IPAC2021 - Classification: MC3: Novel Particle Sources and Acceleration Techniques / A22 Plasma Wakefield Acceleration

Paper	Title	Page
MOPAB148	Liénard-Wiechert Numerical Radiation Modeling for Plasma Acceleration Experiments at FACET-II	517
	M. Yadav, G. Andonian, C.E. Hansel, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, O. Williams, Y. Zhuang UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Marina del Rey, California, USA O. Apsimon, A. Perera, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, A. Perera, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by DE-SC0009914 (UCLA) and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. Future plasma acceleration experiments at FACET-II will measure betatron radiation in order to provide single-shot non-destructive beam diagnostics. We discuss three models for betatron radiation: a new idealized particle tracking code with Liénard-Wiechert radiation, a Quasi-Static Particle-in-Cell (PIC) code with Liénard-Wiechert radiation, and a full PIC code with radiation computed via a Monte-Carlo QED Method. Predictions of the three models for the E-310 experiment are presented and compared. Finally, we discuss beam parameter reconstruction from the double differential radiation spectrum.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB148
About •	paper received ※ 24 May 2021 paper accepted ※ 01 June 2021 issue date ※ 17 August 2021
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MOPAB149	Ion Motion in Flat Beam Plasma Accelerators	521
	M. Yadav, C.E. Hansel, J.B. Rosenzweig UCLA, Los Angeles, California, USA O. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work was supported by UCLA and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. This work is done on SCARF Cluster. Intense beams, such as those in proposed plasma based linear colliders, can not only blow out electrons to form a bubble but can also attract ions towards the beam. This violates the assumption that the ions are stationary on the timescale of the beam, which is a common assumption for shorter and less intense beams. While some research has been done on understanding the physics of ion motion in blowout Plasma Wakefield Accelerators (PWFAs), this research has almost exclusively focused on cylindrically symmetric beams, rather than flat asymmetric emittance beams which are often used in linear colliders in order to minimize beamstrahlung at the final focus. This contribution investigates both analytically and computationally ion motion of a flat beam scenario in order to understand the basic physics as well as how to mitigate emittance growth, beam hosing and quadrupole.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB149
About •	paper received ※ 24 May 2021 paper accepted ※ 17 June 2021 issue date ※ 11 August 2021
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MOPAB166	Wakefield Excitation by a Sequence of Laser Pulses in Plasma	568
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). PIC simulation by means of 2.5D UMKA code * of the wakefield excitation by a sequence of three Gaussian laser pulses in plasma was carried out. The dependence of excited wakefield intensity on power and width of laser pulses was investigated. It was shown the coherent addition of wakefield, excited by each laser pulse of the sequence, for linear case, while for the nonlinear case the coherency was destroyed. The profiled sequence of laser pulses was also considered. The possibility to obtain the same total wakefield excited by the profiled sequence of laser pulses with decreasing intensity, as for the uniform sequence was studied. * G. I. Dudnikova et al. Comp. Techn. 10 (2005) 37.
	Poster MOPAB166 [2.638 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB166
About •	paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 15 August 2021
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MOPAB167	Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse	571
	D.S. Bondar KhNU, Kharkov, Ukraine V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: The study is supported by the National Research Foundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299). Recently the proposal to use X-ray Exawatt pulse for particle acceleration in a crystal has been declared . Short X-ray high-power pulse excites wakefield in electron plasma of metallic density which can be used for high gradient acceleration of charged particles. This wakefield is suited for laser wakefield acceleration. In this paper there are simulated with PIC code UMKA: excitation of the large wakefield amplitude up to several TV/m in electron plasma of metallic density by a powerful X-ray laser pulse; laser-plasma wakefield acceleration of self-injected electron bunch in such setup; combined acceleration by plasma wakefield driven by a laser pulse (LPWA) and by self-injected electron bunch (PWFA). T.Tajima. Eur. Phys. J. Special Topics 223 (2014) 1037.
	Poster MOPAB167 [2.054 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB167
About •	paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 22 August 2021
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TUXB02	Precision Control of Plasma Wakefields for Highly Efficient and Energy-Spread-Preserving Electron Acceleration
	S. Schröder, S. Bohlen, L.A. Boulton, R.T.P. D’Arcy, S. Diederichs, J.M. Garland, P. Gonzalez-Caminal, A. Knetsch, C.A. Lindstrøm, G. Loisch, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper, B. Schmidt, B. Sheeran, G.E. Tauscher, S. Wesch, J.C. Wood, J. Zemella DESY, Hamburg, Germany L.A. Boulton USTRAT/SUPA, Glasgow, United Kingdom J. Chappell UCL, London, United Kingdom
	Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. These applications require an energy-efficient acceleration process with a well-controlled energy spectrum, both of which can be achieved simultaneously by tailoring the plasma wakefield. A prerequisite for such control of the wakefield is its precise measurement. Here we discuss a new measurement technique that enables femtosecond-level sampling of the longitudinal electric fields and that is particularly powerful due to its operational simplicity. Using this method, we experimentally demonstrated optimal beam loading in a nonlinear electron-driven plasma accelerator by wakefield flattening at the few-percent level. Bunches were accelerated at a gradient of 1.3 GV/m and with an energy-transfer efficiency of (42±4)% while preserving per-mille energy spreads with full charge coupling. These results open the door to the high-quality operation of future plasma accelerators through precise control of the acceleration process. S. Schröder, et al. Nat Commun 11, 5984 (2020) ** C.A. Lindstrøm, et al. Phys. Rev. Lett. 126, 014801 (2021)
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TUXB06	High Transformer Ratio Plasma Wakefield Acceleration and Current Profile Reconstruction Using Emittance Exchange
	R.J. Roussel Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA G. Andonian, A. Deng, C.E. Hansel, G.E. Lawler, W.J. Lynn, R. Robles, J.B. Rosenzweig, K. Sanwalka UCLA, Los Angeles, California, USA S. Baturin Northern Illinois University, DeKalb, Illinois, USA M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J. Seok, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA
	Funding: This work is supported by the Department of Energy, Office of High Energy Physics, under Contract No. DESC0017648. To overcome limits on total acceleration achievable in plasma wakefield accelerators, specially shaped drive beams can be used to increase the transformer ratio, implying that the drive beam deceleration is minimized in comparison with acceleration obtained in the wake. We report the results of a nonlinear PWFA, high transformer ratio experiment using high-charge, longitudinally asymmetric drive beams in a plasma cell. An emittance exchange process is used to generate variable drive current profiles, in conjunction with a long (multiple plasma wavelength) witness beam. The witness beam is energy-modulated by the wakefield, yielding a response that contains detailed spectral information in a single-shot measurement. Using these methods, we generate a variety of beam profiles and characterize the wakefields, directly observing beam-loaded transformer ratios up to 7.8. Further, a spectrally-based current reconstruction technique, validated by 3D particle-in-cell simulations, is introduced to obtain the drive beam profile from the decelerating wakefield data.
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TUPAB138	Determination of the Phase of Wakefield Driven by a Self-Modulated Proton Bunch in Plasma	1710
	K. Moon, M. Chung UNIST, Ulsan, Republic of Korea P. Muggli MPI-P, München, Germany
	Funding: This work was partly supported by the National Research Foundation of Korea (Nos. NRF-2016R1A5A1013277 and NRF-2020R1A2C1010835) The phase of wakefield driven by a self-modulated proton bunch depends on the type of seeding method and by the beam-plasma parameters.* Particularly when a preceding electron bunch generates seed wakefield, the proton bunch modulation is strongly affected by the seed bunch dynamics along with the plasma. Intrinsic wakefield dephasing from self-modulation of proton bunch can lead to complex evolution of the bunch and wakefield, making it difficult to design an experimental setup for witness beam injection. Using the particle-in-cell code FBPIC,** we investigate in detail the trends of seed electron and driver proton bunch parameter sensitivity to the phase of wakefield in time in the proton bunch frame. We focus on the parameters affecting the phase of the wakefield through the beam’s radial dynamics, such as beam emittance, radial size, energy, and beam to plasma density ratio. Parameter variations are compared to those in the case of the phase of wakefield driven by a non-evolving seed bunch. F. Batsch, arXiv:2012.09676 [physics.plasm-ph] *R. Lehe, M. Kirchen, I.A. Andriyash, B.B. Godfrey, and J.-L. Vay, Comput. Phys. Comm. 203, 66-82 (2016)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB138
About •	paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021
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TUPAB141	On the Development of a Low Peak-Power, High Repetition-Rate Laser Plasma Accelerator at IPEN	1713
	A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.P. Nunes UFRGS, Porto Alegre, Brazil R.E. Samad, F.B.D. Tabacow, N.D. Vieira, A.V.F. Zuffi IPEN-CNEN/SP, São Paulo, Brazil
	Funding: FAPESP (Grant #2018/25961), CNPq and CAPES. In this work, the current status on the development of a laser plasma accelerator at the Nuclear and Energy Research Institute (Instituto de Pesquisas Nucleares e Energéticas, IPEN/CNEN), in São Paulo, Brazil, is presented. Short pulses to be produced by an under-development near-TW, kHz laser system will be used to ionize a gas jet, with a density profile designed to optimize the self-injection of plasma electrons. The same laser pulse will also drive a plasma wakefield, which will allow for electron acceleration in the self-modulated regime. The current milestone is to develop the experimental setup, including electron beam and plasma diagnostics, required to produce electron bunches with energies of a few MeV. Once this has been achieved, the next milestone is to produce beams with energies higher than 50 MeV. Besides kickstarting the laser wakefield accelerator (LWFA) technology in Brazil, this project aims to pave the way for conducting research on the production of radioisotopes by photonuclear reactions, triggered by LWFA-accelerated beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB141
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 10 August 2021
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TUPAB142	Simulation Study of Laser Wakefield Acceleration Varying the Down-Ramp Length of a Gas Jet	1717
	R.P. Nunes UFRGS, Porto Alegre, Brazil A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.E. Samad, N.D. Vieira IPEN-CNEN/SP, São Paulo, Brazil
	In this work, particle-in-cell simulations were carried out to investigate the role of the down-ramp length of a H\textsubscript{2} gas jet in accelerating electrons ionized by the laser pulse. The laser and plasma density were chosen so that the system is operating in the self-modulated regime. Preliminary results show how the down-ramp length can control the injection of electrons in the first bubble induced in the plasma by the laser pulse.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB142
About •	paper received ※ 20 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021
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TUPAB143	Laser Pulse Dynamics in the Self-Modulated Regime	1721
	R.P. Nunes UFRGS, Porto Alegre, Brazil A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil E.P. Maldonado ITA, São José dos Campos, Brazil R.E. Samad, N.D. Vieira IPEN-CNEN/SP, São Paulo, Brazil
	In this work, particle-in-cell simulations were carried out to investigate the dynamics of a laser pulse propagating along a H₂ gas jet. The laser-driven wakefield and the density of ionized electrons are analyzed during the pulse propagation through the gas jet. The laser and plasma quantities were chosen in order to have the system operating in the self-modulated regime. Results show how the self-modulation fragments the laser pulse, originating higher-amplitude pulses that can induce bubble formation with wave-breaking and particle injection.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB143
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021
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TUPAB145	Methods for Numerical Noise Mitigation in Quasistatic Three-Dimensional Particle-in-Cell Code LCODE3D	1725
	I.Yu. Kargapolov, K.V. Lotov, A. Sosedkin Budker INP & NSU, Novosibirsk, Russia I.A. Shalimova ICM&MG SB RAS, Novosibirsk, Russia I.A. Shalimova, P.V. Tuev NSU, Novosibirsk, Russia P.V. Tuev BINP SB RAS, Novosibirsk, Russia
	We discuss a new quasistatic 3D particle-in-cell code LCODE3D for simulating plasma wakefield acceleration, which is a modified version of the quasistatic 2D3V code LCODE, focus on the numerical noise of the plasma solver and propose methods for reducing it. We compare different particle shape functions, as these functions affect the code stability. We also introduce the so-called dual plasma approach, which improves stability and dampens small-scale noise. After applying the proposed methods, the results of the new code closely agree with LCODE simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB145
About •	paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 25 August 2021
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TUPAB146	High Brightness Electron Beams from Dragon Tail Injection and the E-312 Experiment at FACET-II	1728
	P. Manwani, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA D.L. Bruhwiler RadiaSoft LLC, Boulder, Colorado, USA B. Hidding USTRAT/SUPA, Glasgow, United Kingdom M.D. Litos Colorado University at Boulder, Boulder, Colorado, USA
	Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0009914 The advent of optically triggered injection in multi component plasma wakefield accelerators has been shown to enable a substantial increase in witness electron beam quality. Here we present a novel way of using the overlap of laser and beam radial fields to locally liberate electrons from the tunneling ionization of the non-ionized gas species. These liberated ultracold electrons gain sufficient energy to be trapped in the accelerating phase at the back of the plasma blowout. This method of controlled injection has advantages in precision timing since injection is locked to peak beam current and has the potential of generating beams with very low emittance and energy spread. This method has been investigated using particle-in-cell (PIC) simulations. This scenario corresponds to a planned experiment, E-312, at SLAC’s FACET-II facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB146
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021
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TUPAB147	Asymmetric Beam Driven Plasma Wakefields at the AWA	1732
	P. Manwani, H.S. Ancelin, G. Andonian, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Santa Monica, 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, Division of High Energy Physics under Contract No. DE-SC0017648 and DE-SC0009914 In future plasma wakefield acceleration-based scenarios for linear colliders, beams with highly asymmetric emittance are expected. In this case, the blowout region is no longer axisymmetric, but elliptical in cross-section, which implies that the focusing is not equal in the two transverse planes. In this paper, we analyze simulations for studying the asymmetries in flat-beam driven plasma acceleration using the round-to-flat-beam transformer at the Argonne Wakefield Accelerator. Beams with high charge and emittance ratios, in excess of 100:1, are routinely available at the AWA. We use particle-in-cell codes to compare various scenarios including a weak blowout, where the plasma focusing effect exhibits higher order mode asymmetry. Further, practical considerations for tunable plasma density using capillary discharge and laser ionization are compared for implementation into experimental designs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB147
About •	paper received ※ 20 May 2021 paper accepted ※ 13 July 2021 issue date ※ 02 September 2021
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TUPAB148	Optical-Period Bunch Trains to Resonantly Excite High Gradient Wakefields in the Quasi-Nonlinear Regime and the E-317 Experiment at FACET-II	1736
	P. Manwani, C.E. Hansel, N. Majernik, J.B. Rosenzweig, M. Yadav UCLA, Los Angeles, 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. DE-SC0009914 and National Science Foundation under Grant No. PHY-1549132 Periodic electron bunch trains spaced at the laser wavelength created via inverse free electron laser (IFEL) bunching can be used to resonantly excite plasmas in the quasi-nonlinear (QNL) regime. The excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. The resulting plasma density perturbation is extremely nonlinear locally, but preserves the resonant response of the plasma electrons at the plasma frequency. This excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. To match the resonance condition, the plasma wavelength has to be equal to the laser period of a few microns. This corresponds to a high density plasma resulting in extremely large wakefield amplitudes. Matching the beam into such a dense plasma requires an extremely short focusing beta function. We present the beam-plasma interaction using quasi-static particle-in-cell (PIC) simulations and discuss the micro-bunching and focusing mechanism required for this scheme which would be a precursor to the planned experiment, E-317, at SLAC’s FACET-II facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB148
About •	paper received ※ 20 May 2021 paper accepted ※ 08 July 2021 issue date ※ 19 August 2021
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TUPAB153	Modeling of Capillary Discharge Plasmas for Wakefield Accelerators and Beam Transport	1740
	N.M. Cook, J.A. Carlsson, S.J. Coleman, A. Diaw, J.P. Edelen RadiaSoft LLC, Boulder, Colorado, USA E.C. Hansen, P. Tzeferacos Flash Center for Computational Science, Chicago, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0018719. Next generation accelerators demand sophisticated beam sources to reach ultra-low emittances at large accelerating gradients, along with improved optics to transport these beams without degradation. Capillary discharge plasmas can address each of these challenges. As sources, capillaries have been shown to increase the energy and quality of wakefield accelerators, and as active plasma lenses they provide orders-of-magnitude increases in peak magnetic field. Capillaries are sensitive to energy deposition, heat transfer, ionization dynamics, and magnetic field penetration; therefore, capillary design requires careful modeling. We present simulations of capillary discharge plasmas using FLASH, a publicly-available multi-physics code developed at the University of Chicago. We report on the implementation of 2D and 3D models of capillary plasma density and temperature evolution with realistic boundary and discharge conditions. We then demonstrate laser energy deposition to model channel formation for guiding intense laser pulses. Lastly, we examine active capillary plasmas with varying fill species and compare our simulations against experimental studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB153
About •	paper received ※ 24 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021
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TUPAB155	Obtaining Accelerated Electron Bunch of High Quality in Plasma Wakefield Accelerator	1744
	R.T. Ovsiannikov KhNU, Kharkov, Ukraine I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299." Earlier, high-gradient accelerating electrons of a relativistic beam was demonstrated. However, due to dynamic processes in the plasma, there are problems in maintaining the small size and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating wakefields. Also, the question arises about the values of the limiting bunch dimensions at which the accelerating process is stable. To form a stable accelerated electron bunch, a method is usually used that involves the formation of the same accelerating fields at the location of the bunch. The same fields (plateau due to beam loading (see , )) in the region of the accelerated bunch allow all its parts to move as a whole, and ensure the preservation of the spatial distribution of electrons over time, which, in fact, means an accelerated beam of good quality. In this report, the problem of electron bunch accelerating by a short or long electron driver-bunch is considered. Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301. ** Maslov V.I. et al. Problems of Atomic Science and Technology. 6 (2020) 47.
	Poster TUPAB155 [1.723 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB155
About •	paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 23 August 2021
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TUPAB156	Optimal Field Shape, Accelerating Positron Bunch in Plasma Wakefield	1747
	R.T. Ovsiannikov KhNU, Kharkov, Ukraine I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299. The quality of the electron or positron beam, accelerated in plasma accelerators, is still insufficient for applications. Accurate control over the properties of the electron or positron beam is a key issue for wakefield plasma accelerators. The effect of the presence of a witness-beam (the effect of the spatial charge distribution of the witness beam) (see [, ]) to compensate the energy spread of the positron beam in plasma wakefield accelerators has been studied. This paper presents the results of a numerical simulation on the optimization of the parameters of the driver-bunch and witness-bunch for the formation of a self-consistent longitudinal distribution of the accelerating plateau-type field, which leads to the same values of the wakefield for the whole bunch of accelerated particles and minimizing bunch degradation during acceleration by means of an ion-driver-bunch with external injection into the plasma wake accelerator. The dependence of the longitudinal distribution of the accelerating wakefield on the density and shape of the accelerated bunch in the blowout regime was investigated. Plateau formation and energy spread compensation were observed. Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301. ** Katsouleas T. et al. Particle Accelerators. 22 (1987) 81.
	Poster TUPAB156 [1.200 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB156
About •	paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 25 August 2021
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TUPAB157	Obtaining Long Accelerated Electron Bunch of Good Quality in Plasma Wakefield Accelerator at High Transformer Ratio	1750
	R.T. Ovsiannikov KhNU, Kharkov, Ukraine I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko NSC/KIPT, Kharkov, Ukraine
	Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299." The efficiency of electron acceleration by a wakefield, excited in a plasma by an electron bunch, is determined by the transformer ratio (see , ). The transformer ratio is the ratio of energy acquired by the witness to energy lost by the driver. The transformer ratio can be increased by shaping driver-bunch. In this work, using a non-linear version of the 2d3v code lcode (see *), numerical simulation of excitation of a wakefield in a plasma in blowout regime by a shaped relativistic electron bunch was performed. There is also the problem of maintaining the small dimension and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating gradient and the transformer ratio. Also, the question arises about the values of the limiting dimension of the witness-bunch at which the acceleration process is stable. Numerical simulation solves the problem of electron bunch acceleration of the best quality with simultaneous maximization of the transformer ratio and maximization of the witness bunch length, at which the accelerating gradient and the focusing force are constant. Maslov V.I. et al. Problems of Atomic Science and Technology. 4 (2012) 128. Baturin S.S., Zholents A. Phys. Rev. ST Accel. Beams. 20 (2017) 061302. *Lotov K.V. Phys. Plasmas. 5 (1998) 785.
	Poster TUPAB157 [1.920 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB157
About •	paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021
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TUPAB158	Electron Witness Constraints for AWAKE	1753
	J.P. Farmer, P. Muggli MPI-P, München, Germany E. Gschwendtner CERN, Meyrin, Switzerland L. Liang The University of Manchester, Manchester, United Kingdom M.S. Weidl MPI/IPP, Garching, Germany
	The AWAKE project at CERN successfully demonstrated the use of a proton driver to accelerate an electron witness in plasma. One of the key goals for AWAKE Run2 is to better control this acceleration, separating the proton-beam-modulation and electron-acceleration stages in order to achieve high energy electrons with high beam quality. Controlled acceleration additionally requires careful tuning of the witness bunch parameters at the injection point. In this work, we use particle-in-cell simulations to study the tolerances for this matching, and discuss techniques to loosen these constraints. Adli et al. (AWAKE Collaboration), Nature (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB158
About •	paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 11 August 2021
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TUPAB159	Awake Run 2 at CERN	1757
	E. Gschwendtner CERN, Meyrin, Switzerland
	The AWAKE Run 2 experiment, starting in 2021 at CERN, aims to achieve high-charge bunches of electrons accelerated to high energy (~10 GeV) while maintaining beam quality. AWAKE Run 2 also aims to show that the process is scalable so that, by the end of the run, the AWAKE-scheme technology could be used for first particle physics applications. The first two phases of Run 2 include the investigation of the seeding of the proton bunch self-modulation with the current electron beam in the existing AWAKE facility and the test of a second new plasma source with a density step allowing to maintain strong accelerating fields. In the third phase of Run 2, electrons with an energy of 150 MeV, produced in a newly installed electron source, will be injected into a second plasma source and accelerated to high energies (several GeVs) while keeping good emittance. In the fourth phase, it is planned to replace the second plasma source with a scalable one, which eventually could be used for long-distance acceleration and first applications. In this paper, we present the program of the four phases of AWAKE Run 2, the technical challenges and the proposed schedule.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB159
About •	paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 19 August 2021
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TUPAB160	Preparation for Electron-Seeding of Proton Bunch Self-Modulation in AWAKE	1761
	G. Zevi Della Porta, E. Gschwendtner, L. Verra CERN, Meyrin, Switzerland K. Moon UNIST, Ulsan, Republic of Korea P. Muggli, L. Verra MPI, Muenchen, Germany
	The next milestone of the Advanced Wakefield Experiment (AWAKE) at CERN will be to demonstrate that the self-modulation of a long proton bunch can be seeded by a short electron bunch preceding it. This seeding method will lead to phase-reproducible self-modulation of the entire proton bunch, as required for the future AWAKE program. In the Spring of 2021, before receiving proton beams from the CERN SPS, AWAKE plans to hold a dry run of the electron seeding experiments, to commission the system and to determine the parameter scans that will be used in experiments with protons. Electron bunches of 10-20 MeV with varying charge, radius, emittance and energy will be sent in 10 m of low-density plasma. The effects of beam-plasma interactions on the amplitude of the wakefields driven by the different bunches will be studied by observing the energy spectra at the end of the plasma. This paper presents preliminary experimental results from the first two days of measurements as well as the beginning of a simulation-based study of electron propagation in plasma.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB160
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 27 August 2021
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TUPAB163	Developing a 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring	1765
	E. Panofski, J. Dirkwinkel, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, T. Parikh, P.A. Walker, P. Winkler DESY, Hamburg, Germany C. Braun, 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 E. Bründermann, B. Härer, A.-S. Müller, C. Widmann KIT, Karlsruhe, Germany M. Kaluza, A. Sävert HIJ, Jena, Germany
	The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB163
About •	paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 21 August 2021
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WEPAB174	Study of the Electron Seeded Proton Self-Modulation Using FBPIC	3008
	L. Liang, G.X. Xia The University of Manchester, Manchester, United Kingdom A. Bonatto Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil L. Liang, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This work is supported by the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1 In order to make a full use of the whole proton bunch to drive large amplitude plasma wakefields and suppress the uncontrolled growth of any possible instabilities at the head of the proton bunch, the AWAKE Run 2 experiment plans to use an electron bunch to seed the formation of the proton bunch self-modulation. Additionally, a density step in the plasma channel will be used to freeze the selfmodulation process to keep the wakefield amplitude. In this work, numerical simulations performed with FBPIC are used to investigate the electron seeded proton self-modulation and the effect of the plasma density step as well.
	Poster WEPAB174 [1.751 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB174
About •	paper received ※ 10 May 2021 paper accepted ※ 28 June 2021 issue date ※ 24 August 2021
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WEPAB175	Simulation Study of Electron Beam Acceleration with Non-Gaussian Transverse Profiles for AWAKE Run 2	3012
	L. Liang, G.X. Xia The University of Manchester, Manchester, United Kingdom J.P. Farmer MPI-P, München, Germany L. Liang, G.X. Xia Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: The authors would like to acknowledge the support from the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1 In the physics plan for AWAKE Run 2, two known effects, beam loading the longitudinal wakefield and beam matching to the pure plasma ion channel, will be implemented for the better control of electron acceleration. It is founded in our study of beam matching that the transverse profile of the initial witness beam have a significant impact on its acceleration quality. In this paper, particle-in-cell (PIC) simulations are used to study factors that affect the acceleration quality of electron beams with different transverse profiles.
	Poster WEPAB175 [1.860 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB175
About •	paper received ※ 10 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021
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THPAB126	Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL	4009
	K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith KIT, Karlsruhe, Germany
	A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126
About •	paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 02 September 2021
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THPAB140	Modelling Seeded Self Modulation of Long Elliptical Bunches in Plasma	4030
	A. Perera, O. Apsimon, C.P. Welsch The University of Liverpool, Liverpool, United Kingdom O. Apsimon, C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom J. Resta-López IFIC, Valencia, Spain
	Funding: This work was supported by STFC Centre for Doctoral Training in Data-Intensive Science (LIV. DAT) under grant ST/P006752/1 and the STFC Scientific Computing Department’s SCARF cluster. The stability of particle bunches undergoing seeded self-modulation (SSM) over tens or hundreds of meters is crucial to the generation of GV/m wakefields that can accelerate electron beams as proposed for use in several high energy plasma-based linear colliders. Here, 3D particle-in-cell simulations using QuickPIC are compared to an analytical model of seeded self-modulation (SSM) of elliptical beam envelopes using linear wakefield theory. It is found that there is quantitative agreement between simulations and analytical predictions for the envelope in the early growth of the SSM. A scaling law is derived for the reduction of the maximum overall modulation growth rate with aspect ratio and is found to match well with simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB140
About •	paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021
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THPAB155	Strong Quadrupole Wakefield Based Focusing in Dielectric Wakefield Accelerators	4059
	W.J. Lynn, G. Andonian, N. Majernik, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: Grant number: DOE HEP Grants DE-SC0017648, DE-SC0009914, and National Science Foundation Grant No. PHY-1549132. We propose here to exploit the quadrupole wakefields in an alternating symmetry slab-based dielectric wakefield accelerator (DWA) to produce second-order focusing. The resultant focusing is found to be strongly dependent on longitudinal position in the bunch. We analyze this effect with analytical estimates and electromagnetic PIC simulations. We examine the use of this scenario to induce beam stability in very high gradient DWA, with positive implications for applications in linear colliders and free-electron lasers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB155
About •	paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 19 August 2021
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THPAB332	Development of a Pair of 182 GHz Two-Half Power Extractor and Accelerator for Short Pulse RF Breakdown Study	4435
	J.H. Shao, J.G. Power ANL, Lemont, Illinois, USA R.B. Agustsson, S.V. Kutsaev, A.Yu. Smirnov RadiaBeam, Santa Monica, California, USA
	High-frequency structures are favorable in structure wakefield acceleration for their strong beam-structure interaction. Recent progress of advanced fabrication technologies, such as high-precision two-half milling and additive machining, has enabled experimental research of mm-wave/THz structures. In this work, we have designed a pair of 182 GHz two-half copper power extractor and accelerator for short pulse RF breakdown study. When driven by a 182 GHz 4-bunch train with 4 nC total charge and 0.3 mm rms bunch length, the power extractor will generate 0.4 ns ~8 MW RF pulses and the corresponding gradient in the single-cell accelerator will reach ~460 MV/m. RF and mechanical design of the proof-of-concept structures will be reported in this manuscript.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB332
About •	paper received ※ 26 May 2021 paper accepted ※ 19 July 2021 issue date ※ 26 August 2021
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Paper

Title

Page

Liénard-Wiechert Numerical Radiation Modeling for Plasma Acceleration Experiments at FACET-II

517

M. Yadav, G. Andonian, C.E. Hansel, N. Majernik, P. Manwani, B. Naranjo, J.B. Rosenzweig, O. Williams, Y. Zhuang
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Marina del Rey, California, USA
O. Apsimon, A. Perera, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, A. Perera, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by DE-SC0009914 (UCLA) and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1.
Future plasma acceleration experiments at FACET-II will measure betatron radiation in order to provide single-shot non-destructive beam diagnostics. We discuss three models for betatron radiation: a new idealized particle tracking code with Liénard-Wiechert radiation, a Quasi-Static Particle-in-Cell (PIC) code with Liénard-Wiechert radiation, and a full PIC code with radiation computed via a Monte-Carlo QED Method. Predictions of the three models for the E-310 experiment are presented and compared. Finally, we discuss beam parameter reconstruction from the double differential radiation spectrum.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB148

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paper received ※ 24 May 2021 paper accepted ※ 01 June 2021 issue date ※ 17 August 2021

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MOPAB149

Ion Motion in Flat Beam Plasma Accelerators

521

M. Yadav, C.E. Hansel, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
O. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work was supported by UCLA and the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1. This work is done on SCARF Cluster.
Intense beams, such as those in proposed plasma based linear colliders, can not only blow out electrons to form a bubble but can also attract ions towards the beam. This violates the assumption that the ions are stationary on the timescale of the beam, which is a common assumption for shorter and less intense beams. While some research has been done on understanding the physics of ion motion in blowout Plasma Wakefield Accelerators (PWFAs), this research has almost exclusively focused on cylindrically symmetric beams, rather than flat asymmetric emittance beams which are often used in linear colliders in order to minimize beamstrahlung at the final focus. This contribution investigates both analytically and computationally ion motion of a flat beam scenario in order to understand the basic physics as well as how to mitigate emittance growth, beam hosing and quadrupole.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB149

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paper received ※ 24 May 2021 paper accepted ※ 17 June 2021 issue date ※ 11 August 2021

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MOPAB166

Wakefield Excitation by a Sequence of Laser Pulses in Plasma

568

D.S. Bondar
KhNU, Kharkov, Ukraine
V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: The study is supported by the National Research Fundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
PIC simulation by means of 2.5D UMKA code * of the wakefield excitation by a sequence of three Gaussian laser pulses in plasma was carried out. The dependence of excited wakefield intensity on power and width of laser pulses was investigated. It was shown the coherent addition of wakefield, excited by each laser pulse of the sequence, for linear case, while for the nonlinear case the coherency was destroyed. The profiled sequence of laser pulses was also considered. The possibility to obtain the same total wakefield excited by the profiled sequence of laser pulses with decreasing intensity, as for the uniform sequence was studied.
* G. I. Dudnikova et al. Comp. Techn. 10 (2005) 37.

Poster MOPAB166 [2.638 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB166

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paper received ※ 17 May 2021 paper accepted ※ 20 May 2021 issue date ※ 15 August 2021

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MOPAB167

Wakefield Excitation in Plasma of Metallic Density by a Laser Pulse

571

D.S. Bondar
KhNU, Kharkov, Ukraine
V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: The study is supported by the National Research Foundation of Ukraine under the program "Leading and Young Scientists Research Support" (project # 2020.02/0299).
Recently the proposal to use X-ray Exawatt pulse for particle acceleration in a crystal has been declared *. Short X-ray high-power pulse excites wakefield in electron plasma of metallic density which can be used for high gradient acceleration of charged particles. This wakefield is suited for laser wakefield acceleration. In this paper there are simulated with PIC code UMKA: excitation of the large wakefield amplitude up to several TV/m in electron plasma of metallic density by a powerful X-ray laser pulse; laser-plasma wakefield acceleration of self-injected electron bunch in such setup; combined acceleration by plasma wakefield driven by a laser pulse (LPWA) and by self-injected electron bunch (PWFA).
* T.Tajima. Eur. Phys. J. Special Topics 223 (2014) 1037.

Poster MOPAB167 [2.054 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB167

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paper received ※ 17 May 2021 paper accepted ※ 21 May 2021 issue date ※ 22 August 2021

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TUXB02

Precision Control of Plasma Wakefields for Highly Efficient and Energy-Spread-Preserving Electron Acceleration

S. Schröder, S. Bohlen, L.A. Boulton, R.T.P. D’Arcy, S. Diederichs, J.M. Garland, P. Gonzalez-Caminal, A. Knetsch, C.A. Lindstrøm, G. Loisch, A. Martinez de la Ossa, J. Osterhoff, K. Poder, L. Schaper, B. Schmidt, B. Sheeran, G.E. Tauscher, S. Wesch, J.C. Wood, J. Zemella
DESY, Hamburg, Germany
L.A. Boulton
USTRAT/SUPA, Glasgow, United Kingdom
J. Chappell
UCL, London, United Kingdom

Plasma-wakefield accelerators driven by intense particle beams promise to significantly reduce the size of future high-energy facilities. These applications require an energy-efficient acceleration process with a well-controlled energy spectrum, both of which can be achieved simultaneously by tailoring the plasma wakefield. A prerequisite for such control of the wakefield is its precise measurement. Here we discuss a new measurement technique that enables femtosecond-level sampling of the longitudinal electric fields and that is particularly powerful due to its operational simplicity*. Using this method, we experimentally demonstrated optimal beam loading in a nonlinear electron-driven plasma accelerator by wakefield flattening at the few-percent level**. Bunches were accelerated at a gradient of 1.3 GV/m and with an energy-transfer efficiency of (42±4)% while preserving per-mille energy spreads with full charge coupling. These results open the door to the high-quality operation of future plasma accelerators through precise control of the acceleration process.
* S. Schröder, et al. Nat Commun 11, 5984 (2020)
** C.A. Lindstrøm, et al. Phys. Rev. Lett. 126, 014801 (2021)

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TUXB06

High Transformer Ratio Plasma Wakefield Acceleration and Current Profile Reconstruction Using Emittance Exchange

R.J. Roussel
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
G. Andonian, A. Deng, C.E. Hansel, G.E. Lawler, W.J. Lynn, R. Robles, J.B. Rosenzweig, K. Sanwalka
UCLA, Los Angeles, California, USA
S. Baturin
Northern Illinois University, DeKalb, Illinois, USA
M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J. Seok, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA

Funding: This work is supported by the Department of Energy, Office of High Energy Physics, under Contract No. DESC0017648.
To overcome limits on total acceleration achievable in plasma wakefield accelerators, specially shaped drive beams can be used to increase the transformer ratio, implying that the drive beam deceleration is minimized in comparison with acceleration obtained in the wake. We report the results of a nonlinear PWFA, high transformer ratio experiment using high-charge, longitudinally asymmetric drive beams in a plasma cell. An emittance exchange process is used to generate variable drive current profiles, in conjunction with a long (multiple plasma wavelength) witness beam. The witness beam is energy-modulated by the wakefield, yielding a response that contains detailed spectral information in a single-shot measurement. Using these methods, we generate a variety of beam profiles and characterize the wakefields, directly observing beam-loaded transformer ratios up to 7.8. Further, a spectrally-based current reconstruction technique, validated by 3D particle-in-cell simulations, is introduced to obtain the drive beam profile from the decelerating wakefield data.

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TUPAB138

Determination of the Phase of Wakefield Driven by a Self-Modulated Proton Bunch in Plasma

1710

K. Moon, M. Chung
UNIST, Ulsan, Republic of Korea
P. Muggli
MPI-P, München, Germany

Funding: This work was partly supported by the National Research Foundation of Korea (Nos. NRF-2016R1A5A1013277 and NRF-2020R1A2C1010835)
The phase of wakefield driven by a self-modulated proton bunch depends on the type of seeding method and by the beam-plasma parameters.* Particularly when a preceding electron bunch generates seed wakefield, the proton bunch modulation is strongly affected by the seed bunch dynamics along with the plasma. Intrinsic wakefield dephasing from self-modulation of proton bunch can lead to complex evolution of the bunch and wakefield, making it difficult to design an experimental setup for witness beam injection. Using the particle-in-cell code FBPIC,** we investigate in detail the trends of seed electron and driver proton bunch parameter sensitivity to the phase of wakefield in time in the proton bunch frame. We focus on the parameters affecting the phase of the wakefield through the beam’s radial dynamics, such as beam emittance, radial size, energy, and beam to plasma density ratio. Parameter variations are compared to those in the case of the phase of wakefield driven by a non-evolving seed bunch.
*F. Batsch, arXiv:2012.09676 [physics.plasm-ph]
**R. Lehe, M. Kirchen, I.A. Andriyash, B.B. Godfrey, and J.-L. Vay, Comput. Phys. Comm. 203, 66-82 (2016)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB138

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paper received ※ 19 May 2021 paper accepted ※ 21 June 2021 issue date ※ 30 August 2021

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TUPAB141

On the Development of a Low Peak-Power, High Repetition-Rate Laser Plasma Accelerator at IPEN

1713

A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.P. Nunes
UFRGS, Porto Alegre, Brazil
R.E. Samad, F.B.D. Tabacow, N.D. Vieira, A.V.F. Zuffi
IPEN-CNEN/SP, São Paulo, Brazil

Funding: FAPESP (Grant #2018/25961), CNPq and CAPES.
In this work, the current status on the development of a laser plasma accelerator at the Nuclear and Energy Research Institute (Instituto de Pesquisas Nucleares e Energéticas, IPEN/CNEN), in São Paulo, Brazil, is presented. Short pulses to be produced by an under-development near-TW, kHz laser system will be used to ionize a gas jet, with a density profile designed to optimize the self-injection of plasma electrons. The same laser pulse will also drive a plasma wakefield, which will allow for electron acceleration in the self-modulated regime. The current milestone is to develop the experimental setup, including electron beam and plasma diagnostics, required to produce electron bunches with energies of a few MeV. Once this has been achieved, the next milestone is to produce beams with energies higher than 50 MeV. Besides kickstarting the laser wakefield accelerator (LWFA) technology in Brazil, this project aims to pave the way for conducting research on the production of radioisotopes by photonuclear reactions, triggered by LWFA-accelerated beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB141

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 10 August 2021

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TUPAB142

Simulation Study of Laser Wakefield Acceleration Varying the Down-Ramp Length of a Gas Jet

1717

R.P. Nunes
UFRGS, Porto Alegre, Brazil
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.E. Samad, N.D. Vieira
IPEN-CNEN/SP, São Paulo, Brazil

In this work, particle-in-cell simulations were carried out to investigate the role of the down-ramp length of a H\textsubscript{2} gas jet in accelerating electrons ionized by the laser pulse. The laser and plasma density were chosen so that the system is operating in the self-modulated regime. Preliminary results show how the down-ramp length can control the injection of electrons in the first bubble induced in the plasma by the laser pulse.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB142

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paper received ※ 20 May 2021 paper accepted ※ 15 June 2021 issue date ※ 13 August 2021

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TUPAB143

Laser Pulse Dynamics in the Self-Modulated Regime

1721

R.P. Nunes
UFRGS, Porto Alegre, Brazil
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
E.P. Maldonado
ITA, São José dos Campos, Brazil
R.E. Samad, N.D. Vieira
IPEN-CNEN/SP, São Paulo, Brazil

In this work, particle-in-cell simulations were carried out to investigate the dynamics of a laser pulse propagating along a H₂ gas jet. The laser-driven wakefield and the density of ionized electrons are analyzed during the pulse propagation through the gas jet. The laser and plasma quantities were chosen in order to have the system operating in the self-modulated regime. Results show how the self-modulation fragments the laser pulse, originating higher-amplitude pulses that can induce bubble formation with wave-breaking and particle injection.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB143

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 21 August 2021

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TUPAB145

Methods for Numerical Noise Mitigation in Quasistatic Three-Dimensional Particle-in-Cell Code LCODE3D

1725

I.Yu. Kargapolov, K.V. Lotov, A. Sosedkin
Budker INP & NSU, Novosibirsk, Russia
I.A. Shalimova
ICM&MG SB RAS, Novosibirsk, Russia
I.A. Shalimova, P.V. Tuev
NSU, Novosibirsk, Russia
P.V. Tuev
BINP SB RAS, Novosibirsk, Russia

We discuss a new quasistatic 3D particle-in-cell code LCODE3D for simulating plasma wakefield acceleration, which is a modified version of the quasistatic 2D3V code LCODE, focus on the numerical noise of the plasma solver and propose methods for reducing it. We compare different particle shape functions, as these functions affect the code stability. We also introduce the so-called dual plasma approach, which improves stability and dampens small-scale noise. After applying the proposed methods, the results of the new code closely agree with LCODE simulation results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB145

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paper received ※ 19 May 2021 paper accepted ※ 17 June 2021 issue date ※ 25 August 2021

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TUPAB146

High Brightness Electron Beams from Dragon Tail Injection and the E-312 Experiment at FACET-II

1728

P. Manwani, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colorado, USA
B. Hidding
USTRAT/SUPA, Glasgow, United Kingdom
M.D. Litos
Colorado University at Boulder, Boulder, Colorado, USA

Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0009914
The advent of optically triggered injection in multi component plasma wakefield accelerators has been shown to enable a substantial increase in witness electron beam quality. Here we present a novel way of using the overlap of laser and beam radial fields to locally liberate electrons from the tunneling ionization of the non-ionized gas species. These liberated ultracold electrons gain sufficient energy to be trapped in the accelerating phase at the back of the plasma blowout. This method of controlled injection has advantages in precision timing since injection is locked to peak beam current and has the potential of generating beams with very low emittance and energy spread. This method has been investigated using particle-in-cell (PIC) simulations. This scenario corresponds to a planned experiment, E-312, at SLAC’s FACET-II facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB146

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paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 22 August 2021

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TUPAB147

Asymmetric Beam Driven Plasma Wakefields at the AWA

1732

P. Manwani, H.S. Ancelin, G. Andonian, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Santa Monica, 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, Division of High Energy Physics under Contract No. DE-SC0017648 and DE-SC0009914
In future plasma wakefield acceleration-based scenarios for linear colliders, beams with highly asymmetric emittance are expected. In this case, the blowout region is no longer axisymmetric, but elliptical in cross-section, which implies that the focusing is not equal in the two transverse planes. In this paper, we analyze simulations for studying the asymmetries in flat-beam driven plasma acceleration using the round-to-flat-beam transformer at the Argonne Wakefield Accelerator. Beams with high charge and emittance ratios, in excess of 100:1, are routinely available at the AWA. We use particle-in-cell codes to compare various scenarios including a weak blowout, where the plasma focusing effect exhibits higher order mode asymmetry. Further, practical considerations for tunable plasma density using capillary discharge and laser ionization are compared for implementation into experimental designs.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB147

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paper received ※ 20 May 2021 paper accepted ※ 13 July 2021 issue date ※ 02 September 2021

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TUPAB148

Optical-Period Bunch Trains to Resonantly Excite High Gradient Wakefields in the Quasi-Nonlinear Regime and the E-317 Experiment at FACET-II

1736

P. Manwani, C.E. Hansel, N. Majernik, J.B. Rosenzweig, M. Yadav
UCLA, Los Angeles, 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. DE-SC0009914 and National Science Foundation under Grant No. PHY-1549132
Periodic electron bunch trains spaced at the laser wavelength created via inverse free electron laser (IFEL) bunching can be used to resonantly excite plasmas in the quasi-nonlinear (QNL) regime. The excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. The resulting plasma density perturbation is extremely nonlinear locally, but preserves the resonant response of the plasma electrons at the plasma frequency. This excitation can produce plasma blowout conditions using very low emittance beams despite having a small charge per bunch. To match the resonance condition, the plasma wavelength has to be equal to the laser period of a few microns. This corresponds to a high density plasma resulting in extremely large wakefield amplitudes. Matching the beam into such a dense plasma requires an extremely short focusing beta function. We present the beam-plasma interaction using quasi-static particle-in-cell (PIC) simulations and discuss the micro-bunching and focusing mechanism required for this scheme which would be a precursor to the planned experiment, E-317, at SLAC’s FACET-II facility.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB148

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paper received ※ 20 May 2021 paper accepted ※ 08 July 2021 issue date ※ 19 August 2021

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TUPAB153

Modeling of Capillary Discharge Plasmas for Wakefield Accelerators and Beam Transport

1740

N.M. Cook, J.A. Carlsson, S.J. Coleman, A. Diaw, J.P. Edelen
RadiaSoft LLC, Boulder, Colorado, USA
E.C. Hansen, P. Tzeferacos
Flash Center for Computational Science, Chicago, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0018719.
Next generation accelerators demand sophisticated beam sources to reach ultra-low emittances at large accelerating gradients, along with improved optics to transport these beams without degradation. Capillary discharge plasmas can address each of these challenges. As sources, capillaries have been shown to increase the energy and quality of wakefield accelerators, and as active plasma lenses they provide orders-of-magnitude increases in peak magnetic field. Capillaries are sensitive to energy deposition, heat transfer, ionization dynamics, and magnetic field penetration; therefore, capillary design requires careful modeling. We present simulations of capillary discharge plasmas using FLASH, a publicly-available multi-physics code developed at the University of Chicago. We report on the implementation of 2D and 3D models of capillary plasma density and temperature evolution with realistic boundary and discharge conditions. We then demonstrate laser energy deposition to model channel formation for guiding intense laser pulses. Lastly, we examine active capillary plasmas with varying fill species and compare our simulations against experimental studies.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB153

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paper received ※ 24 May 2021 paper accepted ※ 29 July 2021 issue date ※ 30 August 2021

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TUPAB155

Obtaining Accelerated Electron Bunch of High Quality in Plasma Wakefield Accelerator

1744

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299."
Earlier, high-gradient accelerating electrons of a relativistic beam was demonstrated. However, due to dynamic processes in the plasma, there are problems in maintaining the small size and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating wakefields. Also, the question arises about the values of the limiting bunch dimensions at which the accelerating process is stable. To form a stable accelerated electron bunch, a method is usually used that involves the formation of the same accelerating fields at the location of the bunch. The same fields (plateau due to beam loading (see *, **)) in the region of the accelerated bunch allow all its parts to move as a whole, and ensure the preservation of the spatial distribution of electrons over time, which, in fact, means an accelerated beam of good quality. In this report, the problem of electron bunch accelerating by a short or long electron driver-bunch is considered.
* Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301.
** Maslov V.I. et al. Problems of Atomic Science and Technology. 6 (2020) 47.

Poster TUPAB155 [1.723 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB155

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 23 August 2021

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TUPAB156

Optimal Field Shape, Accelerating Positron Bunch in Plasma Wakefield

1747

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299.
The quality of the electron or positron beam, accelerated in plasma accelerators, is still insufficient for applications. Accurate control over the properties of the electron or positron beam is a key issue for wakefield plasma accelerators. The effect of the presence of a witness-beam (the effect of the spatial charge distribution of the witness beam) (see [*, **]) to compensate the energy spread of the positron beam in plasma wakefield accelerators has been studied. This paper presents the results of a numerical simulation on the optimization of the parameters of the driver-bunch and witness-bunch for the formation of a self-consistent longitudinal distribution of the accelerating plateau-type field, which leads to the same values of the wakefield for the whole bunch of accelerated particles and minimizing bunch degradation during acceleration by means of an ion-driver-bunch with external injection into the plasma wake accelerator. The dependence of the longitudinal distribution of the accelerating wakefield on the density and shape of the accelerated bunch in the blowout regime was investigated. Plateau formation and energy spread compensation were observed.
* Romeo S., Ferrario M., Rossi A.R. Phys. Rev. Accel. Beams. 23 (2020) 071301.
** Katsouleas T. et al. Particle Accelerators. 22 (1987) 81.

Poster TUPAB156 [1.200 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB156

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paper received ※ 18 May 2021 paper accepted ※ 16 June 2021 issue date ※ 25 August 2021

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TUPAB157

Obtaining Long Accelerated Electron Bunch of Good Quality in Plasma Wakefield Accelerator at High Transformer Ratio

1750

R.T. Ovsiannikov
KhNU, Kharkov, Ukraine
I.P. Levchuk (Yarovaya), V.I. Maslov, I.N. Onishchenko
NSC/KIPT, Kharkov, Ukraine

Funding: "This work is supported by National Research Fundation of Ukraine "Leading and Young Scientists Research Support", grant agreement # 2020.02/0299."
The efficiency of electron acceleration by a wakefield, excited in a plasma by an electron bunch, is determined by the transformer ratio (see *, **). The transformer ratio is the ratio of energy acquired by the witness to energy lost by the driver. The transformer ratio can be increased by shaping driver-bunch. In this work, using a non-linear version of the 2d3v code lcode (see ***), numerical simulation of excitation of a wakefield in a plasma in blowout regime by a shaped relativistic electron bunch was performed. There is also the problem of maintaining the small dimension and small energy spread of the accelerated electron bunch while maintaining sufficient values of the accelerating gradient and the transformer ratio. Also, the question arises about the values of the limiting dimension of the witness-bunch at which the acceleration process is stable. Numerical simulation solves the problem of electron bunch acceleration of the best quality with simultaneous maximization of the transformer ratio and maximization of the witness bunch length, at which the accelerating gradient and the focusing force are constant.
*Maslov V.I. et al. Problems of Atomic Science and Technology. 4 (2012) 128.
**Baturin S.S., Zholents A. Phys. Rev. ST Accel. Beams. 20 (2017) 061302.
***Lotov K.V. Phys. Plasmas. 5 (1998) 785.

Poster TUPAB157 [1.920 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB157

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paper received ※ 18 May 2021 paper accepted ※ 23 June 2021 issue date ※ 30 August 2021

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TUPAB158

Electron Witness Constraints for AWAKE

1753

J.P. Farmer, P. Muggli
MPI-P, München, Germany
E. Gschwendtner
CERN, Meyrin, Switzerland
L. Liang
The University of Manchester, Manchester, United Kingdom
M.S. Weidl
MPI/IPP, Garching, Germany

The AWAKE project at CERN successfully demonstrated the use of a proton driver to accelerate an electron witness in plasma*. One of the key goals for AWAKE Run2 is to better control this acceleration, separating the proton-beam-modulation and electron-acceleration stages in order to achieve high energy electrons with high beam quality. Controlled acceleration additionally requires careful tuning of the witness bunch parameters at the injection point. In this work, we use particle-in-cell simulations to study the tolerances for this matching, and discuss techniques to loosen these constraints.
*Adli et al. (AWAKE Collaboration), Nature (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB158

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paper received ※ 19 May 2021 paper accepted ※ 14 June 2021 issue date ※ 11 August 2021

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TUPAB159

Awake Run 2 at CERN

1757

E. Gschwendtner
CERN, Meyrin, Switzerland

The AWAKE Run 2 experiment, starting in 2021 at CERN, aims to achieve high-charge bunches of electrons accelerated to high energy (~10 GeV) while maintaining beam quality. AWAKE Run 2 also aims to show that the process is scalable so that, by the end of the run, the AWAKE-scheme technology could be used for first particle physics applications. The first two phases of Run 2 include the investigation of the seeding of the proton bunch self-modulation with the current electron beam in the existing AWAKE facility and the test of a second new plasma source with a density step allowing to maintain strong accelerating fields. In the third phase of Run 2, electrons with an energy of 150 MeV, produced in a newly installed electron source, will be injected into a second plasma source and accelerated to high energies (several GeVs) while keeping good emittance. In the fourth phase, it is planned to replace the second plasma source with a scalable one, which eventually could be used for long-distance acceleration and first applications. In this paper, we present the program of the four phases of AWAKE Run 2, the technical challenges and the proposed schedule.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB159

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 19 August 2021

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TUPAB160

Preparation for Electron-Seeding of Proton Bunch Self-Modulation in AWAKE

1761

G. Zevi Della Porta, E. Gschwendtner, L. Verra
CERN, Meyrin, Switzerland
K. Moon
UNIST, Ulsan, Republic of Korea
P. Muggli, L. Verra
MPI, Muenchen, Germany

The next milestone of the Advanced Wakefield Experiment (AWAKE) at CERN will be to demonstrate that the self-modulation of a long proton bunch can be seeded by a short electron bunch preceding it. This seeding method will lead to phase-reproducible self-modulation of the entire proton bunch, as required for the future AWAKE program. In the Spring of 2021, before receiving proton beams from the CERN SPS, AWAKE plans to hold a dry run of the electron seeding experiments, to commission the system and to determine the parameter scans that will be used in experiments with protons. Electron bunches of 10-20 MeV with varying charge, radius, emittance and energy will be sent in 10 m of low-density plasma. The effects of beam-plasma interactions on the amplitude of the wakefields driven by the different bunches will be studied by observing the energy spectra at the end of the plasma. This paper presents preliminary experimental results from the first two days of measurements as well as the beginning of a simulation-based study of electron propagation in plasma.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB160

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 27 August 2021

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TUPAB163

Developing a 50 MeV LPA-Based Injector at ATHENA for a Compact Storage Ring

1765

E. Panofski, J. Dirkwinkel, T. Hülsenbusch, A.R. Maier, J. Osterhoff, G. Palmer, T. Parikh, P.A. Walker, P. Winkler
DESY, Hamburg, Germany
C. Braun, 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
E. Bründermann, B. Härer, A.-S. Müller, C. Widmann
KIT, Karlsruhe, Germany
M. Kaluza, A. Sävert
HIJ, Jena, Germany

The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavor is conducted in close collaboration between Deutsche Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena. In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB163

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paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 21 August 2021

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WEPAB174

Study of the Electron Seeded Proton Self-Modulation Using FBPIC

3008

L. Liang, G.X. Xia
The University of Manchester, Manchester, United Kingdom
A. Bonatto
Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, Brazil
L. Liang, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This work is supported by the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1
In order to make a full use of the whole proton bunch to drive large amplitude plasma wakefields and suppress the uncontrolled growth of any possible instabilities at the head of the proton bunch, the AWAKE Run 2 experiment plans to use an electron bunch to seed the formation of the proton bunch self-modulation. Additionally, a density step in the plasma channel will be used to freeze the selfmodulation process to keep the wakefield amplitude. In this work, numerical simulations performed with FBPIC are used to investigate the electron seeded proton self-modulation and the effect of the plasma density step as well.

Poster WEPAB174 [1.751 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB174

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paper received ※ 10 May 2021 paper accepted ※ 28 June 2021 issue date ※ 24 August 2021

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WEPAB175

Simulation Study of Electron Beam Acceleration with Non-Gaussian Transverse Profiles for AWAKE Run 2

3012

L. Liang, G.X. Xia
The University of Manchester, Manchester, United Kingdom
J.P. Farmer
MPI-P, München, Germany
L. Liang, G.X. Xia
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: The authors would like to acknowledge the support from the Cockcroft Institute Core Grant and the STFC AWAKE Run 2 grant ST/T001917/1
In the physics plan for AWAKE Run 2, two known effects, beam loading the longitudinal wakefield and beam matching to the pure plasma ion channel, will be implemented for the better control of electron acceleration. It is founded in our study of beam matching that the transverse profile of the initial witness beam have a significant impact on its acceleration quality. In this paper, particle-in-cell (PIC) simulations are used to study factors that affect the acceleration quality of electron beams with different transverse profiles.

Poster WEPAB175 [1.860 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB175

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paper received ※ 10 May 2021 paper accepted ※ 25 June 2021 issue date ※ 02 September 2021

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THPAB126

Operational Experience and Characterization of a Superconducting Transverse Gradient Undulator for Compact Laser Wakefield Accelerator-Driven FEL

4009

K. Damminsek, A. Bernhard, J. Gethmann, A.W. Grau, A.-S. Müller, Y. Nie, M.S. Ning, S.C. Richter, R. Rossmanith
KIT, Karlsruhe, Germany

A 40-period superconducting transverse gradient undulator (TGU) has been designed and fabricated at Karlsruhe Institute of Technology (KIT). Combining a TGU with a Laser Wakefield Accelerator (LWFA) is a potential key for realizing an extremely compact Free Electron Laser (FEL) radiation source. The TGU scheme is a viable option to compensate the challenging properties of the LWFA electron beam in terms of beam divergence and energy spread. In this contribution, we report on the operational experience of this TGU inside its own cryostat and show the current status of the TGU and the further plan for experiments. This work is supported by the BMBF project 05K19VKA PlasmaFEL (Federal Ministry of Education and Research).

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB126

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paper received ※ 19 May 2021 paper accepted ※ 25 August 2021 issue date ※ 02 September 2021

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THPAB140

Modelling Seeded Self Modulation of Long Elliptical Bunches in Plasma

4030

A. Perera, O. Apsimon, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
O. Apsimon, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J. Resta-López
IFIC, Valencia, Spain

Funding: This work was supported by STFC Centre for Doctoral Training in Data-Intensive Science (LIV. DAT) under grant ST/P006752/1 and the STFC Scientific Computing Department’s SCARF cluster.
The stability of particle bunches undergoing seeded self-modulation (SSM) over tens or hundreds of meters is crucial to the generation of GV/m wakefields that can accelerate electron beams as proposed for use in several high energy plasma-based linear colliders. Here, 3D particle-in-cell simulations using QuickPIC are compared to an analytical model of seeded self-modulation (SSM) of elliptical beam envelopes using linear wakefield theory. It is found that there is quantitative agreement between simulations and analytical predictions for the envelope in the early growth of the SSM. A scaling law is derived for the reduction of the maximum overall modulation growth rate with aspect ratio and is found to match well with simulation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB140

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paper received ※ 19 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021

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THPAB155

Strong Quadrupole Wakefield Based Focusing in Dielectric Wakefield Accelerators

4059

W.J. Lynn, G. Andonian, N. Majernik, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: Grant number: DOE HEP Grants DE-SC0017648, DE-SC0009914, and National Science Foundation Grant No. PHY-1549132.
We propose here to exploit the quadrupole wakefields in an alternating symmetry slab-based dielectric wakefield accelerator (DWA) to produce second-order focusing. The resultant focusing is found to be strongly dependent on longitudinal position in the bunch. We analyze this effect with analytical estimates and electromagnetic PIC simulations. We examine the use of this scenario to induce beam stability in very high gradient DWA, with positive implications for applications in linear colliders and free-electron lasers.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB155

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paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 19 August 2021

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THPAB332

Development of a Pair of 182 GHz Two-Half Power Extractor and Accelerator for Short Pulse RF Breakdown Study

4435

J.H. Shao, J.G. Power
ANL, Lemont, Illinois, USA
R.B. Agustsson, S.V. Kutsaev, A.Yu. Smirnov
RadiaBeam, Santa Monica, California, USA

High-frequency structures are favorable in structure wakefield acceleration for their strong beam-structure interaction. Recent progress of advanced fabrication technologies, such as high-precision two-half milling and additive machining, has enabled experimental research of mm-wave/THz structures. In this work, we have designed a pair of 182 GHz two-half copper power extractor and accelerator for short pulse RF breakdown study. When driven by a 182 GHz 4-bunch train with 4 nC total charge and 0.3 mm rms bunch length, the power extractor will generate 0.4 ns ~8 MW RF pulses and the corresponding gradient in the single-cell accelerator will reach ~460 MV/m. RF and mechanical design of the proof-of-concept structures will be reported in this manuscript.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB332

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paper received ※ 26 May 2021 paper accepted ※ 19 July 2021 issue date ※ 26 August 2021

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