LPC meeting summary 31-10-2022 - final
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LPC meeting summary 31-10-2022 - final |
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Main purpose of the meeting: Scheduling of last 4 weeks, VdM planning
1) Introduction (Brian)
Topics: scheduling of last 4 weeks of 2022, LHC performance, plans for VdM scans
VELO insertion ramp-up now completed
ALICE high rate test ongoing
SND access on Friday morning to replace emulsion
MD2: quench test moved to floating MD (Nov 22). Access on Nov 23 morning likely possible.
2 MD’s ask for luminosity: one on Sunday with ~150b colliding and one on Monday with ~ 3 nominals.
SB > 50% in October, >60% in last 10 days.
6 fb-1 delivered October 22-28, 7 days with ~ 1 fb-1/day, record fill with ~870pb-1.
~ 28 fb-1 delivered to ATLAS/CMS so far
Now reaching SB with intensities of ~1.42x10^11 ppb.
Target of PU=54 now reached at start of SB at 60cm.
Optimal fill length ~ 11-12h, suggest to keep it a bit longer than that.
Pushing further?
S78 heat load now above 180W/half-cell.
ATLAS PU limit currently at 54.
Inner triplet heat load limit (2x10^34) only 5% higher.
Comment from Stephane/JW: can blow up the emittance a bit in the injectors. This is preferred over offset-leveling.
Other option is collinearity knob.
Hybrid scheme tested ~10days ago. With change in AGK, we can have ~same #bunches (2454) and keep INDIVs.
2-8% luminosity possible (may have to blow up, or offset-level).
Q to ATLAS and CMS: prefer to keep things stable or go to hybrid (and gain a few %)?
Q from Valerie: is it envisaged to change the filling scheme often in 2023?
A from Brian: the hope is to replace some 8b4e by 48b when/if S78 conditions further.
A from Stephane: next year, no reason to change filling scheme till 1.8x10^11.
LHC limit exploration:
- would like to explore actual triplet heatload limit by pushing peak luminosity above 2x10^34.
During ONE regular fill, would slowly go up to 2.1, 2.2, … x 10^34 over ~1h of full and observe the cryo behaviour.
- collision fill with 1.6x10^11 ppb to observe stability (reduced # bunches) — will be tested during MD2. Would give PU=70 without offset leveling.
Expect both tests in last 2 weeks of November.
Q from Stephane: will the max acceptable PU in the experiments increase soon? (to be discussed later)
VdM planning:
- more time needed for machine revalidation?
- order of IP2/8 and IP1/5 scans?
- no ramp-up needed if we have regular 2462b fill?
A(JW): likely not
VELO aperture during VdM scan: slight bulging affects aperture limit.
Some options:
- limit crossing angle (>240 urad)
- limit scan range to 3.1 sigma
- not close VELO fully
Preference of LHCb (Federico):
- Keep crossing angle fixed.
- Ghost charge measurement: close VELO fully but limit scan ragne to 3sigma.
- Length Scale Calibration: not close VELO completely and have the wide 4.5 sigma scan.
To be confirmed by experts.
Ion test: foreseesn 2 periods of ~5h SB. First with INDIV’s, second with 50ns trains for IP1/2/5.
Expect to lumi-level IP1/5 for good fraction of fill.
Schedule on slide 14 is not correct.
Joint Accelarator Performance workshop (old “Evian” + “Montreux”) on Dec 5-8 at CERN.
Brian will give presentation.
Input requested:
- detector performance and issues in 2022 (1 slide/expt)
- view of machine operation from experiments (what can be improved?)
- special runs
- options for standard running in 2023
- PU increase possible?
Q from Stephane?
- granularity of beta* steps ok for 2023?
- is beta* of 2m in LHCb still right for 2023?
Next meeting on Nov 7th.
2) Round Table
ALICE (Federico)
- next round of high rate tests this week
- want to flip magnet polarity sometime around Wed to NEG NEG. Dipole will stay during NEG during MD2. Can solenoid go OFF during MD2?
- ion test programme sounds fine. Mostly interested in the fill with the trains.
LHCb (Federico)
SMOG commissioning in next fill (?).
VdM discussion inside LHCb will happen in next days.
Plan of work for after VdM scan: mu scan up to mu=7, emittance scan procedure, magnet OFF fill, ion test.
Q (Witold): trigger ok for ghost charge measurement?
A (Federico): yes, we can park the data and run the trigger offline if needed.
CMS (Gianni)
Ion test:
- would be useful to have short period of high collision rate (as high as possible, e.g. 1h)
- would be useful to have 6h SB to commission detectors and perform workflow test.
- preference for filling scheme with trains in CMS for 2nd fill
ATLAS (Joerg)
Ion test:
- HI group would like to have a minimum of ~0.13 ub-1 data which is ~1M MB events
- for detector commissioning
- not enough data for performance studies or trigger rate predictions
- not physics measurements foreseen
- prefer second fill with trains
- support leveling to limit burn-off
Q (Brian): do you need 1h of high rate (like CMS)?
A (ATLAS HI group): would be very useful indeed.
Feedback on hybrid filling scheme:
- 10-20 GeV shift to the turn-on of J75 trigger observed (reduction of rate in forward region)
- multijet looks 4J15 minimally affected.
- MET turn-on looks to shift 10-20 GeV
- HLT b-jet seledtion not seen to be degraded.
- impact on analysis not yet fully assessed
- alternate L1 calo scenarios could be tested in future 8b4e fills
Please start emittance scan only after 5 minutes in ATLAS.
Comment from Michi: you can VETO it by sending a flag over DIP.
CMS/VdM (Joscha)
Fill A (LHCb/ALICE fill):
- 3h block for length scale scans
- can be split in 1h+2h blocks
- no constraints on order in fill
Fill B (ATLAS/CMS fill):
- 3x 3h blocks = total 9h
-- block 1: VdM + beam-imaging
-- block 2: VdM + diagonal
-- block 3: VdM + offset, length scale
- block 1 + 2 are crucial to have in one fill
- block 3 for consistency checks
- prefer to start not too late into the fill with block 1
Fill C (μ scans): 1.5h for CMS scans
Remarks:
- head-on when no scans in CMS
- special VdM HLT menu for all of Fill B (scans and head-on times), for Fill A and C only needed during scans ○ need at least 3h of head-on during Fill B
- when full length scale scans not in Fill A, need to add 2h scans to Fill B (or new fill)
- are the filling schemes on LPC website final? → required inputs for preparation of HLT menu
- emittance and super-separation scans already included in time estimates of Fill B
Details of fills on slides 3-7.
Would also like to have a BSRT calibration fill before the end of the year. TBD.
ATLAS/VdM (Witold)
Request to have the filling schemes finalized soon.
Order of Ip2/8 and IP1/5 blocks: happy with current sequence
Mu-scan fill: at least 1 colliding INDIV, flexible for the rest
Slide 3: parasitic use of validation fill. Will need some SB.
JW: not sure there is enough time to do this, TBD.
Details of fills on slides 3-10.
Mu-scan fill: if we keep bunch intensity of 1.45x10^11 ppb, do the ATLAS mu scan at beta*=60, then level down to beta*=30cm, then do CMS mu scan.
If the bunch intensity is lower (~1.2x10^11 ppb), can do both scans at beta*=30cm.
Q (Martino): can ALICE take data with mu 1-5% during the VdM fills. No objections.