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The 8th LHC Operations Evian Workshop will be held on 12-14 December 2017 in the Hotel Ermitage in EVIAN (74), France.
Attendance is by invitation only.
The principal aims of the workshop are to:
| Chair: Rende Steerenberg | Program Committee |
| Co-Chair: Jorg Wenninger | Wolfgang Bartmann |
| Enrico Bravin | |
| Editors of the Proceedings | Massimo Giovannozzi |
| Theodoros Argyropoulos | Wolfgang Hofle |
| Sylvia Dubourg | Elias Metral |
| Georges Trad | Stefano Redaelli |
| Rende Steerenberg | |
| Informatics & Infrastructure support | Jorg Wenninger |
| Hervé Martinet | Markus Zerlauth |
| Workshop Secretary: Sylvia Dubourg |
Abstract:
This paper summarises the LHC machine availability for the standard proton physics period in 2017. The paper considers first operational aspects, such as beam mode ratios, beam dump causes, fill length and turn-around. Following this, a detailed breakdown of all faults and their impact upon LHC is given, with notable faults and new root causes identified. This paper concludes with a comparison of 2017 to 2016 LHC availability performance, giving the principle changes which have been observed.
This paper gives the basic metrics of LHC availability in 2017, which are expanded upon by dedicated talks at this workshop. This work has been produced and ratified by the Availability Working Group which has compiled fault information for the period in question using the Accelerator Fault Tracker.
v11 corrects a mistake presented in v10 in the 2016-17 fault paretos
An injector fault was missing:
was incorrectly labelled as "NON BLOCKING" when the data was first extracted.
The time spent in Operations in 2017 was about 30% of the total time for physics, much larger than what achieved in previous years. This will be analyzed and possible causes drawn. Operations will then be split in its separate phases and some consideration and suggestions for optimization will be proposed.
Abstract:
For the first year the Accelerator Fault Statistics (AFT) was implemented and employed by the LHC injectors. In this paper, the LHC downtime due to the injector chain will be analysed with data from AFT and compared to last year [1]. The main root faults from the injectors will be explained. In addition, it will be outlined how AFT is currently used in the injectors, open issues and future improvements.
Abstract:
The performance of the LHC magnet circuits for the proton physics run in 2017 is evaluated. This contribution focuses on the availability of magnet powering (PC) and protection systems (QPS, EE, FMCM and Interlocks) and evaluates the impact of the new deployments, mainly the FGClite and RPADO power converters, on the overall performance of the machine. Finally, a comparison with 2016 availability is presented.
Abstract:
In this talk, the dependability of CERN’s Beam Instrumentation (BI) in 2017 is presented. All faults which contributed to LHC downtime are analysed, categorised and compared to previous years to isolate recurrent failures and evaluate trends. Special attention is given to the Beam Loss Monitoring system and their Sanity Checks which was the highest contribution to the BI downtime in 2017. Finally, actions taken to remedy the situation as well as on-going reliability analysis and upgrade efforts to improve the overall performance in the future are discussed.
Abstract:
This contribution will detail the summary of the LHC TDE dump block observations during the 2017 operational run, eventual limitations and the current plans for the YETS. Details will be provided on the efforts made to reduce potential downtime of the machine, including the interferometer readings, the redesign of the downstream window and graphite oxidation studies. Long-term perspectives for LS2 and LS3 will be provided as well in order to guarantee the long-term operability and availability of the dump block assembly.
Abstract:
The availability of the LHC ADT and RF systems in 2017 is presented in details, including high- and low-power RF and RF controls. A comparison with 2016 availability is performed. The full-detuning scheme, commissioned early this year, has been operational throughout the year and the first experience with this scheme is summarised. New operational diagnostics, implemented this year, are shown as well. Finally, the latest findings from beam dynamics studies and measurements, which have implications for the operation today and in the near future, are highlighted.
Abstract:
This talk will cover feedback from the experiments on the 2017 run, including the high luminosity 13 TeV running, as well as the scheduled special runs that took place. It will include feedback on the 8b4e BCS scheme that was developed as a mitigation of the 16L2 issue observed during the 2017 run. In addition it will cover feedback on new operational features that were implemented for the first time in 2017, for example the RF full-detuning, crossing-angle anti-levelling, luminosity levelling, and the use of 30cm B* with ATS optics.
Abstract:
This contribution presents a general overview of the LHC operation in 2017. It outlines the experience gained during the year after all the machine improvements (ATS optics, 30cm beta* and crossing angle levelling at IPs 1 and 5, RF full-detuning, etc.) that were put in place since 2016 and how the daily operational procedure was affected. New software tools or updates on the existing ones are discussed with emphasis on their application during the operation. Possible further improvements or still pending ones from the 2016 requests are finally presented.
Abstract:
In 2017 optics commissioning strategy for low-beta operation underwent a major revision. Where formerly the beam-based commissioning exclusively considered linear dynamics, the new approach is based on a combined commissioning of linear and nonlinear optics. Details of the updated strategy will be reviewed, together with associated impacts on optics quality and operation. New procedures for coupling compensation will be presented, as will requirements for commissioning in 2018.
Abstract:
The LHC collimation system is aimed at ensuring a safe machine operation; it provides the LHC with passive protection, minimizing the risk of magnet quenches induced by beam losses. In 2017, the LHC collimation system confirmed its excellent performance, with no magnet quenches due to losses from circulating beams while accommodating changes in machine configurations. The system availability in 2017 was also very good. The present work reviews key elements of past year operation, from initial commissioning with beam to beam losses, lifetime and collimator hierarchy.
Abstract:
In 2017, three major developments with serious implications on the beam lifetime took place: the deployment of the crossing angle orchestration (allowing to act on it even in stable beams), the reduction of beta* from 40 to 30 cm and the switch to 8b4e (and later BCS) beams. These actions have been closely followed up with Dynamic Aperture (DA) simulations and, when possible, also Machine Developments (MDs), aiming at maintaining the beam lifetime on the optimum for the luminosity production. The fill-by-fill follow-up was enabled by new tools for the LHC performance analysis based on modelling and measurements. While the predictions of the machine settings massively rely on CERN’s computing resources, the performance analysis requires inputs from several instruments; the difficulties encountered in both cases will be presented together with recommendations for the future.
Abstract:
Events linked to fast losses in the 16L2 half cell have plagued a large part of the 2017 Run. While the analysis of what happened is intentionally left for the Chamonix workshop, this contribution will gather the available observations and the understanding of the situation as predicted by simulations and models, before the warm-up planned during the ongoing YETS. It will also evaluate the impact of the 16L2 events on global LHC performance in 2017.
Abstract:
The observations of coherent instabilities are compared to the expectations based on the beam instability model. Their impact in the different phases of the LHC operation and the corresponding mitigations strategies are discussed, with an emphasis on the developed diagnostics.
Abstract:
The first part of the presentation will summarize the overall cryogenic performance and availability for 2017 and the expected performance for 2018 taking into account the beam induced heat loads in the inner triplets magnets and the beam screen circuits. The second part will focus on the update of the expected cryogenic limitations as well as on the available cryogenic power studies and associated tuning in order to deliver the required cooling power with respect to the 2018 beams operational conditions. The feedforward controls and refrigeration capacity improvements on the inner triplets and beam screen circuits will be discussed.
Abstract:
The injectors have delivered different beam types for luminosity production in the LHC during the 2017 run. Besides the nominal beam with 25 ns spacing and 72 bunch batches at PS extraction, the batch-compression-merging- splitting (BCMS) beam with multiples of 48 bunches at extraction from the SPS has been produced. The reduced number of bunches per batch from the PS is compensated by almost twice smaller transverse emittance. The vacuum related issues in the LHC (16L2 cell) could be mitigated by switching to the so-called 8b4e beam, where mini-batches of 8 bunches are followed by 4 empty bunch positions in between. Thanks to the flexibility of the injectors, a higher brightness version of the 8b4e has been prepared to quickly react to the needs of the LHC. In this presentation, an overview of the beams from the injector complex is given, describing how the beams are produced and summarizing their characteristics, achieved performance and specific limitations. In view of the operation in 2018, the expected beam parameters are presented, as well as a reminder of possible alternative beam types from the injectors.
Abstract:
The emittance preservation of high brightness beams is crucial for obtaining the required future luminosities. A tight budget for the emittance degradation along the injector chain is thus necessary. The presentation will give an overview of 2017 emittance measurements with operational beams in the injector chain, and show possible emittance growth during the cycle and at the transfers. The measurements depend strongly on the performance and limitations of the instrumentation to measure the transverse emittance. The tools to calculate and monitor the emittance, various studies to reduce emittance growth, and cross-calibration studies between accelerators will be summarized, finally leading to prospects for 2018.
Abstract:
Along the continuous optimization of the LHC cycle during the recent years, injection became more and more the beam mode where the biggest potential for reducing time and hence to increase the LHC luminosity production is foreseen. This contribution will outline the main actions done during this period and highlight the main periods where time could be gained. Further, it will look into major pitfalls and try to evaluate potential mitigation strategies. Where possible, this will be backed by statistics from quality checking tools along the accelerator chain, including a new diagnostics tool which was put in place last year to identify causes for unsuccessful injections in the LHC.
Abstract:
Hardware limitations due to the intercepting devices in the SPS, the SPS-to-LHC transfer lines and the LHC will be briefly reviewed with potential operation beam in mind for 2018. Heating issues in the LHC injection kicker magnet (MKI) are also a possible future limiting factor for LHC’s availability. Prior to LS1 one of the MKIs occasionally exhibited high temperatures leading to significant turnaround times before beam could be safely re-injected. After a successful impedance mitigation campaign during LS1, the MKI temperature has been below the Curie point and did not limit LHC availability: simulations suggest that they will remain fully operational with nominal RUN2 beam parameters. To investigate intensity limits in view of the 2018 run, different filling scenarios have been considered. A prototype MKI magnet is scheduled for installation during YETS 2017/2018 upgraded to reduce dynamic vacuum activity and relocate beam induced losses within the magnet. The main design changes are outlined and the corresponding thermal behaviour and intensity limits are discussed.
Abstract:
In 2016, part of the luminosity performance improvement for the ion run could be achieved by reducing the PS batch spacing in the SPS. The same optimisation process was then applied to proton beams resulting in the reduction of both SPS and LHC batch spacing in 2017 operation, i.e. to 200 and 800 ns respectively. In this contribution, the operation with and evolution of the new injection settings over 2017 is presented, together with the stability of rise-time of the individual switches for the two kicker systems. The luminosity gain following these changes is also evaluated and the expected luminosity for potential beam filling patterns in 2018 is investigated. Finally, the possibility for further improvements is discussed.
Abstract:
In view of the newly implemented variable Abort Gap Keeper (AGK), this talk will review the protection layers that should prevent an injection of beam into the abort gap and identify the critical regions inside the abort gap. In particular, it will examine the accidental injection of several bunches into the abort gap after a filling-pattern change in September 2017 and discuss the lessons learned.
Abstract:
Measuring the beam transverse emittance is fundamental in every accelerator, in particular for the LHC, where its precise determination and its preservation is essential to maximize the luminosity and thus the performance of the colliding beams. In this contribution, a review of the status of the synchrotron radiation monitors, the beam gas vertex detector and the wirescanners will be presented alongside the assessment of the obtained performance. The new features implemented and the issues encountered during 2017’s operation will be highlighted. Additionally, the interventions and improvements planned for the coming winter shutdown will be discussed.
Abstract:
This talk will briefly outline the main methods to measure the luminosity and to calibrate the luminosity detectors in the LHC experiments. It will discuss the size of the systematic uncertainties on the measured luminosity at the online and offline level. In addition it will include a discussion on any possible imbalance between the luminosities delivered to ATLAS and CMS during the 2017 run.
Abstract:
The emittance of the LHC beams when arriving in collisions is a key parameter for luminosity. Hence, the emittance of the beams from the injector complex needs to be preserved as well as possible throughout the cycle for maximum luminosity. Moreover, due to the V/H crossing scheme in IP1 and 5, non-round emittances yield different luminosities for ATLAS and CMS. Such a difference was e.g. observed in 2016 proton physics operation.
This contribution analyzes the emittance evolution throughout the LHC nominal cycle in 2017. The emittance growth from injection to collisions is studied and the different emittance measurements are compared. Reproducible bunch patterns are shown and differences between the operational beam types (BCMS, 8b4e) are highlighted. Also, the roundness of the beams and the impact on the ATLAS to CMS luminosity ratio is assessed.
Abstract:
The LHC luminosity model developed to describe and follow the evolution of the machine luminosity is presented and compared to 2017 data. The model is based on the main mechanisms of luminosity degradation, such as intrabeam scattering, synchrotron radiation, elastic scattering and luminosity burn-off. It was initially introduced for the 2016 run. For the 2017 run, the model is compared with data at the Flat Bottom (450 GeV) and Flat Top (6500 GeV) energies. The evolution of the relevant machine parameters: emittance and beam lifetimes are presented for the entire 2017 run, and the results are compared to the 2016 observations.
Abstract:
The Machine Development studies performed over the last years have been analysed with the aim to assess their merit for operation of the LHC. Special attention is given to those MDs which have found a direct operational use. MDs more indirectly related to operation, like machine protection or hardware development, are also identified. It is also tried to estimate which MDs performed over the last years are expected to find their application in the 2018 operation of the LHC.
Abstract:
LHC is ending 2017 with an unprecedented performance. We analyse the possible next steps in machine developments
to continue improving performance in coming runs, upgrades and future accelerators.
Abstract:
After almost 10 years of beam operation, machine studies at the LHC are becoming more and more advanced and complex. This translates into a need for advanced software tools to acquire, log, manipulate, analyze machine data as well as to control the installed equipment. The different teams, often in collaboration, have developed several innovative solutions for this purpose. This contribution will review the existing experience and identify the main lessons learnt and directions for future development.
Abstract:
In 2017, four Machine Development (MD) periods were scheduled at the LHC with the goal to study beam parameters and new ways to optimise the operation of the machine (LHC and HL-LHC). Before the start of the studies certain preparation and coordination is required in order to guarantee a successful MD (if the machine availability permits). This talk will try to review the rMPP procedures, communication between LHC and injections and possible ways to improve the full process including current web tools.
Abstract:
The contribution will discuss the input of the experiments for the operation of the LHC in 2018. The expectations of the experiments for the pp run are presented together with the constraints (e.g. pile-up, peak luminosity, beam parameters, constraints from forward physics experiments) for effective physics data-taking. Requests for possible special runs will be discussed. The expectations for the foreseen Heavy Ion run will be shown.
Abstract:
Re-starting the LHC after the YETS 2017/18 will include the revalidation of Sector 12 after its warm up as well as a repetition of powering and machine checkout tests as a function of the modifications applied to the relevant systems. This contribution will recall the main activities, the implied risks and resulting revalidation needs as well as the resulting planning to allow for an efficient restart of the LHC with beam in 2018 for its last year of operation of Run 2.
Abstract:
The last month of operation in 2018 will be devoted to Pb-Pb physics and no protons will be available from the injectors. The goal is to build on the techniques for reaching high peak and integrated Pb-Pb luminosity established in the 2015 run. The choices of machine configuration and optics, levelling strategies, beam parameters from the injectors and luminosity estimates are discussed taking into account the requirements of the experiments as presently known.
Abstract:
This talk will present the expectations for the LHC Beam Instrumentation and Transverse Damper (ADT) going into the 2018 run. Planned upgrades during the YETS will be presented and opportunities for future development in order to better exploit the available instrumentation will be discussed.
Abstract:
Luminosity levelling is expected to be a key ingredient to boost the LHC performance and, at the same time, probe future operational scenarios, in view of HL-LHC. In this perspective, the potential and limitations of the different filling schemes from the injectors are compared in terms of their luminosity reach, taking into account emittance evolution, pile-up and heat load limits. Guided by operational experience, MDs and beam dynamics simulations, the different beam parameters (current, beta*, crossing angle, emittance) and optimal machine settings (tune, chromaticity, octupoles) are proposed for maximising integrated luminosity.
Abstract:
2017 was an excellent year for the LHC. Amazing results were achieved, producing slightly more than 50 fb-1 and demonstrating great flexibility in LHC operation; 2018 will be a very important year as it will mark the end of Run2. A similar result has to be achieved, while start exploring HL-LHC operational configuration. The choice of operational configuration is therefore crucial to ensure success; many options are explored and discussed in this presentation, including choice on crossing angle and beta* value, beta* levelling configuration and improvements of operational cycle.
Abstract:
During the 2017 run of the LHC, several applications and tools underwent improvements and new features were added. Next to others, the main focus was on a new system for coupling measurement, based on the ADT AC-Dipole and the luminosity control system, to which e.g. separation- and crossing-angle levelling functionality was added. For 2018, it is foreseen to push these systems even further: Beta* levelling functionality is on its way to be available in the luminosity control system and new approach for precise tune measurements through ADT excitation and pickups is in the planning stage. This talk gives an overview about the relevant improvements done in 2017 and an outlook of what is foreseen to be improved for the 2018 run.