LPC meeting summary 14-03-2022 - final

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Minutes and Summary

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)


Part 1:


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.



Part 2:


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:


CMS (Andrea)


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.



LHCb (Federico)


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. 



ALICE (Federico)



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. 



ATLAS (Joerg):


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?

A: yes


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. 



FASER/SND (Ettore)


Proposal for first full emulsion installation on week 29 or 30.


Q(Brian): less than 1 shift needed?

A: yes, 


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)