IPAC2022 - Classification: MC3: Novel Particle Sources and Acceleration Techniques / A22: Plasma Wakefield Acceleration

Paper	Title	Page
MOPLXGD2	Progress Towards Demonstration of a Plasma-Based FEL	6
	E. Chiadroni LNF-INFN, Frascati, Italy
	Plasma-based technology promises a revolution in the field of particle accelerators by pushing beams to gigaelectronvolt energies within centimeter distances. Several experiments are ongoing world-wide towards demonstration of a plasma based FEL enabling the realization of ultra-compact facilities for user applications like Free-Electron Lasers (FEL). The progress towards a plasma based FEL user facility is here reported, with particular focus on the recent results about the first experimental evidence of FEL lasing by a compact (3 cm) particle beam-driven plasma accelerator at the SPARC_LAB test facility. The status and prospects are discussed.
	Slides MOPLXGD2 [17.683 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPLXGD2
About •	Received ※ 12 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 30 June 2022
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MOIYGD2	Recent Progress of Compact LAser Plasma Accelerator at Peking University
	C. Lin PKU, Beijing, People’s Republic of China
	Usually large energy spread and shot-to-shot stability are the bottlenecks of laser accelerator in applications. Recently proton beam with energies less than 10 MeV, <1% energy spread, several to tens of pC charge can be stably produced and transported in Compact LAser Plasma Accelerator (CLAPA) at Peking University. The CLAPA beam line is an object-image point analysing system, which ensures the transmission efficiency and energy selection accuracy for proton beams with initial large divergence angle and energy spread. A spread-out Bragg peak (SOBP) is produced with high precision beam control, which is essential for cancer therapy. Other primary application experiments based on laser-accelerated proton beam have also been carried out, such as FLASH irradiation, Laser Ion trace probe, proton radiograph, stress testing for tungsten, irradiation of semiconductor sensor to simulate the space irradiation environment and so on.
	Slides MOIYGD2 [5.369 MB]
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MOOYGD1	Experiments Towards High-Repetition Rate Plasma Wakefield Acceleration at FLASHForward
	G. Loisch, J. Beinortaite, G.J. Boyle, R.T.P. D’Arcy, S. Diederichs, J.M. Garland, P. Gonzalez-Caminal, C.A. Lindstrøm, J. Osterhoff, T. Parikh, S. Schreiber, S. Schröder, M. Thévenet, S. Wesch, M. Wing DESY, Hamburg, Germany J. Chappell, M. Wing UCL, London, United Kingdom B. Foster JAI, Oxford, United Kingdom P. Gonzalez-Caminal Universität Hamburg, Hamburg, Germany
	Beam-driven plasma-wakefield acceleration (PWFA) is one of the most promising techniques to reduce significantly the size and cost of future lepton accelerators. Huge steps have been taken in the last decades towards achieving high acceleration gradients with simultaneous beam-quality preservation. However, in order to match both the luminosity demands of high-energy physics and the brilliance requirements of photon science, PWFA must be capable of accelerating thousands of bunches per second ’ orders of magnitude beyond the current state of the art. Historically, investigation of the rate limitation in plasmas was limited by the number of bunches available from the accelerator front-end. The FLASHForward facility, which is driven by the superconducting linac of the FLASH free-electron laser, is the first experiment capable of addressing this issue. We report here on first experimental results from the facility, aimed at determining the repetition rate limit of plasma accelerators arising from fundamental plasma processes* and finally advancing the repetition rate of PWFA from proof-of-principle experiments at a few bunches per second to a competitive plasma accelerator. * R. D’Arcy et al., Recovery time of a plasma-wakefield accelerator, Nature (in press)
	Slides MOOYGD1 [2.953 MB]
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MOOYGD2	The AWAKE Experiment in 2021: Performance and Preliminary Results on Electron-Seeding of Self-Modulation	21
	E. Gschwendtner, L. Verra, G. Zevi Della Porta CERN, Meyrin, Switzerland P. Muggli, L. Verra MPI, Muenchen, Germany P. Muggli MPI-P, München, Germany L. Verra TUM, Munich, Germany
	The future programme of the Advanced Wakefield (AWAKE) experiment at CERN relies on the seeded self-modulation of an entire proton bunch, resulting in phase-reproducible micro-bunches. This important milestone was achieved during the 2021 proton run by injecting a short electron bunch ahead of the proton bunch, demonstrating for the first time the electron-seeding of proton bunch self-modulation. This talk describes the programme, performance and preliminary results of the AWAKE experiment in the 2021 proton run, and introduces the program of the 2022 proton run. The observation of electron-seeded self-modulation opens new avenues of exploration which will be studied in 2022, including the effect of a phase difference between the front and the back of a proton bunch and the possibility of reproducibly seeding the hosing instability using the electron beam.
	Slides MOOYGD2 [7.040 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOOYGD2
About •	Received ※ 07 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022
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WEOZGD1	Design of an LPA-Based First-Stage Injector for a Synchrotron Light Source	1639
	X.Y. Shi, H.S. Xu IHEP, Beijing, People’s Republic of China
	Study of plasma-based acceleration has been a frontier of accelerator community for decades. The beam performance obtained from a laser-plasma based accelerator (LPA) becomes higher and higher. Nowadays, a combination of LPAs and the conventional RF accelerators is a trend. One of the interesting directions to go is to replace a LINAC by an LPA as the first-stage injector of a synchrotron light source. In this paper, we present a physical design of a 500 MeV LPA-based first-stage injector for a synchrotron light source.
	Slides WEOZGD1 [8.971 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZGD1
About •	Received ※ 15 June 2022 — Revised ※ 22 June 2022 — Accepted ※ 25 June 2022 — Issue date ※ 04 July 2022
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WEOZGD2	Status and Prospects for the Plasma-Driven Attosecond X-Ray (PAX) Experiment at FACET-II
	C. Emma, R.M. Hessami, K. Larsen, A. Marinelli, R. Robles SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02- 76SF00515. Plasma-driven light source development has recently made significant progress with the demonstration of plasma-FEL gain and the work of multiple facilities towards plasma-FEL development . In this paper, we report on the status and prospects for one-such plasma-driven light source effort, the Plasma-driven Attosecond X-ray (PAX) experiment at FACET-II * . This unique experimental thrust seeks to generate 100-attosecond long electron beams using plasma accelerators and use these beams as drivers for an attosecond X-ray source. This approach is motivated by the possibility to generate ultra-short high power attosecond X-ray pulses, as well as the order-of-magnitude increased tolerances of this method to emittance, energy spread and pointing jitter compared to a plasma-driven XFEL starting from noise. We present recent experimental developments in the process of demonstrating this concept at FACET-II and discuss potential extensions of this method to scale towards shorter wavelengths in the future. * W. Wang et al Nature 595, 516 2021; R. Pompili Proc. of EAAC 2021; C. Emma et al High Power Laser Science and Engineering, 2021, Vol. 9, e57, ** C. Emma et al APL Photonics 6, 076107 2021
	Slides WEOZGD2 [5.088 MB]
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WEPOST029	First Start-to-End Simulations of the 6 GeV Laser-Plasma Injector at DESY	1757
	S.A. Antipov, I.V. Agapov, R. Brinkmann, Á. Ferran Pousa, M.A. Jebramcik, A. Martinez de la Ossa, M. Thévenet DESY, Hamburg, Germany
	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.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST029
About •	Received ※ 02 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022
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WEPOST030	Multitask Optimization of Laser-Plasma Accelerators Using Simulation Codes with Different Fidelities	1761
	Á. Ferran Pousa, M. Kirchen, A. Martinez de la Ossa, M. Thévenet DESY, Hamburg, Germany S.T.P. Hudson, J.M. Larson ANL, Lemont, Illinois, USA A. Huebl, R. Lehé, J.-L. Vay LBNL, Berkeley, USA S. Jalas University of Hamburg, Hamburg, Germany
	When designing a laser-plasma acceleration experiment, one commonly explores the parameter space (plasma density, laser intensity, focal position, etc.) with simulations in order to find an optimal configuration that, for example, minimizes the energy spread or emittance of the accelerated beam. However, laser-plasma acceleration is typically modeled with full particle-in-cell (PIC) codes, which can be computationally expensive. Various reduced models can approximate beam behavior at a much lower computational cost. Although such models do not capture the full physics, they could still suggest promising sets of parameters to be simulated with a full PIC code and thereby speed up the overall design optimization. In this work we automate such a workflow with a Bayesian multitask algorithm, where each task has a different fidelity. This algorithm learns from past simulation results from both full PIC codes and reduced PIC codes and dynamically chooses the next parameters to be simulated. We illustrate this workflow with a proof-of-concept optimization using the Wake-T and FBPIC codes. The libEnsemble library is used to orchestrate this workflow on a modern GPU-accelerated high-performance computing system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST030
About •	Received ※ 08 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 14 June 2022
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WEPOST032	Status Report of the 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring	1768
	E. Panofski, C. Braun, J. Dirkwinkel, J.B. Gonzalez, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, P.A. Walker, P. Winkler DESY, Hamburg, Germany E. Bründermann, B. Härer, A.-S. Müller, A.I. Papash, C. Widmann KIT, Karlsruhe, Germany T.F.J. Eichner, L. Hübner, S. Jalas, L. Jeppe, M. Kirchen, P. Messner, M. Schnepp, M. Trunk, C.M. Werle University of Hamburg, Hamburg, Germany M. Kaluza, A. Sävert HIJ, Jena, Germany
	Laser-based plasma accelerators (LPA) have successfully demonstrated their capability to generate high-energy electron beams with intrinsically short bunch lengths and high peak currents at a setup with a small footprint. These properties make them attractive drivers for a broad range of different applications including injectors for rf-driven, ring-based light sources. In close collaboration the Deutsches Elektronen-Synchrotron (DESY), the Karlsruhe Institute of Technology (KIT) and the Helmholtz Institute Jena aim to develop a 50 MeV plasma injector and demonstrate the injection into a compact storage ring. This storage ring will be built within the project cSTART at KIT. As part of the ATHENA (Accelerator Technology HElmholtz iNfrAstructure) project, DESY will design, setup and operate a 50 MeV plasma injector prototype for this endeavor. This contribution gives a status update of the 50 MeV LPA-based injector and presents a first layout of the prototype design at DESY in Hamburg.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST032
About •	Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 14 June 2022
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WEPOST034	Magnetic Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FELs	1772
SUSPMF035	use link to see paper's listing under its alternate paper code
	K. Damminsek, A. Bernhard, H.J. Cha, A.W. Grau, A.-S. Müller, M.S. Ning, Y. Tong KIT, Karlsruhe, Germany S.C. Richter CERN, Meyrin, Switzerland R. Rossmanith DESY, Hamburg, Germany
	Funding: Federal Ministry of Education and Research of Germany and the Development and Promotion of Science and Technology Talents Project (DPST) A transverse gradient undulator (TGU) is a key component compensating for the relatively large energy spread of Laser Wakefield Accelerator (LWFA)-generated electron beams for realizing a compact Free Electron Laser (FEL). A superconducting TGU with 40 periods has been fabricated at the Karlsruhe Institute of Technology (KIT). In this contribution, we report that the superconducting TGU has been commissioned with nominal operational parameters at an off-line test bench. An experimental set-up for mapping the magnetic field on a two-dimensional grid in the TGU gap has been employed for the magnetic characterization. We show the first preliminary results of these measurements showing the longitudinal quality, the transverse gradient and the transient behaviour of the superconducting TGU field.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST034
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022
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WEPOST035	Spectroscopic Measurements as Diagnostic Tool for Plasma-Filled Capillaries	1776
SUSPMF102	use link to see paper's listing under its alternate paper code
	S. Arjmand, L. Crincoli, D. Pellegrini INFN/LNF, Frascati, Italy M.P. Anania, A. Biagioni, G. Costa, M. Ferrario, M. Galletti, V.L. Lollo, R. Pompili LNF-INFN, Frascati, Italy M. Del Franco ENEA C.R. Frascati, Frascati (Roma), Italy D. Giulietti UNIPI, Pisa, Italy A. Zigler The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	The research concerns the study of the plasma sources for plasma-based accelerators (PBAs) at the SPARC_LAB test-facility (LNF-INFN). The interest in compact accelerators, overcoming the gigantism of the conventional radio-frequency (RF) accelerators, is growing in High Energy Physics. The plasma-based accelerating gradients can attain the GV/m scale. At the SPARC_LAB test-facility, a plasma device is under development. It consists of a capillary in which one or more inlets inject neutral gas (Hydrogen), ionized by a high-voltage (HV) discharge. Electron density has been measured as a function of time through the Stark broadening profiles of the Balmer line.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST035
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 04 July 2022
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WEPOST039	Mapping Charge Capture and Acceleration in a Plasma Wakefield of a Proton Bunch Using Variable Emittance Electron Beam Injection	1780
	E. Granados, A.-M. Bachmann, E. Chevallay, S. Döbert, V.N. Fedosseev, F. Friebel, S.J. Gessner, E. Gschwendtner, S.Y. Kim, S. Mazzoni, M. Turner, L. Verra CERN, Meyrin, Switzerland A.-M. Bachmann, L. Verra MPI, Muenchen, Germany S.Y. Kim UNIST, Ulsan, Republic of Korea S.Y. Kim ANL, Lemont, Illinois, USA J.T. Moody MPI-P, München, Germany
	In the Phase 2 of the AWAKE first experimental run (from May to November 2018), an electron beam was used to probe and test proton-driven wakefield accelera-tion in a rubidium plasma column. The witness electron bunches were produced using an RF-gun equipped with a Cs₂Te photocathode illuminated by a tailorable ultrafast ultraviolet (UV) laser pulse. The construction of the UV beam optical system enabled appropriate transverse beam shaping and control of its pulse duration, size, and position on the photocathode, as well as time delay with respect to the ionizing laser pulse that seeds the plasma wakefields in the proton bunches. Variable photocathode illumination provided the required flexibility to produce electron bunches with variable charge, emittance, and injection trajectory into the plasma column. In this work, we analyze the overall charge capture and shot-to-shot reproducibility of the proton-driven plasma wakefield accelerator with various UV illumination and electron bunch injection parameters.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST039
About •	Received ※ 23 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022
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WEPOST041	Physical Aspects of Collinear Laser Injection at SLAC FACET-II E-310: Trojan Horse Experiment	1787
	M. Yadav, Ö. Apsimon, E. Kukstas, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C.E. Hansel, P. Manwani, B. Naranjo, J.B. Rosenzweig UCLA, Los Angeles, USA B. Hidding USTRAT/SUPA, Glasgow, United Kingdom
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, un-der Contract No. DE-SC0009914, and the STFC grant ST/P006752/1. The Facility for Advanced Accelerator Experimental Tests (FACET-II) is a test accelerator infrastructure at SLAC dedicated to the research and development of advanced accelerator technologies. We performed simulations of electron beam driven wakefields, with collinear lasers used for ionization injection of electrons. We numerically generated a witness beam using the OSIRIS code in an up ramp plasma as well as uniform plasma regimes. We report on challenges and details of the E-310 experiment which aims to demonstrate this plasma photocathode injection at FACET-II. We examine the phenomena beam hosing and drive beam depletion. Details of the witness beam generated are discussed. Computation of betatron-radiation X-ray spatial distribution and critical energy are done for FACET-II low emittance beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST041
About •	Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 23 June 2022
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WEPOST042	Radiation Diagnostics for AWA and FACET-II Flat Beams in Plasma	1791
	M. Yadav, Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom H.S. Ancelin, G. Andonian, P. Manwani, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, DE-SC0017648 - AWA and STFC grant ST/P006752/1 , In energy beam facilities like FACET and AWA, beams with highly asymmetric emittance are of interest because they are the preferred type of beam for linear colliders. That is ultimately the motivation: building a plasma based LC. In this case, the blowout region is no longer symmetric around an axis is not equal in the two transverse planes. Focusing is required to keep the particles within the tight apertures and characterizing these accelerators shows the benefits of employing ultra low beam emittances. Beams with high charge and high emittance ratios in excess of 100:1 are available at AWA. If the focusing will not be equal, then we will have different radiation signatures for the flat and symmetric beams in plasma. We use OSIRIS particle-in-cell codes to compare various scenarios including a weak blowout and a strong blowout. Further, we determine the radiation generated in the system by importing particle trajectories into a Liénard Weichert code. We discuss future steps towards full diagnostics of flat beams using radiation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST042
About •	Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 05 July 2022
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WEPOST043	An Effective-Density Model for Accelerating Fields in Laser-Graphene Interactions	1795
	C. Bonțoiu, Ö. Apsimon, E. Kukstas, C.P. Welsch, M. Yadav The University of Liverpool, Liverpool, United Kingdom A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil J. Resta-López ICMUV, Paterna, Spain G.X. Xia UMAN, Manchester, United Kingdom
	Funding: This work was supported by STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) With the advancement of high-power UV laser technology, the use of nanostructures for particle acceleration attracts renewed interest due to its possibility of achieving TV/m accelerating gradients in solid state plasmas. Electron acceleration in ionized materials such as carbon nanotubes and graphene is currently considered as a potential alternative to the usual laser wakefield acceleration (LWFA) schemes. An evaluation of the suitability of a graphene target for LWFA can be carried out using an effective density model, thus replacing the need to model each layer. We present a 2D evaluation of the longitudinal electric field driven by a short UV laser pulse in a multi-layer graphene structure, showing that longitudinal fields of ~5 TV/m are achievable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST043
About •	Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022
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WEPOST045	Simulating Enhanced Focusing Effects of Ion Motion in Adiabatic Plasmas	1798
	D.R. Chow, C.E. Hansel, P. Manwani, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, USA Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom
	Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. The FACET-II facility offers the unique opportunity to study low emittance, GeV beams and their interactions with high density plasmas in plasma wakefield acceleration (PWFA) scenarios. One of the experiments relevant to PWFA research at FACET-II is the ion collapse experiment E-314, which aims to study how ion motion in a PWFA can produce dual-focused equilibrium. As nonlinear focusing effects due to nonuniform ion distributions have not been extensively studied; we explore the difficulties of inducing ion motion in an adiabatic plasma and examines the effect an ion column has on beam focusing. A case study is performed on a system containing a plasma lens and adiabatic PWFA. Ions in the lens section are assumed to be static, while simulations of an adiabatic matching section are modified to include the effects of ion column collapse and their nonlinear focusing fields. Using the parameters of the FACET-II beam, we find that a collapsed ion column amplifies the focusing power of a plasma without compromising emittance preservation. This led to a spot size orders of magnitude less than that of a simply matched beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST045
About •	Received ※ 07 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 25 June 2022
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WEPOST046	Beam Matching in an Elliptical Plasma Blowout Driven by Highly Asymmetric Flat Beams	1802
SUSPMF037	use link to see paper's listing under its alternate paper code
	P. Manwani, H.S. Ancelin, G. Andonian, N. Majernik, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Marina del Rey, California, USA G. Ha, J.G. Power ANL, Lemont, Illinois, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom M. Yadav Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914. Particle beams with highly asymmetric emittance ratios, or flat beams, are employed at accelerator facilities such as the AWA and foreseen at FACET-II. Flat beams have been used to drive wakefields in dielectric structures and are an ideal candidate for high-gradient wakefields in plasmas. The high aspect ratio produces a blowout region that is elliptical in cross section and this asymmetry in the ion column structure creates asymmetric focusing in the two transverse planes. The ellipticity of the plasma blowout decreases as the normalized peak current increases, and gradually approaches an axisymmetric column. An appropriate matching condition for the beam envelope inside the elliptical blowout is introduced. Simulations are performed to investigate the ellipticity of the resultant wakefield based on the initial drive beam parameters, and are compared to analytical calculations. The parameter space for two cases at the AWA and FACET facilities, with requirements for plasma profile and achievable fields, is presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST046
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022
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WEPOST048	Excitation of Very High Gradient Plasma Wakefields From Nanometer Scale Beams	1806
	P. Manwani, H.S. Ancelin, G. Andonian, D.R. Chow, N. Majernik, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Marina del Rey, California, USA R. Robles SLAC, Menlo Park, California, USA M. Yadav The University of Liverpool, Liverpool, United Kingdom M. Yadav Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was performed with the support of the US Department of Energy under Contract No. DESC0009914. The plasma based terawatt attosecond project at SLAC, termed PAX, offers near mega-Ampere beams that could be used to demonstrate plasma wakefield acceleration at very high gradients (TV/m). The beam has a large aspect ratio which allows it to be used at high densities since the longitudinal beam size is lower than the plasma skin depth. This beam can be focused using a permanent magnitude quadrupole (PMQ) triplet to further reduce its transverse size. Since the beam is extremely short compared to the plasma skin depth, it behaves like a delta-function perturbation to the plasma. This reduces the expected focusing effect of the ion column and simulations show that only the tail of the beam is notably focused and decelerated. This scenario is investigated with attendant experimental considerations discussed. The creation of the witness beam by the deceleration of the tail of the beam is also discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST048
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 29 June 2022
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WEPOPT021	A Discharge Plasma Source Development Platform for Accelerators: The ADVANCE Lab at DESY	1886
	J.M. Garland, R.T.P. D’Arcy, M. Dinter, S. Karstensen, S. Kottler, G. Loisch, K. Ludwig, J. Osterhoff, A. Rahali, A. Schleiermacher, S. Wesch DESY, Hamburg, Germany
	Novel plasma-based accelerators, as well as advanced, high-gradient beam-manipulation techniques’for example passive or active plasma lenses’require reliable and well-characterized plasma sources, each optimized for their individual task. A very efficient and proven way of producing plasmas for these applications is by directly discharging an electrical current through a confined gas volume. To host the development of such discharge-based plasma sources for advanced accelerators, the ATHENA Discharge deVelopment ANd Characterization Experiment (ADVANCE) laboratory has been established at DESY. In this contribution we introduce the laboratory, give a summary of available infrastructure and diagnostics, as well as a brief overview of current and planned scientific goals.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT021
About •	Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022
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WEPOTK030	Modelling Growth and Asymmetry in Seeded Self-Modulation of Elliptical Beams in Plasma	2122
	A. Perera, Ö. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom Ö. Apsimon, A. Perera, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by STFC UK grant ST/P006752/1. The Authors are grateful for computing time provided by the STFC Scientific Computing Department’s SCARF cluster. The seeded self-modulation (SSM) of long particle bunches for the generation of gigavolts-per-meter wakefields that can accelerate witness electron beams was first shown using the Super Proton Synchrotron beam as a driver by the AWAKE experiment. The stability of the produced microbunch trains over tens or hundreds of meters is crucial for extrapolating this scheme as proposed for use in several high energy plasma-based linear colliders. However, aside from the competing hosing instability, which has been shown to be suppressible by SSM when that process saturates, few works have examined other effects of transverse asymmetry in this process. Here, we use analytical modelling and 3D particle-in-cell simulations with QuickPIC to characterise the impact on the SSM growth process due to transverse asymmetry in the beam. A metric is constructed for asymmetry in simulation results, showing that the initial azimuthal complexity changes only slightly during SSM growth. Further, we show quantitative agreement between simulations and analytical predictions for the scaling of the reduction SSM growth rate with unequal aspect ratio of the initial beam profile. These results serve to inform planning and tolerances for both AWAKE and other SSM-based novel acceleration methods in the future.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK030
About •	Received ※ 09 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 23 June 2022
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WEPOTK064	Generating Sub-Femtosecond Electron Beams at Plasma Wakefield Accelerators	2217
	R. Robles, C. Emma, R.M. Hessami, K. Larsen, A. Marinelli SLAC, Menlo Park, California, USA
	Funding: This work was supported by US Department of Energy Contracts No. DE-AC02-76SF00515 and by the DOE, Laboratory Directed Research and Development program at SLAC, under contract DE-AC02-76SF00515. The Plasma-driven Attosecond X-ray source (PAX) project at FACET-II aims to produce attosecond EUV/soft x-ray pulses with milijoule-scale pulse energy via nearly coherent emission from pre-bunched electron beams. In the baseline approach, a beam is generated using the density downramp injection scheme with a percent-per-micron chirp and 1e-4 scale slice energy spread. Subsequent compression yields a current spike of just 100 as duration which can emit 10 nm light nearly coherently due to its strong pre-bunching. In this work, we report simulation studies of a scheme to generate similarly short beams without relying on plasma injection. Instead, we utilize a high-charge beam generated at an RF photocathode, with its tail acting as the witness bunch for the wake. The witness develops a percent-per-micron chirp in the plasma which is then compressible downstream. The final bunch length demonstrated here is as short as 100 nm, and is limited primarily by emittance effects. The configurations studied in this work are available for experimental testing at existing PWFA facilities such as FACET-II. APL Photonics 6, 076107 (2021)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK064
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 16 June 2022
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WEPOMS015	Basic Relations of Laser-Plasma Interaction in the 3D Relativistic, Non-Linear Regime	2265
	D.F.G. Minenna, E. Bargel, L. Batista, P.A.P. Nghiem CEA-IRFU, Gif-sur-Yvette, France
	In the approximation where the plasma is considered as a fluid, basic relations are derived to describe the plasma wave driven by an ultra-intense laser pulse. A set of partial differential equations is obtained. It is then numerically solved to calculate the resulting 3D electric field structure that can be used as accelerating cavities for electrons. The laser strength parameter is varied to investigate regimes from weakly nonlinear up to total cavitation where all the initial electrons of the plasma are expelled.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS015
About •	Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 10 July 2022
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Paper

Title

Page

Progress Towards Demonstration of a Plasma-Based FEL

6

E. Chiadroni
LNF-INFN, Frascati, Italy

Plasma-based technology promises a revolution in the field of particle accelerators by pushing beams to gigaelectronvolt energies within centimeter distances. Several experiments are ongoing world-wide towards demonstration of a plasma based FEL enabling the realization of ultra-compact facilities for user applications like Free-Electron Lasers (FEL). The progress towards a plasma based FEL user facility is here reported, with particular focus on the recent results about the first experimental evidence of FEL lasing by a compact (3 cm) particle beam-driven plasma accelerator at the SPARC_LAB test facility. The status and prospects are discussed.

Slides MOPLXGD2 [17.683 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPLXGD2

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Received ※ 12 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 30 June 2022

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MOIYGD2

Recent Progress of Compact LAser Plasma Accelerator at Peking University

C. Lin
PKU, Beijing, People’s Republic of China

Usually large energy spread and shot-to-shot stability are the bottlenecks of laser accelerator in applications. Recently proton beam with energies less than 10 MeV, <1% energy spread, several to tens of pC charge can be stably produced and transported in Compact LAser Plasma Accelerator (CLAPA) at Peking University. The CLAPA beam line is an object-image point analysing system, which ensures the transmission efficiency and energy selection accuracy for proton beams with initial large divergence angle and energy spread. A spread-out Bragg peak (SOBP) is produced with high precision beam control, which is essential for cancer therapy. Other primary application experiments based on laser-accelerated proton beam have also been carried out, such as FLASH irradiation, Laser Ion trace probe, proton radiograph, stress testing for tungsten, irradiation of semiconductor sensor to simulate the space irradiation environment and so on.

Slides MOIYGD2 [5.369 MB]

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MOOYGD1

Experiments Towards High-Repetition Rate Plasma Wakefield Acceleration at FLASHForward

G. Loisch, J. Beinortaite, G.J. Boyle, R.T.P. D’Arcy, S. Diederichs, J.M. Garland, P. Gonzalez-Caminal, C.A. Lindstrøm, J. Osterhoff, T. Parikh, S. Schreiber, S. Schröder, M. Thévenet, S. Wesch, M. Wing
DESY, Hamburg, Germany
J. Chappell, M. Wing
UCL, London, United Kingdom
B. Foster
JAI, Oxford, United Kingdom
P. Gonzalez-Caminal
Universität Hamburg, Hamburg, Germany

Beam-driven plasma-wakefield acceleration (PWFA) is one of the most promising techniques to reduce significantly the size and cost of future lepton accelerators. Huge steps have been taken in the last decades towards achieving high acceleration gradients with simultaneous beam-quality preservation. However, in order to match both the luminosity demands of high-energy physics and the brilliance requirements of photon science, PWFA must be capable of accelerating thousands of bunches per second ’ orders of magnitude beyond the current state of the art. Historically, investigation of the rate limitation in plasmas was limited by the number of bunches available from the accelerator front-end. The FLASHForward facility, which is driven by the superconducting linac of the FLASH free-electron laser, is the first experiment capable of addressing this issue. We report here on first experimental results from the facility, aimed at determining the repetition rate limit of plasma accelerators arising from fundamental plasma processes* and finally advancing the repetition rate of PWFA from proof-of-principle experiments at a few bunches per second to a competitive plasma accelerator.
* R. D’Arcy et al., Recovery time of a plasma-wakefield accelerator, Nature (in press)

Slides MOOYGD1 [2.953 MB]

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MOOYGD2

The AWAKE Experiment in 2021: Performance and Preliminary Results on Electron-Seeding of Self-Modulation

21

E. Gschwendtner, L. Verra, G. Zevi Della Porta
CERN, Meyrin, Switzerland
P. Muggli, L. Verra
MPI, Muenchen, Germany
P. Muggli
MPI-P, München, Germany
L. Verra
TUM, Munich, Germany

The future programme of the Advanced Wakefield (AWAKE) experiment at CERN relies on the seeded self-modulation of an entire proton bunch, resulting in phase-reproducible micro-bunches. This important milestone was achieved during the 2021 proton run by injecting a short electron bunch ahead of the proton bunch, demonstrating for the first time the electron-seeding of proton bunch self-modulation. This talk describes the programme, performance and preliminary results of the AWAKE experiment in the 2021 proton run, and introduces the program of the 2022 proton run. The observation of electron-seeded self-modulation opens new avenues of exploration which will be studied in 2022, including the effect of a phase difference between the front and the back of a proton bunch and the possibility of reproducibly seeding the hosing instability using the electron beam.

Slides MOOYGD2 [7.040 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOOYGD2

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Received ※ 07 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022

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WEOZGD1

Design of an LPA-Based First-Stage Injector for a Synchrotron Light Source

1639

X.Y. Shi, H.S. Xu
IHEP, Beijing, People’s Republic of China

Study of plasma-based acceleration has been a frontier of accelerator community for decades. The beam performance obtained from a laser-plasma based accelerator (LPA) becomes higher and higher. Nowadays, a combination of LPAs and the conventional RF accelerators is a trend. One of the interesting directions to go is to replace a LINAC by an LPA as the first-stage injector of a synchrotron light source. In this paper, we present a physical design of a 500 MeV LPA-based first-stage injector for a synchrotron light source.

Slides WEOZGD1 [8.971 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEOZGD1

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Received ※ 15 June 2022 — Revised ※ 22 June 2022 — Accepted ※ 25 June 2022 — Issue date ※ 04 July 2022

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WEOZGD2

Status and Prospects for the Plasma-Driven Attosecond X-Ray (PAX) Experiment at FACET-II

C. Emma, R.M. Hessami, K. Larsen, A. Marinelli, R. Robles
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02- 76SF00515.
Plasma-driven light source development has recently made significant progress with the demonstration of plasma-FEL gain and the work of multiple facilities towards plasma-FEL development *. In this paper, we report on the status and prospects for one-such plasma-driven light source effort, the Plasma-driven Attosecond X-ray (PAX) experiment at FACET-II ** . This unique experimental thrust seeks to generate 100-attosecond long electron beams using plasma accelerators and use these beams as drivers for an attosecond X-ray source. This approach is motivated by the possibility to generate ultra-short high power attosecond X-ray pulses, as well as the order-of-magnitude increased tolerances of this method to emittance, energy spread and pointing jitter compared to a plasma-driven XFEL starting from noise. We present recent experimental developments in the process of demonstrating this concept at FACET-II and discuss potential extensions of this method to scale towards shorter wavelengths in the future.
* W. Wang et al Nature 595, 516 2021; R. Pompili Proc. of EAAC 2021; C. Emma et al High Power Laser Science and Engineering, 2021, Vol. 9, e57,
** C. Emma et al APL Photonics 6, 076107 2021

Slides WEOZGD2 [5.088 MB]

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WEPOST029

First Start-to-End Simulations of the 6 GeV Laser-Plasma Injector at DESY

1757

S.A. Antipov, I.V. Agapov, R. Brinkmann, Á. Ferran Pousa, M.A. Jebramcik, A. Martinez de la Ossa, M. Thévenet
DESY, Hamburg, Germany

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.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST029

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Received ※ 02 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 16 June 2022

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WEPOST030

Multitask Optimization of Laser-Plasma Accelerators Using Simulation Codes with Different Fidelities

1761

Á. Ferran Pousa, M. Kirchen, A. Martinez de la Ossa, M. Thévenet
DESY, Hamburg, Germany
S.T.P. Hudson, J.M. Larson
ANL, Lemont, Illinois, USA
A. Huebl, R. Lehé, J.-L. Vay
LBNL, Berkeley, USA
S. Jalas
University of Hamburg, Hamburg, Germany

When designing a laser-plasma acceleration experiment, one commonly explores the parameter space (plasma density, laser intensity, focal position, etc.) with simulations in order to find an optimal configuration that, for example, minimizes the energy spread or emittance of the accelerated beam. However, laser-plasma acceleration is typically modeled with full particle-in-cell (PIC) codes, which can be computationally expensive. Various reduced models can approximate beam behavior at a much lower computational cost. Although such models do not capture the full physics, they could still suggest promising sets of parameters to be simulated with a full PIC code and thereby speed up the overall design optimization. In this work we automate such a workflow with a Bayesian multitask algorithm, where each task has a different fidelity. This algorithm learns from past simulation results from both full PIC codes and reduced PIC codes and dynamically chooses the next parameters to be simulated. We illustrate this workflow with a proof-of-concept optimization using the Wake-T and FBPIC codes. The libEnsemble library is used to orchestrate this workflow on a modern GPU-accelerated high-performance computing system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST030

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Received ※ 08 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 14 June 2022

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WEPOST032

Status Report of the 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring

1768

E. Panofski, C. Braun, J. Dirkwinkel, J.B. Gonzalez, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, P.A. Walker, P. Winkler
DESY, Hamburg, Germany
E. Bründermann, B. Härer, A.-S. Müller, A.I. Papash, C. Widmann
KIT, Karlsruhe, Germany
T.F.J. Eichner, L. Hübner, S. Jalas, L. Jeppe, M. Kirchen, P. Messner, M. Schnepp, M. Trunk, C.M. Werle
University of Hamburg, Hamburg, Germany
M. Kaluza, A. Sävert
HIJ, Jena, Germany

Laser-based plasma accelerators (LPA) have successfully demonstrated their capability to generate high-energy electron beams with intrinsically short bunch lengths and high peak currents at a setup with a small footprint. These properties make them attractive drivers for a broad range of different applications including injectors for rf-driven, ring-based light sources. In close collaboration the Deutsches Elektronen-Synchrotron (DESY), the Karlsruhe Institute of Technology (KIT) and the Helmholtz Institute Jena aim to develop a 50 MeV plasma injector and demonstrate the injection into a compact storage ring. This storage ring will be built within the project cSTART at KIT. As part of the ATHENA (Accelerator Technology HElmholtz iNfrAstructure) project, DESY will design, setup and operate a 50 MeV plasma injector prototype for this endeavor. This contribution gives a status update of the 50 MeV LPA-based injector and presents a first layout of the prototype design at DESY in Hamburg.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST032

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Received ※ 07 June 2022 — Revised ※ 11 June 2022 — Accepted ※ 12 June 2022 — Issue date ※ 14 June 2022

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WEPOST034

Magnetic Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FELs

1772

SUSPMF035

use link to see paper's listing under its alternate paper code

K. Damminsek, A. Bernhard, H.J. Cha, A.W. Grau, A.-S. Müller, M.S. Ning, Y. Tong
KIT, Karlsruhe, Germany
S.C. Richter
CERN, Meyrin, Switzerland
R. Rossmanith
DESY, Hamburg, Germany

Funding: Federal Ministry of Education and Research of Germany and the Development and Promotion of Science and Technology Talents Project (DPST)
A transverse gradient undulator (TGU) is a key component compensating for the relatively large energy spread of Laser Wakefield Accelerator (LWFA)-generated electron beams for realizing a compact Free Electron Laser (FEL). A superconducting TGU with 40 periods has been fabricated at the Karlsruhe Institute of Technology (KIT). In this contribution, we report that the superconducting TGU has been commissioned with nominal operational parameters at an off-line test bench. An experimental set-up for mapping the magnetic field on a two-dimensional grid in the TGU gap has been employed for the magnetic characterization. We show the first preliminary results of these measurements showing the longitudinal quality, the transverse gradient and the transient behaviour of the superconducting TGU field.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST034

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022

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WEPOST035

Spectroscopic Measurements as Diagnostic Tool for Plasma-Filled Capillaries

1776

SUSPMF102

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S. Arjmand, L. Crincoli, D. Pellegrini
INFN/LNF, Frascati, Italy
M.P. Anania, A. Biagioni, G. Costa, M. Ferrario, M. Galletti, V.L. Lollo, R. Pompili
LNF-INFN, Frascati, Italy
M. Del Franco
ENEA C.R. Frascati, Frascati (Roma), Italy
D. Giulietti
UNIPI, Pisa, Italy
A. Zigler
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

The research concerns the study of the plasma sources for plasma-based accelerators (PBAs) at the SPARC_LAB test-facility (LNF-INFN). The interest in compact accelerators, overcoming the gigantism of the conventional radio-frequency (RF) accelerators, is growing in High Energy Physics. The plasma-based accelerating gradients can attain the GV/m scale. At the SPARC_LAB test-facility, a plasma device is under development. It consists of a capillary in which one or more inlets inject neutral gas (Hydrogen), ionized by a high-voltage (HV) discharge. Electron density has been measured as a function of time through the Stark broadening profiles of the Balmer line.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST035

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 04 July 2022

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WEPOST039

Mapping Charge Capture and Acceleration in a Plasma Wakefield of a Proton Bunch Using Variable Emittance Electron Beam Injection

1780

E. Granados, A.-M. Bachmann, E. Chevallay, S. Döbert, V.N. Fedosseev, F. Friebel, S.J. Gessner, E. Gschwendtner, S.Y. Kim, S. Mazzoni, M. Turner, L. Verra
CERN, Meyrin, Switzerland
A.-M. Bachmann, L. Verra
MPI, Muenchen, Germany
S.Y. Kim
UNIST, Ulsan, Republic of Korea
S.Y. Kim
ANL, Lemont, Illinois, USA
J.T. Moody
MPI-P, München, Germany

In the Phase 2 of the AWAKE first experimental run (from May to November 2018), an electron beam was used to probe and test proton-driven wakefield accelera-tion in a rubidium plasma column. The witness electron bunches were produced using an RF-gun equipped with a Cs₂Te photocathode illuminated by a tailorable ultrafast ultraviolet (UV) laser pulse. The construction of the UV beam optical system enabled appropriate transverse beam shaping and control of its pulse duration, size, and position on the photocathode, as well as time delay with respect to the ionizing laser pulse that seeds the plasma wakefields in the proton bunches. Variable photocathode illumination provided the required flexibility to produce electron bunches with variable charge, emittance, and injection trajectory into the plasma column. In this work, we analyze the overall charge capture and shot-to-shot reproducibility of the proton-driven plasma wakefield accelerator with various UV illumination and electron bunch injection parameters.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST039

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Received ※ 23 May 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022

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WEPOST041

Physical Aspects of Collinear Laser Injection at SLAC FACET-II E-310: Trojan Horse Experiment

1787

M. Yadav, Ö. Apsimon, E. Kukstas, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.E. Hansel, P. Manwani, B. Naranjo, J.B. Rosenzweig
UCLA, Los Angeles, USA
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, un-der Contract No. DE-SC0009914, and the STFC grant ST/P006752/1.
The Facility for Advanced Accelerator Experimental Tests (FACET-II) is a test accelerator infrastructure at SLAC dedicated to the research and development of advanced accelerator technologies. We performed simulations of electron beam driven wakefields, with collinear lasers used for ionization injection of electrons. We numerically generated a witness beam using the OSIRIS code in an up ramp plasma as well as uniform plasma regimes. We report on challenges and details of the E-310 experiment which aims to demonstrate this plasma photocathode injection at FACET-II. We examine the phenomena beam hosing and drive beam depletion. Details of the witness beam generated are discussed. Computation of betatron-radiation X-ray spatial distribution and critical energy are done for FACET-II low emittance beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST041

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Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 23 June 2022

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WEPOST042

Radiation Diagnostics for AWA and FACET-II Flat Beams in Plasma

1791

M. Yadav, Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
H.S. Ancelin, G. Andonian, P. Manwani, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, DE-SC0017648 - AWA and STFC grant ST/P006752/1 ,
In energy beam facilities like FACET and AWA, beams with highly asymmetric emittance are of interest because they are the preferred type of beam for linear colliders. That is ultimately the motivation: building a plasma based LC. In this case, the blowout region is no longer symmetric around an axis is not equal in the two transverse planes. Focusing is required to keep the particles within the tight apertures and characterizing these accelerators shows the benefits of employing ultra low beam emittances. Beams with high charge and high emittance ratios in excess of 100:1 are available at AWA. If the focusing will not be equal, then we will have different radiation signatures for the flat and symmetric beams in plasma. We use OSIRIS particle-in-cell codes to compare various scenarios including a weak blowout and a strong blowout. Further, we determine the radiation generated in the system by importing particle trajectories into a Liénard Weichert code. We discuss future steps towards full diagnostics of flat beams using radiation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST042

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Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 05 July 2022

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WEPOST043

An Effective-Density Model for Accelerating Fields in Laser-Graphene Interactions

1795

C. Bonțoiu, Ö. Apsimon, E. Kukstas, C.P. Welsch, M. Yadav
The University of Liverpool, Liverpool, United Kingdom
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
J. Resta-López
ICMUV, Paterna, Spain
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: This work was supported by STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT)
With the advancement of high-power UV laser technology, the use of nanostructures for particle acceleration attracts renewed interest due to its possibility of achieving TV/m accelerating gradients in solid state plasmas. Electron acceleration in ionized materials such as carbon nanotubes and graphene is currently considered as a potential alternative to the usual laser wakefield acceleration (LWFA) schemes. An evaluation of the suitability of a graphene target for LWFA can be carried out using an effective density model, thus replacing the need to model each layer. We present a 2D evaluation of the longitudinal electric field driven by a short UV laser pulse in a multi-layer graphene structure, showing that longitudinal fields of ~5 TV/m are achievable.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST043

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Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 20 June 2022

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WEPOST045

Simulating Enhanced Focusing Effects of Ion Motion in Adiabatic Plasmas

1798

D.R. Chow, C.E. Hansel, P. Manwani, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, USA
Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1.
The FACET-II facility offers the unique opportunity to study low emittance, GeV beams and their interactions with high density plasmas in plasma wakefield acceleration (PWFA) scenarios. One of the experiments relevant to PWFA research at FACET-II is the ion collapse experiment E-314, which aims to study how ion motion in a PWFA can produce dual-focused equilibrium. As nonlinear focusing effects due to nonuniform ion distributions have not been extensively studied; we explore the difficulties of inducing ion motion in an adiabatic plasma and examines the effect an ion column has on beam focusing. A case study is performed on a system containing a plasma lens and adiabatic PWFA. Ions in the lens section are assumed to be static, while simulations of an adiabatic matching section are modified to include the effects of ion column collapse and their nonlinear focusing fields. Using the parameters of the FACET-II beam, we find that a collapsed ion column amplifies the focusing power of a plasma without compromising emittance preservation. This led to a spot size orders of magnitude less than that of a simply matched beam.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST045

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Received ※ 07 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 23 June 2022 — Issue date ※ 25 June 2022

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WEPOST046

Beam Matching in an Elliptical Plasma Blowout Driven by Highly Asymmetric Flat Beams

1802

SUSPMF037

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P. Manwani, H.S. Ancelin, G. Andonian, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Marina del Rey, California, USA
G. Ha, J.G. Power
ANL, Lemont, Illinois, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914.
Particle beams with highly asymmetric emittance ratios, or flat beams, are employed at accelerator facilities such as the AWA and foreseen at FACET-II. Flat beams have been used to drive wakefields in dielectric structures and are an ideal candidate for high-gradient wakefields in plasmas. The high aspect ratio produces a blowout region that is elliptical in cross section and this asymmetry in the ion column structure creates asymmetric focusing in the two transverse planes. The ellipticity of the plasma blowout decreases as the normalized peak current increases, and gradually approaches an axisymmetric column. An appropriate matching condition for the beam envelope inside the elliptical blowout is introduced. Simulations are performed to investigate the ellipticity of the resultant wakefield based on the initial drive beam parameters, and are compared to analytical calculations. The parameter space for two cases at the AWA and FACET facilities, with requirements for plasma profile and achievable fields, is presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST046

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022

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WEPOST048

Excitation of Very High Gradient Plasma Wakefields From Nanometer Scale Beams

1806

P. Manwani, H.S. Ancelin, G. Andonian, D.R. Chow, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Marina del Rey, California, USA
R. Robles
SLAC, Menlo Park, California, USA
M. Yadav
The University of Liverpool, Liverpool, United Kingdom
M. Yadav
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was performed with the support of the US Department of Energy under Contract No. DESC0009914.
The plasma based terawatt attosecond project at SLAC, termed PAX, offers near mega-Ampere beams that could be used to demonstrate plasma wakefield acceleration at very high gradients (TV/m). The beam has a large aspect ratio which allows it to be used at high densities since the longitudinal beam size is lower than the plasma skin depth. This beam can be focused using a permanent magnitude quadrupole (PMQ) triplet to further reduce its transverse size. Since the beam is extremely short compared to the plasma skin depth, it behaves like a delta-function perturbation to the plasma. This reduces the expected focusing effect of the ion column and simulations show that only the tail of the beam is notably focused and decelerated. This scenario is investigated with attendant experimental considerations discussed. The creation of the witness beam by the deceleration of the tail of the beam is also discussed.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST048

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Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 29 June 2022

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WEPOPT021

A Discharge Plasma Source Development Platform for Accelerators: The ADVANCE Lab at DESY

1886

J.M. Garland, R.T.P. D’Arcy, M. Dinter, S. Karstensen, S. Kottler, G. Loisch, K. Ludwig, J. Osterhoff, A. Rahali, A. Schleiermacher, S. Wesch
DESY, Hamburg, Germany

Novel plasma-based accelerators, as well as advanced, high-gradient beam-manipulation techniques’for example passive or active plasma lenses’require reliable and well-characterized plasma sources, each optimized for their individual task. A very efficient and proven way of producing plasmas for these applications is by directly discharging an electrical current through a confined gas volume. To host the development of such discharge-based plasma sources for advanced accelerators, the ATHENA Discharge deVelopment ANd Characterization Experiment (ADVANCE) laboratory has been established at DESY. In this contribution we introduce the laboratory, give a summary of available infrastructure and diagnostics, as well as a brief overview of current and planned scientific goals.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT021

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Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 09 July 2022

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WEPOTK030

Modelling Growth and Asymmetry in Seeded Self-Modulation of Elliptical Beams in Plasma

2122

A. Perera, Ö. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
Ö. Apsimon, A. Perera, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by STFC UK grant ST/P006752/1. The Authors are grateful for computing time provided by the STFC Scientific Computing Department’s SCARF cluster.
The seeded self-modulation (SSM) of long particle bunches for the generation of gigavolts-per-meter wakefields that can accelerate witness electron beams was first shown using the Super Proton Synchrotron beam as a driver by the AWAKE experiment. The stability of the produced microbunch trains over tens or hundreds of meters is crucial for extrapolating this scheme as proposed for use in several high energy plasma-based linear colliders. However, aside from the competing hosing instability, which has been shown to be suppressible by SSM when that process saturates, few works have examined other effects of transverse asymmetry in this process. Here, we use analytical modelling and 3D particle-in-cell simulations with QuickPIC to characterise the impact on the SSM growth process due to transverse asymmetry in the beam. A metric is constructed for asymmetry in simulation results, showing that the initial azimuthal complexity changes only slightly during SSM growth. Further, we show quantitative agreement between simulations and analytical predictions for the scaling of the reduction SSM growth rate with unequal aspect ratio of the initial beam profile. These results serve to inform planning and tolerances for both AWAKE and other SSM-based novel acceleration methods in the future.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK030

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Received ※ 09 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 23 June 2022

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WEPOTK064

Generating Sub-Femtosecond Electron Beams at Plasma Wakefield Accelerators

2217

R. Robles, C. Emma, R.M. Hessami, K. Larsen, A. Marinelli
SLAC, Menlo Park, California, USA

Funding: This work was supported by US Department of Energy Contracts No. DE-AC02-76SF00515 and by the DOE, Laboratory Directed Research and Development program at SLAC, under contract DE-AC02-76SF00515.
The Plasma-driven Attosecond X-ray source (PAX) project at FACET-II aims to produce attosecond EUV/soft x-ray pulses with milijoule-scale pulse energy via nearly coherent emission from pre-bunched electron beams. In the baseline approach*, a beam is generated using the density downramp injection scheme with a percent-per-micron chirp and 1e-4 scale slice energy spread. Subsequent compression yields a current spike of just 100 as duration which can emit 10 nm light nearly coherently due to its strong pre-bunching. In this work, we report simulation studies of a scheme to generate similarly short beams without relying on plasma injection. Instead, we utilize a high-charge beam generated at an RF photocathode, with its tail acting as the witness bunch for the wake. The witness develops a percent-per-micron chirp in the plasma which is then compressible downstream. The final bunch length demonstrated here is as short as 100 nm, and is limited primarily by emittance effects. The configurations studied in this work are available for experimental testing at existing PWFA facilities such as FACET-II.
*APL Photonics 6, 076107 (2021)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK064

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Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 16 June 2022

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WEPOMS015

Basic Relations of Laser-Plasma Interaction in the 3D Relativistic, Non-Linear Regime

2265

D.F.G. Minenna, E. Bargel, L. Batista, P.A.P. Nghiem
CEA-IRFU, Gif-sur-Yvette, France

In the approximation where the plasma is considered as a fluid, basic relations are derived to describe the plasma wave driven by an ultra-intense laser pulse. A set of partial differential equations is obtained. It is then numerically solved to calculate the resulting 3D electric field structure that can be used as accelerating cavities for electrons. The laser strength parameter is varied to investigate regimes from weakly nonlinear up to total cavitation where all the initial electrons of the plasma are expelled.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS015

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Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 10 July 2022

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