The CERN SPS injection kicker magnets (MKP) were developed in the 1970’s, before beam power deposition was considered an issue. There are two types of these magnets in the SPS: MKP-S (small aperture) and MKP-L (large aperture) versions. The MKP-L magnets are very lossy from a beam impedance perspective: this would be an issue during SPS operation with the higher intensity beams needed in the future for HL-LHC. Hence, a beam screen has been developed, which is inserted in the aperture of each MKP-L module. The screen consists of silver fingers applied to alumina U-shaped chambers: the fingers have been optimized to achieve both adequately low beam induced power deposition and good high voltage (HV) behaviour. A surface coating, with a low secondary electron yield, is applied to the inner surface of the alumina chambers to reduce dynamic vacuum. The low-impedance MKP-L has been extensively HV tested in the lab before installation in the SPS. This paper briefly presents the design and focuses on the operational experience in the SPS, including heating and vacuum.

Advanced Series on Directions in High Energy PhysicsThe High Luminosity Large Hadron Collider, pp. 427-443 (2024) Open AccessChapter 19: Injection and Beam Dump SystemsC. Bracco, M. J. Barnes, W. Bartmann, M. Calviani, D. Carbajo Perez, E. Carlier, L. Ducimetiere, M. I. Frankl, B. Goddard, J. Jowett, A. Lechner, N. Magnin, A. Perillo Marcone, T. Polzin, V. Rizzoglio, V. Senaj, L. Vega, V. Vlachodimitropoulos, and C. WiesnerC. BraccoCERN, SY Department, Genève 23, CH-1211, Switzerland, M. J. BarnesCERN, SY Department, Genève 23, CH-1211, Switzerland, W. BartmannCERN, SY Department, Genève 23, CH-1211, Switzerland, M. CalvianiCERN, SY Department, Genève 23, CH-1211, Switzerland, D. Carbajo PerezFormer CERN member, Switzerland, E. CarlierCERN, SY Department, Genève 23, CH-1211, Switzerland, L. DucimetiereCERN, SY Department, Genève 23, CH-1211, Switzerland, M. I. FranklFormer CERN member, Switzerland, B. GoddardCERN, SY Department, Genève 23, CH-1211, Switzerland, J. JowettCERN, EP Department, Genève 23, CH-1211, Switzerland, A. LechnerCERN, SY Department, Genève 23, CH-1211, Switzerland, N. MagninCERN, SY Department, Genève 23, CH-1211, Switzerland, A. Perillo MarconeCERN, SY Department, Genève 23, CH-1211, Switzerland, T. PolzinFormer CERN member, Switzerland, V. RizzoglioFormer CERN member, Switzerland, V. SenajCERN, SY Department, Genève 23, CH-1211, Switzerland, L. VegaCERN, SY Department, Genève 23, CH-1211, Switzerland, V. VlachodimitropoulosFormer CERN member, Switzerland, and C. WiesnerCERN, TE Department, Genève 23, CH-1211, Switzerlandhttps://doi.org/10.1142/9789811278952_0019Cited by:0 (Source: Crossref) PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Some of the elements of the LHC injection and extraction systems will be upgraded or replaced to adapt to the increased beam brightness and intensity of the HL-LHC beams [1; 2]. The injection main protection absorber will be replaced with new hardware which will be able to absorb and withstand 288 HL-LHC bunches in case of an injection kicker failure. The compatibility with injection of 320 bunches (four batches of 80 HL-LHC bunches [3]) was also verified. One auxiliary injection protection collimator in Point 2 will be displaced closer to the interaction point (IP) to increase the acceptance of the ALICE Zero-Degree Calorimeter. The injection kickers, which suffered already from electron cloud, degraded vacuum and beam induced heating while operating with LHC beams, will be upgraded with several modifications to mitigate these effects. The compatibility of the LHC beam dump system with the increased beam intensities of the HL-LHC beams still needs to be fully assessed. However, the dump protection devices, as well as the dump absorber block and its entrance and exit windows needs an upgrade or replacement. The studies include the definition of the possible worst failure scenarios for the extraction and dilution kickers and the consequences on the different dump elements. Finally, the extraction and dilution system will be upgraded to improve its reliability by reducing the risk of erratics, monitoring the status of the system and reacting faster in case of failures. FiguresReferencesRelatedDetails Recommended The High Luminosity Large Hadron ColliderMetrics History Information© Oliver S Brüning and Lucio RossiThis is an open access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC BY) License.PDF download

PUMA, antiProton Unstable Matter Annihilation, is a nuclear-physics experiment at CERN aiming at probing the surface properties of stable and rare isotopes by use of low-energy antiprotons. Low-energy antiprotons offer a very unique sensitivity to the neutron and proton densities at the annihilation site, i.e. in the tail of the nuclear density. Today, no facility provides a collider of low-energy radioactive ions and low-energy antiprotons: while not being a collider experiment, PUMA aims at transporting one billion antiprotons from ELENA, the Extra-Low-ENergy Antiproton ring, to ISOLDE, the rare-isotope beam facility of CERN. PUMA will enable the capture of low-energy antiprotons by short-lived nuclei and the measurement of the emitted radiations. In this way, PUMA will give access to the so-far largely unexplored isospin composition of the nuclear-radial-density tail of radioactive nuclei. The motivations, concept and current status of the PUMA experiment are presented.

The Super Proton Synchrotron (SPS) injection system plays a fundamental role to preserve the quality of injected high-brightness beams for the Large Hadron Collider (LHC) physics program and to maintain the maximum storable intensity. The present system is the result of years of upgrades and patches of a system not conceived for such intensities and beam qualities. In this study, we propose the design of a completely new injection system for the SPS using multi-level numerical optimisation, including realistic hardware assumptions. We also present how this hierarchical optimisation framework can be adapted to other situations for optimal accelerator system design.

A 100 TeV center-of-mass energy frontier proton collider, in a new tunnel of 80-100 km circumference, is a central part of CERN's Future Circular Colliders (FCC) design study. The designs of the injection and extraction systems of the FCC are initially based upon the parameters of the injection and extraction systems of the Large Hadron Collider and a preliminary study of the FCC beam optics and lattice. The injection and, in particular, the extraction systems of the FCC have to be highly reliable. In order to achieve high reliability, solid state switches will be used for the generators of the injection and extraction systems. This paper discusses topologies of these kicker systems, which are presently under consideration.

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100TeV. Its unprecedented centre of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.

The LHC Run II has seen hardware changes and performance evolution of the LHC injection system. In this talk, the evolution, over the whole run, of the main systems involved in the injection process is presented. Particular attention is dedicated to the analysis of the data of the injection quality and its evolution over the last years. Finally, a general review of the performances and their reach for Run III is discussed.

The performance of the LHC Beam Dump System (LBDS) during Run II beam operations are presented in terms of rate and type of failures of the extraction (MKB) and dump (MKD) kickers. New faults were also identified and they are described together with their impact on the beam distribution at the dump protection elements and the TDE assembly. Foreseen and proposed mitigations, on the MKB/MKD magnets, generators, and controls, in order to minimise possible beam intensity and brightness limitations, are addressed. The reasons and functionality of the BETS TCDQ are reminded together with the present operational constraints, which will still hold in Run III. Main changes and issues encountered with the XPOC analysis and acknowledgment procedure are treated. Updates are given on the operational experience with the variable AGK after the accidental injection of bunches in the abort gap in 2017. The evolution of the execution and validation procedure for the asynchronous beam dump test and the further planned improvements are covered. Finally, recommendations are given for a proper scheduling of the LBDS commissioning time after LS2.

In response to the 2013 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) study was launched, as an international collaboration hosted by CERN. This study covers a highest-luminosity high-energy lepton collider (FCC-ee) and an energy-frontier hadron collider (FCC-hh), which could, successively, be installed in the same 100 km tunnel. The scientific capabilities of the integrated FCC programme would serve the worldwide community throughout the 21st century. The FCC study also investigates an LHC energy upgrade, using FCC-hh technology. This document constitutes the second volume of the FCC Conceptual Design Report, devoted to the electron-positron collider FCC-ee. After summarizing the physics discovery opportunities, it presents the accelerator design, performance reach, a staged operation scenario, the underlying technologies, civil engineering, technical infrastructure, and an implementation plan. FCC-ee can be built with today’s technology. Most of the FCC-ee infrastructure could be reused for FCC-hh. Combining concepts from past and present lepton colliders and adding a few novel elements, the FCC-ee design promises outstandingly high luminosity. This will make the FCC-ee a unique precision instrument to study the heaviest known particles (Z, W and H bosons and the top quark), offering great direct and indirect sensitivity to new physics.

The LHC turn-around time is impacted by the control of injection losses and trajectories. While shot-to-shot trajectory variations dominated the injection efficiency during LHC Run 1, several improvements of hardware and operational settings allowed for a high rate of successful injections during Run 2. Injection losses and trajectories are analysed and presented for the high intensity proton runs, as well as for different beam types used from the injectors. Based on this analysis, an outlook is shown for the HL-LHC era, where double the bunch intensity will have to be injected. EVOLUTION OF INJECTION LOSSES The LHC injection quality monitoring includes several tens of loss monitors in the injection and primary collimator region to allow for an efficient analysis of each injection. The complete set of monitors is needed to detect issues which are specific to certain locations. When analysing the trend of injection losses over several years, many of these monitors give redundant information and can be reduced to the most representative ones distinguishing transverse and longitudinal losses. Transverse losses originate from transfer line collimators (TCDI) cutting the transverse beam tails and resulting in loss showers impacting beam loss monitors of the superconducting magnets in the ring from the outside. Longitudinal losses are caused by particles captured in buckets neighbouring the nominally filled buckets and transported until the injection in LHC. These satellite bunches are deflected by the rising and falling edges of the injection kicker and lost on the injection dump and primary collimators. For longitudinal losses the monitors on the injection dump TDI are most representative. Monitors on the matching quadrupoles Q8 for beam 1 (B1) and Q7 for B2 are the most sensitive to the transverse shower from the TCDIs. For B1 also the loss monitor on the dipole interconnect 7L2 (BOT) was included due to its particularly low dump thresholds and therefore relevance for injection efficiency. In Fig. 1 the distribution of injection losses over dump threshold is shown for each production year of Run 1 (2011 and 2012) and Run 2 (2015-2018). Only injections with bunch trains of 12 bunches or more in periods of luminosity production with protons are taken into account. Periods of commissioning, machine development, special and ion runs are excluded from this analysis. The loss range is visualised for up to 120% of the dump threshold which cuts higher loss events. The ratios of loss events above 20% including the ones above 120% of the dump threshold are shown in Fig. 2. In Fig. 1 it can be seen that injections in Run 1 were dominated by transverse losses which was the opposite in Run 2. Transverse losses dominate mostly in 2011, which Figure 1: Distribution of injection losses for B1 (left column) and B2 (right column) from 2018 (top row) going backwards to Run 1. Transverse losses on Q8 and Q7 are shown in green, longitudinal losses on the TDI in blue. was traced back to shot-to-shot variations of the injection line trajectory caused by power converter ripple of the SPS extraction septa [1]. This ripple was reduced by a factor 2 for the B1 extraction septum in the stop between 2011 and 2012 and improved in LS1 for the B2 extraction septum, which can be observed on the transverse losses of both lines. From Run 1 to Run 2 transverse losses increase for B1, this is less pronounced for B2 which shows cleaner injections than B1 throughout both runs. The B1/B2 difference is most 10th Int. Partile Accelerator Conf. IPAC2019, Melbourne, Australia JACoW Publishing ISBN: 978-3-95450-208-0 doi:10.18429/JACoW-IPAC2019-WEPMP030 MC4: Hadron Accelerators T12 Beam Injection/Extraction and Transport WEPMP03

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries.

In view of the newly implemented variable Abort Gap Keeper (AGK), this paper 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. INTRODUCTION: ABORT GAP MKD rise time and abort gap To avoid losses during the rise time of the LHC extraction kickers (MKD), a 3 μs long abort gap in the circulating ring has to be kept free of particles. The first RF bucket outside the abort gap is defined as Bucket 1. Particles in Bucket 1 receive a kick corresponding to 100 percent of the reference kick. This is ensured by adjusting the time delay of theMKD waveforms accordingly. To ensure that no beam is injected into the abort gap, the last legal injection bucket is given by the length of the abort gap and the maximum length of the injected bunch trains, with the latter corresponding to the injection kicker (MKI) flat-top length. This leads to a required length of the socalled Abort Gap Keeper (AGK), which is given by the sum of the abort gap length and the maximum injected bunch train length. A schematic overview of the MKD waveform and the required Abort Gap Keeper length is shown in Fig. 1. Figure 1: Extraction kicker (MKD) waveform. The 3 μs long abort gap for the MKD rise time and the required Abort Gap Keeper (AGK) length are indicated. Drawing modified from [1]. ∗ christoph.wiesner@cern.ch Accidental injection into the abort gap leads to the same consequences as a so-called asynchronous beam dump. Asynchronous beam dumps can be caused by loss of synchronisation of the MKD rise time with the abort gap, e.g. in case of failure of the Trigger Synchronisation Unit (TSU), or by erratic pre-firing of an extraction kicker. In all of these cases, the beam is swept over the machine aperture by the rising edge of the MKDs. Therefore, dedicated diluter blocks are installed in Point 6 to protect the downstream elements. This includes the TCDQ, which is located upstream of the Q4 quadrupole, and the TCDS, which is located upstream of the extraction septa (MSD). An overview is shown in Fig. 2. Figure 2: Overview of the TCDQ and TCDS diluter blocks in Point 6 [2]. Beam losses and abort-gap population The loss profile during such an event strongly depends on the longitudinal beam distribution during the approximately 3 μs long MKD rise time. A measured abort-gap population during a regular asynchronous beam dump test is depicted in Fig. 3 in blue. For these tests, a single bunch is placed in Bucket 1 and the radio frequency is switched off, such that the beam debunches and drifts into the abort gap [3]. Four regions can be distinguished. The particles that receive a small kick escape the TCDQ. They recirculate in the ring and are either lost at downstream collimators or extracted at the second turn. The particles that receive a stronger kick are lost on the TCDQ or on the TCDS, respectively. Finally, the particles that are close to Bucket 1 escape the TCDS and are extracted at the first turn. They enter the dump channel, but follow a non-nominal trajectory. Therefore, in order to understand the loss behaviour in case of asynchronous beam dumps, it is not sufficient to consider only the total abort-gap population. This is illustrated in Fig. 4. The top graph shows measured beam losses at the TCDQ as a function of the total abort-gap population for all asynchronous beam dump tests performed in 2016/17. No obvious correlation is visible. However, by plotting the Figure 3: Measured abort-gap population during an asynchronous beam dump test on May 15, 2016. The regions of particles that would hit the TCDQ, hit the TCDS, and the ones extracted on the first or second turn, respectively, are highlighted. The expected kick from the MKDs is depicted in orange. beam losses as a function of protons calculated to hit the TCDQ, the expected correlation of losses over impacting protons becomes visible (bottom graph). The region close to the TCDQ edge is considered the most critical region inside the abort gap. The reason is that, on the one hand, the particles just escaping the TCDQ have the highest risk of hitting and potentially damaging collimators in the ring, while, on the other hand, the particles that hit the TCDQ close to its edge have the highest probability of causing quenches to the superconducting magnets in Point 6. Beam losses and energy dependence In addition, the consequences of an asynchronous beam dump depend strongly on the beam energy. A dedicated Machine Development time (MD) to investigate the consequences of asynchronous beam dumps was performed during the MD4 block in December 2017 (MD2930: “Asynchronous BeamDump Test with Bunched Beam”). It demonstrated that, at least for current beam optics, even a full 450GeV train hitting the TCDQ does not lead to a quench of superconducting magnets. This was validated with trains of 48 bunches and intensities of up to 1.25 × 1011 protons per bunch. However, at a beam energy of 6.5 TeV, a single pilot bunch with 1.8 × 1010 protons was sufficient to cause the beam-induced quench of one main dipole (MB.A8R6) and one quadrupole (MQY.4R6) for Beam 1 and one quadrupole (MQY.4L6) for Beam 2. For a full asynchronous dump with filled abort gap, the situation at top-energy would get worse. Since the TCDQ half-gap position (in millimetres) is reduced with increasing beam energy, the number of bunches that would fully hit the Figure 4: Beam losses at the TCDQ for all 34 asynchronous beam dump tests 2016/2017 as a function of the total abortgap population (top) and as a function of protons calculated to hit the TCDQ (bottom). TCDQ increases from approximately 14 at injection energy to approximately 21 at 6.5 TeV. Table 1 lists the TCDQ parameters for injection and flat-top energy. Table 1: TCDQ settings for injection and flat-top energy. Beam Energy TCDQ position Number of bunches hitting the TCDQ

One option for a future circular collider at CERN is to build a 13.5 TeV hadron synchrotron, or High Energy LHC (HE-LHC) in the LHC tunnel. Injection and dump systems will have to be upgraded to cope with the higher beam rigidity and increased damage potential of the beam. The required modifications of the beam transfer hardware are highlighted in view of technology advancements in the field of kicker switch technology. An optimised straight section optics is shown.

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.

The Future Circular Collider (FCC-hh) beam dump system must provide a safe and reliable extraction and dilution of the stored beam onto a dump absorber. Energy deposition studies show that damage limits of presently used absorber materials will already be reached for single bunches at 50 TeV. A fast field rise of the extraction kicker is required in order to sufficiently separate swept single bunches on the extraction protection absorbers in case of an asynchronous beam dump. In line with this demand is the proposal of a highly segmented extraction kicker system which allows for accepting a single kicker switch erratic and thus, significantly reduces the probability of an asynchronous beam dump. Superconducting septa are foreseen to limit the overall system length and power consumption. Two extraction system concepts are presented and evaluated regarding overall system length, energy deposition on absorbers, hardware requirements, radiation issues, and layout flexibility.

The paper presents the outstanding studies performed in 2016 in preparation of the PS Booster upgrade, within the LHC Injector Upgrade project (LIU), to provide twice higher brightness and intensity to the High-Luminosity LHC.Major changes include the increase of injection and extraction energy, the implementation of a H− charge-exchange injection system, the replacement of the present Main Power Supply and the deployment of a new RF system (and related Low-Level), based on the Finemet technology. Although the major improvements will be visible only after the upgrade, the present machine can already benefit of the work done, in terms of better brightness, transmission and improved reproducibility of the present operational beams. Studies address the space-charge limitations at low energy, for which a detailed optics model is needed and for which mitigation measurements are under study, and the blow-up reduction at injection in the downstream machine, for which the beams need careful preparation and transmission. Moreover they address the requirements and the reliability of new beam instrumentation and hardware that is being installed in view of LIU.

In the framework of the LHC Injector Upgrade (LIU) project an upgrade of the existing PS proton injection kicker system for 2 GeV operation is in progress. The upgrade is based on the operation of the existing kicker system in short circuit mode. This paper briefly reviews the deployed modifications to the system to obtain the specified reduction of pulse reflections unavoidably induced by such a configuration. The implementation of improvements to the magnet entry box, transmission cables and the short circuit plug with integrated LC-filter are described as well as tests and measurements during the 2016/17 annual shutdown. The impact of the residual pulse shape structure on the beam performance for the reference LIU beam is discussed. The paper concludes with a performance analysis, a comparison of measurements vs. simulations and an outlook to the remaining modifications during the next long shut down. INTRODUCTION For the LHC Injectors Upgrade (LIU) project [1] several options for the injection of 2 GeV beams into the PS ring have been analysed [2]. Considering the updated kicker requirements [3] an upgrade of the existing injection kicker system (KFA-45) comprising operation in permanent short circuit (SC) mode has been developed. The challenges are the increased rise time in SC-mode caused by the pulse travelling twice through the magnet as well as the mitigation of higher ripple amplitudes. Table 1: Nominal Voltage for Operation in SC-mode Parameter No. of Modules Unit Value Voltage (1.4 GeV) 4 kV 40 3 kV 53 2 kV 80 Voltage (2.0 GeV) 4 kV 57 3 kV 76 Nominal SC-mode voltage settings for the injection of 1.4 GeV and 2.0 GeV beams are outlined in Table 1 considering also failure cases (missing modules). In terminated mode the system provided a nominal kick angle of 4.3 mrad for 1.4 GeV beams when being pulsed at ~77 kV which corresponds to a current of 1.47 kA. For 2.0 GeV beams a current of 1.91 kA is needed which is provided by the upgraded system when being pulsed at 57 kV. UPGRADE MODIFICATIONS The KFA-45 upgrade consists of four major modifications: the permanent short circuit with integrated filter, the ferrite loaded connection box extension, the LEMO ferrites modification and the module dephasing. The simulations and development of the upgrade features have been described in [4] already. SC-plug and Filter Figure 1 shows the finally deployed oil insulated permanent SC-plug which short circuits the termination resistor (TMR) at the level of the former SC-mode thyratron. It features an integrated coil which serves as filter to mitigate the flat top ripple and has either two, three or four turns which can be exchanged for system tuning. As a fall back solution (until 2 GeV beams will be operational) the plug can be replaced by a blank flange turning the system back into terminated mode. Figure 1: SC-plug with integrated filter coil. Table 2: SC-plug: Measured Inductance for Two, Three and Four Turn Version Parameter No. of turns Unit Value Inductance 2 nH 190 3 nH 310 4 nH 430 Table 2 indicates the measured coil inductance and is to be compared with the measured waveforms in Figs. 4-6. The modified magnet with the installed SC-plug instead of the SC-thyratron and thyratron auxiliaries is shown together with the new connection box extension in Fig. 2. The orange box indicates the short circuited TMRs which are kept until LS2 for project risk mitigation. The removal of the TMR during LS2 will also allow to remove the oil distribution board and piping below. Connection Box Extension Each of the KFA-45 magnet modules is connected via two parallel 52.6 Ω SF6 gas filled coaxial high voltage cables. To house the intended ferrite rings a cylindrical SF6 gas filled extension of the magnet connection box was put in place for each of the eight cables. It houses one WEPVA023 Proceedings of IPAC2017, Copenhagen, Denmark ISBN 978-3-95450-182-3 3308 Co py rig ht © 20 17 CC -B Y3. 0 an d by th er es pe ct iv ea ut ho rs 07 Accelerator Technology T16 Pulsed Power Technology ferrite disc of 20 mm height and provides space for 2 disc if needed. In total eight ferrite discs are installed. Figure 2: KFA-45 magnet after EYETS modifications: new magnet connection box extension (red), removed SCthyratron and SC-plug (blue arrow) and TMR (orange). Dephasing The concept of dephasing the individual modules such that the flat top ripple seen by the beam (ideally) cancels out has been described in [4]. The calculated cable length has been verified by VNA measurements and all cable length have been fitted with connectors after high voltage testing and chemical analysis of the dielectric. The length installed for each cable pair per module is shown in Table 3. The dephasing cable installation required a resynchronization of the main and dump switch in order to not compromise the rise and fall times. As the reflections travel several times through the dephasing cables the intended effect is still present even if the main switch trigger is moved by the additional cable length (in time). Table 3: Dephasing Cables: Required and Measured Length Module No. Required length [m] Measured length [ns] Measured length [m] 1 3.5 3.54, 3.54 2 5.4 29.45, 29.77 5.39, 5.45 3 8.4 46, 45.86 8.43, 8.4 4 11.13 60.8, 60.8 11.14, 11.14 LEMO Ferrite Modification The initial upgrade program included a modification of the ferrite loaded LEMO connectors close to the main switch. Figure 3: Measured post pulse ripple current of module 1 with five (blue) and three (black) LEMO ferrites. Analogue circuit simulations suggested a slight reduction of flat top ripple when removing part of these five pulse steepening ferrite rings whilst the increase in rise time stayed stable and acceptable. Measurements showed however that taking out three of the five ferrite rings results in a considerable post pulse ripple excursion (Fig. 3). It was decided to keep all LEMO ferrites installed also in view of a faster rise time. UPGRADE PERFORMANCE An intensive test program has been performed to verify the hardware availability and performance after the modifications. Methodology The assessment of the kicker performance is not straight forward. The kicker itself provides no means for direct field measurements and for inserting a field probe one of the adjacent main bending units would need to be removed. Consequently only current measurements on the magnet modules output have been performed and are compared with expectations from current and field simulations. For definitive verification beam based measurements are being developed [5] and are planned for the PS start up period. SC-plug and Filter Different filter coils have been produced as outlined. They have been tested in module four and behave as predicted by analogue circuit simulations. Figure 4 illustrates the measurement results which clearly show the advantage of the filter coil and the decreasing ripple with increasing coil inductance. Figure 4: Measured current at the output of module 4 for different coils with two (black), three (blue) and four (red) turns mounted to the SC-plug and a direct SC (magenta). Figure 5 shows the rising edge indicating an overshoot mitigation as expected. The undershoot does not decrease in the same way which is explained by the low pass characteristic of the filter. The same effect can be seen on the falling edge (Fig. 6) extending the fall time with increasing inductance. Therefore the filter is beneficial for flat top ripple mitigation but has potential impact on the system rise and fall times. In favour of faster rise & fall time parameters and because the flat top ripple is further mitigated by the dephasing concept the two turn coil has been chosen and was installed on all four modules. 150

The most critical failure scenarios for LHC machine protection concern the injection and dump systems. In view of operation at higher energy and intensity and in light of the experience gained during Run 1, several upgrades were put in place to further enhance the reliability of these systems. Changes were applied both to the protection elements and the kickers (magnets, related electronics, powering systems and interlock logic). The effective performance of the injection and extraction systems and the impact on operation and machine availability are reviewed with respect to forecasts. Extrapolations to operation at 7 TeV and further increased intensity are drawn.

The CERN PS Booster recombination lines (BT) will be upgraded following the extraction energy increase foreseen for the long shutdown 2 (LS2) and meant to reduce the direct space-charge tune shift in the PS injection for the future HL-LHC beams. Henceforth the main line elements, recombination septa, quadrupoles and dipoles must be scaled up to this energy. An increase in the beam rigidity by a factor 1.3 requires the same factor in the field integral of the septa, ∫ Bdl, in order to bend the same angle and preserve the present recombination geometry, which is one of the main upgrade constraints. This paper describes the new optics, in particular in the new and longer septa. In addition we consider the upgrade of the so called BTM line that brings the beam to the external dump and where emittance measurements are taken thanks to three pairs of grids. The new proposed optics has also the advantage to simplify the design of the new dipoles. Here we study this new optics and the issues related to the emittance measurement at the new higher energy. INTRODUCTION TO THE RECOMBINATION LINES The four transfer lines that extract protons from each ring of the PSB to the PS (BT1, BT2, BT3, BT4) are recombined in the BT line (Fig. 1). Figure 1: Scheme of the PSB ejection lines, not to scale From the BT line, the beam can go to three different locations: to the PS (BTP line), to the ISOLDE facility (BTY) or to a dump (BTM). BT.BHZ10 is the switch magnet to the BTP line and BTY.BVT101 is the switch magnet o BTY (off when sending to the dump). Figure 2 represents the scheme of the BT-BTM magnets. A set of three couples of SEM grids lo-cated in the BTM line is used for the emittance measurement in the two planes. In this paper we describe the works on the recombination part (in green in Fig. 1) and the BT-BTM line (in red). Figure 2: Scheme of the BT-BTM line. Quadrupoles are shown in red and dipoles in blue. It corresponds to the red line in Fig. 1. UPGRADING The LHC Injectors Upgrade (LIU) project [1] aims to an injection energy in the PS of 2 GeV, so that the present lines must work at that energy. In addition, the upgrade of the recombination lines must not hinder a possible upgrade of the ISOLDE faclity from 1.4 to 2.0 GeV. In particular, the energy upgrade translates into a 30% increase in beam rigidity, so that the same increase have to followed by the field integral ∫ Bdl in all the bending elements: dipoles, septa and kickers. At the same time, a working energy of 1.4 GeV must be allowed in terms of element acceptances. The present 1.0-GeV working energy will be discarded after long shutdown 2 (LS2). OPTICS In order to deal with the different users of the extracted beams from the PSB, four different optics configurations for the BT-BTM line exist [2]: