LPC meeting summary 06-02-2023 - final
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LPC meeting summary 06-02-2023 - final |
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Main purpose of the meeting: The main purpose of the meeting was to have a first feedback from the Chamonix Workshop as well as a first look at the schedule for 2023, including the preliminary 2023 LHC commissioning schedule.
Introduction (Filip Moortgat)
The Director of Research has appointed a new (deputy) LPC coordinator, Federico Alessio from LHCb. Niels Tuning and Elena Dall’Occo have been appointed LHCb Run Coordinator and deputy respectively, by the LHCb Collaboration Board.
Studies are still ongoing regarding the value of PileUp (PU) at which ATLAS/CMS will take data in 2023. Three values are currently under evaluation by the two experiments:
PU=60 is currently considered positively by both experiments
PU=65 is under consideration by both experiments
PU=70 is currently strongly disfavored
Joerg Stelzer commented that for ATLAS PU=65 could be possible following more HLT nodes installed and eventually commissioned. It is however noted that commissioning is ongoing and it is tricky.
From Cryogenics, there are three regions of operations regarding the PU values:
A “Normal Operational zone” up to PU=63
A “Possible but risky zone” between PU=63 and 70
A “Forbidden Operational zone” above PU=70.
It is then commented that the limit from cryo is an additional argument to stay PU<=-63, however it was commented that the number is not precise and can only be observed operationally.
Nevertheless, up until PU=60 there are currently no problems foreseen
The Electricity costs for 2023 will be very high, almost doubled with respect to 2022 and any previous operational year. This is the main reason by which operations will mandatorily stop on October 30th 2023.
Filip noted that the extra cost already includes the special price fare with EDF and that only 20% of the price outside the capped value accounts for the huge peak.
An important operational aspect was noted regarding the LHC, in which the Cryogenics system can switch to an “Economy mode” (Eco) whenever possible.
Jorg Wenninger commented that the switchover should take about 24 hours, including cryo recovery.
The Triplet Task Force reported that the triplet radiation distribution is significantly affected by the triplet quadrupole polarity and crossing angle orientation.
Filip made a precision that the 500 fb-1 mentioned in the slide refer to Run1, Run2 and Run3 together.
A reduction of 25% of the total Run3 integrated radiation dose on the triplets is possible if an inversion of polarity is implemented starting in 2024.
More studies are still ongoing regarding this reduction
It is however expected that a large loss of acceptance will happen for PPS and AFP
Mario Deile commented that if implemented PPS would almost entirely lose its acceptance.
Maciej Trzebinski commented that feedback from AFP can be provided but they need optics files
Stephane Fartouk responded that the files for optics are ready and will be provided.
Witold Kozanecki highlighted that the calibration transfer is very important and the crossing angle effects are a major source of error in its measurement
It is also proposed that if the polarity flip happens, the midyear IR1 crossing angle polarity flip should be advanced to 2023, with a proposal to do it in TS1.
Stephane Fartouk commented that the proposal was initially foreseen to happen in 2025. If maintained, there is a risk of overshoot with the inversion (negative) and it needs to be done, then it is proposed to do it in TS1 in 2023.
Jamie Boyd responded that for FASER this will not be great because there is not enough time to prepare to the change of crossing angle in IP1. Currently FASER is calibrated for DOWN/negative crossing in ATLAS.
Maciej Trzebinski asks if validations are needed after the change of crossing.
Jorg Wenninger responded that validations are necessary and therefore TS1 is not great because quite some time will have to be spent in revalidating the machine.
Filip commented that more discussions are needed before making a decision.
Later in the meeting Jorg commented that TS1 is so advanced in the schedule that it follows only 4 weeks of physics production. Therefore it may make more sense to start directly with the change of crossing angle.
Jamie Boyd responded that this will seriously impact FASER for the reasons defined before.
In slide 9 the schedule for 2023 and in slide 10 a first commissioning schedule was discussed. A link to the google spreadsheet for the LHC recommissioning was provided in the agenda.
Jorg Wenninger briefly commented on the schedule: the preliminary first Stable Beams at 450 GeV per beam are scheduled on Thursday April 6th. It was highlighted that this is the Thursday just before the Easter week-end. More Stable Beams at 450 GeV are expected over the week-end as well.
Filip Moortgat added that experiments are expected to comment on the proposal.
Niels Tuning replied that probably some resistance to the schedule will be shown by LHCb, in particular regarding early tests with the LHCb VELO following the LHC vacuum incident.
Jorg Wenninger commented that OP has started preparing a webpage centralizing all links regarding operations.
Jorg Wenninger also added that while the very first beams are currently pinned down on the schedule for March 27th, this is a Monday and it should follow the machine checkout. It is then likely that such a date will shift by 2 days to March 25th.
The 90m beta* run is now scheduled for June 24th, immediately after the TS1.
There were no objections to the proposal so it will end up in the schedule.
Later in the meeting Witold Kozanecki asked for clarifications regarding revalidation of the machine after TS1 and whether this will this impact the 90m beta* star and the following Van der Meer runs.
Jorg Wenninger commented that no there will be no revalidation prior to the 90m beta* run because data taking is performed in ADJUST and the VdM are not done with trains, so train revalidation can be done afterwards.
Teh 3/6 km beta* run scheduling has to be adapted to some limitations. In particular, availability of experts (see ATLAS presentation) and limitations from injectors (HiRadMAt).
Jorg Wenninger commented that HiRadMat may be a problem only if there are many injections very closely done. In principle, this is not the case for the high beta runs.
Filip Moortgat highlighted that if a first run is not put in July in week 29 preceding the MD2 in week 30, then the only possible date is week 35. This is possible, but leaves almost no contingency and if the run does not happen this year, this will not be possible to be done next year.
Mario Deile commented that TOTEM would prefer to keep the option in July.
In the last slide, Filip commented at the next LPC meeting, currently scheduled for February 27th, there will be a first presentation regarding the ion run by Roderick
Roderick confirmed this is ok.
Filip Moortgat commented that the emulsion for FASER and SND scheduling needs consideration for dark room booking.
ATLAS (Joerg Stelzer)
A few operational requests from ATLAS have been collected and presented.
ATLAS asks for splash events: 10 events per side with as low as possible intensity and splashes for horizontal muons, 1M events per side.
ATLAS will take data in collisions at 450 GeV per beam.
In these runs, AFP and ALFA are requesting to be inserted, in particular following the repair that happened in ALFA.
Jorg Wenninger asked how much insertion is requested.
Maciej Trzebinski responded that this is to be understood. Conversely Maciej asked how much they can insert without Beam Based Alignment.
It was suggested to continue the discussion offline.
ATLAS will request one low-mu run for AFP during the intensity ramp-up.
ATLAS also reminded that the toroid will remain off for the start of the ramp-up to collect muon alignment data.
ATLAS requests one indiv colliding bunch for trigger commissioning, throughout the full year.
ATLAS/ALFA has a few comments regarding the schedule and preparation of the high beta running in 2023
Week 29 is fine for ATLAS regarding the 3/6 km high beta* run, but it must take place between Monday-Friday due to unavailability of experts during the week-end.
Jorg Wenninger commented that if this is the case then the most logical thing would be to continue with the MD block in teh week-end and not wait for the MOnday after. This will need to be agreed early on.
ATLAS requests attention toward a few items in order to make the preparation as thorough as possible
Optics team usually carries out a series of tests in view of the preparation. ATLAS hinted that this could be done during a previous MD. Jorg Wenninger also pointed out that preparation time for the high beta* runs should come out of operation time, not MD.
It is also requested that background conditions in ALFA are verified. Jorg Wenninger commented that this is ok, but what and when needs to be decided.
In this sense, ATLAS/ALFA commented that finding settings with minimal background is crucial.
Roderick Bruce asked what in particular ALFA cares about in terms of background, whether it is rates or distribution.
Hasko Stenzel responded that they care about both actually.
ATLAS/ALFS also asks about the status of the 3/6 km beta* optics development as well as where the decision between 90 and 120m can be taken
Mario commented that 120m was put forward by TOTEM and that it is not that different for ALFA. It would be preferred if the injectors could provide not too small emittance as a higher beta* would lower the peak pileup. Acceptance wise is very similar, so 120m would be preferred.
Filip Moortgat that a decision will be taken considering the constraints.
Mario Deile commented that all the aforementioned comments are valid for TOTEM as well. Mario also suggested that it may be useful to have a meeting at some point between collimation, ALFA and TOTEM.
Roderick Bruce responded that this topic could be discussed in a Collimation WG meeting.
ATLAS/ALFA has also a few comment regarding operations in the high beta* runs
During the 90m run, ALFA will be inserted and non-SB data taking is fine.
During the 3/6 km run, ATLAS will need to turn on the Inner Detector for ~two fills during the 5-day program to measure beam width and calibrate luminosity response
Idea is to keep ID participation as low as possible, and the total time needs to be defined.
For that, ATLAS would require STABLE BEAMS or at least some form of QUIET BEAMS
Jorg Wenninger commented that it doesn’t really make much sense to declare SBs as collimators move and the LHC is not validated.
Joerg Stelzer responded that in that case a procedure needs to be defined as no risks should be taken with ID powering if SB are not declared.
Witold Kozanecki commented that for the 3/6 km run a luminosity calibration must be done as it is likely one of the biggest systematics.
Jorg asked if TOTEM will be operated during the 3/6 km beta* run
Mario Deile responded that yes it will be operated but not for long periods.
AFP will be in garage position for both 90m and 3/6 km beta* runs.
Brian Petersen reminded that collimation limits should be checked beforehand to avoid unwanted dumps.
ATLAS highlighted an ongoing discussion regarding the impact of TCL6 collimator settings on AFP.
Current settings for Run3 lead to more radiation for the AFP FAR station
The settings of TCL6 at 2sigma are tighter in Run3, corresponding to 1.2mm
Too much radiation meant that it was impossible to perform threshold scans and tuning of the SIT modules, as well as interventions were impossible as the limit of 50 uS was reached within a few minutes.
The ongoing discussion is based on two approaches
Open the collimator, but this has a negative impact on FASER as it increases track multiplicity and trigger rates
INstallation of extra shielding
Try the opening of the TCL6 to 2 mm, as FLUKA simulation would already give a good indication if this might work.
Jamie Boyd confirmed that 2mm for FASER is ok.
Roderick Bruce commented that one could probably have a look at previous FLUKA simulations as they can already give an indication
Maciej Trzebinski confirmed that there are only passive radiation monitors in the area and cannot do time window measurements.
Stephane Fartouk commented that optics should be studies.
ATLAS lastly described their strategy regarding PU choices in 2023
Minimal target for 2023 would be PU=60 at L=2.01x10^34cm-2s-1
Operations at PU=65 is being considered. Studies are ongoing to conclude on teh ability of the ID to cope with the expected bandwidth as well as it is not excluded that L1 trigger thresholds may need to be raised to keep the rate below the operational value of ~95kHz.
Operating at PU=70 would provide an increase in luminosity that would benefit the physics reach, but it does not seem achievable by the ATLAS inner tracking system.
In conclusion, ATLAS prefers to start at PU=60 until the LHC reaches stable operations with the full machine and a stable operating point regarding the commissioning of the Phase-I trigger systems is reached. After that, a careful rise of the luminosity and pileup will be done.
Filip Moortgat confirmed that such a plan is sound.
CMS (Gianni Masetti)
In addition to the content of the slide, Gianni underlined that the requests from CMS have not yet been collected and will be presented in following LPC meetings.
Gianni asked LHC-OP experts how many crossing angles changes will be done during the leveling.
Jorg Wenninger responded that the change of crossing angle happens at every step. The criteria for change is 5% or at least 30 minutes. This was confirmed by Stephane Fartouk.
Michi Hostettler commented that the steps are designed in such a way that each step would be done approximately every 30 minutes considering the expected decrease.
Joerg Stelzer asked how a different leveled luminosity could be achieved in ATLAS and CMS.
Jorg Wenninger responded that this can be done with offset leveling, but it is highlighted that it is not possible to have both ATLAS and CMS with beat* and separation leveling at the same time.
ALICE (Andrea Ferrero)
The ALICE magnets will remain OFF until the machine restarts. ALICE requested LHC-OP to inform them regarding when magnets are required and if both solenoid and dipole.
Jorg Wenninger responded that it will be followed up
ALICE plans a low-field scan and 0B data taking for alignment during the machine ramp-up
JC Gayde from the LHC asked ALICE to provide feedback on the vertex position in IP2 as there is a suspicion of a +0.2mm vertical misalignment. ALICE will provide feedback.
It was however commented by Andrea that what is really critical is the longitudinal position that will be carefully checked.
LHCb (Niels Tuning)
LHCb is currently evaluating the consequences of the LHC vacuum incident in the VELO detector. Three options are on the table as described in the slides. A decision is yet to be taken and the LHCb Technical Coordinator will present the options and the baseline at the LMC on Wednesday February 8th.
Nevertheless, Niels Tuning commented that whatever the option is chosen, while the commissioning will be ongoing as planned with all sub-detectors, the LHCb physics programme is strongly affected.
AoB
Michi Hostettler reminded everybody that before starting there will be a dry run with a cycle of handshake-DIP exchange tests. For the test, the interlocks need to be cleared after the DSO test that happens on March 10th.
Stephane Fartouk commented that the beta* leveling is now calibrated for nominal conditions. Stephane asked to clarify what the strategy for 2023 regarding beta* leveling is.
Filip Moortgat responded that the strategy is the same as in 2022: reach the leveling goal as quickly as possible and then stay leveled. However, more clarifications will be done offline.
Michi Hostettler responded that in the first few cycles, one may desire to do one step and then reoptimize just to make sure everything is understood, rather than rush through the steps.