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The Large Hadron Collider (LHC) is one of the largest scientific instruments ever built. Since opening up anew energy frontier for exploration in 2010, it has gathered a global user community of about 9000 scientists working in fundamental particle physics and the physics of hadronic matter at extreme temperature and density. To sustain and extend its discovery potential, the LHC will need a major upgrade in the 2020s. This will increase its instantaneous luminosity (rate of collisions) by a factor of five beyond the original design valueand the integrated luminosity (totalnumber of collisions) by a factor ten. The LHC is already a highly complexand exquisitely optimised machine so this upgrade must be carefully conceived and will require new infrastructures(underground and on surface)and over a decade to implement. The new configuration, known as High Luminosity LHC (HL-LHC), relies on a number of key innovations that push accelerator technology beyond its present limits. Among these are cutting-edge 11–12Tesla superconducting magnets, compact superconducting cavities for beam rotation with ultra-precise phase control, new technology and physical processes for beam collimation and 100 metre-long high-power superconducting links with negligible energy dissipation, all of which required several years of dedicated R&D; effort on a global international level. The present document describes the technologies and components that will be used to realise the projectand is intended to serve as the basis for the detailed engineering design of the HL-LHC.

Physics Beyond Colliders is an exploratory study aimed at exploiting the full scientific potential of CERN's accelerator complex and its scientific infrastructure in the next two decades through projects complementary to the LHC, HL-LHC and other possible future colliders. These projects should target fundamental physics questions that are similar in spirit to those addressed by high-energy colliders, but that require different types of beams and experiments. A kick-off workshop held in September 2016 identified a number of areas of interest and working groups have been set-up to study and develop these directions. All projects currently under consideration are presented including physics motivation, a brief outline of the experimental set-up and the status of the corresponding beam and detector technological studies. The proposals are also put in context of the worldwide landscape and their implementation issues are discussed. Comments: This document (66 pages, 19 figures) is the summary document of the Physics Beyond Colliders (PBC) study. It follows the PBC mandate and draws on a whole set of documents produced in the context of PBC (this https URL), in particular the reports of the QCD and BSM working groups also available at arXiv: 1901.04482 and arXiv: 1901.09966

Substantial upgrades were carried out to the MKI beam screen during LSl: MKI heating has not lirrrited LHC operation since LSl, and is not expected to do so during Run 2. Similarly, during LSl, the vacuum systems on the interconnects between MKl magnets were upgraded: as a result there haven't been any issues with SIS vacuum thresholds on the interconnects between adjacent MKls. However, during 2016, dynamic pressure increase on the MKISD-QS interconnect limited the number of bunches that could be injected for Beam 2. The MKIZD kicker magnet caused several issues during 2016, including limiting the length of the field pulse from August onwards and a high impedance contact from October. As a result of firrther deterioration of the high impedance contact the MKIZD was exchanged during TS3. During November the Surveillance Voltage Monitoring system interlocked the MKIZ installation on several occasions. This paper reviews the MKI performance during 2016, the plans for the EYETS and the expected performance during 2017.

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.

The potential for a superconducting proton linac (SPL) at CERN started to be seriously considered at the end of the 1990s. In the first conceptual design report (CDR), published in 2000 [1], most of the 352 MHz RF equipment from LEP was re-used in an 800 m long linac, and the proton beam energy was limited to 2.2 GeV. During the following years, the design was revisited and optimized to better match the needs of a high-power proton driver for neutrino physics. The result was a more compact (470 m long) accelerator capable of delivering 5 MW of beam power at 3.5 GeV, using state-of-the-art superconducting RF cavities at 704 MHz. It was described in a second CDR, published in 2006 [2]. Soon afterwards, when preparation for increasing the luminosity of the LHC by an order of magnitude beyond nominal became an important concern, a low-power SPL (LP-SPL) was studied as a key component in the renovation of the LHC injector complex. The combination of a 4 GeV LP-SPL injecting into a new 50 GeV synchrotron (PS2) was proposed to replace the ageing Linac2, PSB, and PS. In a later stage, if necessary for future physics programmes (neutrino production or generation of radioactive ion beams), the linac could be brought up to multimegawatt beam power by upgrading the cooling, the electrical infrastructure, and the power supplies. The construction of the low-energy front end of the LP-SPL started in 2008 as the Linac4 project [3], aimed at the replacement of Linac2, with the potential for being adapted later to the needs of a low-power or high-power SPL (HP-SPL). In parallel, the R&D on the superconducting linac continued, initially to refine the design of the LP-SPL and afterwards that of the HP-SPL. This report presents the design of the LP-SPL and the work accomplished in preparing a proposal for new LHC injectors with the support of the European Commission under the Framework Programmes 6 and 7 and in collaboration with multiple laboratories and institutions worldwide. The status of the R&D towards an HP-SPL is summarized.

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 performance target for Upgrade Scenario 2 (US2) was defined for the purposes of the RLIUP meeting as accumulating 3000 fb−1 in the years to 2035. As shown earlier in the meeting, this sets the requirement for 270 fb−1 per year of operation after LS3. The presentations in Session 4 were arranged to evaluate the performance of HLLHC given the assumed baseline upgrade path, to present the optimum beam parameters in collision and from the injectors, to evaluate whether the injectors could reach the required parameters in view of the LIU upgrades, and to then investigate possible alternative (i.e. non-baseline) ideas or possibilities for improving the performance reach of HLLHC and its injector chain. The session concluded with two talks, one on the challenges and outlook for improving the achieved physics availability of HL-LHC, and the second on the analysis of the possible issues with the baseline 25 ns bunch spacing and the estimate of the performance potential with the alternative option of 50 ns.

This document describes the work in the PSB, PS and SPS that is required for upgrade scenario 1. It will be shown that the requirements on the hardware work needed for upgrade scenario 1 are identical to the ones of the upgrade scenario 2 [1]. The various activities are detailed as well as their dependencies and an estimate given for the duration of the necessary shutdowns and recommissioning periods with beam. It is mentioned whether some decisions are still to be taken and are related to information to be obtained after LS1. Another important aspect is the evaluation of the risks related to the upgrade interventions and operational complexity, which concern schedule, beam characteristics as well as reliability and overall performance. It has been studied if part of the activities could be spread out over several machine stops, and as conclusion the preferred scenario will be presented.

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 principal aims of the workshop are to: • Suggest operational parameter ranges for re-commissioning and operation in 2015; • Establish re-commissioning requirements for beam based LHC systems; • Establish planning for re-commissioning 2015; • Revisit overall strategy for 2015 (bunch spacing, scrubbing, special runs, MD etc.); • Provide input to Chamonix 2014. Chair: Mike LAMONT Deputy Chairs: Malika MEDDAHI, Brennan GODDARD Editors of the Proceedings: Brennan GODDARD, Sylvia DUBOURG Informatics & infrastructure support: Pierre CHARRUE Workshop Secretary: Sylvia DUBOURG

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.

The hardware status of the LHC Beam Dumping System (LBDS) after the many announced system improvements performed during Long Shutdown 1 (LS1) will be presented. The latest estimates of expected availability and reliability of the LBDS after LS1 will be summarized. The readiness of LBDS for LHC start-up, including the progress of the reliability runs, as well as the commissioning plan will be discussed. A list of the tests with beam required to validate the system after LS1 will be proposed.

The present intensity and brightness limitations of the LHC injector synchrotrons for 25 ns beams are space charge, beam loading, instabilities in the transverse and longitudinal planes and electron cloud effects. This paper reviews how these performance limitations are expected to change after implementing the mitigation measures foreseen within the Upgrade Scenario 2. The question is addressed whether the beam performance will match the requirements of the HL-LHC project. In particular, we assume operational scenarios with 25 ns beams produced with the traditional bunch splitting scheme in the PS and with the already tested batch compression scheme. A set of baseline parameters at LHC injection is then established based on extrapolation from the beam characteristics achieved in 2012 and the expected gains from the upgrades.

This report contains the Proceedings of the "Review of LHC and Injector Upgrade Plans" (RLIUP), held in the Centre de Convention, Archamps, France, 29–31 October 2013. The RLIUP examined the parameters of the LIU and HL-LHC projects following the experience and changes in the beam parameters experienced over the previous two years. It discussed which level of integrated luminosity will necessitate a replacement of the inner detectors and the insertions, the importance of reaching 3000 $fb^{-1}$ or the minimum integrated luminosity which would be tolerated. The main outcome of RLIUP is a staged path from the LHC performance at the end of 2012 to the required performance for the HL-LHC, along with a number of important recommendations on the work organization of the coming years.

The principle aims of the workshop are to: review and capture 2012 LHC beam operations experience; review system performance; examine the foreseen challenges and limitations of post long shutdown operations; have a look at possible running scenarios in the post long shutdown era.

UFOs (Unidentified Falling Objects) are potentially a major luminosity limitation for nominal LHC operation. With large-scale increases of the BLM thresholds, their impact on LHC availability was mitigated in the second half of 2011. For higher beam energy and lower magnet quench limits, the problem is expected to be considerably worse, though. Therefore, in 2011, the diagnostics for UFO events were significantly improved, dedicated experiments and measurements in the LHC and in the laboratory were made and complemented by FLUKA simulations and theoretical studies. In this paper, the state of knowledge is summarized and extrapolations for LHC operation after LS1 are presented. Mitigation strategies are proposed and related tests and measures for 2012 are specified.

The main upgrades of the injector chain in the framework of the LIU project will only be implemented in the second long shutdown (LS2), in particular the increase of the PSB energy to 2 GeV or the implementation of cures/solutions against instabilities/e-cloud effects. On the other hand, Linac4 will become available by the end of 2014. Until the end of 2015 it may replace Linac2 at short notice, taking 50 MeV protons in the PSB via the existing injection system but with reduced performance. Afterwards, the H- injection equipment will be ready and Linac4 could be connected for 160MeV H- injection into the PSB during a prolonged winter shutdown before LS2. The anticipated beam performance of the LHC injectors after LS1 in these different cases is presented. Space charge on the PS flat-bottom will remain a limitation because the PSB to PS transfer energy will stay at 1.4 GeV. As a mitigation measure new RF manipulations are presented which can improve brightness for 25 ns bunch spacing, allowing for more than nominal luminosity in the LHC.

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.

At the start of the 2011 physics run quite some margin in the performance of the injectors was available and identified. Following the fast increase of the performance of the LHC itself during 2011, these margins have very much been exploited and some have even been pushed further. In view of further increase in the LHC luminosity, the 2012 performance reach of the injectors will be reviewed. One of the arising topics is satellite bunches from the injectors. Until now concerted effort went into supressing satellite bunches to a minimum, but a recent successful test with "controlled" satellites might make their routine production and characterisation an important topic in 2012.

The performance of the LHC injection and extraction systems and the main problems encountered during 2012 operation are described. Special attention is dedicated to the stability of the transfer lines, steering frequency, sensitivity to beam and machine changes, injection protection collimators setup and the consequent impact on operation and possible machine protection issues. The improvements foreseen for operation with injection of up to 288 bunches after LS1 in terms of stability, availability and safety are explored. The modifications foreseen to strengthen the reliability of the LHC Beam Dumping System and the new TCDQ hardware for operation at 6.5 TeV with high intensity beams are introduced.

Emittance measurements during the LHC proton run 2011 indicated a blow-up of 20 % to 30 % from LHC injection to collisions. This presentation will show the emittance preservation throughout the different parts of the LHC cycle and discuss the current limitations on emittance determination. An overview of emittance preservation through the injector complex as function of bunch intensity will also be given. Possible sources for the observed blow-up and required tests in 2012 will be presented. Possible improvements of emittance diagnostics and analysis tools for 2012 will be shown.

Injection and beam dumping is considered for a 16.5 TeV hadron accelerator in the current LHC tunnel, with an injection energy in the range 1 - 1.3 TeV. The present systems are described and the possible upgrade scenarios investigated for higher beam rigidity. In addition to the required equipment performance, the machine protection related aspects are explored. The expected constraints on the machine layout are also given. The technological challenges for the different equipment subsystems are detailed, and areas where R&D is necessary are highlighted., 6 pages, contribution to the EuCARD-AccNet-EuroLumi Workshop: The High-Energy Large Hadron Collider, Malta, 14 -- 16 Oct 2010; CERN Yellow Report CERN-2011-003, pp. 128-133