LPC meeting summary 14-03-2022 - final
Main purpose of the meeting: Lumi levelling strategy and experimental request for initial beam period.
1) Introduction (Brian)
Q: is there any advantage to have physical meeting, why not stay in zoom?
A (Brian): informal chats can be useful to solve issues quickly.
Comment (Michi): for OP, there is a preference to have the meeting in the room close to the CCC. Zoom from the CCC is noisy.
2) Lumi levelling and offline lumi in NXCALS (Michi Hostettler)
Q (Federico ALICE): what are the steps in lumi for IP2/8 (offset leveling)
A: for offset leveling, one can agree on the step. Can be every 10 minutes.
Q(David): DIPs not needed for levelling, right?
A: only for seperation leveling
Q(David): lumi signal of ATLAS/CMS used?
A: want to be able to pick the lumi signal, in case there is a problem with ATLAS or CMS lumi signal.
Q(Jorg Stelzer): emittance scan at the end?
A: prefer emittance scan at the end
Q(Gianni): how quick you move from the left to the right in slide 8?
A: depends on how smoothly it works. Before many steps
Q(Witold): frequency of trims? after every beta* step?
A: more frequently, every 0.1 sigma (every minute in simulation)
Comment (Witold): need to check in ATLAS what the impact would be. In ATLAS one assumes that lumi is constant in a lumi block (1min). This may have implications on
the final luminosity determination (goal better than 1%).
A: would be nice to test it during commissioning period, to see if it would be feasible or not.
ATLAS will follow up on the units of the online bunch-by-bunch luminosity .
Comments (Witold): may have been fixed at the end of 2018. To be checked.
3) Round table:
Comment (Michi): it was said that some test may take place on back-up date. Next time I will warn experiments again before doing this.
Q(Brian): PPS status?
A: Still being installed. Expect update tomorrow.
VELO-A will not be ready to be installed by cavern closure.
More details in LMC next Wednesday.
Magnet off as long as VELO is not in.
Emittance scans: request to offset the beams in opposite plane of the scan to avoid maximal lumi from head-on
Q(Brian): can commission closing of VELO with one side?
A(F): Yes, procedures can be commissioned. Cannot be fully closed at 450 GeV, but no problem for commissioning procedure.
For manget scan: prefer to do it at 75b step (mu = 1.4%)
LHC-ALICE communication could not be tested due to faulty board; fixed now and ready to test again.
Comment (Michi): what about next Thursday March 17th 10:00 (TBC)? Need to open injection HS. Other experiments will also receive the HS requests (don’t need to react).
ATLAS/LHCb/CMS are fine with this.
Q(Jorg S): 3 and 12 bunch steps are 1 step or 2 steps (one or two times 2/3 days)?
A (F): does not matter for ALICE.
A (Brian): In 2028, there were 2 fills with 3 bunches and 1 fill with 12 bunches.
Comments on requests during commissioning period on slide 3.
Q(Brian): How long lead time for AFP experts is needed?
A: week or so.
Q(Brian): for the muons from scraping beams … this is at injection energy?
Q (Roderik): what procedure is needed here? scrape the beam with the collimators
C (Witold): we did it in March 2010. What was done is:
First align collimators (TCT) on beam. Than try to mvoe the TCT in a little bit to scrape the tails.
Gave irregular response. Then, the horizontal tune knobs were used to a tertiary resonance to produce a rate that was fine for ATLAS.
C (Roderick): Can do this now with blowup of transverse dampers.
C (Roderik): Concerning backgrounds measurements: try to do it during commissioning. If not good enough, can request MD.
Proposal for first full emulsion installation on week 29 or 30.
Q(Brian): less than 1 shift needed?
Q(Brian):how precise do you need to know the date? 2 week window fine?
A: to be clarified with experts
4) Request for beam (Brian)
slide 2: LHCb: dedicated TDI shots no longer needed
slide 3: muons for ATLAS: 1 bunch low intensity, 900 GeV, TCT quite closed, blowup with ADT.
slide 3: non-linearity scan: VdM optics may not be commissioned yet. Need to understand when this needs to be done. How important is this to happen early?
It should be 2 hours in total, single fill, non-colliding in IP1/5.
slide 3: BBA of ATP can happen at 900 GeV
slide 4: LHCb: spectrometer does not need to be ON. Can be determined by LHC.
slide 5: no stable beam needed. Only luminomiters on. To happen after first 900 GeV collisions.
slide 6: ALICE: with 75 bunches. 5 fills since solenoid field changes.
slide 6: ATLAS: very low mu run to come at the end? (TBD in LBOC)