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)