Search

Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand 13th International Particle Accelerator Conference, IPAC22, Bangkok, Thailand, 12 Jun 2022 - 17 Jun 2022; Geneva : JACoW 1757-1760 (2022). doi:10.18429/JACoW-IPAC2022-WEPOST029, DESY is studying the feasibility of a 6 GeV laser-plasma injector for top-up operation of its future flagship synchrotron light source PETRA IV. A potential design of such an injector involves a single plasma stage, a beamline for beam capture and phase space manipulation, and a X-band rf energy compressor. Numerical tracking with realistic beam distributions shows that an energy variation below 0.1%, rms and a transverse emittance about 1 nm-rad, rms can be achieved under realistic timing, energy, and pointing jitters. PETRA IV injection efficiency studies performed with a conservative 5% beta-beating indicate negligible beam losses for the simulated beams during top-up. Provided the necessary progress on high-power lasers and plasma cells, the laser plasma injector could become a competitive alternative to the conventional injector chain., Published by JACoW, Geneva

Physical review letters 129(9), 094801 (2022). doi:10.1103/PhysRevLett.129.094801, Laser-plasma accelerators outperform current radio frequency technology in acceleration strength by orders of magnitude. Yet, enabling them to deliver competitive beam quality for demanding applications, particularly in terms of energy spread and stability, remains a major challenge. In this Letter, we propose to combine bunch decompression and active plasma dechirping for drastically improving the energy profile and stability of beams from laser-plasma accelerators. Realistic start-to-end simulations demonstrate the potential of these postacceleration phase-space manipulations for simultaneously reducing an initial energy spread and energy jitter of ∼1–2% to ≲0.1%, closing the beam-quality gap to conventional acceleration schemes., Published by APS, College Park, Md.

An injection scheme is proposed to realize electron trapping in sub-relativistic plasma wakefield accelerators. A laser under oblique angle of incidence ionizes a dopant gas in plasma and ponderomotively accelerates the released electrons into the direction of wake propagation. This process enables electron trapping in the wakefield even for a wakefield potential below the trapping threshold. We study the scheme theoretically and by means of particle-in-cell (PIC) simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads.

Plasma wakefield accelerators driven by either laser or electron beams have shown great potential for future applications. Output beam quality from plasma has improved tremendously over the past decade. This, to a large extend, was enabled by progress in high-performance computing and numerical techniques based on particle-in-cell simulations. In this proceedings paper, we present two recent simulation studies, on hybrid plasma accelerators and on plasmabased laser focusing, opening new avenues in the application of compact accelerators and for the generation of high-brightness electron beams.

New journal of physics 22, 123003 (2020). doi:10.1088/1367-2630/abc9ee, An injection scheme is proposed to realize electron trapping in sub-relativistic plasma wakefield accelerators. A laser under oblique angle of incidence ionizes a dopant gas in plasma and ponderomotively accelerates the released electrons into the direction of wake propagation. This process enables electron trapping in the wakefield even for a wakefield potential below the trapping threshold. We study the scheme theoretically and by means of particle-in-cell (PIC) simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads., Published by IOP, [London]

10th International Particle Accelerator Conference, IPAC’19, Melbourne, Australia, 19 May 2019 - 24 May 2019; Geneva, Switzerland : JACoW Publishing 2286-2290 (2019). doi:10.18429/JACOW-IPAC2019-WEZPLS2, Beam driven wakefield acceleration (PWFA) schemes in plasmas are among the most promising candidates for novel, compact accelerators. Several aspects of PWFA are under investigation at the Photoinjector Test facility at DESY in Zeuthen (PITZ). One of the main characteristics of these accelerators is the ratio between field strength usable for acceleration and decelerating field strength in the driver bunch, the so called transformer ratio. To reach high transformer ratios usually shaped bunches, e.g. with ramped current profiles are employed as drivers. The so-called self-modulation instability, which causes transverse modulation of a bunch longer than the plasma wavelength, is proposed as a means of supplying short driver bunches for proton-driven PWFA. This talk will give an overview on experimental results in these two aspects of PWFA at PITZ with a focus on the production of electron bunches enabling high transformer ratio acceleration by shaping the photocathode laser pulses of a photoinjector and the demonstration of high transformer ratio PWFA. Simulations and further developments on the shaping techniques, allowing highly flexible electron bunches for future plasma wakefield accelerators are also presented., Published by JACoW Publishing, Geneva, Switzerland

10th International Particle Accelerator Conference, IPAC’19, Melbourne, Australia, 19 May 2019 - 24 May 2019; Geneva, Switzerland : JACoW Publishing 3616-3618 (2019). doi:10.18429/JACOW-IPAC2019-THPGW017, The self-modulation instability (SMI) of long (in respect to the plasma wavelength) charged particle beams passing through plasma enables the use of currently existing high energy charged particle beams as drivers for plasma wakefield accelerators. At the Photo Injector Test facility at DESY in Zeuthen (PITZ) the SMI of electron beams is studied *, **. An enhanced experimental setup includes a plasma channel of variable length which allows to investigate in details the development stages of the SMI by measuring the instability growth rate and phase velocity as a function of propagation distance in the plasma. In this contribution we present the experimental setup improvements, first measurement results and supporting beam dynamics simulations., Published by JACoW Publishing, Geneva, Switzerland

6 pp. (2019)., A non-resonant streaming instability driven by cosmic-ray currents, also called Bell's instability, is proposed as a candidate for providing the required magnetic turbulence of efficient diffusive shock accelerations. To demonstrate the saturation level and mechanism of the non-resonant streaming instability in a laboratory environment, we attempt to develop an experiment at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). As an electron beam is used to replace the proton beam to carry the cosmic-ray current in our experiment, the polarization of the non-resonant streaming instability will be modified from the left-handed (LH) mode to the right-handed (RH) mode. The theoretical instability analysis shows that the growth rate of this RH non-resonant mode may be smaller than it of the LH resonant mode. However the LH resonant mode can be ignored in our experiment while the expected wavelength is longer than the used plasma cell. The results of PIC simulations will also support this contention and the occurrence of non-resonant streaming instability in our experiment.

10th International Particle Accelerator Conference, IPAC’19, Melbourne, Australia, 19 May 2019 - 24 May 2019; Geneva, Switzerland : JACoW Publishing 3612-3615 (2019). doi:10.18429/JACOW-IPAC2019-THPGW016, The Photo Injector Test Facility at DESY in Zeuthen (PITZ) carries out studies of beam-driven plasma wakefield acceleration (PWFA). The facility possesses a flexible photocathode laser beam shaping system and a variety of diagnostics including a high-resolution dipole spectrometer and an rf deflector which enables the observation of the longitudinal phase space of electron beams after their passage through a plasma. Two plasma sources are available: a gas discharge plasma cell and a photoionized lithium vapor plasma cell. Studies at PITZ include investigations of the self-modulation instability of long electron beams and the high transformer ratio, i.e., the ratio between the maximum accelerating field behind the drive beam and the decelerating field within the beam. This overview includes the experimental results and plans for future experiments., Published by JACoW Publishing, Geneva, Switzerland

Focusing petawatt-level laser beams to a variety of spot sizes for different applications is expensive in cost, labor and space. In this paper, we propose a plasma lens to flexibly resize the laser beam by utilizing the laser self-focusing effect. Using a fixed conventional focusing system to focus the laser a short distance in front of the plasma, we can adjust the effective laser beam waist within a certain range, as if a variety of focusing systems were used with the plasma lens acting as an adjustable eyepiece in a telescope. Such a setup is a powerful tool for laser wakefield accelerator experiments in state-of-art petawatt laser projects and allows for scanning focal spot parameters.

DPG - Frühjahrstagung 2018, Würzburg, Germany, 19 Mar 2018 - 23 Mar 2018, Plasma acceleration has attracted a lot of attention in the past decade due to successful acceleration of electrons with gradients exceeding those of conventional accelerator technology by orders of magnitude. An experimental programme was started at the Photoinjector Test Facility, DESY Zeuthen (PITZ), to study aspects of the acceleration mechanisms in beam-driven plasma wakes. Original goals were the investigation of the self-modulation instability and the acceleration of particles with high ratios between energy gain of accelerated and energy loss of wake-driving particles. The goals were later on extended by studies on other wakefield acceleration mechanisms and laboratory studies of acceleration mechanisms in space plasmas as a source of PeV-scale cosmic ray particles. A brief overview of the experiments including experimental results, simulations and plans for future studies is presented.

18th Advanced Accelerator Concepts Workshop, AAC 2018, Denver, America, 12 Aug 2018 - 17 Aug 2018, Ultra-high intensity lasers are important tools to study the micro structures of our physical world, to investigate extreme states of matter, and to accelerate particles to ultra-relativistic energies. Focussing high power laser pulses to high intensities requires large, inflexible, and expensive optics, with their size determined by material breakdown properties. In this presentation we propose to flexibly control the laser beam size, and thus, intensity by utilizing an in-plasma focussing scheme. Owing to the strong interaction of high-power lasers with plasma and the high plasma breakdown threshold, the laser beam can be effectively modulated over short propagation distances. Such laser plasma lenses may prove valuable for future laser wakefield acceleration studies.

9th International Particle Accelerator Conference, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018; Jacow 5 pp. (2018)., Plasma-based accelerators are a promising novel technology that could signiĄcantly reduce the size and cost of future accelerator facilities. However, the typical quality and stabil-ity of the produced beams is still inferior to the requirements of Free Electron Lasers (FELs) and other applications. We present here our recent work in understanding the limita-tions of this type of accelerators, particularly on the energy spread and bunch length, and possible mitigating measures for future applications, like the plasma-based FEL in theEuPRAXIA design study., Published by Jacow

Physics of plasmas 25(7), 079902 (2018). doi:10.1063/1.5046689, We would like to correct a typographical error which was introduced in Eqs. (5), (11), (14), (20a), and (20b) during revision of Ref. 1. The series expansion of the plasmaelectron phase space density to the first order of 〈x〉 and 〈px〉 [Eq. (5) in Ref. 1] correctly reads fp≈ fp0 - cos θ (〈x〉∂r+ 〈px〉∂pr)fp,0The zeroth-order term, fp,0, was not printed in Ref. 1. Accordingly, the correct expansion of the wakefield potential [Eq. (11) in Ref. 1] is ψ(r,θ) ≈ ψ0(r) -cos θ Xp∂rψ0(r), the correct expansion of the source term of the wakefield potential [Eq. (14) in Ref. 1] is S(r, θ) ≈ S0(r) - cos θ Xp∂rS0(r), and the correct expansions of the force terms [Eqs. (20a) and (20b) in Ref. 1] are Fr,b≈ Fr,b,o- cos θ Xb∂rFr,b,0, Fr,b≈ Fr,p,o- cos θ 〈x〈 ∂rFr,p,0, The zeroth order terms in Eqs. (5), (11), (14), (20a), and (20b) are missing in the printing of Ref. 1 but were fully taken into account for the calculation of all derived equations of the mathematical model. The developed mathematical model and physical conclusions in Ref. 1 are therefore all unaltered by, and consistent with, the above corrections., Published by American Institute of Physics, Melville, NY

9th International Particle Accelerator Conference, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018; Geneva, Switzerland : JACoW Publishing 1648-1650 (2018). doi:10.18429/JACoW-IPAC2018-TUPML047, The transformer ratio, the ratio between maximum accelerating field and maximum decelerating field in the driving bunch of a plasma wakefield accelerator (PWFA), is one of the key aspects of this acceleration scheme. It not only defines the maximum possible energy gain of the PWFA but it is also connected to the maximum percentage of energy that can be extracted from the driver, which is a limiting factor for the efficiency of the accelerator. Since in linear wakefield theory a transformer ratio of 2 cannot be exceeded with symmetrical drive bunches, any ratio above 2 is considered high. After the first demonstration of high transformer ratio acceleration in a plasma wakefield at PITZ, the photoinjector test facility at DESY, Zeuthen site, limiting aspects of the transformer ratio are under investigation. This includes e.g. the occurrence of bunch instabilities, like the transverse two stream instability, or deviations of the experimentally achieved bunch shapes from the ideal., Published by JACoW Publishing, Geneva, Switzerland

3rd European Advanced Accelerator Concepts Workshop, EAAC 2017, La Biodola, Isola d'Elba, Italy, 24 Sep 2017 - 30 Sep 2017, The beam-driven FLASHForward experiment 1 (X-1) aims at the generation of high-brightness electron bunches for photon science applications in several centimeters of plasma, with the plasma acting both as a cathode and accelerator.The 1 GeV electron-bunch with a peak current of 2.5 kA and a synchronized TW-laser system makes FLASHForward a unique facility[1] to study controlled electron-injection into plasma wakes.With density downramp injection, witness bunches of ~1 kA peak current at emittances well below 1 µm are achievable[2]. The sharp plasma density gradients are produced by means of controlled gas flow[3] or by localized laser ionization transverse to the electron-beam orbit[4]. Precise laser-to-electron-beam synchronization enables controlled injection as e.g. the Trojan Horse scheme[5], which is predicted to support sub-0.1-µm-emittance witness bunches.experimental installation status, planning, and prospects of the FLASHForward X-1 experiments are presented.

3rd European Advanced Accelerator Concepts Workshop, EAAC 2017, La Biodola, Isola d'Elba, Italy, 24 Sep 2017 - 30 Sep 2017, Staging of plasma-wakefield accelerators is essential to utilise them in particle physics or other applications requiring high energy beams.Quality preservation in external beam injection is one of the key missing milestones towards this goal.This and other topics related to the plasma booster will be studied at FLASHForward, a unique beam-driven plasma wakefield acceleration facility currently under construction at DESY (Hamburg, Germany),in the frame of the FLASHForward X-2 experiment.High-quality 1 GeV-class electron beams with $\mu m$-emittances from the free-electron laser FLASH will be utilised to generate driver-witness pairsby using a mask in a dispersive section.Alternatively, it is possible to generate two independent bunches directly in the photocathode electron-gun by using a double-pulse laser.In this contribution, the physics case and the current status of the FLASHForward X-2 experiment will be reviewed.The experimental installation will be described, with a focus on the electron beam line.Electron beam dynamics and Particle-in-Cell simulations will be presented

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.

38th International Free-Electron Laser Conference, FEL2017, Santa Fe, USA, 20 Aug 2017 - 25 Aug 2017; 4 pp. (2017)., FLASHForward is the Future-ORiented Wakefield Accelerator Research and Development project at the DESY free-electron laser (FEL) facility FLASH. It aims to produce high-quality, GeV-energy electron beams over a plasma cell of a few centimeters. The plasma is created by means of a 25 TW Ti:Sapphire laser system. The plasma wakefield will be driven by high-current-density electron beams extracted from the FLASH accelerator. The project focuses on the advancement of plasma-based particle acceleration technology through the exploration of both external and internal witness-beam injection schemes. Multiple conventional and cutting-edge diagnostic tools, suitable for diagnosis of short electron beams, are under development. The design of the post-plasma beamline sections will be finalized based on the result of these aforementioned diagnostics. In this paper, the status of the project, as well as the progress towards achieving its overarching goal of demonstrating FEL gain via plasma wakefield acceleration, is discussed.

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, 1692-1695 (2017). doi:10.18429/JACoW-IPAC2017-TUPIK006, FLASHForward is a beam-driven plasma wakefield acceleration facility, currently under construction at DESY (Hamburg, Germany), aiming at the stable generation of electron beams of several GeV with small energy spread and emittance. High-quality 1 GeV-class electron beams from the free-electron laser FLASH will act as the wake driver. The setup will allow studies of external injection as well as density-downramp injection. With a triangular-shaped driver beam electron energies of up to 5 GeV from a few centimeters of plasma can be anticipated. Particle-In-Cell simulations are used to assess the feasibility of each technique and to predict properties of the accelerated electron bunches. In this contribution the current status of FLASHForward, along with recent experimental developments and upcoming scientific plans, will be reviewed., Published by JACoW, Geneva

8th International Particle Accelerator Conference, Copenhagen, Denmark, 14 May 2017 - 19 May 2017; JACoW, Geneva, Switzerland 1718-1720 (2017). doi:10.18429/JACoW-IPAC2017-TUPIK018, Plasma wakefield acceleration (PWFA), the acceleration of particles in a plasma wakefield driven by high current-density particle bunches, is one of the most promising candidates for a future compact accelerator technology. A key aspect of this type of acceleration is the ratio between the accelerating fields experienced by a witness beam and the decelerating fields experienced by the drive beam, called the transformer ratio. As for longitudinally symmetrical bunches this ratio is limited by the fundamental theorem of beamloading to 2 in the linear regime*, a transformer ratio above this limit is considered high. This can be reached by using a modulated drive bunch or a shaped train of drive bunches. So far, only the latter case has been shown for wakefields in a RF-structure**. We show the experimental setup, simulations and first, preliminary results of high transformer ratio acceleration experiments at the Photoinjector Test Facility at DESY in Zeuthen (PITZ)., Published by JACoW, Geneva, Switzerland

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

3rd European Advanced Accelerator Concepts Workshop, EAAC 2017, La Biodola, Isola d'Elba, Italy, 24 Sep 2017 - 30 Sep 2017, Witness beam quality preservation (in particular energy spread and emittance) for external injection scenarios in plasma-based accelerators is a crucial requirement for downstream applications such as Free Electron Lasers. Due to the complexity of the beam-plasma interaction, extensive studies of possible mechanisms to preserve beam quality are usually done using particle-in-cell (PIC) simulations.The sheer number of possible properties and simulation settings involved result in time-consuming iterations over the corresponding parameter space. Analytical descriptions of the witness beam evolution could allow for quick optimizations and provide useful limits for further investigations. However, these models are often limited to strong assumptions and not capable of rendering higher order details of the beam evolution along the whole acceleration procedure.The study of instabilities arising from the introduction of beams with non-symmetric distributions can be efficiently tackled by means of an analytic model for the evolution of the statistical moments of the beam distributions, introduced by Mehrling et al. We report on results from the application of this model to the evolution of transverse beam properties of a witness beam in a plasma wakefield, including benchmarks with existing PIC codes such as HiPACE and the SANA model.

Nuclear Photonics 2016, NP2016, Monterey, California, USA, 16 Oct 2016 - 21 Oct 2016 ; (2016)., FLASHForward is a beam-driven plasma wakefield accelerator located at Deutsches Elektronen Synchrotron (DESY) in Hamburg, Germany. Within the FLASHForward project, laser-driven as well as beam-driven plasma waves enable acceleration of electron beams with energies from tens of MeV to a few GeV. The characterization of these electrons is important to control and improve this acceleration technique.The production of inverse Compton scattering (ICS) offers a possibility to measure electron beam parameters due to the dependence of the produced photons on the electron parameters. A numerical study of ICS radiation produced in experiments at FLASHForward was performed, using an ICS simulation code and the results from particle-in-cell simulations. The possibility of determining electron beam properties from measurements of the x-ray source was explored for a wide range of experimental conditions.The simulations show that the measurement of electron spectrum and divergence is in principle possible with the detection of ICS photons. In addition, transverse probing of the electron beam using ultra-short laser pulses allows to obtain longitudinal information about the electron beam in multi shot experiments. However, the detection of the produced ICS radiation, with photon energies of several MeV for the electron beams of interest, remains challenging.1. A. Aschikhin et al. “The FLASHForward facility at DESY,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip. 806 (2016).2. W. J. Brown and F. V. Hartemann, “Three-dimensional time and frequency-domain theory of femtosecond x-ray pulse generation through Thomson scattering,” Phys. Rev. Spec. Top. - Accel. Beams, 7, 060703 (2004).3. R. A. Fonseca et al., “OSIRIS: A Three-Dimensional, Fully Relativistic Particle in Cell Code for Modeling Plasma Based Accelerators,” Computational Science — ICCS 2002, 2331 (2002).4. T. Mehrling et al., “HiPACE: a quasi-static particle-in-cell code,” Plasma Phys. Control. Fusion 56, 8 (2014).

58th Annual Meeting of the APS Division of Plasma Physics, San Jose, USA, 31 Oct 2016 - 4 Nov 2016 ; (2016)., Laser driven plasma wakefield accelerators have been explored as a potential compact, reproducible source of relativistic electron bunches, utilising an electric field of many GV/m. Control over injection of electrons into the wakefield is of crucial importance in producing stable, mono-energetic electron bunches. Density tailoring of the target, to control the acceleration process, can also be used to improve the quality of the bunch. By using gas jets to provide tailored targets it is possible to provide good access for plasma diagnostics while also producing sharp density gradients for density down-ramp injection. OpenFOAM hydrodynamic simulations were used to investigate the possibility of producing tailored density targets in a supersonic gas jet. Particle-in-cell simulations of the resulting density profiles modelled the effect of the tailored density on the properties of the accelerated electron bunch. Here, we present the simulation results together with preliminary experimental measurements of electron and x-ray properties from LPWA experiments using gas jet targets and a 25 TW, 25 fs Ti:Sa laser system at DESY.

The 5th annual meeting of the LAOLA collaboration, Wismar, Germany, 21 Jun 2016 - 22 Jun 2016 ; (2016)., In the context of FLASHForward laser wakefield tests, 2D simulations have been carried on with OSIRIS PIC code. Ionization injection with a gas jet doped with 1% Nitrogen and gaussian density downramp injection have been simulated. We present therefore the working points obtained for BOND laser from the collaboration between simulation group and laser wakefield beam line people.

Bose-Einstein correlations of like-sign charged hadrons produced in deep-inelastic electron and positron scattering are studied in the HERMES experiment using nuclear targets of $^1$H, $^2$H, $^3$He, $^4$He, N, Ne, Kr, and Xe. A Gaussian approach is used to parametrize a two-particle correlation function determined from events with at least two charged hadrons of the same sign charge. This correlation function is compared to two different empirical distributions that do not include the Bose-Einstein correlations. One distribution is derived from unlike-sign hadron pairs, and the second is derived from mixing like-sign pairs from different events. The extraction procedure used simulations incorporating the experimental setup in order to correct the results for spectrometer acceptance effects, and was tested using the distribution of unlike-sign hadron pairs. Clear signals of Bose-Einstein correlations for all target nuclei without a significant variation with the nuclear target mass are found. Also, no evidence for a dependence on the invariant mass $W$ of the photon-nucleon system is found when the results are compared to those of previous experiments.

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

Journal of Instrumentation 8(05), 49 (2013). doi:10.1088/1748-0221/8/05/P05012, For the final running period of HERA, a recoil detector was installed at the HERMES experiment to improve measurements of hard exclusive processes in charged-lepton nucleon scattering. Here, deeply virtual Compton scattering is of particular interest as this process provides constraints on generalised parton distributions that give access to the total angular momenta of quarks within the nucleon. The HERMES recoil detector was designed to improve the selection of exclusive events by a direct measurement of the four-momentum of the recoiling particle. It consisted of three components: two layers of double-sided silicon strip sensors inside the HERA beam vacuum, a two-barrel scintillating fibre tracker, and a photon detector. All sub-detectors were located inside a solenoidal magnetic field with an integrated field strength of 1 T. The recoil detector was installed in late 2005. After the commissioning of all components was finished in September 2006, it operated stably until the end of data taking at HERA end of June 2007. The present paper gives a brief overview of the physics processes of interest and the general detector design. The recoil detector components, their calibration, the momentum reconstruction of charged particles, and the event selection are described in detail. The paper closes with a summary of the performance of the detection system., Published by Inst. of Physics, London

Physical review research 3(4), L042005 (2021). doi:10.1103/PhysRevResearch.3.L042005, We present the experimental demonstration of density downramp injection at a gas-dynamic shock in a beam-driven plasma accelerator. The ultrashort driver electron beam with a peak-current exceeding 10 kA allows operation in the blowout regime and enables injection of electron witness bunches at gentle density ramps, i.e., longer than the plasma wavelength, which nurtures prospects for ultralow bunch emittance. By precision control over the position of injection we show that these bunches can be energy-tuned in acceleration gradients of near 120 GV m���1., Published by APS, College Park, MD

Applied Sciences 9(13), 2626 - (2019). doi:10.3390/app9132626, Fundamental similarities and differences between laser-driven plasma wakefield acceleration (LWFA) and particle-driven plasma wakefield acceleration (PWFA) are discussed. The complementary features enable the conception and development of novel hybrid plasma accelerators, which allow previously not accessible compact solutions for high quality electron bunch generation and arising applications. Very high energy gains can be realized by electron beam drivers even in single stages because PWFA is practically dephasing-free and not diffraction-limited. These electron driver beams for PWFA in turn can be produced in compact LWFA stages. In various hybrid approaches, these PWFA systems can be spiked with ionizing laser pulses to realize tunable and high-quality electron sources via optical density downramp injection (also known as plasma torch) or plasma photocathodes (also known as Trojan Horse) and via wakefield-induced injection (also known as WII). These hybrids can act as beam energy, brightness and quality transformers, and partially have built-in stabilizing features. They thus offer compact pathways towards beams with unprecedented emittance and brightness, which may have transformative impact for light sources and photon science applications. Furthermore, they allow the study of PWFA-specific challenges in compact setups in addition to large linac-based facilities, such as fundamental beam–plasma interaction physics, to develop novel diagnostics, and to develop contributions such as ultralow emittance test beams or other building blocks and schemes which support future plasma-based collider concepts., Published by MDPI, Basel

In the field of plasma wakefield acceleration (PWFA) significant progress has been made throughout the recent years. However, an important issue in building plasma based accelerators that provide particle bunches suitable for user applications will be a high transformer ratio, i.e. the ratio between maximum accelerating field in the witness and maximum decelerating fields in the driver bunch. The transformer ratio for symmetrical bunches in an overdense plasma is naturally limited to 2*. Theory and simulations show that this can be exceeded using asymmetrical bunches. Experimentally this was proven in RF-structures**, but not in PWFA. To study transformer ratios above this limit in the linear regime of a plasma wake, an experimental scheme tailored to the unique capabilities of the Photoinjector Test Facility Zeuthen PITZ, a 20-MeV electron accelerator at DESY, is being investigated. This includes analytical plasma wakefield calculations, numerical simulations of beam transport and plasma wakefields, as well as preparatory studies on the photocathode laser system and the plasma sources., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

Scientific reports 9(1), 17690 (2019). doi:10.1038/s41598-019-53887-8, Plasma-based accelerators (PBAs), having demonstrated the production of GeV electron beams in only centimetre scales, offer a path towards a new generation of highly compact and cost-effective particle accelerators. However, achieving the required beam quality, particularly on the energy spread for applications such as free-electron lasers, remains a challenge. Here we investigate fundamental sources of energy spread and bunch length in PBAs which arise from the betatron motion of beam electrons. We present an analytical theory, validated against particle-in-cell simulations, which accurately describes these phenomena. Significant impact on the beam quality is predicted for certain configurations, explaining previously observed limitations on the achievable bunch length and energy spread. Guidelines for mitigating these contributions towards high-quality beams are deduced., Published by Macmillan Publishers Limited, part of Springer Nature, [London]

Physical review letters 120(14), 144802 (2018). doi:10.1103/PhysRevLett.120.144802, Self-modulation of an electron beam in a plasma has been observed. The propagation of a long (several plasma wavelengths) electron bunch in an overdense plasma resulted in the production of multiple bunches via the self-modulation instability. Using a combination of a radio-frequency deflector and a dipole spectrometer, the time and energy structure of the self-modulated beam was measured. The longitudinal phase space measurement showed the modulation of a long electron bunch into three bunches with an approximately 200 keV=c amplitude momentum modulation. Demonstrating this effect is a breakthrough for proton-driven plasma accelerator schemes aiming to utilize the same physical effect., Published by APS, College Park, Md.

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., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

[Proceedings of the 8th International Particle Accelerator Conference : IPAC2017 14 - 19 May 2017, Bella Center, Copenhagen, Denmark]Editors: Volker RW Schaa (GSI, Darmstadt, Germany); Gianluigi Arduini (CERN, Geneva, Switzerland); Juliana Pranke (ESS, Lund, Sweden); Mike Seidel (PSI, Villigen, Switzerland); Mats Lindroos (ESS, Lund, Sweden) 8th International Particle Accelerator Conference, IPAC2017, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; Geneva, Switzerland : JACoW, 1265-1268(2017). doi:10.18429/JACoW-IPAC2017-TUOBB3, Published by JACoW, Geneva, Switzerland

The 10th International Conference on Inertial Fusion Sciences and Applications , IFSA2017, Saint Malo, France, 11 Sep 2017 - 15 Sep 2017, The diffusive shock acceleration at the forward shocks of shell-type supernova remnants is believed as a prime process to generate high energy cosmic ray particles. For efficient acceleration, Bell’s instability, driven by streaming cosmic rays, is proposed as a candidate for providing the required magnetic turbulence in the upstream region of the shock [1]. This nonresonant and nearly purely growing electromagnetic instability had been investigated with MHD studies and Particle-In-Cell (PIC) simulations, it shows that the magnetic field fluctuations stronger than the background interstellar field is possible theoretically [1,2]. In order to examine the saturation level and mechanism of Bell’s instability in the laboratory, we attempt to develop a laboratory experiment by using the plasma cell and electron source of the PITZ group of DESY. Before the actual experiment, here we would present the numerical investigations, based mainly on the fully kinetic PIC simulations, that study physical conditions for the Bell’s instability to occur in our laboratory experiment and its expected properties.

Self-modulation (SM) of proton beams in plasma has recently gained interest in context with the ongoing PWFA experiment of the AWAKE collaboration at CERN. Instrumental for that experiment is the SM of a proton beam to generate bunchlets for resonant wave excitation and efficient acceleration. A fundamental understanding of the underlying physics is vital, and hence an independent experiment has been set up at the beamline of the Photo Injector Test Facility at DESY, Zeuthen Site (PITZ), to study the SM of electron beams in a plasma. This contribution presents simulation results on SM experiments at PITZ using the particle-in-cell code HiPACE. The simulation study is crucial to optimize the beam and plasma parameters for the experiment. Of particular interest is the energy modulation imprinted onto the beam by means of the generated wakefields in the plasma. With the support of simulations the observation of this information in the experiment can be used to deduce key properties of the accelerating electric fields such as their magnitude and their phase velocity, both of significant importance for the design of self-modulated plasma-based acceleration experiments., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Physical review accelerators and beams 24(10), 101302 (2021). doi:10.1103/PhysRevAccelBeams.24.101302, Electron beams to be accelerated in beam-driven plasma wakes are commonly formed by a photocathode and externally injected into the wakefield of a preceding bunch. Alternatively, using the plasma itself as a cathode offers the possibility of generating ultrashort, low-emittance beams by trapping and accelerating electrons from the ambient plasma background. Here, we present a beam-driven plasma cathode realized via laser-triggered density-downramp injection, showing stable beam formation over more than a thousand consecutive events with an injection probability of 95 %. The plasma cathode is highly tunable, resulting in the injection of electron bunches of tens of pC of charge, energies of up to 79 MeV, and relative energy spreads as low as a few percent and the achieved stability allowed for the first multi-shot evaluation of the emittance of injected beams., Published by American Physical Society, College Park, MD

The EuPRAXIA project aims at designing the world’s first accelerator based on plasma-wakefield advanced technique, which can deliver a 5 GeV electron beam with simultaneously high charge, low emittance and low energy spread to user’s communities. Such challenging objectives can only have a chance to be achieved when particular efforts are dedicated to identify the subsequent issues and to find the way to solve them. Many injection/acceleration schemes and techniques have been explored by means of thorough simulations in more than ten European institutes to sort out the most appropriate ones. The specific issues of high charge, high beam quality and beam extraction then transfer to the user’s applications, have been tackled with many innovative approaches*. This article highlights the different advanced methods that have been employed by the EuPRAXIA collaboration and the preliminary results obtained. The needs in terms of laser and plasma parameters for such an accelerator are also summarized., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

This paper describes the utilization of beam-driven plasma wakefield acceleration to implement a high-quality plasma cathode via density-downramp injection in a short injector stage at the FLASHForward facility at DESY. Electron beams with charge of up to 105 pC and energy spread of a few percent were accelerated by a tunable effective accelerating field of up to 2.7 GV/m. The plasma cathode was operated drift-free with very high injection efficiency. Sources of jitter, the emittance and divergence of the resulting beam were investigated and modeled, as were strategies for performance improvements that would further increase the wide-ranging applications for a plasma cathode with the demonstrated operational stability

In this work, new concepts for solving some of the current challenges of plasma-based acceleration are proposed and explored. These concepts, which rely on a combination of plasma-acceleration stages with a magnetic chicane, show that GeV-range beams with sub-percent energy stability and an unprecedented sub-per-mille energy spread could be produced. Achieving such a low energy spread, which is at least an order of magnitude below current state-of-the-art, has only been possible thanks to an improved understanding of the beam dynamics in this type of accelerators and the subsequent analytical modelling of previously unaccounted sources of energy spread. In addition to proof-of-principle simulations and conceptual designs, a comprehensive study of sensitivity and tolerances of the acceleration concept is included here. This systematic study has only been possible thanks to a fast particle tracking code which has been integrally developed within this work. The positive findings presented here provide a new way towards the realization of reliable and high-quality plasma-based accelerators with a broad range of applications. Among these, the outstanding beam properties that can be reached with the presented schemes would allow for the demonstration of compact plasma-driven free-electron lasers. Thanks to these good prospects, the conceptual design of a 6 GeV accelerator based on the presented methods, which has been realized as part of this work, has been selected as a baseline option for the international EuPRAXIA project. Several of the ideas and studies carried out within this thesis have been published in peer-reviewed journals including Physical Review Letters and Scientific Reports.