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Summary of ARIES WP6 APEC & iFAST WP5.2 PAF joint Brainstorming & Strategy Workshop (BSW22) R. Assmann (DESY), C. Carli (CERN), A. Faus-Golfe (IJCLab), E. Fol (CERN), G. Franchetti (GSI & GU Frankfurt), R. Jacobsson (CERN), V. Kain (CERN), F. Kling (DESY), M.W. Krasny (LPNHE), R. Ischebeck (PSI), A. Scheinker (LANL), V. Shiltsev (FNAL), R. Tomas Garcia (CERN), F. Zimmermann (CERN) edited by the BSW2022 workshop organisers A. Faus-Golfe (IJCLab), G. Franchetti (GSI & GU Frankfurt), F. Zimmermann (CERN) The ARIES WP6 APEC & iFAST WP5.2 PAF joint Brainstorming & Strategy Workshop (BSW22) from 30 March to 1 April 2022 addressed (1) present and future AI accelerator applications, and (2) beam requirements and accelerators for the dark sector. For both themes a number of conclusions were formulated. For example, dielectric acceleration appears to be an interesting approach for dark sector searches, calling for a suitable DLA accelerator design and experimental demonstration, while Machine Learning will become a community standard, and should be used for the design optimization of future machines. An intriguing proposal was the use of the LHC based Gamma Factory for driving a subcritical reactor with integrated waste transmutation., This project has received funding from the European Union's Horizon 2020 Research and Innovation programme under Grant Agreements No. 730871 (ARIES) and 101004730 (iFAST).

The FCC-ee collider baseline foresees four different energy operation modes: Z, WW, H(ZH) and ttbar. An optional fifth mode, called s-channel Higgs production mode, could allow the measurement of the electron Yukawa coupling, in dedicated runs at 125 GeV centre-of-mass energy, provided that the centre-of-mass energy spread, can be reduced by at least an order of magnitude (5-10 MeV). The use of a special collision technique: a monochromatization scheme is one way to accomplish it. There are several methods to implement a monochromatization scheme. One method, named transverse monochromatization scheme, consists of introducing a dispersion different from zero but opposite sign for the two colliding beams at the Interaction Point (IP); In this paper we will report about the first attempt to design a new optics to implement a transverse monochromatic scheme for the FCC-ee Higgs production totally compatible with the standard mode of operation without dispersion at the IP., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

During the preparatory phase of the International Linear Collider (ILC) project, all technical development and engineering design needed for the start of ILC construction must be completed, in parallel with intergovernmental discussion of governance and sharing of responsibilities and cost. The ILC Preparatory Laboratory (Pre-lab) is conceived to execute the technical and engineering work and to assist the intergovernmental discussion by providing relevant information upon request. It will be based on a worldwide partnership among laboratories with a headquarters hosted in Japan. This proposal, prepared by the ILC International Development Team and endorsed by the International Committee for Future Accelerators, describes an organisational framework and work plan for the Pre-lab. Elaboration, modification and adjustment should be introduced for its implementation, in order to incorporate requirements arising from the physics community, laboratories, and governmental authorities interested in the ILC., 48 pages, 5 figures

The main goal of the Accelerator Test Facility 2 (ATF2) is to demonstrate the feasibility of future linear colliders’ final focus systems. The Ultra-low β^{*} optics of ATF2 is designed to have the same chromaticity level as CLIC. To ease the tuning procedure, a pair of octupoles was installed in ATF2 in 2017. This paper reports the optimizations performed to the octupoles’ setup for Ultra-low β^{*} optics including the new alignment technique, based on the waist shift and the new tunning knobs constructed for this optics. The full tuning procedure including the static errors is simulated for this setup., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The Compact Linear Collider (CLIC) could provide e⁺e⁻ collisions in two detectors simultaneously possibly at a repetition frequency twice the design value. In this paper, a novel dual Beam Delivery System (BDS) design is presented including optics designs and the evaluation of luminosity performance with synchrotron radiation (SR) and solenoid effects for both energy stages of CLIC, 380 GeV and 3 TeV. In order to develop the novel optics design, parameters such as the longitudinal and the transverse detector separations were optimized. The luminosity performance of the novel CLIC scheme was evaluated by comparing the different BDS designs for both energy stages of CLIC. The dual CLIC BDS design provides a good luminosity and proves to be a viable candidate for future linear collider projects., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The first stage of the Compact Linear Collider (CLIC) is planned to be at the center-of-mass energy of 380 GeV. The final focus system (FFS) was re-optimized for this energy and for L* of 6 m (distance between the Interaction Point (IP) and the last quadrupole, QD0). Furthermore, the FFS optics was optimized for the vertical beta-function of 70 microns to approach the Hourglass effect limit. This paper reports the exploration of shortening the Final Doublet (FD) within the FFS to reduce the chromaticity. In addition, an alternative optics design is investigated with a different dispersion profile along the FFS, which outperforms the previous optics with the same β^{*}, increasing luminosity by 5 %., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The KEK accelerator test faciliry (ATF) conducts R&D on a beam for the Linear Collider. The damping ring provides a low emittance electron beam and the final focus test beamline (ATF2) provides studies on small beam of nanometer level by utilizing a low emittance beam. These R&D are conducted under the ATF international collaboration with many contributions of graduate students around the world. A review meeting to discuss the further studies at ATF will be held on Septem- ber 29, 2020 as a short tele-conference. This report provides the information necessary for discussion. We summarize the remaining studies that will be done in the coming years and ILC preparatory period for further improvements of nanometer beam techno- logy, and the use of ATF facility as a test bench for ILC subsystem in the preparatory period and after. The possible utilizations of the ATF/ATF2 beams for R&D beyond Linear Colliders are also presented.

One of the main requests for future linear colliders is to achieve a nanometer vertical beam size at the Interaction Point (IP). Accelerator Test Facility 2 (ATF2) represents a scale down implementation of the final focus system (FFS) concept based to test the novel local chromaticity correction scheme that is implemented in the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) designs. After several years of operations and commissioning, σy∗ of 41 ± 3 nm was measured at ATF2 with the nominal βy∗ optics in 2016. This paper reports the experimental tuning study done with the ultra-low βy∗ during March 2019 beam operation. This optics has a level of chromaticity comparable with CLIC one and it is expected to reduce σy∗ below 40 nm.

CompactLight (XLS) is an International Collaboration of 24 partners and 5 third parties, funded by the European Union through the Horizon 2020 Research and Innovation Programme. The main goal of the project, which started in January 2018 with a duration of 36 months, is the design of an hard X-ray FEL facility beyond today’s state of the art, using the latest concepts for bright electron photo-injectors, high-gradient accelerating structures, and innovative shortperiod undulators. The specifications of the facility and the parameters of the future FEL are driven by the demands of potential users and the associated science cases. In this paper we will give an overview on the ongoing activities and the major results achieved until now.

This document describes with analytical and numerical methods, i.e., approximated mathematical expressions and particle tracking runs, the process of bunch length compression of relativistic electron beams in linear accelerators. In particular, it reviews state-of-the-art compression options, based on magnetic insertions and radio-frequency (RF) accelerators, for the increase of peak current and preservation of the six-dimensional beam brightness as requested by x-ray freeelectron lasers (FELs). After a theoretical introduction to the topic, guidelines for the determination of the compression scheme for the CompactLight FEL are provided, by considering for example RF compression in combination with four dipoles chicanes. The study considers single particle dynamics, tolerance budget and collective effects involved in the compression process. On the basis of FEL specifications, the main parameters of the electron beam and of the compressors in the CompactLight accelerator are illustrated. Finally, a preliminary RF design of X-band and Ka-band accelerating cavities to support magnetic compression is presented. As a result, this review of most advanced electron beam compression schemes provides a solid basis for the definition of the beam manipulation aimed to meet the requirements of CompactLight FEL., On behalf of the CompactLight Collaboration.

The H2020 CompactLight Project aims at designing the next generation of compactX-rays Free-Electron Lasers, relying on very high gradient accelerating structures (X-band, 12 GHz), the most advanced concepts for high brightness electron photo injectors, and innovative compact short-period undulators. Compared to existing facilities, the proposed facility will benefit from a lower electron beam energy, due to the enhanced undulators performance, and will be significantly more compact, with a smaller footprint, as a consequence of the lower energy and the high-gradient X-band structures. In addition, the whole infrastructure will also have a lower electrical power demand as well as lower construction and running costs.

The Platform for Research and Applications with Electrons (PRAE) is a multidisciplinary R facility gathering subatomic physics, instrumentation, radiobiology and clinical research around a high-performance electron accelerator with beam energies up to 70 MeV. In this paper we report the complete optics design and performance evaluation of a Very High Energy Electron (VHEE) innovative radiobiology study, in particular by using Grid mini-beam and FLASH methodologies, which could represent a major breakthrough in Radiation Therapy (RT) treatment modality., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The Accelerator Test Facility 2 (ATF2) at KEK is a prototype for the Final Focus Systems of the future e⁺e⁻ linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). In this paper both simulation and experimental results are presented with special emphasis on intensity-dependent effects. The importance of these effects is shown using the PLACET code and realistic ATF2 machine simulations (including beam jitter, misalignment, wakefield, Beam Based Alignment (BBA) correction, …). The latest experimental results are also presented, in particular the impact of the beam intensity on the beam size at the IP., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Field emitted electrons have important consequences in the operation of high-gradient RF accelerating structures both by generating so-called dark currents and initiating RF breakdown. The latter is an important limitation of the performance in such devices. Another kind of vacuum discharge that primarily affects the operation of lower-field RF components, for example those used in space applications, is multipactor. Theoretical simulations using CST Particle Studio, show that field emitted electrons generated in the high field regions of high-gradient accelerating cavities migrate to low field regions under ponderomotive forces potentially triggering multipactor there. This phenomenon is an interplay between high field and low field processes which may have as a consequence that multipactor actually affects to the performance of high-gradient cavities because field emitted electrons might reduce the timescales for the onset of multipactor., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The FCC-ee is a high-luminosity, high-precision circular collider to be constructed in a new 100 km tunnel in the Geneva area. The physics case is well established and the FCC-ee operation is foreseen at 91 GeV (Z-pole), 160 GeV (W pair production threshold), 240 GeV (Higgs resonance) and 365 GeV (t-tbar threshold). Due to the large 6D production emittance and important thermal load in the production target, the positron injector, in particular the positron source, is one of the key elements of the FCC-ee, requiring special attention. To ensure high reliability of the positron source, conventional and hybrid targets are currently under study. The final choice of the positron target will be made based on the estimated performances. In this framework, we present a preliminary design of the FCC-ee positron source, with detailed simulation studies of positron production, capture and primary acceleration., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Dark current is particularly relevant during operation in high-gradient linear accelerators. Resulting from the capture of field emitted electrons, dark current produces additional radiation that needs to be accounted for in experiments. In this paper, an analysis of dark current is presented for four accelerating structures that were tested and conditioned in CERN’s X-band test facility for CLIC. The dependence on power, and therefore on accelerating gradient, of the dark current signals is presented. The Fowler-Nordheim equation for field emission seems to be in accordance with the experimental data. Moreover, the analysis shows that the current intensity decreases as a function of time due to conditioning, but discrete jumps in the dark current signals are present, probably caused by breakdown events that change the emitters’ location and intensity., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The Future Circular Collider (FCC-hh) is being designed as a 100 km ring that should collide 50 TeV proton beams. At 8.3 GJ, its stored beam energy will be a factor 28 higher than what has been achieved in the Large Hadron Collider, which has the highest stored beam energy among the colliders built so far. This puts unprecedented demands on the control of beam losses and collimation, since even a tiny beam loss risks quenching superconducting magnets. We present in this article the design of the FCC-hh collimation system and study the beam cleaning through simulations of tracking, energy deposition, and thermo-mechanical response. We investigate the collimation performance for design beam loss scenarios and potential bottlenecks are highlighted., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The case for a lepton collider to explore the physics opened up by the discovery of the Higgsboson is widely accepted. The International Linear Collider being proposed in Japan withan initial energy of 250 GeV has the potential to study the Higgs sector in great detail. Theinternational - including European - interest for the project is very large.This document complements the KEK ILC action plan from 2016 and provides an overviewof European expertise and possible contributions to the ILC preparation phase. It is basedon the assumption that ILC will be realized as an international project led by Japan, with astrong international participation. It does not provide or rely on specific levels of the Europeancontribution to the project, but builds on the European capabilities and technical expertise.

The high-gradient performance of an accelerating structure prototype for a medical proton linac is presented. The structure was designed and built using technology developed by the CLIC collaboration and the target application is the TULIP (Turning Linac for Proton therapy) proposal developed by the TERA foundation. The special feature of this design is to produce gradient of more than 50 MV /m in low-β accelerating structures (v/c=0.38). The structure was tested in an S-band test stand at CERN. During the tests, the structure reached over above 60 MV/m at 1.2 μs pulse length and breakdown rate of about 5x10⁻⁶ bpp. The results presented include ultimate performance, long term behaviour and measurements that can guide future optimization., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

An S-Band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN* and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid 2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described. An S-band High-Gradient (HG) Radio Frequency (RF) laboratory is under construction and commissioning at IFIC. The purpose of the laboratory is to perform investigations of high-gradient phenomena and to develop normal-conducting RF technology, with special focus on RF systems for hadron-therapy. The layout of the facility is derived from the scheme of the Xbox-3 test facility at CERN [1] and uses medium peak-power (7.5 MW) and high repetition rate (400 Hz) klystrons, whose RF output is combined to drive two testing slots to the required power. The design and construction of the various components of the system started in 2016 and has been completed. The installation and commissioning of the laboratory is progressing, with first results expected before mid-2018. The technical characteristics of the different elements of the system and the commissioning status together with preliminary results are described.

The PRAE project (Platform for Research and Applications with Electrons) aims at creating a multidisciplinary R&D facility in the Orsay campus gathering various scientific communities involved in radiobiology, subatomic physics, instrumentation and particle accelerators around an electron accelerator delivering a high-performance beam with energy up to 70 MeV and later 140 MeV, in order to perform a series of unique measurements and future challenging R&D. In this paper we report the first start-to-end simulations from the RF gun, going through the linac and finally to the different experimental platforms. The beam dynamics simulations have been performed using a concatenation of codes. In particular for the linac the RF-Track code recently developed at CERN will be used and benchmarked. The different working points have been analysed in order to minimise the transverse emittance and the beam energy spread including space charge effects at low electron energies., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

H2020 CompactLight Project aims at designing the next generation of compact hard X-Rays Free-Electron Lasers, relying on very high accelerating gradients and on novel undulator concepts. CompactLight intends to design a compact Hard X-ray FEL facility based on very high-gradient acceleration in the X band of frequencies, on a very bright photo injector, and on short-period/superconductive undulators to enable smaller electron beam energy. If compared to existing facilities, the proposed facility will benefit from a lower electron beam energy, due to the enhanced undulators performance, be significantly more compact, as a consequence both of the lower energy and of the high-gradient X-band structures, have lower electrical power demand and a smaller footprint. CompactLight is a consortium of 24 institutes (21 European + 3 extra Europeans), gathering the world-leading experts both in the domains of X-band acceleration and undulator design., Proceedings of the 60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources, FLS2018, Shanghai, China

The future circular hadron collider (FCC-hh) will have an unprecedented proton beam energy of 50 TeV, and total stored beam energy of 8.4 GJ. We discuss current developments in the collimation system design, and methods with which the challenges faced due to the high energies involved can be mitigated. Finally simulation results of new collimation system designs are presented., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The objectives of the PACMAN* project are to improve the precision and accuracy of the alignment of accelerator components. Two steps of alignment are concerned: the fiducialisation, i.e. the determination of the reference axis of components w.r.t alignment targets, and the initial alignment of components on a common support assembly. The main accelerator components considered for the study are quadrupoles, 15 GHz BPM and RF structures from the Compact LInear Collider (CLIC) project. Different methods have been developed to determine the reference axis of these components with a micrometric accuracy, as well as to determine the position of this reference axis in the coordinate frame of the common support assembly. The tools and methods developed have been validated with success on dedicated test setups using CLIC components. This paper will provide a compilation of the main achievements and results obtained., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The IFIC High-Gradient (HG) Radio Frequency (RF) laboratory is designed to host a high-power infrastructure for testing HG S-band normal-conducting RF accelerating structures and has been under construction since 2016. The main objective of the facility is to develop HG S-band accelerating structures and to contribute to the study of HG phenomena. A particular focus is RF structures for medical hadron therapy applications. The design of the laboratory has been made through collaboration between the IFIC and the CLIC RF group at CERN. The layout is inspired by the scheme of the Xbox-3 test facility at CERN, and it has been adapted to S-band frequency. In this paper we describe the design and construction status of such a facility., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

In the framework of the PACMAN project we have developed a test set-up to measure the electromagnetic centre of high gradient accelerating structures for alignment purposes. We have demonstrated with previous simulation studies that a resolution of 1 m is possible. The improvements applied on the technique and on the set-up, calibrations and the equipment instrumentation allows the measurement of the electromagnetic centre, with a final precision of 1.09 m in the horizontal plane and 0.58 m in the vertical plane. The experimental measurements and the simulation studies as a support to justify the numbers obtained are presented and discussed., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

In this paper we study the discrepancy found between the wakefield impact effect induced by a rectangular tapered collimator prototype for ATF2 calculated using analytical models, calculated from CST PS numerical simulations and implemented in the tracking code PLACET v1.0.0. In order to get consistent results between the analytical calculations, CST PS simulations and the tracking code PLACET v1.0.0 the collimator wakefield module in PLACET v1.0.0 has to be modified. The changes have been implemented in the tracking code PLACET v1.0.1.

The international Future Circular Collider (FCC) study is designing hadron, lepton and lepton-hadron colliders based on a new 100 km tunnel in the Geneva region. The main focus and ultimate goal of the study are high-luminosity proton-proton collisions at a centre-of-mass energy of 100 TeV, using 16 T Nb3Sn dipole magnets. Specific FCC beam dynamics issues are related to the large circumference, the high brightness - made available by radiation damping -, the small geometric emittance, unprecedented collision energy and luminosity, the huge amount of energy stored in the beam, large synchrotron radiation power, plus the injection scenarios. In addition to the FCC-hh proper, also a High-Energy LHC (HE-LHC) is being explored, using the FCC-hh magnet technology in the existing LHC tunnel, which can yield a centre-of-mass energy around 25 TeV., Proceedings of the 57th ICFA Advanced Beam Dynamics Workshop on High-Intensity and High-Brightness Hadron Beams, HB2016, Malmö, Sweden

Direct Higgs production in e⁺e⁻ collisions at the FCC is of interest if the centre-of-mass energy spread can be reduced by at least an order of magnitude. A mono-chromatization scheme, to accomplish this, can be realized with horizontal dispersion of opposite sign for the two colliding beams at the interaction point (IP). We review approaches from historical mono-chromatization studies, then derive a set of IP parameters which would provide the required performance in FCC e⁺e⁻ collisions at 63 GeV beam energy, compare these with the baseline optics parameters at neighbouring energies (45.6 and 80 GeV), comment on the effect of beamstrahlung, and, finally, discuss the modifications of the FCC-ee final-focus optics needed to obtain the required parameters., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The proposed CERN FCC-hh proton-proton collider will operate at unprecedented per-particle (50 TeV) and total stored beam energies (8.4 GJ). These high energies create the requirement for an efficient collimation system in order to protect the accelerator components and experiments. In order to verify the performance of proposed collimation system designs, loss map simulations have been performed using the code Merlin. Results for the current baseline layout are presented for both betatron and off-momentum loss maps., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

To achieve a high accelerating gradient of 100 MV/m, the CLIC project under study at CERN uses a 23 cm long tapered normal-conducting travelling wave Accelerating Structure (AS) operating at 12 GHz. Minimisation of the long-range wakefields (WF) is assured by damping of the HOM through four radial waveguides in each cell without distorting the accelerating mode. As an extension of them, there are four bent waveguides called WF monitors (WFM) in the middle cell with two RF pick-ups. To obtain a small beam emittance in the collision point, micro-metric pre-alignment of the AS is required. We work to find the electrical centre of the AS through the use of the asymmetry in the RF scattering parameters created by an off-centre conductive wire, stretched along the axis. The accuracy required is of 7 μm with a resolution of 3.5 μm for the WFM signals including the acquisition electronics. Our simulations have shown that a resolution of 1 μm is possible using a calibrated VNA. Measurement results and improvements of the final accuracy will be presented and discussed., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

In collaboration with LAPP and IFIC, two units of a prototype stripline Beam Position Monitor (BPM) for the CLIC Drive Beam (DB), and its associated readout electronics have been successfully installed and tested in the Two-Beam-Module (TBM) at the CLIC Test Facility 3 (CTF3) at CERN. This paper gives a short overview of the BPM system and presents the performance measured under different Drive Beam configurations., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The CLIC project, currently under study at CERN is an electron-positron collider at 3 TeV centre-of-mass energy and luminosity of 2*1034 cm⁻²s^{−1}. Achieving such luminosity requires a beam dimension of 1 nm in the vertical plane and high beam stability. The TD24 is a traveling wave structure operating at 12 GHz designed to reach 100 MV/m at constant gradient. It consists of two coupling cells and 24 disks. The RF is coupled from cell to cell though an iris of 5.5 mm. To minimize the occurrence of wake-fields and minimize the emittance growth Δεy below 5%, the pre-alignment precision of the electrical centre of the accelerating structure (AS) on its support has to be better than 7 μm. Following, the AS is actively aligned with beam using the wake-field monitor (WFM) signals, with a resolution of 3.5 μm. A test bench for laboratory measurements has been designed and exploits the asymmetry created by RF scattering parameters of an off-centre conductive wire, stretched to locate the electromagnetic centre of the AS. Simulations and preliminary measurement results are presented., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

The Pre-Damping Rings (PDRs) and Damping Rings (DRs) of CLIC are required to reduce the beam emittances to the small values required for the main linacs. The injection and extraction, from the PDRs and DRs, are performed by kicker systems. To achieve both low beam coupling impedance and reasonable broadband impedance matching to the electrical circuit, striplines have been chosen for the kicker elements. Prototype striplines have been built: tests and measurements of these striplines have started. The goal of these tests is to characterize, without beam, the electromagnetic response of the striplines. The tests have been carried out at CERN. To study the signal transmission through the striplines, the measured S-parameters have been compared with simulations. In addition, measurements of longitudinal beam coupling impedance, using the coaxial wire method, are reported and compared with simulations., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The post-linac energy collimation system of CLIC is designed to fulfill an essential function of protection of the Beam Delivery System (BDS) against miss-steered beams generated by failure modes in the main linac. Guaranteeing the collimator survivability in case of direct beam impact is very challenging, if we take into account the need to deal with an unprecedented transverse beam energy density per beam of the order of GJ/mm². This translates into a high damage potential of uncontrolled beams. In this paper we present an alternative nonlinear energy collimation system as a potential solution to guarantee the survival of the collimators. The performance and error tolerances of this system are studied by means of beam tracking simulations, and compared with those of the conventional baseline CLIC energy collimation system.

In this paper we review the status of the studies on nonlinear collimation schemes for the LHC. Concretely we describe the design of a nonlinear optics for betatron cleaning in IR7. The aim is to investigate alternative nonlinear collimation systems to reduce the collimator-induced impedance that may limit the beam intensity towards the LHC luminosity upgrade. The performance of the LHC nonlinear collimation system is studied by means of tracking simulations and compared with the present LHC system. Furthermore, the advantages and possible limitations of such nonlinear collimation scheme are discussed.

We study the feasibility of using a multi-Optical Transition Radiation (mOTR) system for fast transverse emittance reconstruction and x-y coupling correction in the Ring to Main Linac (RTML) of the future linear colliders: ILC and CLIC. OTR monitors are mature and reliable diagnostic tools that could be very suitable for the setup and tuning of the machine in single-bunch mode. Here we study the requirements for a mOTR system adapted to the optical conditions and beam parameters of the RTML of both the ILC and CLIC.

Performance limiting high-power rf phenomenon occur in both transmitter systems in satellites and high-gradient accelerating structures in particle accelerators. In satellites the predominant effect is multipactor while in accelerators it is breakdown. Both communities have studied their respective phenomena extensively and developed particular simulation tools and experimental techniques. A series of experiments to directly compare measurements made under multipactor and breakdown conditions has been initiated with the objective to crosscheck and compare the physics, simulation tools and measurement techniques.

The International Large Detector (ILD) is a concept for a detector at the International Linear Collider, ILC. The ILC will collide electrons and positrons at energies of initially 500 GeV, upgradeable to 1 TeV. The ILC has an ambitious physics program, which will extend and complement that of the Large Hadron Collider (LHC). A hallmark of physics at the ILC is precision. The clean initial state and the comparatively benign environment of a lepton collider are ideally suited to high precision measurements. To take full advantage of the physics potential of ILC places great demands on the detector performance. The design of ILD is driven by these requirements. Excellent calorimetry and tracking are combined to obtain the best possible overall event reconstruction, including the capability to reconstruct individual particles within jets for particle ow calorimetry. This requires excellent spatial resolution for all detector systems. A highly granular calorimeter system is combined with a central tracker which stresses redundancy and efficiency. In addition, efficient reconstruction of secondary vertices and excellent momentum resolution for charged particles are essential for an ILC detector. The interaction region of the ILC is designed to host two detectors, which can be moved into the beam position with a push-pull scheme. The mechanical design of ILD and the overall integration of subdetectors takes these operational condition s into account. The International Large Detector (ILD) is a concept for a detector at the International Linear Collider, ILC. The ILC will collide electrons and positrons at energies of initially 500 GeV, upgradeable to 1 TeV. The ILC has an ambitious physics program, which will extend and complement that of the Large Hadron Collider (LHC). A hallmark of physics at the ILC is precision. The clean initial state and the comparatively benign environment of a lepton collider are ideally suited to high precision measurements. To take full advantage of the physics potential of ILC places great demands on the detector performance. The design of ILD is driven by these requirements. Excellent calorimetry and tracking are combined to obtain the best possible overall event reconstruction, including the capability to reconstruct individual particles within jets for particle ow calorimetry. This requires excellent spatial resolution for all detector systems. A highly granular calorimeter system is combined with a central tracker which stresses redundancy and efficiency. In addition, efficient reconstruction of secondary vertices and excellent momentum resolution for charged particles are essential for an ILC detector. The interaction region of the ILC is designed to host two detectors, which can be moved into the beam position with a push-pull scheme. The mechanical design of ILD and the overall integration of subdetectors takes these operational conditions into account.

The collimation system of a Linear Collider must serve multiple purposes and fulfill a number of constraints. In particular, we require that the collimation system should sustain the impact of off-energy bunches and have a large chromatic bandwidth, in addition to ensuring a high collimation efficiency and tolerable wake fields. We describe the design of a nonlinear energy collimation system for CLIC at 3 TeV, in which skew sextupoles are used to blow up the vertical beam size at the spoiler, so as to guarantee collimator survival in case of beam impact. Its properties, like chromatic bandwidth and collimation survival, are evaluated and compared with those of the baseline linear collimation system.

In 2003 and 2004 nonlinear chromaticity, amplitude detuning, chromatic phase advance, resonance driving terms and off-energy orbits were measured in the CERN SPS at 14 GeV/c and 26 GeV/c, respectively. From the nonlinear chromaticity, the SPS optics model has been updated, by adjusting the strength of nonlinear field errors in dipoles and quadrupoles. Furthermore, we have added to the model the effect of the displacement of all main bends and the voluntary misalignments of all the other elements of the machine. We compare the field errors with those founded in 2002, 2001 and 2000. The tune shifts with transverse amplitude, driving terms, etc., predicted by this nonlinear optics model are compared with direct measurements.

In 2002, nonlinear chromaticity, coupling, amplitude-dependent detuning, chromatic phase advance, resonance driving terms, and off-energy orbits were measured in the CERN SPS at 26 GeV/c. The optics model has been updated by adjusting the strengths of nonlinear field errors in the dipoles and quadrupoles, so as to reproduce the measured nonlinear chromaticity. We compare the field errors deduced in 2002, measuring over a larger momentum range, with those found in 2001 and 2000. The resolution is improved by averaging over all turn-by-turn position monitors in the ring instead of using a single dedicated pick up ('tune meter'). Computations using two different optics codes, MAD and SAD, indicate the sensitivity to matching algorithm and magnet representation. To validate the nonlinear optics model, the predicted tune shifts with transverse amplitude, driving terms of low-order resonance, etc., are compared with direct measurements.