LPC meeting summary 01-08-2022 - final
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LPC meeting summary 01-08-2022 - final |
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Main purpose of the meeting: Discuss planning for August and post TS1 run
The ramp-up to 1200 bunches have been completed and the LHC is
entering a period focused more on physics production. Most of the
special commissioning steps for the ramp-up are done. The main items
remaining are the optics in the ramp (scheduled for Thursday),
completion of the full RF detuning and the last crystal collimator tests.
The crystal test is needed as input to a decision on the PbPb collision energy.
The Abort Gap Keeper setting will also need one more update in order
to accommodate the full 2748 bunches.
Two issues have come up with luminosity leveling. ATLAS has trouble
with the readout of the TRT at pile-up above about 40. As CMS also has
large dead time at high pile-up from one detector, it has been agreed
that for now beta* leveling will be done to about mu=40. Additional
leveling can be done with offset leveling in one experiment, if needed
and pre-warned. For LHCb the luminosity signal is not yet 100%
reliable and there have been two cases where the luminosity ended up
higher than the experiment was ready for. For now the agreement is to
keep the automatic leveling off and LHC will apply leveling by hand
when the luminosity signal is confirmed reliable by the LHCb shifter.
For the planning of special runs after TS1, an additional mu-scan for
ATLAS has been added to the calibration transfer fill and the LHCf run
has been moved earlier, before the ALICE/LHCb vdM scan. The latter was
done to ensure that LHCf can be removed during a working day, though
Lorenzo is investigating if it would also be possible to do the
exchange over the weekend. Witold noted that with the ALICE/LHCb and
ATLAS/CMS scans back-to-back, there will be a heavy load on luminosity
experts that need to participate in both from ATLAS. The LPCs will see
if it is possible to schedule the length-scale calibration outside the
ALICE/LHCb scan. Witold also enquired about the status of the DCCT
precision calibration and the BSRL instrument needed for the vdM
calibrations.
The next LPC meeting is scheduled for August 15 and 29.
ALICE is still seeing a shift in the longitudinal vertex position by about 10mm
towards ATLAS. For two fills, the shift was about 30mm, but this was due to a non-optimized
crossing-plane. ATLAS and CMS will check their vertex positions and based on that
a small shift through RF recogging will be attempted.
In the next days, ALICE will level at 1 MHz and 5MHz to test high
rate/load running before the p-p reference run and PbPb physics run.
The ALICE BCM dump threshold will be raised, but none of the LHC BLMs are expected to be
an issue as the rate is still very low by LHC standards.
CMS is mostly done with commissioning test and taking good data.
For now CMS is ok with leveling at mu=40, but they might want to go for higher pile-up
for testing out their problematic hardware component.
Since the first 600 bunch fills, ATLAS has had issues
with part of the TRT readout at mu>40. Solutions are being
investigated. For the LHCf run in September, the ZDC will be installed
to improve the hadronic energy resolution and as a test toward the
PbPb run in November. AFP also wish to be included which will require
beam-based alignment during the commissioning phase, though no
calibration data is needed. Jorg Wenninger noted that it might be
possible to do some of the setup and alignment just before MD1 and
TS1.
There was also a request to insert AFP and run at low mu during
the 600b fill. However, this would extend the length of that fill as
MPP requires 2-5 hours of head-on collisions as part of the post TS1
ramp-up.
For the beta*=90m run in November, ALFA would like to be inserted in
order to do detector commissioning. This should not put additional
requirements on the preparations and the physics run apart from a
beam-based alignment also with ALFA.
The plan is to install LHCf and ZDC on September 13 of TS1 and remove
the systems again on the Friday after LHCf run. LHCf is in contact
with relevant technical groups. A geometric survey will be needed during the
installation.