans to validate track load of 50 kHz ions
- Should correspond to 3.5-4MHz of p-p running
- Also used for conditioning detector at high charge
- Need to long fills for these tests, preferably during working hours
- Plan to go to 5 MHz at some point
- The rate should be raised slowly, so one can check the rate in TCT BLM which was at 30% of the dump threshold at 3.5 MHz rate
ATLAS:
- This morning ATLAS had a cooling failure, requiring urgent access
- Looks like a faulty sensor
- Currently still powering back up
- The pile-up is limited to mu=52-53 with the current HLT system
- Plan to use access on Wednesday
- ATLAS is using VELO insertion fills to commission their phase-I calorimeter trigger
- No need to assign more time than planned for the VELO insertion test
- Since the first 2400b fills after TS1, the luminosity calibration was changed, reducing the peak luminosity by 5% at mu=40-50
- Effect is even larger at lower pile-iup