Abstract
The 10th LHC operations workshop aims at preparing the operational scenario for run 3 with particular emphasis on the post-LS2 re-commissioning and the 2022 running scenario. This includes:
| Chair: Rende Steerenberg | Program Committee |
| Theodoros Argyropoulos | |
| Co-Chair: Jörg Wenninger | Chiara Bracco |
| Enrico Bravin | |
| Andrea Calia | |
| Stéphane Fartoukh | |
| Michi Hostettler | |
| Giovanni Iadarola | |
| Delphine Jacquet | |
| Elias Métral | |
| Workshop Secretary: Sylvia Dubourg | Daniele Mirarchi |
| David Nisbet | |
| Tobias Persson | |
| Stefano Redaelli | |
| Matteo Solfaroli | |
| Rende Steerenberg | |
| Helga Timko | |
| Rogelio Tomas | |
| Georges Trad | |
| Jörg Wenninger | |
| Daniel Wollmann |
This presentation summarises the experience with the LHC powering tests following the Long Shudown 2, also in the context of previous hardware commissioning campaigns. The talk will focus on the successful execution of the various commissioning steps, highlighting the encountered problems, the identified solutions and key decisions taken, with particular emphasis on the training phase of the main dipole circuits. The lessons learned during the re-commissioning of sectors 23 and 78 will be covered in detail. The talk will conclude with an overview of the outstanding tests to be performed in 2021 and the plans for the commissioning after the YETS2021/2022.
The two weeks of beam test in October 2021 marked an important milestone in the re-commissioning of the LHC after the Long Shutdown 2 (LS2). After almost 3 years of shutdown, first beams were back circulating in the LHC as of October 19, 2021. After one week of setup with pilot bunches, collisions were re-established with nominal bunches at 450 GeV.
This contribution summarises the main findings and achievements of the beam test and highlights their implications for the 2022 run. Operational and organizational aspects are also discussed, in particular the impact of the restrictions due to the Covid-19 pandemic on LHC beam operation.
The talk will give an overview of the Year End technical Stop 2021-22, including the activities related to the RF finger repair in S23, maintenances, consolidation and HL-LHC. The methodology of the handover between EN-ACE and BE-OP will be also described identifying major milestones.
The frame of programmed stops during run 3 will be commented, explaining the methodology which will be in place to coordinate activities during this period.
In the framework of the LIU project, the whole injector chain has undergone substantial modifications during LS2. While 2021 operations in the injectors has mostly focused on the the re-establishment of pre-LS2 beam performance of the non-LHC-type fixed target beams, a large effort has been invested to commission the LHC proton and lead ion beams during machine development and special commissioning periods. Thanks to these studies the LIU intensity and brightness ramp up for proton beams and the SPS slip stacking commissioning for ion beams are already well underway. This contribution summarises the 2021 experience with LHC beams in the injectors and highlights the challenges faced. Furthermore, the available beam types and the expected performance for LHC operation in 2022 are presented, together with an outlook of beam parameters to be expected throughout Run 3.
During the LS2, major upgrades to the injection protection system were implemented. In particular with the replacement of TDI, new TCDIL, new TCLIA and a new optics of the TI8 transferline. The impact of those changes on beam commissioning and operation will be addressed in this contribution.
Recent updates to the IQC and the prospects of beam steering with high intensity trains will also be discussed. Finally, the readiness for Run3, its extension and beyond for HL-LHC will also be addressed.
Two 6-t beam dumps, made of a graphite core encapsulated in a stainless steel vessel, are employed to absorb the energy of the two Large Hadron Collider (LHC) intense proton beams during operation. Operational issues started to appear in 2015 during LHC Run 2 (2014-2018) as a consequence of the progressive increase of the LHC beam kinetic energy, requiring technical interventions in the highly radioactive areas around the dumps. Nitrogen gas leaks appeared after highly energetic beam impacts and instrumentation measurements indicated an initially unforeseen movement of the dumps. A computer modelling analysis campaign was launched to understand the origin of these issues, including both Monte Carlo simulations to model the proton beam interaction as well as advanced thermo-mechanical analyses. The main findings were that the amount of instantaneous energy deposited in the dump vessel leads to a strong dynamic response of the whole dump and high accelerations (above 2000g). Based on these findings, an upgraded design, including a new support system and beam dump windows, was implemented to ensure the dumps' compatibility with the more intense beams foreseen during LHC Run 3 (2022-2025) of 539 MJ per beam. The contribution will review the refurbishment of the core, the current spare strategy, any potential limitations in view of Run 3 and the technical activities supporting the operation in Run 3.
An overview of the existing LHC beam dump vacuum window is presented, and its main limitations are discussed. The new design is then introduced and its compatibility with the HL-LHC beam parameters is analysed. Improvement in reliability, operation flexibility, spare strategy and possible replacement scenario during operation run will also be detailed. Finally, the status of the installation carried out during the YETS 21-22 is going to be presented.
The LHC relies on a complex collimation system to protect against unavoidable beam losses and to minimize the risk of quenching the superconducting magnets. During LS2, 16 new collimators were installed to improve the system's performance in various aspects. In addition, 2 new crystal collimators are planned for installation in the YETS2021. This presentation will provide a status report of the final Run 3 collimation system together with an overview of the deployed interlock strategy. The collimation commissioning plans in terms of hardware and software will then be presented, including the latest requirements following the 2021 beam test.
The Tune & Orbit Feedback system has been heavily renovated during LS2 based on the experience gained over the Run2 of the LHC. In the first part of this presentation, the hardware, software and operational changes will be presented.
Given that Tune & Orbit Feedback is one of the key systems of the LHC, extensive testing has been performed to validate the new software requirements. These tests follow industry-standard best practices including black-box testing, continuous integration and acceptance tests in a closed-loop simulated environment. Testing methodology, experience and results will be explained.
The renovated system has been validated during the 2021 LHC Beam Test and the results, along with the impact on the Run3 LHC operation, will be presented.
During the LHC second long shutdown (LS2), most of the beam instruments in the LHC were updated and consolidated to cope with the higher brightness and intensity of the injected beams and prepare for the future High-Luminosity LHC. An overview on the major hardware and software changes carried out through LS2 is given, highlighting the first results achieved during the 2021 pilot beam tests and the expected performance and limitations of those instruments for Run3.
During LS2, ADT and ADTObsBox have received a substantial upgrade. New low noise BPM electronics were
developed and successfully tested with beam in October 2021 in the LHC. Power amplifiers in the tunnel underwent
maintenance and were equipped with new tetrodes. The ADTObsBox has been completely redesigned using state of the
art computing hardware and new low and high level software. All these upgrades allow to operate ADT in Run3 with
significantly improved performance and will provide more features to operations and accelerator physics teams. Many
previously experimental features should become operational tools in Run 3.
During the commissioning for the beam test, we have learned a lot about the new system. From this experience we have
developed procedures and tools to optimize the setting up for the restart. ADT is ready for the restart in 2022 with
robust feedback, all extra features known from the previous runs and the possibility for new special features and modes
of operation during Run 3.
This presentation will look at some of the more significant software changes to the control system since the end of Run 2, and will provide bigger-picture motivation and strategy around them.
Topics will include development languages and tools, the evolving GUI strategy, the new logging service (NXCALS) and the refresh of the post-mortem system.
There will be a reflection on the implications of these changes with respect to operations in 2021, and an outlook for a number of the identified areas of improvement will be provided.
Modification of LBDS during LS2 aimed increasing of the beam dump system reliability in several ways: 1. upgrade of HV switch insulator design to reduce sparking probability; 2. increasing capacitance of energy storage capacitors resulting in reduced nominal voltages on generators and on magnets; 3. replacement of SEB sensitive HV semiconductor switches by less sensitive ones; 4. modification of the dilution kickers retriggering philosophy to reduce risk of critically low dilution kick due to anti-phase in case of erratic firing of one kicker. Post LS2 failure rate estimation at 7 TeV is now lower than pre LS2 one at 6.5 TeV. Upgraded LBDS system was tested up to 7.25 TeV in the tunnel for the whole system and up to 7.5 TeV in laboratory as a type test without any issues. Thanks to upgraded performance of the new triggering system of extraction generators and faster propagation speed in retriggering system, the delay of retrigger in case of asynchronous dump was reduced from original ~1.3 us down to less than 900 ns, thus resulting in lower risk of protection systems damage. We do not expect negative impact of eventual 1-year extension of Run 3 on LBDS reliability under nominal beam intensity conditions
A brief summary of system changes during LS2 is given, with emphasis on the exchange of cryo-module 2B1. Based on the experience with 2021 recommissioning and the pilot test run, lessons learned are analyzed and the plan for 2022 commissioning is presented. Estimated beam and RF parameters are presented for Run III, for different intensity regimes, and necessary changes in operational working points are discussed. Finally, we address the impact of a possible one-year extension to Run III.
During LS2 all LHC experiments have performed detector maintenance and upgrades to improve physics performance. For LHCb and ALICE this enables them to take data at significantly higher luminosity. The performance goals, luminosity limitations as well as special requests/constraints for the running conditions will be presented for both proton and heavy ion running. The forward physics program has been extended for Run 3 with several new dedicated experiments which will be briefly presented along with the overall plans and requests for the forward physics experiments. Run 3 foresees multiple special runs, such as oxygen beams and high beta* running and a proposed special run plan will be presented including implications of a 1-year extension of Run 3.
The completion of the LIU project will enable LHC to inject beams twice as bright as in Run 2 (both from lower emittance and higher intensity). The LHC Run 3 Configuration Working Group (LCR3) has reached a solid proposal for the Run 3 operational scenario to maximize integrated luminosity. This talk presents key aspects of this proposal including a roadmap with key validation milestones, optics and performance estimates together with implications from extending Run 3 by one extra year.
In Run 3 using a combination of beta* and crossing angle settings, the instantaneous luminosity delivered to the high-intensity interaction points IP1 and IP5 of LHC will be leveled to a maximum of 2e34 cm-2s-1 in collisions, from a few hours (in 2022) up more than 10 hours (in 2023/2024). This leveled value is set by the cryo-cooling capacity of the existing inner triplet and, slightly in the shadow, by the experiments to match their capacity to absorb the interaction data in their trigger and DAQ systems. While this goal applies to the instantaneous beam luminosity considering all bunches, bunch-to-bunch variations may change the picture, require further adjustments, and may impose constraints to the leveled goal. In this presentation we will go through the key results from Run 2 data on bunch-to-bunch luminosity variations in collisions. We would explain their origins, the observations during collisions in the Run 2 fills, along with expectations for Run 3 conditions. We will also try to propose strategy to balance the conflicting requirement of a maximum average (beam) luminosity leveling with that from bunch-to-bunch variations for an overall optimal exploitation of the leveling time and integrated luminosity. The situation of LHCb will also be analysed.
The present LHC lifetime is directly linked with the radiation dose limit that can be withstood by the beam line elements around the ATLAS and CMS detectors, in particular the insulator material used in the coils of the superconducting magnets composing the final focus triplet string and the normal conducting modules of the separation dipole. The peak dose profile along the aforementioned coils is due to the collision debris generated at the Interaction Point and depends on the coil aperture and several operational parameters, such as beam energy, crossing plane, crossing angle magnitude and sign. Detailed estimations of the dose values reached so far and expected through Run 3 are presented, including the scenario of 1-year extension, and the effect of mitigation measures is quantified.
The restart of the LHC operation in 2022 for three years of physics production, namely Run3, coincides with the completion of the injector’s upgrade, aiming to increase the beam brightness by a factor of two (achieved both from improved emittance and increased intensity). Such an increase of the beam intensity is accompanied by an enhancement of the strong non-linear fields produced by beam-beam interactions, which is the dominating factor of performance degradation during collisions. In the presence of strong non-linearities such as beam-beam effects, the selection of the appropriate machine settings given the expected beam parameters during the operational cycle of the LHC is of paramount importance in order to ensure its optimal performance. To guide the orchestration of these parameters, a multi-parametric Dynamic Aperture (DA) simulation framework has been developed and successfully employed in Run2. Using this framework, this talk illustrates the preservation of the DA and thus, of the beam lifetime, during the most important processes of the LHC hypercycle such as the LHCb crossing angle rotation, the tune change, the collapse of the separation bumps and the luminosity leveling. Other effects such as beam-beam induced beta-beating and the impact of beam- beam effects on the closed orbit are also discussed.
The LHC beam stability is evaluated throughout the different beam processes for Run 3, considering the beneficial effect of the collimator upgrade as well as the increased brightness with respect to Run 2. The related recommendations in terms of Landau octupole strength, chromaticity, damper gain and optics corrections are thus provided. Finally, a plan is proposed for measurements during Run 3 in order to further improve the LHC impedance model and consolidate the knowledge of the stability limits. The benefit from the possible deployment of new diagnostic tools and measurements techniques will be discussed.
This talk gives an overview of the foreseen running periods for Pb-Pb and p-Pb operation in Run 3, as well as the foreseen machine configuration and expected beam parameters. The projected luminosity performance will be presented, as well as possible paths for improvement. In addition, the tentative plans for the LHC pilot run with oxygen beams will be discussed.
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The LHC beam operation will restart in March 2022, the commissioning will be a challenge. Many systems will have to be made operational again after the Long Shutdown and their performance checked. Thanks to the LIU upgrade, the injector complex will deliver beams with increased intensity and reduced emittance. The response of the LHC and its technical systems will have to be verified. This talk highlights the main milestones and requirements for the 2022 beam commissioning. A glance at the different machine configurations required in 2022 will also be given.
In Run 2, routine LHC operation was done for the first time with 25 ns bunch spacing, leading to an increased electron cloud production. Although significant mitigation through beam-induced scrubbing was achieved, electron cloud affected beam stability and quality throughout the run. In addition, strong heat loads were generated on the beam screens of the superconducting magnets, with a large variation between magnets and arcs, in some cases approaching the nominal cooling capacity delivered by the corresponding cryogenic plant. In view of measurements, studies and interventions performed during Run 2 and the following Long Shutdown 2, the prospects for electron cloud effects during Run 3 will be discussed. The requirements for scrubbing, estimates of the required and available cooling capacity, as well as forecasts for electron cloud instabilities will be presented, considering also the availability of higher brightness beams after the completion of the LHC Injectors Upgrade.
The LHC Beam Loss monitoring system is a key element in machine protection. Near 4000 beam loss detectors, ionisation chambers, are installed along the LHC protecting machine equipment by triggering a beam extraction in less than 3 LHC turns. Each detector is able to trigger a beam dump when its signal exceeds predetermined thresholds as function of the beam energy and 12 different running sums. In LS1 there was a big effort to make more uniform the BLM thresholds families for the superconducting magnets which was proven to be very successful on controlling and minimising the thresholds changes during the Run 2. However thresholds at the collimators, devices where the beam losses are concentrated, are still relying on the initial model and damage limits estimates. This talk will describe the changes foreseen for Run 3 for the beam loss thresholds at collimation in Point 7, where main betatron halo cleaning occurs, based on new damage limits from quench tests studies and updated energy deposition simulations, including new collimator materials like MoGr. Additional BLM threshold changes for Run 3 will be outlined.
Dust particles interacting with the proton beams - commonly referred as UFOs - were the main source of transient beam losses in the past operation of the LHC. UFOs gave rise to 40 premature beam dumps and 8 dipole quenches in Run 2, resulting in the loss of more than 200 hours of beam time. The risk of dumps and quenches critically depends on the UFO event rate, which had significantly degraded after LS1. If a similar de-conditioning is observed after LS2, UFOs can have a relevant impact on the machine performance in 2022, in particular due to the reduced quench margin at 6.8 TeV and the higher shower-induced energy density in coils. This talk summarizes the present understanding of UFOs, the lessons learned from Run 2 and the increased risk of quenches at 6.8 TeV. Based on this input, UFO-related BLM threshold strategies for 2022 are discussed and expectations concerning dumps and quenches are presented. The talk also the outlines the impact of a possible 1-year extension of Run 3.
During Run 3 of the LHC, the stored energy per beam is expected to reach 500 MJ. In addition, new scenarios, as the extended use of beta* levelling, will increase the operational complexity. The talk will review the commissioning strategy of the machine-protection systems in 2022,considering the experience of the recent beam test. It will then examine the existing intensity limits and discuss the machine-protection challenges for Run 3.
In the beginning of Run 2, the beta was 80 cm and it was gradually squeezed down to finally reach 25 cm in 2018. In Run 3, the goal is to reach a beta of 30 cm already during the first year, which poses a series of challenges as to commission several production optics in the start-up. In Run 2 it was demonstrated that coupling control was critical for beam stability and luminosity production. Furthermore the correction of non-linearities was fundamental to enable accurate linear optics corrections. In this talk, we outline the plans for linear and nonlinear optics corrections needed to guarantee safe machine operation and to deliver design luminosity to the experiments. This talk also presents the plans and newly developed methods to correct coupling, explaining the improvements in tools, setup and methodology to further improve the corrections and the efficiency of the commissioning. Finally, a short summary of the observations during the 2021 beam tests is presented.
A comprehensive review of experience gained during the 2021 test beam is presented, on which perspective on 2022 beam commissioning are built. The main focus is given to the beam-based alignment and validation strategy of collimation performance, together with proposed settings with non favourable TCT/TCDQ phase advance. Global and local aperture measurements are discussed, and relative implications of performance reach are reported. The impact of a possible 1-year extension to Run 3 is addressed.
This presentation gives an overview of the different Machine Development topics and time required in 2022, as they have been identified by the different teams participating in the MD program. The possibility of synergies between the different topics is studied. With this in mind, an estimate of the total time required for MDs in 2022 is given and compared with the present draft schedule.
The advantages and disadvantages of having MDs outside the scheduled MD blocks during the commissioning and physics period are analysed. The roles of the different parties involved in the organisation of MDs – the LHC Studies Working Group (LSWG), the Operations Team and the Machine Protection Panel – are highlighted. Foreseen changes in the MD request form and procedures are presented.
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