Minutes and Summary

Main purpose of the meeting: Chamonix summary, Re-commissioning plan discussion

25th January 2024 Topic: Chamonix summary, Re-commissioning plan discussion

Federico Alessio (Introduction)

(Jorg Wenninger) Commented that it is hoped that the baseline scenario partial RP will be confirmed in the next LMC as otherwise timelines become very tight.

(Michi Hostettler) Commented that there has already been a leveling test with ATLAS but they also want another one as well. ALICE and LHCb also transmit the step size via DIP to reach the leveled value. ATLAS and CMS do not want to do this, so it is proposed that if the step size is set to zero then the LHC tools will be used to determine the step size. This was agreed by all the experiments as a good solution.

(Jorg Wenninger) In Ions we have the cryo in eco-mode which needs to happen after the pp reference run such that there will need to be a day lost at the end of the pp reference run to do this switch. It was pointed out the ZDC installation needs to happen before the pp reference run so having the ions next to the technical stop would not help the situation.

(Meike Danisch) It was clarified that the previous 3 pb-1 requested by ALICE was when it was intended to have a 2023 and a 2024 pp reference run and 4.5 pb-1 is the current request. It was clarified that ALICE will level at a higher value than last year during the pp reference run which makes the delivery of 4.5 pb-1 in 6 days possible, but does require good performance. It was clarified that the 6 days includes the VIP visit, VdM scan and mini intensity ramp-up but the commissioning is done before.

(Federico Alessio) The hope is to complete the pp reference data taking in 2024 such that more days of HI data-taking can take place in 2025. This would be a net gain of 3 HI data-taking days; 1 extra day in 2024 against 2 setup + 2 data-taking in 2025.

(Catrin Bernius) It was asked if the cryo change to eco-mode would happen straight after the pp reference run or after a few runs of PbPb. This is usually done straight away. They usually ask for a full 24 hours but are usually ready within 12 hours. It was pointed out that it would be ideal if this overlapped with the VIP visit, but this doesn't look possible with the current timetable.

Jorg Wenninger, Matteo Solfaroli Camillocci (Re-commissioning plan, first draft)

(Silvia Franchino) It was asked if the recabling has been done for the partial RP. Yes, the point 1 cabling was done last year and there is nothing to be done at point 5. It should be noted that "partial" is not half as there are no crossing plane changes and only polarity changes in point 1 and not at point 5. The polarity is completely, not partially, reversed in point 1.

(Jorg Wenninger) It was clarified that it is one of the 4 marked days that the cryo will go to high heat load. The procedure only takes one day.

(Matteo Camillocci) During week 9 powering tests will be done which can be used to confirm the change in cooling between sectors. This affects the potential filling schemes.

(Jamie Boyd) There was a reminder that in the week of March 18th the FASER and SND emulsions will be installed.

(Jamie Boyd) It was asked if there was possibilities of access during the powering tests. This is possible, but it isn't parasitic. This will be discussed offline.

(Stephane Fartoukh) The optics are being prepared and will be released soon. It was asked which should be prioritized; VdM or HI optics? The VdM is needed earlier.

Andrea Ferrero (ALICE)

(Andrea Ferrero, Catrin Bernius, Jorg Wenninger) It was asked what steps will be done for the ramp-up. It is expected that the same steps with the same time spent at each step as last year, but the filling schemes will be different due to the lack of 8b4e.

Giovanni Cavallero (LHCb)
 
(Jorg Wenninger) It was pointed out that to move the triplet alignment by several milimeters you would need to warm it up to room temperature which will only be done in LS3. From the Optics side it might be possible to bump but it depends on the strength of the correctors and the direction of the correction. This would need to be done before loss maps and stable beams, or it would be changed at TS1. This will need to be followed up by optics and collimation experts.

(Federico Alessio) It was asked if it is known why 2022 and 2023 are different. 2022 and 2023 are only a little different and quite a lot of things have changed for LHCb between Run 2 and Run 3.
 
(Stephane Fartoukh) It was asked what would be a useful correction if we can't make it all the way to 0,0. In principle getting back to 0.8 mm, like in Run 2, would be beneficial.

Silvia Franchino (ATLAS)

(Jorg Wenninger) For the ZDC communication issue usually the vaccuum team would contact the equipment owner. For the future we should think how to avoid this.

(Maciej Trzebinski) It was pointed out that to remove the ALFA interlock there needs to be changes on the LHC side as well as within ATLAS. There is an ALFA channel in BIS such that the relevant LHC team needs to remove this.

(Michi Hostettler) It was pointed out that we were already at the SPS lower limit when doing splashes. This is why it was suggested to use the 2nd or 3rd turn.

(Jorg Wenninger) To do horizontal muons without crossing angle we would need to do this earlier in the schedule. There are lots of requests during this early period but we will try to accomodate this.

(Matteo Camillocci) It was asked what partially inserted (for AFP) means at 900 GeV. This is about 15 sigma, but this is when the sigma is very big so it is around 12 mm. Beam based alignment is not needed for the 900 GeV data. This will be checked again with the new optics when they are released.

(Silvia Franchino) It is important for the collisions at injection that we have "stable beams" declared, the "proton physics" mode, and the "collisions" flag otherwise the detector will not turn on properly.

(Silvia Franchino) It would be nice to know when we will need to mask the BCM. When you see OMC in the spreadsheet it is likely that BCM will need to be masked. There are a lot of these shifts.

(Catrin Bernius) We take data when loss maps are being taken so it would be good to let ATLAS know in advance when these will happen.

(Meike Danisch) For the pp reference run what pile-up is requested. For ATLAS this is 4, for CMS it will be less than 10.

(Maciej Trzebinski, Michi Hostettler) For the interlock tests there are two parts. One within ATLAS where we test internally. It was asked if the other test is necessary which has to be done in coordination with the LHC where the full matrix of beam types is tested. There will be the handshake and cycle test which will go through the modes, and we should see if AFP/ALFA would generate a dump. For further tests you need to ask MPP what they desire.

Giulia Negro (CMS)

(Silvia Franchino) It was asked when the 2-3 colliding bunches run would happen. This has to be after the commissioning period rather during the intensity ramp-up. If ATLAS was to use this they would need the stable beams flag. It was asked if this is needed before the VdM and this is not needed. Also if this is not being used by other experiements a single bunch would be preferred so a full turn of data could be measured to see the decay over micro-seconds.

(Federico Alessio) For the pp reference run we need the physics impact of not doing it.

(Federico Alessio) How much data is needed at injection energy? This is being discussed and CMS will report back at the next LPC.