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Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand 13th International Particle Accelerator Conference, IPAC`22, Bangkok, Thailand, Thailand, 12 Jun 2022 - 17 Jun 2022; [Geneva] : JACoW Publishing, Geneva, Switzerland 279-283 (2022). doi:doi:10.18429/JACoW-IPAC2022-MOPOPT021, The ARES linear accelerator at DESY aims to deliver stable and well-characterized electron bunches with durations down to the sub-fs level. Such bunches are highly sought after to study the injection into novel high-gradient accelerating structures, test diagnostics devices, or perform autonomous accelerator studies. For such applications, it is advantageous to have a complete and detailed knowledge of the beam properties. Tomographic methods have shown to be a key tool to reconstruct the phase space of beams. Based on these techniques, a novel diagnostics method is being developed to resolve the full 5-dimensional phase space (x,x’,y,y’,z) of bunches including their transverse and longitudinal distributions and correlations. In simulation studies, this method shows an excellent agreement between the reconstructed and the original distribution for all five planes. Here, the 5-dimensional phase space tomography method is presented using a showcase simulation study at ARES., Published by JACoW Publishing, Geneva, Switzerland, [Geneva]

Over the last years, the generation and acceleration of ultra-short, high quality electron beams has attracted more and more interest in accelerator science. Electron bunches with these properties are necessary to operate and test novel diagnostics and advanced high gradient accelerating schemes such as plasma accelerators or dielectric laser accelerators. Furthermore, several medical and industrial applications require high-brightness electron beams. The dedicated R&D facility ARES at DESY will provide such probe beams in the upcoming years. After the setup of the normal-conducting RF photoinjector and linear accelerating structures, ARES successfully started the beam commissioning of the RF gun. This paper gives an overview of the ARES photoinjector setup and summarizes the results of the gun commissioning process. The quality of the first generated electron beams is characterized in terms of charge, momentum, momentum spread and beam size. Additionally, the dependencies of the beam parameters on RF settings are investigated. All measurement results of the characterized beams fulfill the requirements to operate the ARES linac with this RF photoinjector.

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil 12th International Particle Accelerator Conference, IPAC 2021, Campinas, Brazil, 24 Nov 2021 - 28 Nov 2021; JACoW Publishing, Geneva, Switzerland 2983-2985 (2021). doi:doi:10.18429/JACoW-IPAC2021-WEPAB158, Novel accelerator concepts such as all-optical THz based compact accelerators promise to enable new science due to unique features such as reduced timing-jitter and improved space-charge broadening of the generated electron bunches. However, multi-keV electron photo-guns based on short single-cycle THz pulses for acceleration have not been demonstrated experimentally so far. Here, we present a modular THz-driven electron gun with both tunable interaction length and output orifice allowing optimization of the sub-mm interaction volume. First extraction of multi-keV electrons is demonstrated and the parameter space as well as resulting performance of the THz-driven gun by varying the timing of the two single-cycle THz pulses and the UV photo-excitation pulse are explored. Such compact gun prototypes are not only promising as injectors for compact THz-based LINACs but also as source for ultrafast electron diffraction experiments., Published by JACoW Publishing, Geneva, Switzerland

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil 12th International Particle Accelerator Conference, IPAC���21, Campinas, Brazil, 24 May 2021 - 28 May 2021; Geneva : JACoW Publishing 4 pp. (2021). doi:10.18429/JACoW-IPAC2021-MOPAB302, The ARES linear accelerator at the SINBAD facility (DESY) is dedicated to perform accelerator R studies with sub-fs short electron bunches to test novel acceleration techniques and diagnostics devices. Currently, the commissioning of the linac is ongoing and first experiments are being performed. For this, the knowledge of the full phase space of the particle beams is of high interest to, for example, optimize the accelerator performance and identify possible errors in the beam line. Tomographic methods can be used to gain insight into the full 4D transverse phase space and its correlations. Here, simulation results and first experimental preparations of a 4D transverse phase-space tomography of electron bunches at ARES are presented and discussed., Published by JACoW Publishing, Geneva

Various physical and technology-dependent limits are encountered for key performance parameters of accelerators such as high-gradient acceleration, high-field bending, beam size, beam brightness, beam intensity and luminosity. This paper will review these limits and the associated challenges. Possible figures-of-merit and pathways to ultimate colliders will also be explored., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

Scientific reports 9(1), 19912 (2019). doi:10.1038/s41598-019-56433-8, Transverse deflection structures are useful devices for characterizing the longitudinal properties of bunches in electron accelerators. With efforts to produce ever-shorter bunches for applications such as external injection into novel accelerator structures, e.g. plasma cells or dielectric structures, the applicability of deflection structures to measuring ultrashort bunches has been considered. In this paper, charge-density and bunch-length measurements of femtosecond and subfemtosecond bunches at the ARES linac at the SINBAD facility at DESY are studied with simulations and the limitations discussed in detail. The novel polarizable X-band transverse deflection structure (PolariX-TDS) will allow the streaking of bunches at all transverse angles, making a 3D charge-density reconstruction of bunches possible, in addition to the standard 1D charge-density reconstruction and bunch-length measurements. These various measurements of the charge-density distributions of bunches have been simulated, and it is shown that useful information about ultrashort bunches down to subfemtosecond lengths may be obtained using the setup planned for the ARES linac., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Modern particle accelerators and their applications increasingly rely on precisely coordinated interactions of intense charged particle and laser beams. Femtosecond-scale synchronization alongside micrometre-scale spatial precision are essential e.g. for pump-probe experiments, seeding and diagnostics of advanced light sources and for plasma-based accelerators. State-of-the-art temporal or spatial diagnostics typically operate with low-intensity beams to avoid material damage at high intensity. As such, we present a plasma-based approach, which allows measurement of both temporal and spatial overlap of high-intensity beams directly at their interaction point. It exploits amplification of plasma afterglow arising from the passage of an electron beam through a laser-generated plasma filament. The corresponding photon yield carries the spatiotemporal signature of the femtosecond-scale dynamics, yet can be observed as a visible light signal on microsecond-millimetre scales.

EuPRAXIA (European Plasma Research Accelerator with eXcellence In Applications) is a conceptual design study for a compact European infrastructure with multi-GeV electron beams based on plasma accelerators. The concept foresees two main experimental sites, one at INFN in Frascati and one at DESY in Hamburg. In Frascati, an RF injector based on S-band and X-band technology (electron energy up to 1 GeV) will be constructed and used as a drive beam for beam driven plasma acceleration (PWFA) with final electron beam energies up to 5 GeV. At DESY, the focus will be on laser driven plasma acceleration (LWFA) and an RF injector based on S-band technology (electron energy up to 240 MeV) or alternatively a plasma injector (electron energy up to 150 MeV) can be used before the beam is injected into the plasma accelerator for external LWFA and acceleration up to 5 GeV. A single stage approach based on LWFA with internal injection will also be pursued in a second beamline. User areas at both sites will provide access to FEL pilot experiments, positron generation, compact radiation sources, and test beams for HEP detector development. This contribution discusses facility space considerations for the future plasma accelerator research infrastructure of EuPRAXIA., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Dielectric Laser Acceleration (DLA) achieves the high- est gradients among structure-based electron accelerators. The use of dielectrics increases the breakdown field limit, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental demonstrations of DLA in 2013 led to the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. In ACHIP, our main goal is to build an acceler- ator on a silicon chip, which can accelerate electrons from below 100keV to above 1MeV with a gradient of at least 100MeV/m. For stable acceleration on the chip, magnet- only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus spatial harmonic and Alternating Phase Focusing (APF) laser-based focusing tech- niques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to coupling, the Fourier coefficients of neighboring cells are not entirely independent and a field flatness optimization (similarly as in multi-cell cavities) needs to be performed. The simu- lation of the entire accelerator on a chip by a Particle In Cell (PIC) code is possible, but impractical for optimization purposes. Finally, we have also outlined the treatment of wake field effects in attosecond bunches in the grating within DLAtrack6D, where the wake function is computed by an external solver., Proceedings of the 13th Int. Computational Accelerator Physics Conf., ICAP2018, Key West, FL, USA

Modern particle accelerators and their applications increasingly rely on precisely coordinated interactions of intense charged particle and laser beams. Femtosecond-scale synchronization alongside micrometre-scale spatial precision are essential e.g. for pump-probe experiments, seeding and diagnostics of advanced light sources and for plasma-based accelerators. State-of-the-art temporal or spatial diagnostics typically operate with low-intensity beams to avoid material damage at high intensity. As such, we present a plasma-based approach, which allows measurement of both temporal and spatial overlap of high-intensity beams directly at their interaction point. It exploits amplification of plasma afterglow arising from the passage of an electron beam through a laser-generated plasma filament. The corresponding photon yield carries the spatiotemporal signature of the femtosecond-scale dynamics, yet can be observed as a visible light signal on microsecond-millimetre scales.

10th International Particle Accelerator Conference, IPAC'19, Melbourne, Australia, 19 May 2019 - 24 May 2019; JACoW Publishing, Geneva, Switzerland 143-146 (2019). doi:10.18429/JACOW-IPAC2019-MOPGW027, SINBAD (Short and INnovative Bunches and Accelerators at DESY) facility aims to produce ultrashort bunches (sub-fs) at ~100 MeV, suitable for injection into novel accelerators e.g. dielectric Laser acceleration (DLA) and Laser Driven Wakefield acceleration (LWFA). The LWFA experiment demands β functions to be of the order of 1 mm to reduce energy spreads and emittance growth from nonlinearities. Matching such a space charge dominated beam to such constraints with conventional electromagnets is challenging. A Permanent Magnetic Quadrupole (PMQ) triplet is one promising focusing strategy. In this paper, we investigate the performance of a PMQ triplet to fit the requirements of the electron beam properties in a plasma cell and discuss the realizable phase spaces for the LWFA experiment planned at SINBAD., Published by JACoW Publishing, Geneva, Switzerland

10th International Particle Accelerator Conference (IPAC 2019), Melbourne, Australia, 24 May 2019 - 29 May 2019; JACoW Publishing, Geneva, Switzerland 1 pp. (2019). doi:10.18429/JACOW-IPAC2019-TUPRB008, The proposed experiment aims to measure QED in the presence of strong fields and above the Schwinger critical field. An experiment is being considered at the European XFEL, which should be able to measure non-perturbative QED and its transition from the perturbative regime. This paper presents the current status of the LUXE (Laser und XFEL Experiment) design study. First layout considerations; accelerator beam line design, electron and laser beam parameters, radioprotection issues and first results of the start to end simulations will be presented and discussed in detail. An outlook concerning the implementation into the XFEL schedule and timeline of this experiment will be given., Published by JACoW Publishing, Geneva, Switzerland

10th International Particle Accelerator Conference, IPAC'19, Melbourne, AUSTRALIA, 19 May 2019 - 24 May 2019; JACoW Publishing, Geneva, Switzerland 3624-3627 (2019). doi:10.18429/JACOW-IPAC2019-THPGW022, Laser plasma accelerators with external injection of an RF-generated electron beam, providing high accelerating field gradients and increased control over the electron beam injection process, are promising candidates for production electron beams matching the requirements of modern user-applications. The experiments are planned at the SINBAD (Short INnovative Bunches and Accelerators at DESY) facility to test this acceleration technique in the context of the ATHENAe (Accelerator Technology HElmholtz iNfrAstructure) project. In this paper we present numerical studies on the effect of the transverse electron beam jitter on the final quality of a sub-femtosecond, 0.75 pC, 100 MeV electron beam accelerated to 1 GeV energy in the plasma wakefield driven by a 196 TW, 5 J laser pulse., Published by JACoW Publishing, Geneva, Switzerland

10th International Particle Accelerator Conference, IPAC'19, Melbourne, Australia, 19 May 2019 - 24 May 2019; JACoW Publishing, Geneva, Switzerland 3605-3608 (2019). doi:10.18429/JACOW-IPAC2019-THPGW014, Laser-driven hollow core photonic bandgap (PBG) fibers were proposed by Lin in 2001 as high-gradient accelerators. The central defect in the transversely periodic lattice supports an accelerating mode for synchronous acceleration in the ultra-relativistic regime. The optical frequencies in such dielectric laser accelerators motivate a sensitivity and tolerance study to overcome manufacturing imperfections. Finally we discuss the propagation characteristics of Lin-fibers and find that small-bandwidth (~ns) pulses would be needed for efficient acceleration over longer distances., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 396-399 (2019). doi:10.18429/JACOW-FEL2019-WEP036, A collaboration between DESY, PSI and CERN has been established to develop and build an advanced modular X- band transverse deflection structure (TDS) system with the new feature of providing variable polarization of the deflecting force. The prototype of the novel X-band TDS, the Polarizable X-band (PolariX) TDS, was fabricated at PSI following the high-precision tuning-free production process developed for the C-band Linac of the SwissFEL project. Bead-pull RF measurements were also performed at PSI to verify, in particular, that the polarization of the dipole fields does not have any rotation along the structure. The high-power test was performed at CERN and now the TDS is at DESY and has been installed in FLASHForward, where the first streaking experience with beam will be accomplished. We summarize in this paper the status of the project, the results of the bead-pull measurements and the high power test., Published by JACoW Publishing, Geneva, Switzerland

Bunch compressors are essential for the generation of short bunches with applications in e.g. colliders, free electron lasers, and advanced accelerator concepts. The up-and-coming ARES accelerator located at SINBAD, DESY will support the formation of ~100~MeV, pC, sub-fs electron bunches for LWFA research and development. We give an overview on the ARES bunch compressor, providing start-to-end simulations of the machine and an update on its technical design., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

10th International Particle Accelerator Conference, IPAC'19, Melbourne, Australia, 19 May 2019 - 24 May 2019; JACoW Publishing, Geneva, Switzerland 3609-3611 (2019). doi:10.18429/JACOW-IPAC2019-THPGW015, While Laser Plasma Accelerators produce beams with the high output energy required for FELs, up to now the relatively high energy spread has prohibited FEL lasing. Therefore it was proposed to replace the normal FEL undulators by Transverse Gradient Undulators (TGUs). For a first, small scale test of the TGU concept, a 40 period prototype high gradient superconductive TGU was built at KIT and will be tested with beam at the ARES-linac in the new accelerator test facility SINBAD (Short Innovative Bunches and Accelerators at Desy) at DESY. The proposed tests are summarized in this paper., Published by JACoW Publishing, Geneva, Switzerland

Modern high-gain free-electron lasers make use of high-brightness ultra-relativistic electron beams. The uncorrelated energy spread of these beams is upon creation of the beam in the sub-permille range and below the resolution of state-of-the-art diagnostics. One method to determine the slice energy spread is to use an external seed laser to imprint a coherent microbunching structure that gives rise to coherent radiation processes, different radiation sources such as transition radiation, synchrotron radiation, or undulator radiation and others. Here, we present a method and show measurements to determine the slice energy spread using an external seed laser with 266 nm wavelength to produce coherent undulator radiation at higher harmonics. The distribution of these harmonics allows retrieval of the electron beam slice energy spread with high precision., Proceedings of the 38th Int. Free Electron Laser Conf., FEL2017, Santa Fe, NM, USA

In the development of low charge, single-shot diagnostics for high brightness electron beams, Transmission Electron Microscopy (TEM) grids present certain advantages compared to pepper pot masks due to higher beam transmission. In this paper, we developed a set of criteria to optimize the resolution of a point projection image. However, this configuration of the beam with respect to the grid and detector positions implies the measurement of a strongly correlated phase space which entails a large sensitivity to small measurement errors in retrieving the projected emittance. We discuss the possibility of an alternative scheme by inserting a magnetic focusing system in between the grid and the detector, similar to an electron microscope design, to reconstruct the phase space when the beam is focused on the grid., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

9th International Particle Accelerator Conference, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018; Geneva, Switzerland : JACoW Publishing 3808-3811 (2018). doi:10.18429/JACOW-IPAC2018-THPAL068, A collaboration between DESY, PSI and CERN has been established to develop and build an advanced modular X-band transverse deflection structure (TDS) system with the new feature of providing variable polarization of the deflecting force. This innovative CERN design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field. Therefore, the high-precision tuning-free production process developed at PSI for the C-band and X-band accelerating structures will be used for the manufacturing. We summarize in this paper the status of the production of the prototype and the waveguide networks foreseen in the different facilities., Published by JACoW Publishing, Geneva, Switzerland

9th International Particle Accelerator Conference, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018; 6 pp. (2018)., Symmetrically driven dual-grating type DLA (Dielectric Laser Accelerator) linac structures allow for in-channel electric field gradients on the order of GV/m at optical wavelengths. In this work we study the sensitivity of important final beam parameters like mean energy, energy spread and transverse emittance on DLA drive laser as well as input beam parameters. To this end a fast specialized particle tracking code (DLATracker) is used to compute the so called first order sensitivity indices based on a large number of Monte Carlo simulation runs of an exemplary external injection based DLA experiment. The results of this work point out important stability constraints on the drive laser setup and the externally injected electron beam.

60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources, FLS2018, Shanghai, Deutsches Elektronen Synchrotron, China, 4 Mar 2018 - 9 Mar 2018, We present an overview of the dedicated accelerator R&D facility “SINBAD”, currently under construction at DESY. It will host multiple independent experiments related to the generation and acceleration of ultra-short electron bunches and to the development of various advanced acceleration schemes. SINBAD will initially host two experiments: AXSIS and ARES. The AXSIS collaboration aims to generate fs to sub-fs electron bunches at 15-20 MeV using THz-driven dielectric structures, with the objective to generate ultrafast X-ray pulses by inverse Compton scattering. The first stage of the ARES experiment is to set up a 100 MeV S-band electron linac to produce ultra-short electron bunches with excellent beam arrival time stability. The RF-gun is currently being installed and will be commissioned in spring 2018, followed by the installation and commissioning of the accelerating structures. Thereafter in 2019, the electron bunches will be ideally suited for various experiments on advanced accelerator and diagnostics concepts (e.g. DLA experiments in the context of the ACHIP collaboration). In the long term, external injection into a laser driven plasma acceleration stage is also targeted.

38th International Free Electron laser Conference, FEL 2017, Santa Fe, N.M., United States, 20 Aug 2017 - 25 Aug 2017; Geneva : JACoW, 491-494 (2018). doi:10.18429/JACoW-FEL2017-WEP040, The SwissFEL project, under commissioning at the Paul Scherrer Institut (PSI), will produce FEL radiation for soft and hard X-rays with pulse durations ranging from a few to several tens of femtoseconds. A collaboration between DESY, PSI and CERN has been established with the aim of developing and building an advanced X-Band transverse deflector structure (TDS) with the new feature of providing variable polarization of the deflecting force. As this innovative CERN design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field, the high-precision tuning-free assembly procedures developed at PSI for the SwissFEL C-band accelerating structures will be used for the manufacturing. Such a TDS will be installed downstream of the undulators of the soft X-ray beamline of SwissFEL and thanks to the variable polarization of the TDS, it will be possible to perform a complete characterization of the 6D phase-space. We summarize in this work the status of the project and its main technical parameters., Published by JACoW, Geneva

9th International Particle Accelerator Conference IPAC2018, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018; Geneva, Switzerland : JACoW Publishing 1615-1618 (2018). doi:10.18429/JACoW-IPAC2018-TUPML035, Laser Plasma Accelerators produce beams with a significantly higher energy spread (up to a few percent) compared to conventional electron sources. The high energy spread increases significantly the gain length when used for an FEL. In order to reduce the gain length of the FEL the Transverse Gradient Undulators (TGUs) instead of conventional undulators were proposed. In this paper the limits of this concept are discussed using a modified Version of the GENESIS program*., Published by JACoW Publishing, Geneva, Switzerland

Future Light Sources 2018, FLS18, Shanghai, Deutsches Elektronen Synchrotron, China, 4 Mar 2018 - 9 Mar 2018, We present beam dynamics simulations for a proposal of hybrid and compact ultrafast X-ray source based on Inverse Compton Scattering (ICS). The layout consists of an S-band gun as electron source and a dielectric-loaded circular waveguide (DLW) driven by a multicycle THz pulse to accelerate and longitudinally compress the bunch, which could then be used to produce ultrafast X-ray pulses through ICS with an infrared laser pulse. The challenge tackled by this hybrid scheme is to generate ultrashort electron bunches (single fs order to sub-fs rms length), at moderate energies (15 to 20 MeV), with a charge of at least 1 pC and focused to a transverse size around or below 10 µm rms while keeping a compact beamline (≤ 2 m), which has never been achieved using only conventional RF technologies. Simulations from the photocathode up to the ICS point are presented, looking at the influence of various parameters of the accelerating and transverse focusing devices. The properties of the simulated DLW and the requirements for the THz pulse driving it are also presented.

The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

8th International Particle Accelerator Conference, IPAC17, Kopenhagen, Denmark, 15 May 2017 - 19 May 2017; Geneva : JACoW, 2596-2599 (2017). doi:10.18429/JACoW-IPAC2017-WEPAB016, sFLASH, the experimental setup for external seeding of free-electron lasers (FEL) at FLASH, has been operated in the high-gain harmonic generation (HGHG) mode. A detailed characterization of the laser-induced energy modulation, as well as the temporal characterization of the seeded FEL pulses is possible by using a transverse deflecting structure and an electron spectrometer. FEL saturation was reached for the 7th harmonic of the 266 nm seed laser. In this contribution, we present the latest experimental results., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017; Geneva : JACoW, 4 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPAB046, An X-band TDS is a well-known device for the characterization of the longitudinal properties of an electron bunch in a linear accelerator. It is planned that a novel X-band TDS with variable polarization* will be installed within the next few years at SINBAD, an upcoming accelerator R&D facility at DESY**. There are several measurements that can be performed with the TDS, each with specific optics requirements to reach the highest possible resolution and keep induced energy spread to a tolerable level. Quadrupoles will be installed between the TDS and the screen to help satisfy these conditions. In this paper, the requirements for the bunch length measurements, a novel 3D charge density reconstruction technique and slice energy measurements are discussed and some simulation results for the slice energy measurement using example lattices are presented., Published by JACoW, Geneva

International audience; The Horizon 2020 Project EuPRAXIA ('European Plasma Research Accelerator with eXcellence In Applications') aims at producing a design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics (HEP) detector tests, and other applications such as compact X-ray sources for medical imaging or material processing. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. EuPRAXIA aims to be included on the ESFRI roadmap in 2020.

8th International Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva, Switzerland : JACoW, 199-202(2017). doi:10.18429/JACoW-IPAC2017-MOPAB048, In this paper, we investigate with ASTRA simulations the capability of the 3-phase method to reconstruct the length of a fs electron bunch. We show that a standard 3 GHz travelling wave accelerating structure is not suited for this purpose, because of the too important effect of the space-charge forces and of the too small variations of the induced energy spread with the bunch injection phase. Our simulations demonstrate that the use of dielectric-loaded waveguides driven by THz pulses would allow overcoming these two limitations and possibly achieving an ultimate resolution better than 5% for the determination of a 6.25 fs rms bunch length at 100 MeV energy and 1 pC charge. The next steps of the study to better evaluate, in simulations and experiments, the possible sources of degradation of the 3-phase method resolution are also mentioned., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3253-3255(2017). doi:10.18429/JACoW-IPAC2017-WEPVA004, The "Attosecond X-ray Science: Imaging and Spectroscopy" (AXSIS) experiment at DESY will use a dielectric loaded waveguideto accelerate electron bunches up to 15 MeV. Such a linac will be powered by a narrowband multicycle THz-pulse with a central frequency of 300 GHz. In this paper we focus on the reflection of the excited field at a pinhole, on the optimization of the bunch injection time and on the bunch dynamics in the acceleration process. The linac excitation by the THz-pulse and the bunch acceleration in the excited field are investigated using CST and ECHO simulations., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPIK005, We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches., Published by JACoW, Geneva

38th International Free Electron Laser Conference, FEL2017, Santa Fe, NM, USA, 20 Aug 2017 - 25 Aug 2017; 3 pp. (2017)., Modern high-gain free-electron lasers make use of high-brightness ultra-relativistic electron beams. The uncorrelated energy spread of these beams is upon creation of the beam in the sub-permille range and below the resolution of state-of-the-art diagnostics. One method to determine the slice energy spread is to use an external seed laser to imprint a coherent microbunching structure that gives rise to coherent radiation processes, different radiation sources such as transition radiation, synchrotron radiation, or undulator radiation and others. Here, we present a method and show measurements to determine the slice energy spread using an external seed laser with 266 nm wavelength to produce coherent undulator radiation at higher harmonics. The distribution of these harmonics allows retrieval of the electron beam slice energy spread with high precision.

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; 2520-2525(2017). doi:10.18429/JACoW-IPAC2017-WEYB1, Dielectric laser acceleration of electrons has recently been demonstrated with significantly higher accelerating gradients than other structure-based linear accelerators. Towards the development of an integrated 1 MeV electron accelerator based on dielectric laser accelerator technologies, development in several relevant technologies is needed. In this work, recent developments on electron sources, bunching, accelerating, focussing, deflecting and laser coupling structures are reported. With an eye to the near future, components required for a 1 MeV kinetic energy tabletop accelerator producing sub-femtosecond electron bunches are outlined., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017; JACoW, Geneva, Switzerland 1707 - 1710 (2017). doi:10.18429/JACoW-IPAC2017-TUPIK013, External injection into laser wakefield accelerators is one of the possible routes towards high energy, high quality electron beams through plasma acceleration. Among other reasons this is due to the increased control over the electron beam parameters and overall experimental setup when compared to other plasma schemes, such as controlled self-injection. At the future SINBAD (Short INnovative Bunches and Accelerators at DESY) facility at DESY this technique is planned to be tested experimentally through injection and acceleration of a sub-femtosecond electron beam, produced from a conventional RF-injector, with a charge of around 0.7 pC and initial mean energy of 100 MeV at the plasma entrance. A summary of optimisation steps for the potential experimental setup is presented in this paper, including considerations regarding effects of electron beam self-fields and matching of the beam into the plasma stage. The discussion is complemented by first start-to-end simulations of the plasma accelerator setup based on these findings., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva, Switzerland : JACoW, 869-872(2017). doi:10.18429/JACoW-IPAC2017-MOPVA012, We present an overview of the dedicated R&D facility SINBAD which is currently under construction at DESY. The facility will host multiple independent experiments on the acceleration of ultra-short electron bunches and advanced acceleration schemes. In its initial phase, SINBAD will host two experiments: AXSIS and ARES. The AXSIS collaboration aims to accelerate fs-electron bunches to 15 MeV in a THz driven dielectric structure and subsequently create X-rays by inverse Compton scattering. The first stage of the ARES experiment is to set up a 100 MeV S-band electron linac to produce ultra-short electron bunches with excellent beam arrival time stability. Once this is achieved, the electrons will be ideally suited to be injected into experiments for testing advanced accelerator concepts e.g. DLA experiments in the context of the ACHIP collaboration. In the long term, external injection into a laser driven plasma acceleration stage is targeted as well., Published by JACoW, Geneva, Switzerland

8th International Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 4 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPAB049, In this paper, we investigate with ASTRA simulations the achievable performances for several focusing systems considered in the AXSIS project. We focus our attention on the requirements in terms of position of the focal point and bunch transverse size at this point. We show that they cannot be fulfilled with a solenoid resistive electro-magnet, but that it is possible when using a solenoid permanent magnet. The use of a quadrupole doublet proves to be adequate to fulfil the requirement on the position of the focal point and be very close to the one on the bunch transverse size, which could possibly be achieved by a further optimization of the parameters of the doublet. Finally, we also investigate the possibility to use an active plasma lens, showing that it could easily fulfil the requirements but that several points must be carefully studied before considering its implementation., Published by JACoW, Geneva

8th International Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 3260-3263(2017). doi:10.18429/JACoW-IPAC2017-WEPVA006, The concept of dielectric laser accelerators (DLA) has gained increasing attention in accelerator research, because of the high achievable acceleration gradients (GeV/m). This is due to the high damage threshold of dielectrics at optical frequencies. In the context of the Accelerator on a Chip International Program (ACHIP) we plan to inject electron bunches into a laser-illuminated dielectric grating structure. At a laser wavelength of 2 micro-meter the accelerating bucket is, Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 215-218(2017). doi:10.18429/JACoW-IPAC2017-MOPAB052, Longitudinal bunch measurements are typically done with rf-powered transverse deflection structures with operating frequencies 1-12 GHz. We explore the use of mm-scale,THz-driven, dielectric-lined cylindrical waveguides as transverse deflectors by driving the fundamental deflecting mode of the structure, the HEM$_{11}$. We give a brief overview ofthe physics, history, and provide an example with a 5 MeV beam using$\tiny{ASTRA}$ andCST-MWS., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 2646-2649(2017). doi:10.18429/JACoW-IPAC2017-WEPAB032, Up to now two FEL concepts are known in conventional accelerators: 1.) In THz lasers an off-crest cavity adds a chirp to the bunch followed by a bunch compressor. Particles with different energies travel on different trajectories to the radiator. 2.) For EUV and X-ray FELs the beam enters an undulator which produces microbunches which then radiate. In this paper it is proposed to copy the THz laser scheme for EUV lasers. The incoming beam is chirped and a dogleg forces afterwards the particles with different energies to move on different parallel trajectories. Considering a detector plane perpendicular to the trajectories the particles with different energies arrive in general at different times. When in this plane for instance a TGU (Transverse Gradient Undulator) is positioned the emitted radiation in the TGU is monochromatic. If in addition chirp and dogleg are selected in such a way that the particles with different energies arrive at the same time at the entrance of the TGU the radiation is monochromatic and coherent similar to the THz laser concept., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 3264-3267(2017). doi:10.18429/JACoW-IPAC2017-WEPVA007, In this work we present the outline of an experimental setup for dielectric laser acceleration of relativistic electron bunches produced by the ARES linac under construction at the SINBAD facility (DESY Hamburg). The experiment will be performed as part of the Accelerator on a Chip International Program (ACHIP), funded by the Gordon and Betty Moore Foundation. At SINBAD we plan to test the acceleration of already pre-accelerated relativistic electron bunches in a laser-illuminated dielectric grating structure. In addition to the conceptual layout of the experiment we present first start-to-end simulation results for different ARES working points. The simulations are performed using a combination of the well known particle tracking code ASTRA and the self-consistent particle in cell code VSim., Published by JACoW, Geneva

3rd European Advanced Accelerator Concepts Workshop, EAAC 2017, La Biodola, Isola d'Elba, Italy, 24 Sep 2017 - 30 Sep 2017, Plasma wakefield accelerators can be driven by either an intense laser pulse (LWFA) or a high-current particle beam (PWFA). A plasma accelerator combining both schemes consists of a LWFA providing an electron beam which subsequently drives a PWFA in the highly nonlinear regime. This scenario explicitly makes use of the advantages unique to each method, particularly exploiting the capabilities of PWFA schemes to provide energy-boosted high-brightness beams, while the LWFA stage inherently fulfils the demand for compact high-current electron bunches required as PWFA drivers. Effectively, the subsequent PWFA stage operates as a beam brightness and energy booster of the initial LWFA output, aiming to match the demanding beam quality requirements of accelerator based light sources. We present a design study based on theoretical considerations and full-detailed particle-in-cell simulations, aiming to address the feasibility and the capabilities of this promising strategy. Besides, we report on dedicated studies towards the implementation of a proof-of-principle experiment at the DRACO laser facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 1703-1706(2017). doi:10.18429/JACoW-IPAC2017-TUPIK010, Plasma wakefield accelerators can be driven by either a powerful laser pulse (LWFA) or a high-current charged particle beam (PWFA). A plasma accelerator combining both schemes consists of a LWFA providing an electron beam which subsequently drives a PWFA in the highly nonlinear regime. This scenario explicitly makes use of the advantages unique to each method, particularly exploiting the capabilities of PWFA schemes to provide high-brightness beams, while the LWFA stage inherently fulfils the demand for compact high-current electron bunches required as PWFA drivers. Effectively, the sub-sequent PWFA stage operates as beam brightness and energy booster of the initial LWFA output, aiming to match the demanding beam quality requirements of accelerator based light sources. We report on numerical studies towards the implementation of a proof-of-principle experiment at the DRACO laser facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR)., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017; Geneva : JACoW, 3 pp. (2017). doi:10.18429/JACoW-IPAC2017-THPVA007, The SINBAD facility (Short and INnovative Bunches and Accelerators at DESY) is foreseen to provide sub-fs to tens of fs electron bunches for Laser Wake-Field Acceleration (LWFA) experiments. In order to avoid emittance growth in plasma cells with ultra-high accelerating gradients the injection and transport of electron bunches with beta functions of mm-size or even smaller are required. This kind of bunch is usually space-charged dominated since the energy is low (< 200 MeV) while the peak current is high for allowing the electron bunches to be used for Free Electron-Laser (FEL) generation. We present the beamline design and explore the possible beam parameters at the SINBAD linac by start-to-end simulations., Published by JACoW, Geneva

8th International Particle Accelerator Conference, IPAC 2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva : JACoW, 3 pp. (2017). doi:10.18429/JACoW-IPAC2017-MOPIK006, The AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) project aims for development of a compact, fully coherent, THz-driven, attosecond X-ray source. A compact THz driven gun was developed, produced and tested as a source of the ultra-short electron bunches required for the project. To characterize the low energy, low-charge beam produced by such a gun tailored diagnostic devices were developed and commissioned at a test-stand chamber in CFEL (DESY). Results of the first experiments on the production and characterization of the electron beam are presented., Published by JACoW, Geneva

ARES is a planned linear accelerator for R&D for production of ultra-short electron bunches. It will be hosted at the SINBAD facility, at DESY in Hamburg*. The goal of ARES is to produce low charge (0.2-50pC), ultra-short (from few fs to sub-fs) bunches, with high arrival time stability (less than 10fs) for various applications, such as external injection for Laser Plasma Wake-Field acceleration**. The baseline layout of the accelerator foresees an S-band photo-injector which compresses low charge electron bunches via velocity bunching and accelerates them to 100 MeV energy. In the second stage, it is planned to install a third S-band accelerating cavity to reach 200 MeV as well as two X-band cavities: One for the linearization of the longitudinal phase space (subsequently allowing an improved bunch compression) and another one as a transverse deflecting cavity for longitudinal beam diagnostics. Moreover a magnetic bunch compressor is envisaged allowing to cut out the central slice of the beam*** or hybrid bunch compression., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

A new compact versatile linear accelerator named FLUTE (Ferninfrarot Linac Und Test Experiment) is currently under construction at the Karlsruhe Institute of Technology (KIT). It will serve as an accelerator test facility and allow conducting a variety of accelerator physics studies. In addition, it will be used to generate intense, ultra-short THz pulses for photon science experiments. FLUTE consists of a ~7 MeV photo-injector gun, a ~41 MeV S-band linac and a D-shaped chicane to compress bunches to a few femtoseconds. This contribution presents an overview of the project status and the accompanying simulation studies., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The first run of the Large Hadron Collider (LHC) at CERN was very successful and resulted in important physics discoveries. One way of increasing the luminosity in a collider, which gave a very significant contribution to the LHC performance in the first run and can be used even if the beam intensity cannot be increased, is to decrease the transverse beam size at the interaction points by reducing the optical function β∗. However, when doing so, the beam becomes larger in the final focusing system, which could expose its aperture to beam losses. For the LHC, which is designed to store beams with a total energy of 362 MJ, this is critical, since the loss of even a small fraction of the beam could cause a magnet quench or even damage. Therefore, the machine aperture has to be protected by the collimation system. The settings of the collimators constrain the maximum beam size that can be tolerated and therefore impose a lower limit on β*. In this paper, we present calculations to determine safe collimator settings and the resulting limit on β*, based on available aperture and operational stability of the machine. Our model was used to determine the LHC configurations in 2011 and 2012 and it was found that β* could be decreased significantly compared to the conservative model used in 2010. The gain in luminosity resulting from the decreased margins between collimators was more than a factor 2, and a further contribution from the use of realistic aperture estimates based on measurements was almost as large. This has played an essential role in the rapid and successful accumulation of experimental data in the LHC.

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Journal of physics / Conference Series 874, 012032 (2017). doi:10.1088/1742-6596/874/1/012032, The use of external injection in plasma acceleration is attractive due to the high control over the electron beam parameters, which can be tailored to meet the plasma requirements and therefore preserve its quality during acceleration. However, using this technique requires an extremely fine synchronization between the driver and witness beams. In this paper, we present a new scheme for external injection in a laser-driven plasma accelerator that would allow, for the first time, sub-femtosecond timing jitter between laser pulse and electron beam., Published by IOP Publ., Bristol

FLUTE, a new linac-based test facility and THz source is currently being built at the Karlsruhe Institute of Technology (KIT) in collaboration with DESY and PSI. It consists of an RF photo gun and a traveling wave linac accelerating electrons to beam energies of ~41 MeV in the charge range from a few pC up to 3 nC. The electron bunch will then be compressed in a magnetic chicane in the range of 1 - 300 fs, depending on the charge, in order to generate coherent THz radiation with high peak power. An overview of the simulation and hardware status is given in this contribution., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany