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