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Electron-hadron colliders are the ultimate tool for high-precision quantum chromodynamics studies and provide the ultimate microscope for probing the internal structure of hadrons. The electron is an ideal probe of the proton structure because it provides the unmatched precision of the electromagnetic interaction, as the virtual photon or vector bosons probe the proton structure in a clean environment, the kinematics of which is uniquely determined by the electron beam and the scattered lepton, or the hadronic final state accounting appropriately for radiation. The Hadron Electron Ring Accelerator HERA (DESY, Hamburg, Germany) was the only electron-hadron collider ever operated (1991–2007) and advanced the knowledge of quantum chromodynamics and the proton structure, with implications for the physics studied in RHIC (BNL, Upton, NY) and the LHC (CERN, Geneva, Switzerland). Recent technological advances in the field of particle accelerators pave the way to realize next-generation electron-hadron colliders that deliver higher luminosity and enable collisions in a much broader range of energies and beam types than HERA. Electron-hadron colliders combine challenges from both electron and hadron machines besides facing their own distinct challenges derived from their intrinsic asymmetry. This review paper will discuss the major features and milestones of HERA and will examine the electron-hadron collider designs of the Electron-Ion Collider (EIC) currently under construction at BNL, the CERN’s Large Hadron electron Collider (LHeC), at an advanced stage of design and awaiting approval, and the Future Circular lepton-hadron Collider (FCC-eh).

The possibility of two interaction regions (IRs) is a design requirement for Electron-Ion Collider (EIC). There is also a significant interest from the nuclear physics community to have a 2nd IR with measurement capabilities complementary to those of the 1st IR. While the 2nd IR will be in operation over the entire energy range of ~20GeV to ~140GeV center of mass (CM). The 2nd IR can also provide an acceptance coverage complementary to that of the 1st. In this paper, we present a brief overview and the current progress of the 2nd IR design in terms of the parameters, magnet layout, and beam dynamics., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The Future Circular Collider study is exploring possible designs of circular colliders for the post-LHC era, as recommended by the European Strategy Group for High Energy Physics. One such option is FCC-hh, a proton-proton collider with a centre-of-mass energy of 100 TeV. The experimental insertion regions are key areas defining the performance of the collider. This paper presents the first insertion region designs with a complete assessment of the main challenges, as collision debris with two orders of magnitude larger power than current colliders, beam-beam interactions in long insertions, dynamic aperture for optics with peak $\beta$ functions one order of magnitude above current colliders, photon background from synchrotron radiation and cross talk between the insertion regions. An alternative design avoiding the use of crab cavities with a small impact on performance is also presented., Comment: 74 pages

This document provides detailed information on the status of Advanced and Novel Accelerators techniques and describes the steps that need to be envisaged for their implementation in future accelerators, in particular for high energy physics applications. It complements the overview prepared for the update of the European Strategy for particle physics, and provides a detailed description of the field. The scientific priorities of the community are described for each technique of acceleration able to achieve accelerating gradient in the GeV~range or above. ALEGRO working group leaders have coordinated the preparation of their working group contribution and contributed to editing the documents. The preparation of this document was coordinated by the Advanced LinEar collider study GROup, ALEGRO. The content was defined through discussions at the ALEGRO workshop in Oxford UK, March 2018, and an advanced draft was discussed during a one day meeting prior to the AAC workshop in Breckenridge, CO, USA, August 2018. This document was submitted as an addendum to the ALEGRO submission to the European Strategy for Particle Physics., 83 pages

The purpose of the paper is to outline the status of the EIC accelerator designs and to discuss the most significant R&D subjects that have strong connection with developments in Europe, with the purpose of enlarging EICcollaboration both in physics and accelerator, to strengthen synergies with European accelerator projects,and – more generally – to maximize positive impact of fundamental science on society worldwide.

The High Energy LHC (HE-LHC) project is studying the feasibility of a new proton-proton collider with a beam energy of 13.5 TeV. The nominal optics features a β^{*} of 0.25 m and crab-cavities. Here we present a flat-beam optics that can be used with a non-zero crossing angle, in the absence of crab cavities. This is followed by energy deposition studies for the superconducting quadrupoles and dipole separators. The total dose in these magnets coming from the collision debris is evaluated., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The sizes of the beta functions in the final focus triplet of a synchrotron collider have a great impact on the chromaticity and dynamic aperture of the machine. These beta functions are proportional to the square of the length of the final drift so it is desirable to keep it as short as possible whilst leaving enough room for the experiment. In the latest design of the FCC-hh this drift was reduced from 45 m to 40 m. In the following an alternative final focus for this new design will be presented. The effects this change has on the interaction region will examined and discussed., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Optimization of the dual axis asymmetric cavity was performed to minimize the ratio of the peak magnetic and electric fields values to the accelerating voltage, to increase the distance between operating and neighbouring modes as well as to reduce the manufacturing cost of the cavity. To reach the goals several solutions have been suggested bringing the ratios to the acceptable values and leading to simplification of the manufacturing of the structure., Proceedings of the 29\textsuperscript{th} Linear Accelerator Conf., LINAC2018, Beijing, China

The Future Circular Collider (FCC) design study aims to develop the designs of possible circular colliders in the post LHC era. In particular the FCC-hh will aim to produce proton-proton collisions at a center of mass energy of 100 TeV. Initial tracking studies for the FCC-hh lattice at collision energy including field errors on the final focus triplet showed a very low dynamic aperture, most likely affected by the large beta functions and integrated length of the quadrupoles. Using non-linear correctors, the dynamic aperture was increased to acceptable levels; however, the difficulty to have an accurate magnetic model of the magnets required for this correction motivates the development of alternative methods. This work explores the possibility to increase the dynamic aperture by optimizing the phase advance between the main interaction regions. The description of this method along with its impact on the dynamic aperture will be given on this paper., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The international Future Circular Collider (FCC) study comprises the development of a new scientific structure in a tunnel of 100 km. This will allow the installation of a proton collider with a centre of mass energy of 100 TeV, called FCC-hh. An alternative design of the final focus triplet for the FCC-hh has been developed in parallel to the alternative one, and adapted to the constraint of a free length (L*) of 40 m. We discuss in this paper the energy deposition issues as well as the luminosity evolution for two different optics choices: round and flat beams., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Description of the EIR baseline design including a list of beamline elements (type, description, quantity, physical element characteristics). Estimates of the achievable performances at the interaction points. Description of the assumptions taken, requirements and constraints imposed onto the infrastructure and infrastructure services.

Debris from 50 TeV proton-proton collisions at the main interaction point in the FCC-hh may contribute to the background in the subsequent detector. This cross-talk is of possible concern for the FCC-hh due to the high luminosity and energy of the collider. DPMJET-III is used as a collision debris generator in order to assess the muon cross-talk contribution. An analytical calculation of muon range in rock is performed. This is followed by a full Monte Carlo simulation using FLUKA, where the accelerator tunnel has been modelled. The muon cross talk between the adjacent interaction points is assessed and its implications for FCC-hh design are discussed., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

One of the main challenges when designing final focus systems of particle accelerators is maximising the beam stay clear in the strong quadrupole magnets of the inner triplet. Moreover it is desirable to keep the quadrupoles in the inner triplet as short as possible for space and costs reasons but also to reduce chromaticity and simplify corrections schemes. An algorithm that explores the triplet parameter space to optimise both these aspects was written. It uses thin lenses as a first approximation for a broad parameter scan and MADX for more precise calculations. The thin lens algorithm is significantly faster than a full scan using MADX and relatively precise at indicating the approximate area where the optimum solution lies., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The Future Circular Collider (FCC) design study aims to develop the designs of possible circular colliders in the post LHC era. In particular the FCC-hh will aim to produce proton-proton collisions at a center of mass energy of 100 TeV. Given the large beta functions and integrated length of the quadrupoles of the final focus triplet the effect of systematic and random non linear errors in the magnets are expected to have a severe impact on the stability of the beam. Following the experience on the HL-LHC this work explores the implementation of non-linear correctors to minimize the resonance driving terms arising from the errors of the triplet. Dynamic aperture studies are then performed to study the impact of this correction., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The international Future Circular Collider (FCC) study comprises the study of a new scientific structure in a tunnel of 100 km. This will allow the installation of two accelerators, a 45.6'175 GeV lepton collider and a 100-TeV hadron collider. An optimized design of a final-focus system for the hadron collider is presented here. The new design is more compact and enables unequal β^{*} in both planes, whose choice is justified here. This is followed by energy deposition studies, where the total dose in the magnets as a consequence of the collision debris is evaluated., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The experimental interaction region is one of the key areas that define the performance of the Future Circular Collider. In this overview we will describe the status and the evolution of the design of EIR of FCC-hh, focusing on design of the optics, energy deposition in EIR elements, beam-beam effects and machine detector interface issues., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

In this document we will review the design task of the WP3 (EIR), namely EIR optics (task 1), Machine Detector Interface (task 2), and Beam-Beam effects (task 3) and map the related challenges into the constraints and requirements for the other work packages – arc design (WP2), cryogenic beam vacuum (WP4) and magnet design (WP5). We will also include a section on how the EIR WP3 constraints and design optimization issues may affect the design of the Experimental Detector (this is outside the scope of EuroCirCol, but is one of the key activity area of FCC-hh community design efforts).

A parasitic effect of k-modulation is that if the modulated quadrupole has an offset the modulation results in a dipole like kick forcing the beam on a new orbit. This paper presents a new method using the orthonormality of singular value decomposition that uses this new orbit to estimate the offset. This could be used to measure misalignments or crossing angles but could also help improve k-modulation \beta measurements by predicting the parasitic tune change caused by the new orbit not passing through the centre of the sextupoles., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The Future Circular Collider (FCC) design study aims to develop the design of possible circular colliders in the LHC era. In particular the FCC-hh will aim to produce proton-proton collisions at a center of mass energy of 100 TeV. The interaction region has been designed to meet the requirements in terms of energy and luminosity. However, as it is the case in any real accelerator, misalignments in the magnets are likely to occur; the effect of these misalignments, if not properly compensated for, can jeopardize the performance of the machine. This study contemplates alignment and field errors in the interaction region in order to estimate the tolerance necessary to provide a good correction measured in terms of deviation of the orbit and strength of the correctors., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

One of the main challenges when designing final focus systems of particle accelerators is maximising the beam stay clear in the strong quadrupole magnets of the inner triplet. Moreover it is desirable to keep the quadrupoles in the inner triplet as short as possible for space and costs reasons but also to reduce chromaticity and simplify corrections schemes. An algorithm that explores the triplet parameter space to optimise both these aspects was written. It uses thin lenses as a first approximation and MADX for more precise calculations. In cooperation with radiation studies, this algorithm was then applied to design an alternative triplet for the final focus of the Future Circular Collider., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

This document describes the options of EIR design and collider layouts to be considered for further detailed studies. We primarily focus on factors leading to selection of the optimal L* parameter, describe the options considered and the presently selected value, as well as possible further optimization. We also describe studies performed with the present EIR optics, such as orbit correction, muon cross-talk between interaction regions, impact of synchrotron radiation as well as beam-beam effects.

Significant progress has been made in the design of an 18MW Beam Dump for 500 GeV electron/positron beams at an ILC. The beam dump design is based on circulating water with a vortex-like flow pattern to dissipate and remove the energy deposited by the beam. Multi-dimensional technology issues have been addressed to design the beam dump system. Detailed thermal-hydraulic analysis was carried out in all the critical regions of the beam dump which include, 1) location of highest volumetric power deposition by the beam, 2) location of highest linear power deposition, 3) entrance window region, 4) vessel walls etc. Based on this analysis, the sizing of the beam dump and its components, water flow rate and inlet jet velocity, optimum location of the beam path in the beam dump, beam sweep radius etc have been estimated. In addition, preliminary mechanical design of the beam dump, cooling circuit details, sizing of the hydrogen/oxygen recombiner system, ion exchange and 7Be removal, prompt and residual radioactivity studies etc have been carried out. Details of this work will be presented., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

In the Beam Delivery Systems (BDS) for linear colliders that have been designed or built, collimators (or scrapers) are used to suppress backgrounds due to the beam halo. Off-energy and off-axis particles are stopped on the collimator jaws, physically limiting the acceptance of the system. This concept does not scale well to higher beam energy, higher intensity or lower emittance. The increased beam density requires longer and more demanding collimator regions. In contrast, this paper studies the possibility of inserting non-linear optical elements into the Final Focus in order to effectively increase the acceptance of the system. This technique could make the traditional collimation scheme obsolete so that only protection collimators would be needed.

We present a ground motion model for the SLAC site. This model is based on recent ground motion studies performed at SLAC as well as on historical data. The model includes wave-like, diffusive and systematic types of motion. An attempt is made to relate measurable secondary properties of the ground motion with more basic characteristics such as the layered geological structure of the surrounding earth, depth of the tunnel, etc. This model is an essential step in evaluating sites for a future linear collider., Comment: submitted to XX International Linac Conference

3 pp. (2006)., The measurement of the International Linear Collider (ILC) emittance in the ILC beam delivery system (BDS) is simulated. Estimates of statistical and machine-related errors are discussed and the implications for related diagnostics R&D are inferred. A simulation of the extraction of the laser-wire Compton signal is also presented.

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

This document describes the preliminary optics for the experimental insertion region, presented in the form of lattice files to provide a baseline for studying radiation effects, machine detector interface and beam-beam interactions as well as an optimised design for a smooth transit from injection to collision optics. The lattice files are kept in a repository together with the arc optics files.

EuroCirCol is a conceptual design study for a post-LHC research infrastructure based on an energy-frontier 100 TeV circular hadron collider. ​The award of the 2013 Nobel Prize for Physics acknowledged the leading role of Europe in particle physics, which has a global community of over 10'000 scientists. To reinforce its pole position throughout the 21st century, Europe must be ready to propose an ambitious post-LHC accelerator project by 2018/19. This is one of the main recommendations of the updated European Strategy for Particle Physics, adopted by the CERN Council in May 2013. The EuroCirCol conceptual design study is a direct response to this recommendation, carried out through a collaboration of institutes and universities worldwide. A new research infrastructure of such scale depends on the feasibility of key technologies pushed beyond current state of the art. Innovative designs for accelerator magnets to achieve high-quality fields up to 16 T and for a cryogenic beam vacuum system to cope with unprecedented synchrotron light power are required. The effects of colliding two 50 TeV beams must be mastered to meet the physics research requirements. Advanced energy efficiency, reliability and cost effectiveness are key factors to build and operate such an accelerator within realistic time scale and cost. This EC supported project is part of the Future Circular Collider study under European leadership, federating resources worldwide to assess the merits of different post-LHC accelerator scenarios. It forms the core of a globally coordinated strategy of converging activities, involving participants from the ERA and beyond. The main outcome of EuroCirCol, a Conceptual Design Report for the research infrastructure, will be laying the foundation of subsequent infrastructure development actions that will strengthen the ERA as a focal point of global research cooperation and as a leader in frontier knowledge and technologies over the next decades.

The John Adams Institute for Accelerator Science (JAI) has proposed the realisation of the Accelerator Science Laboratory (ASL) at the University of Oxford as a facility for the development of advanced compact light sources enabling accelerator science research and applications. The installation of a compact light source in the ASL is planned with two options for the accelerating technologies. Firstly, a conventional RF based accelerator is considered to be a driver for a short pulse THz coherent synchrotron radiation (CSR). The other option focusses on the radiation produced by a Laser Plasma Accelerator (LPA) advanced accelerator technique that will provide the possibility to shorten the length of the beamline. This paper presents results of the studies on beam dynamics for both options of compact light sources in the ASL., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Could a methodology used for invention in engineering find a role in guiding the innovative process that will be essential for future large-scale accelerator projects?

The Accelerator Science Laboratory (ASL) is under development at the John Adams Institute in Oxford with the aim of fostering advanced accelerator concepts and applications. The option to install a short pulse THz FEL based on a conventional RF accelerator driven by a RF photocathode gun is being investigated. This report presents the concept of the facility, the accelerator physics and FEL studies and engineering integration in the University physics department.

The International Linear Collider Technical Design Report (TDR) describes in four volumes the physics case and the design of a 500 GeV centre-of-mass energy linear electron-positron collider based on superconducting radio-frequency technology using Niobium cavities as the accelerating structures. The accelerator can be extended to 1 TeV and also run as a Higgs factory at around 250 GeV and on the Z0 pole. A comprehensive value estimate of the accelerator is give, together with associated uncertainties. It is shown that no significant technical issues remain to be solved. Once a site is selected and the necessary site-dependent engineering is carried out, construction can begin immediately. The TDR also gives baseline documentation for two high-performance detectors that can share the ILC luminosity by being moved into and out of the beam line in a "push-pull" configuration. These detectors, ILD and SiD, are described in detail. They form the basis for a world-class experimental programme that promises to increase significantly our understanding of the fundamental processes that govern the evolution of the Universe.

The KEK ATF2 facility, with a well instrumented beam line and Final Focus (FF), is a proving ground for linear collider (LC) technology to demonstrate the extreme beam demagnification and spot stability needed for a LC FF*. ATF2 uses water cooled magnets but the baseline ILC calls for a superconducting FF**. Thus we plan to replace some ATF2 FF magnets with superconducting ones made via direct wind construction as planned for the ILC. With no cryogenic supply at ATF2, we look to cool magnets and current leads with a few cryocoolers. ATF2 FF coil winding is underway at BNL and production warm magnetic measurements indicate good field quality. Having FF magnets with larger aperture and better field quality than present FF might allow reducing the beta function at the FF for study of focusing regimes relevant to CLIC. Our ATF2 magnet cryostat will have laser view ports for cold mass movement measurement and FF support and stabilization requirements under study. We plan to make stability measurements at BNL and KEK to relate ATF2 FF magnet performance to that of a full length ILC R prototype at BNL. We want to be able to predict LC FF performance with confidence., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The realization of a photon collider option at a future TeV scale electron linear collider requires the generation of high average power picosecond laser pulses. Recirculating cavities have been proposed to reduce the amount of laser power that needs to be generated, however, these cavities impose stringent limits on the wavefront quality and stability of the laser architecture. We report on a design study of a high average power laser amplifier architecture which can produce the required laser time structure and stability to drive these recirculating cavities., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

24 pp. (2007)., The International Linear Collider (ILC) has a 14 mrad crossing angle in order to aid extraction of spent bunches. As a result of the bunch shape at the interaction point, this crossing angle at the collision causes a large luminosity loss which can be recovered by rotating the bunches prior to collision using a crab cavity. The ILC baseline crab cavity is a 9-cell superconducting dipole cavity operating at a frequency of 3.9 GHz. In this paper the design of the ILC crab cavity and its phase control system, as selected for the RDR1 in February 2007 is described in fuller detail.