Minutes and Summary

Main purpose of the meeting: Discuss new schedule after Cryo intervention, Hi-Intensity MD, Lumi MD, and VdM Scan planning

LPC 23 April 2026

Present (P = in person): Chiara Zampolli (P), Martijn Mulders (P), Eric Torrence (P), Witold Kozanecki (P), Krystian Roslon (P), Silvia Pisano (P), Flavio Pisani (P), Archie Sharma (P), Julia Negro (P), Filip Moortgat (P), David Stickland (P), Aikaterini Nikou (P), Joanna Wanczyk (P), Sofia Kostoglou (P), Daniele Mirarchi (P), Juan Esteban (P), Georges Trad (P), Michi Hostettler (P), Jorg Wenninger (P), Stefano Redaelli (P),  Stephane Willocq, Tatiana Pieloni, Peter Steinberg, Riccardo Longo, Ivan Amos Cali, Vladislav Balagura, Kartik Deepak Bhide, Andres Delannoy, Tomasz Bold, Dragoslav Lazic, Gabriella Pastor, Matteo Solfaroli, Maciej Trzebinski, Antonio Sbrizzi, Ewen Maclean, Benoit Salvant, Mirko Pojer, Jörg Stelzer, Kersin Lantzsch, Kyriacos Skoufaris, Benjamin Kerrigde

 

LPC intro (Chiara Zampolli)

Witold Kozanecki: just for my understanding; what is the advantage of inserting a low-mu fill between the CRYO stop and the vdMeer scan? 
Chiara: we don’t know how long the CRYO intervention will last exactly and we thought it is better for the experiments to have a fixed starting time of the vdMeer scan. After the CRYO the first thing we do is the Loss maps for the vdMeer. Today we will collect feedback from the experiments, to now whether they would rather go directly to the vdMeer or not.

Discussion about the vertex z-position measurements in the experiments  after the RF intervention. Michi Hostettler: in ALICE and LHCb it is stable around 0 because we use the online feedback. For CMS we used the online feedback in High mu, but not in Low mu as we didn’t know how well it would work. The 2cms could also come from a drift of the crossing plane in stable beams. So it is not a given that this is for sure an RF shift. If you think it would make things better for ATLAS and CMS and you think that we know the beamspot well enough, we can of course also switch on the feedback loop for them. … after some discussion it is agreed to try and switch on the feedback loop for CMS in the next Low mu fill to see if things improve.

About the DOROS scans during vdMeer for ATLAS and CMS: after a short discussion it is agreed to do one scan each, at the start of the vdMeer scan.

Short discussion about amplitude scans and tune scans, when they should be done. The Tune measurements should be done 3 times: one at the start of ATLAS, one at the end, and one at the end of CMS. It is all prepared and should take only a few seconds. The amplitude scan needs to be done only once, and can also be done during the loss map fill. Michi Hostettler: a few additional questions
* ALICE and LHb polarities, when do we change? ALICE stays minus-minus (Silvia) and LHCb will change to positive (Flavio) right after the CRYO intervention. LHCb will need a physics fill to do the alignment, before the 1.2 TeV fill. 
* Do we need to move the BRANs out? (Silvia:) yes. 
* The files have been downloaded. Are they all ready and final? (All:) we think yes, but to be checked
* The order of the fills and the experiments: It's basically just because they have different filling schemes, and in SPS, they need to adjust a bit, basically. It would be interesting to tell them which one will come first. (Chiara:) so this is the order. We will do LHCB, Alice first, and then we do Atlas and CMS, but Atlas and CMS, they are taking turns. 

About the unplanned Tests in ADJUST: a general discussion trying to clarify what is causing confusion and what can be done to make it better. Perhaps during LS3 we can look again at the ‘unusual ‘transitions between modes, handshakes and how to improve this. 

Two days of High-Intensity Test (Sofia Kostoglou)

Chiara Zampolli: how long before switching off / on the magnet does CMS need to be warned? Giulia Negro / Filip Moortgat: Not much time. There are no specific constraints. There is a piquet who needs to drive to Point 5. It takes half an hour or so. David Stickland: while the magnet is ramping you can not have the BCML 1. You can have the BCML 2. This is not for lumi, it is a beam loss monitor that can dump the beam. 

Jorg Wenninger: if we end up with the schedule where the two High-Intensity days are disconnected, we can consider starting a shift earlier in the morning, since the first fills are just loss maps, so that the checklists and first steps beyond nominal intensity still happen during the day. And not in the middle of the night. We can also be a bit flexible, depending on when a fill ends. Chiara: for us it is Ok. 

Lumi MD: test at the end of the TCT alignment and next steps (Joanna Wanczyk)

Discussion about the idea of changing the reference value of the collinearity knob. There is general agreement not to deviate from the default settings, as we are talking about potential a very small gain but introducing other unknowns  and it is not at all clear the gain is significant. 

ATLAS (Eric Torrence)

CMS (Julia Negro)

Discussion on whether it is still possible to optimize LHCb while doing lumi scans in ATLAS or CMS, during the 75 or 400 bunch fills at 1.2 TeV. (Michi:) it is a convention not to do this, but if we agree to do it because it is a very compact program, there is an override flag. It can be done. 

ALICE (Silvia Pisano)

LHCb (Flavio Pisani)

David Stickland: if we get to the ATLAS and CMS vdMeer scans by Friday midnight. Do we have enough experts available at the injectors? Jorg Wenninger: we have one shifter available, yes. The injectors must be able to make the beams at any time. David Stickland: I am not asking for anything just wondering if we will have the right people on the injector side. Witold Kozanecki: David is right that we need good control of the beam quality and non-factorisation. [...] Michi Hostettler: I am not even sure the experts can do anything about that. David Stickland insists that for one of the most important measurements of the year we need to have the experts available. The whole point of the 3 weeks of low PU is to get precision luminosity and we need a good VdM session. Georges Trad: no, even if the experts are available, it is not clear that these experts will take any action. The (non-factorisaton) variable was tweaked and optimized on Friday, but beyond that, no measurement is planned to happen. The only control of the outcome we have for the non-factorisation of the beams is from the setup. 

Flavio Pisani: one more thing about the 1.2 TeV and potential overlap with 1st of May. Please keep in mind that will need the vacuum experts to be available to change the gas bottle.

Chiara: we have to leave the room. Let’s continue the discussion downstairs.