Minutes and Summary

Beam test in 2021 (J. Wenninger)

Preparation for a circulating beam test in 2021 started. The following applies for either 1 or 2 week test.

- slide 2: latest version of schedule. Still evolving. No more powering in 2020, only cooldown.
Cooldown of sector 45 should start this week. In April some powering tests in parallel to training multiple sectors.
11T dipoles installation prevents powering tests in neighbouring sectors. 
Maintenance of cooling & electrical installations still to be scheduled.


- slide 3: more detailed schedule. Including “penalties” for parallelism. Training might be longer than 8 weeks.
By early July: 7 of 8 sectors ready for 7(?) TeV. 
Beam test constrained by S67 readiness (including training to 3.5 TeV): not before week 39. Not after week 41 because of ATLAS NSW installation.

- slide 4: schedule could still change due to readiness of experiments (meeting on 23rd) and 11T readiness (S67).

- slide 5: will start system comissioning around mid-April- early May 2022.
For beam test: will need a few days for machine checkout with machine entirely closed (incl. experimental caverns).
 

- slide 6: dry test of beam and accelerator modes (some suppressed now!)

Some people may want lumi/VdM scans?
Significant changes to DIP, need to test.

Would like to start tests with experiments in may-june 2021.

Question: is this acceptable for all experiments?

- slide 7:  safety tests scheduled. Agreed with ALICE and LHCb.
Beam DSO tests still to be scheduled (all caverns need to be closed so needs to be agreed by everyone).

- slide 8: once probe bunches from SPS available: test of extraction of SPS beam on TED.
For extraction from SPS to downstream TEDs in TI2/8, LHC points 2 and 8 need to be closed.

Tentative dates: end of August/beginning of September 2021.
Question: constraints from ALICE or LHCb on these dates?

- slide 9: radiation studies in ATLAS: no RP problem expected.
Maybe problem with collisions.

- side 10:
boundary conditions from RP: few probe beams at injection; a probe beam at X TeV (X>3.5); nominal bunches (max 3 per beam) at injection.

- slide 11: minimum commissioning programme

Question: is there interest in ~1 shift of collisions in stable beams at injection energy for detector commissioning?



Q&A:


Q (Gaelle): what does nominal bunches mean?
A: 10^11 protons/bunch

Q (Michael Rijssenbeek): Roman Pot insertion possible? 

A: No, out of the question in 1 week.

Independently of this: tests of Roman Pots still to be scheduled.

Q: can we have collissions in some of the experiments but not ATLAS?
A: yes, no problem. Can just separate the beams.




Round table with experiments


LHCb (F. Alessio):

DIP exchange with dummy data could be tested already now. Recommissioning the control system from March 2021 onwards for more meaningful tests. Handshakes via software could be tested from March 2021 onwards, via hardware from July 2021. VELO saftey system still needs to be finalized. VELO not available before August 2021. BCM readout not available before June 2021.

All of these dates may suffer from further COVID delays.

Interest in few hours of collisions during beam test.
Would be particularly interesting if stable beams could be declared and one could test the closing procedure of VELO (even without actually closing), since this procedure requires vertices to be reconstructed.
Will not actually close because it may get too close to beam (VELO will get to 3.5 mm from beam, which is 13 sigma at 6.5 TeV but sigma larger at 450 GeV than at 7 TeV).

Beam on TED useful depending on time: if it comes too early, not useful.
In current schedule, commissioning of relevant systems should be ready by August, but tbc.

Comment from Jorg: beam on TED probably probe bunches, because also don’t want to activate anything.



ALICE (T. Gunji):

One more month needed for upgrade of ALICE_LHC_IF project (IF= interface), after that tests of data exchange of DIP can happen.
Ready for testing handshakes via software in 1 month from now, via hardware from May 2021 onwards.

Please give 1-2 weeks notice before the tests. Please notify in case of changes from the LHC side.

Clear interest in collisions at injection energy during beam test. Declaration of stable beams would be highly appreciated.
Also interested in beam on TED: probe beam should be fine. Need BCM to be available, should be ready by middle/end of June. 



ATLAS (K. Lantzsch): 

Dry test for data exchange over DIP, as well as to test handshakes and interlocks: ready now, but would like 2 week warning. 
Not including Roman pots etc.

Collisions during beam test: interested yes, but open configuration without shielding etc., so RP risk. Still being evaluated.
Answer expected in the next weeks.



CMS (G. Boudoul):


Proposed timescale for dry run is fine. Sometime in spring ok.
Few weeks notice appreciated.

Collisions: yes, interested for commissioning. 
Roman Pots will remain in garage position.
Declaration of stable beam would be very much appreciated since new beam spot can be measured with pixels.

Comment form Jorg: organizing an hour or 2 of splashes on collimators should not be a problem,
since need to go around the ring first anyway.


TOTEM (M. Deile):

see slide on “answers to LPC questions”.

DIP test: ready now. Handshakes as well.
Interlocks more complicated. Expected ready after April 2021.
Interest in collisions for shower background with RP in garage.


General comments:

Comment form Jorg: either collisions with stable beam, or no collissions. Too much work otherwise.

Suggestion from Alessio to review DIP document in EDMS (Jorg says they will start looking at this in the coming weeks).




High beta* run (H. Burkhardt)
 

Preparations of optics for high beta* run (parallel beams) during Run 3. Goal is to cover the Coulomb Interference region and measure the rho parameter with good precision.

Requires high beta* increasing with beam energy (for 7+7 TeV: 3km or more). 

Short run, all the work is in the preparation.
After feedback from TOTEM and ALFA, prepared 3km/3km, 3km/6km and 6km/6km options.

Q (Roderick): still enough aperature for low energy?
A (Helmut): not different from before.

Comment from Roderick: Should also plan a test of the collimation setup.

Comment from Brian: Should estimate how much shifts will be needed (and see when to schedule it, in 2022 or 2023)

Comment from Roderick: would be good to have some time between commissioning and actual run (esp. for the collimation and optics).
Comment from Brian: need to start fairly early with first test.



Input from experiments:

TOTEM (M. Deile):  

p 3: which t value needed to have coulomb amplitude = nuclear amplitudy
beta* at least 6km (or 5.5 km if more aggressive on sigma)

p.4-5-6: preference for flat optics (3km, 6km)

Q (Brian): can one get it even more flat to get more lumi?
A (Helmut): will think about it. Can look at Ly specifically.

Q (Vladislav Balagura) Can x-y coupling be a problem for very flat beams?
A (Helmut): don’t expect too much of a problem.


Q (Brian): lumi similar to 2016 … is that what you need?
A (Mario): 350 would be great indeed.



ALTAS/ALPHA (K. Lantzsch):

no strong preference between beam optics candidates, but slight preference for 3/6 km because of best resolution and smallest optics constraint bias.

2 comments:
- important to run as early as possible (raddam to ALFA).
- not interested in run at 13 TeV, only higher energy.

Q (Helmut): 90 m run indeed no crossing angle?
A (Mario): yes: 90 m run: ~ 6 hours. Need to install T2 in last Technical Stop in a given year (the one before the HI run).


Comment Roderick/Stefano:
Collimation to be studied after then optics have been finalized.
Xtal collimation? Setup will remain operational.