Minutes and Summary

Main purpose of the meeting: Summary of low-E lessons, High-Intenstity test, plan of 2026 Pb ion run

LPC 11 May 2026

Present (P = in person): Chiara Zampolli (P), Martijn Mulders (P), Eric Torrence (P), Dragoslav Lazic (P), Joerg Stelzer (P), Krystian Roslon(P), Flavio Pisani (P), Federica Oliva (P), Julia Negro (P), Archie Sharma (P),  David Stickland (P), Roderik Bruce (P), Juan Estban Muller (P),  Jorg Wenninger (P), Georges Trad (P), Michi Hostettler (P), Sune Jakobsen (P), Davide Zuolo, Ivan Amos Cali, Xavier Buffat, Stephane Willocq, Maciej Trzebinski, Brian Petersen, Tomasz Bold, Antonio Sbrizzi, Matthew Nguyen, Riccardo Longo, Peter Steinberg, Andres Delannoy, Anna Sfyrla, Aikaterini Nikou, Silvia Pisano, Mirko Pojer, Joanna Wańczyk, Mario Deile, 

LPC intro (Chiara Zampolli)

(no comments)

Low energy run machine feedback (Jorg Wenninger)

(no slides)

Jorg Wenninger: 
We expected the 1.2 TeV run to be a bit more difficult, but it clearly exceeded all our expectations in difficulty. We realized that the tune spread in collisions was relatively large, although not excessive, because of the different bunch families. If you compare to what we have now in operations, between the non-colliding and the colliding, there's not so much difference compared to what we had at 1.2 TeV. Also, because the beam-beam tune shift, in principle, depends only on the beam brightness, not on the energy. So, it was expected to not be as nice as 6.8 TeV, but it turned out to be a bit worse than this. When looking into it, there's one thing that struck me from the beginning: when we do the tune change to go to collision tunes, which normally is sort of a transparent operation, the lifetime dropped from 1,000 to 1 hour. Which is very, very unusual.
That shouldn't happen. Which is already a sign before you collide, that you're already in a bad state.

And so, one of our first theories is that maybe this is due to electron cloud, because at injection, if you move the tunes upward with trains the beam doesn't like it, because the electron cloud generates a tune spread that goes upward. So we started to look at this theory, and then I realized that in the 75-bunch fill (with 12-bunch trains), it was the same problem even though there is practically no electron cloud.  

However, this morning, I also looked back at the loss map fill, and the loss map fill has no lifetime problem. And the loss maps we do without all the octupoloes and chromaticity. So it may hint to the fact that we have maybe a problem with the third-order resonance that's very strong, and when we crank up all the non-linearities, all of this creates a huge mess.
But I didn't want to put this in slides, because this is all brainstorming at the moment. I decided it's better not to present too many theories. That's more or less where we are. It's a bit unusual. I have to discuss also with the optics guys.

It would actually be interesting to maybe make an optics measurement of nonlinearities during the two weeks at the end, but I'm not sure I'm gonna get this in. 

Summary of the High-Intensity Test - Part 1 (Jorg Wenninger)

Slide 13 (Chiara Zampolli): what if something breaks near the Shottky? 
(Jorgen Wenninger:) it is not the Shottky that breaks it is something in or nearby. This is a room temperature vacuum section so it is probably easier to repair, surely, than a standalone magnet that you have to warm up. 

(Martijn Mulders:) Are these components that will be replaced during LS3? 
(Georges Trad): No, this will stay for HL. 

Plans for the 2026 Pb ion run (Roderik Bruce)

(Maciej Trzebinski) if we will do this beam-based alignment for AFP, what would be the filling scheme? We need to also know a bit in advance to prepare.
(Roderik Bruce:): I don't remember the name by heart, but there's a standard filling scheme where we have colliding ion bunches in all IPs with single bunches, which respects the safe beam flag of 3 x 10^11. I can send you the filling scheme offline if you want.

(Federica Oliva:) When exactly is the TCT alignment test for LHCB? Is it during the intensity ramp-up? 
(Roderik Bruce:) No, the background test for LHCB and Alice is here, with the setup beam. We cannot play around with the TCTs with the full machine. So this is all during the commissioning, when have safe intensity, and we would do this test. And then based on that, it would determine the TCT setting to actually use with the full machine. We then stay deterministically with that setting for the physics run. 

LHCb (Flavio Pisani)

ALICE (Krystian Roslon)

ATLAS (Eric Torrence)
 

(Maciej Trzebinski:) Just to confirm: is the baseline plan that we go for beam-based alignment, and we should prepare for that, and only if there is a really bad delay we insert AFP without it?
(Chiara Zampolli:) Can we confirm it after the meeting, so that I just discuss with Roderik and Martijn for 5 minutes? So after the meeting, we let you know.

CMS (Giulia Negro)

AOB

(Roderik Bruce:) We submitted an MD request for ions, and we have again on the table this request for the new beams from the injectors, with varying 50-25 millisecond spacing. I just wanted to ask the experiments whether this is interesting for you to do another fill with that, or not? 
(Eric Torrence:) Do you mean during the MD period? Yes. I think it's interesting.
(CMS and LHC:) also yes. 
(Roderik Bruce:) Ok good. No, I mean, if the experiments will say, no, it's not interesting, then I think that this MD might fall out, but if you say that it's actually something useful for you, then it is still a good thing to push to have this in the planning,