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During LS2 the LHC injectors will undergo an important upgrade campaign under the LHC Injectors Upgrade (LIU) project. Linac2 will be replaced by Linac4 and additional hardware will be installed in all the synchrotrons of the LHC injectors chain to enable the production of proton beams of double intensity and brightness to be delivered to LHC in the HL-LHC era (i.e. after LS3). The lead (Pb) ion beams, which have already shown their potential to fulfil the HL-LHC goal in terms of single bunch parameters at the LHC injection, will see their bunch number roughly doubled in the LHC thanks to momentum slip stacking in the SPS. The planned evolution of the beam parameters during Run 3 can be summarised as follows. All pre-LS2 proton beams will be recovered by the end of 2021, while intensity and brightness of the LHC beams will be gradually ramped up to the LIU values throughout 2022-2024. The commissioning of momentum slip stacking in the SPS for Pb ions is expected to take place in 2021 to allow delivery of LIU ion beams to LHC for the 2021 Pb-Pb run.

LHC operation in 2016 was limited by the constraints on the maximum allowed intensity in the SPS due to the vacuum leak at the internal dump. The present baseline foresees the replacement of the T1DVG with a new upgraded hardware during the upcoming EYETS. This would allow providing nominal 25 ns to the LHC as well as beams with a brightness well beyond design. Nevertheless, the consequences of an accidental impact of such beams on the intercepting devices in the SPS-to-LHC transfer lines and in the LHC injection regions have to be carefully evaluated. At the same time potential dangers related to faults during the extraction of high intensity beams at top energy have to be taken into account. The survival of all the protection elements and the downstream machine components have to be insured for every operational scenario. Past and present assumptions on possible failure scenarios, their likelihood and effects are reviewed together with the estimated damage limits. Potential intensity and performance limitations are therefore derived for the 20l7 Run in view of the specific beams available.

Losses at injection will be distinguished between the two main loss causes, transverse loss shower from the transfer line collimators and longitudinal loss shower due to satellites which are placed on the kicker field rise and thus improperly kicked into the machine. The dependence of this losses on the different beam types, TL stability and injec-tor performance will be reviewed. A status and potential improvements of the injection quality diagnostics and new values for the SPS and LHC injection kicker rise times will be suggested.

During 2015, injections of 144 bunches into the LHC induced losses of up to 93 % of the dump thresholds on the TDI BLMs. During run 2 these losses were studied in greater detail with diamond based particle detectors. It was found that the main loss contribution is due to ghost bunches, originating from the SPS, swept over the TDI during the rise and fall time of the injection kicker magnet MKI. This contribution will summarize the measurement results (transversal and longitudinal losses) in comparison to run 1. In addition, possible loss mitigations, already applied for a first time during an MD, will be discussed in view of injections of 288 bunches planned for operation in 2016.

To minimise the beam losses at the moment of an LHC beam dump the 3 μs long abort gap should contain as few particles as possible. Its population can be minimised by abort gap cleaning using the LHC transverse damper system. The LHC Run 1 experience is briefly recalled; changes foreseen for the LHC Run 2 are presented. They include improvements in the observation of the abort gap population and the mechanism to decide if cleaning is required, changes to the hardware of the transverse dampers to reduce the detrimental effect on the luminosity lifetime and proposed changes to the applied cleaning algorithms.

High-intensity and high-brightness beams are key ingredients to maximize the LHC integrated luminosity and to exploit its full potential. This contribution describes the optimization of beam and machine parameters to maximize the integrated luminosity as seen by the LHC experiments, by taking into account the expected intensity and brightness reach of LHC itself and its injector chain as well as the capabilities of the detectors for next run and foreseen upgrade scenarios.

The Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) at CERN foresees the simultaneous operation of a proton, a laser and an electron beam. The first stage of the experiment will consist in proving the self-modulation, in the plasma, of a long proton bunch into micro-bunches. The success of this experiment requires an almost perfect concentricity of the proton and laser beam, over the full length of the plasma cell. The complexity of integrating the laser into the proton beam line and fulfilling the strict requirements in terms of pointing precision of the proton beam at the plasma cell are described. The second stage of the experiment foresees also the injection of electron bunches to probe the accelerating wakefields driven by the proton beam. Studies were performed to evaluate the possibility of injecting the electron beam parallel and with an offset to the beam axis. This option would imply that protons and electrons will have to share the last few meters of a common beam line. Issues and possible solutions for this case are presented.

This paper summarizes the current understanding of the issues to be addressed in the injectors in order to fulfill the requirements of the HL-LHC in the framework of the upgrade scenario 1. The required beam parameters in the different accelerators are outlined, and the relevant performance limitations described. Possible beam production schemes are presented, and their relative merits are compared. The upgrades required in the preferred scenario are described and the beam characteristics potentially accessible at LHC injection estimated.

The baseline bunch spacing for LHC high luminosity proton-proton operation after LS3 is 25 ns to maximize the integrated luminosity while keeping the pile-up low. The success of this mode of operation is not guaranteed. Electron cloud, UFOs, long-range beambeam, heating and other effects might make 25 ns operation in the LHC and/or the injectors difficult. This talk will review possible showstoppers in the LHC and injectors for 25 ns operation and discuss possible remedies. An alternative would be re-considering 50 ns operation. An estimate of the 50 ns performance will be given. The question of whether a different upgrade path would have to be chosen in case of 50 ns operation will also be addressed.

The status and commissioning plans of the transfer line and injection hardware are presented with focus on the injection dump and kickers. Modifications of the beam loss monitoring in the injection region, its readiness for the start-up and commissioning strategy are shown. A new interlock strategy for the injection protection elements and the injection septum is introduced. The expected transfer line stability and possibilities to improve the turnaround with optimized SPS supercycles for LHC injection are discussed.

This document summarizes the talks and discussion which took place in the third session of the RLIUP Review. The session was devoted to Performance Improving Consolidation (thereafter PICs) and Upgrade scenario 1. The PICs were defined as the “Replacement or upgrade of a system justified by consolidation but with the goal of improving performance”. The PICs scenario goals were further defined as accumulating 70 fb-1 integrated luminosity per year over a period a 10 years of operation, reaching 1000 fb-1 (starting with an initial integrated luminosity of 300 fb-1). An ‘Upgrade’ was defined as the ‘Replacement or addition of a system to improve the performance, which would otherwise not be necessary’. The Upgrade scenario 1 goals were defined as accumulating 170 fb-1 integrated luminosity per year over a period a 10 years of operation, reaching 2000 fb-1 (starting with an initial integrated luminosity of 300 fb-1). This scenario assumed no crab cavity, no levelling, and a crossing angle adjusted for 12 sigma long range beam-beam separation. The aim of the session was to analyse which beam parameters can reach these targets and what are the related actions on the equipment. In the first part of the session, the PICs were presented and discussed for both the LIU and the HL-LHC project. This part comprised three presentations: “Injectors: PICs: what are we talking about?” by K. Hanke; “LHC: PICs: what are we talking about?’ by P. Fessia and “LIU-HLLHC: PICs: what do we gain in beam performances?” by G. Arduini. The second part of the session was devoted to the Upgrade scenario 1, with four presentations: ‘HLLHC: How to achieve Upgrade Scenario 1 goals in the LHC?’ by O. Brüning; “Work effort in the LHC accelerator for upgrade scenario 1” by E. Todesco; “LIU: Which beams in the injectors fulfil HL-LHC US1 goals?” by S. Gilardoni and “Work effort in the LHC injector complex, including Linac4 connection, for upgrade scenarios” by J.-B. Lallement and B. Mikulec.

A new optics was introduced in the SPS for improving beam stability at high intensity. For transferring the beam to the LHC, the extraction bumps, extraction kickers and transfer lines needed to be adapted to the new optics. In particular, the transfer lines were re-matched and re-commissioned with the new optics. The first operational results are discussed for the SPS extraction, the transfer lines and the LHC injection. A detailed comparison is presented between the old and the new optics of the trajectories, dispersion, losses and other performance aspects.

The world’s first proton driven plasma wakefield acceleration experiment (AWAKE) is presently being studied at CERN. The experimentwill use a high energy proton beam extracted from the SPS as driver. Two possible locations for installing the AWAKE facility were considered: the West Area and the CNGS beam line. The previous transfer line from the SPS to the West Area was completely dismantled in 2005 and would need to be fully re-designed and re-built. For this option, geometric constraints for radiation protection reasons would limit the maximum proton beam energy to 300 GeV. The existing CNGS line could be used by applying only minor changes to the lattice for the final focusing and the interface between the proton beam and the laser, required for plasma ionisation and bunch-modulation seeding. The beam line design studies performed for the two options are presented.

The plans for preparing the LHC injectors to fulfil the needs of the LHC during the next decade have significantly progressed in 2012. Linac4 construction has passed major steps of pre-series fabrication. Hardware developments and beam studies have allowed refining the baseline actions to implement and the beam characteristics achievable at injection into the collider for protons as well as for Lead ions. These achievements are described in this paper, together with the updated project planning matched to the new schedule of the LHC.

Plasma Wakefield acceleration is a rapidly developing field which appears to be a promising candidate technology for future high-energy accelerators. The Proton Driven Plasma Wakefield Acceleration Experiment has been proposed as an approach to eventually accelerate an electron beam to the TeV energy range in a single plasma section. To verify this novel technique, a proof-of-principle demonstration experiment, AWAKE, is proposed using 400 GeV proton bunches from the SPS. Detailed studies on the identification of the best site for the installation of the AWAKE facility resulted in proposing the CNGS facility as best location. Design and integration layouts covering the beam line, the experimental area and all interfaces and services are shown. Among other issues, radiation protection, safety and civil engineering constraints are raised.

The LHC Injectors Upgrade (LIU) Project aims at upgrading the systems in the LHC injection chain, to reliably deliver the beams required by the High-Luminosity LHC (HL-LHC). Given the challenging beam intensities and emittances, a review of the existing beam-intercepting devices is on-going, in order to assess heat loads and consequent thermo-mechanical stresses. Moreover, the exposure of downstream elements to induced shower radiation is assessed. The study is intended to spot possible issues and contribute to the definition of viable design and layout solutions.

All high-intensity LHC beams have to be scraped before extraction from the SPS to remove the non-Gaussian transverse tails of the particle distributions. The tail particles would otherwise cause unacceptably high losses during injection or other phases of the LHC cycle. Studies have been carried out to quantify the scraping using injection losses and emittance measurements from wire scanners as diagnostics. Beams scraped in the SPS were scraped again in the LHC with collimators to investigate possible tail repopulation. The results of these studies will be presented in this paper., peer-reviewed

Challenging beams with much higher brightness than today are required for the LHC to achieve its high luminosity objective after the year 2020. It is the purpose of the LHC Injectors Upgrade (LIU) project to achieve this result, consolidating and upgrading the existing set of synchrotrons (PSB, PS and SPS), and using the new linac presently in construction (Linac4). The anticipated beam characteristics are described and compared to the known limitations in the different accelerators. The foreseen solutions are outlined as well as the planning for their implementation.

Machine protection sets strict requirements for the quality of the injected beam, in particular in the transverse plane. Losses at aperture restrictions and protection elements have to be kept at a minimum. Particles in the beam tails are lost at the tight transfer line collimators and can trigger the LHC beam abort system. These particles have to be removed by scrapers in the vertical and horizontal plane in the SPS. Scraping has become vital for high intensity LHC operation. This paper shows the dependence of injection quality on the SPS scraping and discusses an improved scraper setting up strategy for better reproducibility with the current scraper system.

Following the abort gap cleaning tests performed on 7 October 2011 [1] additional tests were carried out on 13 October 2011 to further investigate the effects of the cleaning on the luminosity production. The abort gap cleaning parameters (strength and duration of the beam excitation kick) were varied and the cleaning effectiveness measured together with the change in luminosity. The outcome is summarised in this note.

During the LHC proton run 2011 large drifts, shot-by- shot and even bunch-by-bunch trajectory variations were observed with the consequence of high losses at injection and frequent lengthy trajectory correction campaigns. The different effects will be quantified and an estimate for downtime caused by them in 2011 will be given. The sources of the instabilities, solutions for 2012 and achievable improvements will be discussed. Possible future up- grades will also be mentioned.

Performance and failures of the LHC injection and ex- traction systems are presented. In particular, a comparison with the 2010 run, lessons learnt during operation with high intensity beams and foreseen upgrades are described. UFOs, vacuum and impedance problems related to the injection and extraction equipment are analysed together with possible improvements and solutions. New implemented features, diagnostics, critical issues of XPOC and IQC applications are addressed.

Injection losses are compared for 2010 and 2011 operation. Mitigation techniques which were put in place in 2010 to reduce losses at injection are described. Issues in 2011 operation, their potential improvements and the performance reach for 2012 are shown.

Injection of 144 bunches into the LHC became fully operational during the 2011 run and a nominal injection of 288 bunches was accomplished during MD time. Several mitigation solutions were put in place to minimise losses from the transfer line (TL) collimators and losses from kicking debunched beam during injection. Nevertheless, shot-by-shot and bunch-by-bunch trajectory variations, as well as long terms drifts, were observed and required a regular resteering of the TL implying a non negligible amount of time spent for injection setup. Likely sources of instability have been identified (i.e. MKE and MSE ripples) and possible cures to optimise 2012 operation are presented. Well defined references for TL steering will be defined in a more rigorous way in order to allow a more straightforward and faster injection setup. Encountered and potential issues of the injection system, in particular the injection kickers MKI, are discussed also in view of injections with a higher number of bunches.