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In the collisions of proposed future circular colliders, like FCC-ee and CEPC, the beamstrahlung regime is classical, i.e. with an "Upsilon parameter" much smaller than 1. In the classical regime, for a constant electromagnetic field a simple relation exists between the average photon energy u and the average squared photon energy u², which is the same as for standard synchrotron radiation in storage rings. This relation breaks down, however, if the electromagnetic field is not constant in time and position, as is the case for a beam-beam collision. We derive an analytical expression for u²/u², considering the case of Gaussian-bunch collisions with crossing angle (and possibly crab waist). We compare our result with the photon energies obtained in beam-beam simulation for FCC-ee at beam energies of 45.6 GeV and 175 GeV, using the two independent codes BBWS and Guineapig. Finally, we re-optimize the FCC-ee parameters of a possible mono-chromatization scheme for direct Higgs production at 125 GeV, derived previously, by applying the refined expression for the rms photon energy., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

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

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

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.

In July 2016, the first X-band test facility operating with two interwoven, 6 MW klystron pulses was commissioned at CERN. Outputting up to 46 MW after pulse compression, the new test stand allows testing of two structures concurrently with repetition rates up to 400 Hz in each line. RF commissioning of all four lines has been completed and testing of high gradient accelerating structures for the Compact Linear Collider has commenced. Operations have been ongoing for more than a year, where dedicated control algorithms have been developed to conditioning the structure and to keep the pulse compressors tuned. Significant progress has been made in understanding the conditioning of two structures that are sharing an interlock and vacuum system. The high repetition rate is already showing the significantly reduced time needed to condition accelerating structures., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

MYRRHA ADS (Accelerator Driven System), the prototype of a nuclear reactor driven by a particle accelerator, is being realized through a staged approach. This paper will explore the Control System (CS) strategy for the current stage of the accelerator R&D, where the goal is injector for the energies up to 5.9 MeV. Accelerator components are being delivered within international semi-industrial partnerships. Currently the RFQ, MYRRHA's first RF structure, is being introduced. It will be followed by the first Medium Energy Beam Transport (MEBT1) and several normal-conducting CH cavities. As the portfolio and number of devices and systems grows there is increased push towards standardization of integration procedures, interfaces to system-wide services, configuration management. Several partners provide components with varying level of vertical integration. The responsibility of the Control System integrator is therefore shifting towards provision of integration guidelines, configuration and deployment of central services and management tools, training to the contributing developers, help with specifications and requirements, quality insurance and acceptance criteria.

A non-interceptive beam current monitor has been developed to investigate the measurement possibilities of low-intensity beams down to 1 nA for proton therapy machines without the drawback of interceptive monitors. This works on the principle of a reentrant cavity resonator such that its fundamental mode resonance frequency of 145.7 MHz matches the second harmonic of the pulse repetition rate of the cyclotron beam i.e. 72.85 MHz. The Driven Modal analysis from the simulation tool ANSYS HFSS was used for parametric model development and to optimize design parameters such as e.g. the position of the inductively coupled pick-ups. A ceramic plate has been inserted in the resonator gap to relax the precision required during manufacturing. A test bench has been designed and constructed for the characterization tests of the prototype. Comparison of the simulated and the experimental scattering parameter from the test bench shows a good agreement., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The Extra Low ENergy Antiproton storage ring (ELENA), which is currently being commissioned at CERN, will further decelerate antiprotons extracted from the Antiproton Decelerator (AD) from 5.3 MeV to energies as low as 100 keV. It will provide high quality beams for the antimatter experiments located within the AD hall. At such low energies, it is important to correctly evaluate the long term beam stability. To provide a consistent explanation of the different physical phenomena affecting the beam, tracking simulations have been performed and the results will be presented in this contribution. These include electron cooling and various scattering effects under realistic conditions. The effects of several imperfections in the electron cooling process will also be discussed. In addition, analytical approximations of the temporal variation of emittance under these conditions will be presented, and compared with numerical simulation results.

RF field phase and amplitude errors are usually not correctly simulated and it is a serious problem especially when in high intensity linear accelerators, the main losses are due to particle leaving the beam acceptance. This new development implemented in TraceWin fixes this issue. The objective is to improve the longitudinal beam dynamics simulation methods, by including more close-to-real models for the cavities tuning procedure. By this way, clear distinction should be done between static and dynamic errors and longitudinal diagnostics accuracy can be clearly defined according to beam dynamics results., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The ESSnuSB project, recently granted by the EU H2020 framework programme for a 4-year design study, proposes to use the proton linac (2 GeV, 5 MW) of the European Spallation Source (ESS) currently in construction in Lund (Sweden) to deliver a neutrino super beam. One of the work packages of this design study is dedicated to the primary proton beam-line completing the linac. It will mainly consist of an accumulator ring to compress the 2.86 ms long beam pulse to 1.32 μs and of a switchyard to distribute the protons onto a 4-target station. Dipoles, steerers, quadrupoles, collimators and several diagnostics will compose the switchyard to ensure the protons to hit the target with desired characteristics. This paper presents the objectives of this work package and the design status of this switchyard system., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

We report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors.

The Beam Test Facility is part of the DAΦNE accelerators system of INFN Frascati National Laboratory. It is a transfer-line optimized for electrons and positrons extracted from the DAΦNE LINAC. An upgrade of the line is scheduled for two purposes: reach a beam energy of 920 MeV (with respect to the actual 750 MeV) and add a new branch to the present transfer line. This new layout foresees six new quadrupoles one fast ramped dipole, two H-shape and one C-shape sector dipoles. The design of the magnets has been completely performed at INFN involving Electromechanical Enterprise partner in the design phase in order to optimise the manufacturing process. This effort lead to a complete set of detailed CAD drawings that can be directly used by manufacturer to build the magnets. The goal is to boost the manufacturing of prototypes and small series from Small and Medium Enterprises. Magnetic measurements will be performed at INFN. This poster is focused on the realization of the two full iron yoke H-shape and C-shape dipoles, respectively with 45 and 15 bending angle. They are characterized by a high flux density of 1.7 T in a gap of 35 mm. They have a bending radius of 1.8 m, Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

Nominal operating conditions for the Compact Linear Collider (CLIC) 380 GeV requires 72 MV/m loaded accelerating gradients for a 180 ns flat-top pulse. Achieving this requires extensive RF conditioning which past tests have demonstrated can take several months per structure, when conditioned at the nominal repetition rate of 50 Hz. At CERN there are three individual X-band test stands currently operational, testing up to 6 structures concurrently. For CLIC's 380 GeV design, 28,000 accelerating structures will make up the main linac. For a large scale conditioning programme, it is important to understand the RF conditioning process and to optimise the time taken for conditioning. In this paper, we review recent X-band testing results from CERN's test stands. With these results we investigate how to optimise the conditioning process and demonstrate the feasibility of pre-conditioning the structures at a higher repetition rate before installation into the main linac., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

As part of the effort to qualify CLIC accelerating struc-tures prototypes, new X-band test facilities have been built and commissioned at CERN in the last years. In this context, a number of RF components have been designed and manufactured aiming at stable operation above 50 MW peak power and several kW of average power. All of them have been tested now in the X-band facility at CERN either as part of the facility or in dedicated tests. Here, we describe shortly the main design and manufac-turing steps for each component, the testing and eventual conditioning as well as the final performance they achieved., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

An innovative and comprehensive experiment (named "Multimat") was successfully carried out at CERN HiRadMat facility on 18 different materials relevant for Collimators and Beam Intercepting Devices. Material samples, tested under high intensity proton pulses of 440 GeV/c, exceeding the energy density expected in HL-LHC, ranged from very light carbon foams to tungsten heavy alloys, including novel composites as graphite/carbides and metal/diamond without and with thin-film coatings. Experimental data were acquired relying on extensive integrated instrumentation (strain gauges, temperature sensors, radiation-hard camera) and on laser Doppler vibrometer. This allows investigating relatively unexplored and fundamental phenomena as dynamic strength, internal energy dispersion, nonlinearities due to inelasticity and inhomogeneity, strength and delamination of coatings and surfaces. By benchmarking sophisticated numerical simulations against these results, it is possible to establish or update material constitutive models, which are of paramount importance for the design of devices exposed to interaction with particle beams in high energy accelerators such as the HL-LHC or FCC-hh., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The High Energy LHC (HE-LHC) proton-proton collider is a proposed replacement of the LHC in the existing 27-km tunnel, with the goal of reaching the centre-of-mass beam energy of 27 TeV. The required higher dipole field can be realized by using 16-T dipoles being developed for the FCC-hh design. A major concern is the dynamic aperture at injection energy due to degraded field quality of the new dipole based on Nb3Sn superconductor, the potentially large energy swing between injection and collision, and the slightly reduced magnet aperture. Another issue is the field in quadrupoles and sextupoles at top energy, for which it may be cost-effective, wherever possible, to stay with Nb-Ti technology. In this study, we explore design options differed by arc lattice, for three choices of injection energy, with the goal of attaining acceptable magnet field and maximum injection dynamic aperture with dipole non-linear field errors.

ESSnuSB proposes to use the proton linac of the European Spallation Source (ESS) currently in construction in Lund (Sweden) to produce a very intense neutrino super beam, in parallel with the spallation neutron production. The ESS linac is expected to be operational by 2023 delivering 5 MW average power, 2 GeV proton beam, with 2.86 ms long pulses at a rate of 14 Hz. The primary proton beam-line completing the linac will consist of an accumulator ring to compress the beam pulses to 1.3 μs and a switchyard to distribute the protons onto the target station. The secondary beam-line producing neutrinos will consist of a four-horn/target station, a decay tunnel and a beam dump. A megaton scale water Cherenkov detector will be located at a baseline of about 500 km in one of the existing mines in Sweden and it will measure the neutrino oscillations. ESSnuSB was recently granted by the European H2020-INFRADEV program to start beginning of 2018 a 4-year design study on the feasibility of such facility. This paper presents the objectives, the steps and the organization of the ESSnuSB DS.

FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.

Due to the relatively infrequent use of electrostatic beamline elements compared with their magnetic counterparts, there are few particle tracking codes which allow for the straightforward implementation of such beamlines. In this contribution, we present 3D tracking methods for beamlines containing electrostatic elements utilising a modified version of the Geant4 based tracking code 'G4beamline'. In 2020 transfer lines will begin transporting extremely low energy (100 keV) antiproton beams from the Extra Low Energy Antiproton (ELENA) ring to the antimatter experiments at CERN. Electrostatic bending and focusing elements have been chosen for the beamlines due to their mass independence and focusing efficiency in the low energy regime. These beamlines form the basis of our model which is benchmarked against simplified tracking simulations. Realistic beam distributions obtained via tracking around ELENA in the presence of collective effects and electron cooling will be propagated along the optimised 3D transfer model to achieve the best beam quality possible for the experiments., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

In the framework of the EuroCirCol collaboration* (work package 4 "Cryogenic Beam Vacuum System"), the fabrication of 3 FCC-hh beam-screen (BS) prototypes has been carried out with the aim of testing them at room temperature at the Karlsruhe Institute of Technology (KIT) 2.5 GeV electron storage ring KARA (KArlsruhe Research Accelerator). The 3 BS prototypes will be tested on a beamline installed by the collaboration, named as BEam Screen TEstbench EXperiment (BESTEX). KARA has been chosen because its synchrotron radiation (SR) spectrum, photon flux and power, match the one foreseen for the 50+50 TeV FCC-hh proton collider. Each of the 3 BS prototypes, 2 m in length, implement a different design feature: 1) baseline design (BD), with electro-deposited copper and no electron-cloud (EC) mitigation features; 2) BD with set of distributed cold-sprayed anti-EC clearing electrodes; 3) BD with laser-ablated anti-EC surface texturing. We present here the results obtained so far at BESTEX and the comparison with extensive montecarlo simulations of the expected outgassing behavior under synchrotron radiation., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada