NAPAC2019 - List of Keywords (plasma)

Paper	Title	Other Keywords	Page
MOYBB2	Recent Advance in ECR Ion Sources	ECR, ion-source, operation, electron	31
	G. Machicoane, N.K. Bultman, P. Morrison, M. Omelayenko, X. Rao FRIB, East Lansing, Michigan, USA D. Arbelaez, R.R. Hafalia, P. Pan, S. Prestemon LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University. High continuous wave (cw) current of highly charged ion beams are required for several heavy ion accelerator facilities including the Facility for Rare Isotope Beams (FRIB). In most cases, Electron-Cyclotron-Resonance (ECR) ion sources remain the only ion source capable to meet the beam intensity requirement for these facilities. Performances of ECR ion source have increased by several order of magnitude since their inception in the 1970s mostly driven by increasing the resonance frequency with today current state of the art ECR ion source operating from 24 to 28 GHz. This paper provides an overview of recent advance in the design and operation of ECR ion source including plans to develop the next generation of ion source capable of operating above 40 GHz. A detailed account of the design and status of the new superconducting ECR ion source in construction for FRIB will also be reported.
	Slides MOYBB2 [9.483 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB2
About •	paper received ※ 02 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019
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MOYBB5	Characterization and Performance of Plasma Window for Gas Flow Restriction in Different Geometries	electron, cathode, target, diagnostics	44
	A. Lajoie NSCL, East Lansing, Michigan, USA J. Gao, F. Marti FRIB, East Lansing, Michigan, USA
	Funding: This work is supported by NSF Award PHY-1565546. The plasma window is a DC cascaded arc whose function is to restrict gas flow from a high pressure region to a low pressure region without the use of any solid separation. As a result, the plasma window allows a greater pressure to be maintained than otherwise possible. This is a beneficial characteristic for gas charge strippers for ion accelerators, since the higher pressures enable the stripper to be shorter and allow the same amount of stripping interactions. The flow rate reduction is established by the increase in gas temperature from the power deposited into the plasma via the cathodes, resulting in a dramatically increased viscosity. The flow rate reduction, depends on the properties of the plasma, including the electron density and temperature, pressure, and electrical conductivity. Understanding these properties in multiple arc geometries - in this work having either 6 mm or 10 mm channel diameter - provides a means optimizing the plasma window for a given design. Determinations of the properties for different conditions are shown, and results are compared with a PLASIMO simulation, which has been shown to yield comparable properties to measurements in an argon arc*. A. Hershcovitch, Phys. Plasma 5, 2130 (1998). J. A. Nolen and F. Marti, Rev. Accel. Sci. Tech. 6, 221 (2013). *G. M. W. Kroesen et al., Plas. Chem. and Plas. Proc. 10, 531 (1990).
	Slides MOYBB5 [4.132 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB5
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLH08	Tests of Cs-Free Operation of the SNS RF H⁻ Ion Sources	operation, ion-source, neutron, power-supply	184
	B. Han, S.M. Cousineau, S.N. Murray, T.R. Pennisi, M.P. Stockli, R.F. Welton ORNL, Oak Ridge, Tennessee, USA T.M. Sarmento, O.A. Tarvainen STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom C. Stinson ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was performed at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract number DE-AC05-00OR22725 for the United States Department of Energy. Tests were performed at SNS in collaboration with visiting colleagues from ISIS, UK to evaluate the uncesiated beam performance of the SNS RF H⁻ ion sources. Two spare experimental sources, one with internal antenna and one with external antenna were used for the tests. The beam currents achieved with Cs-free operations accounted for about 1/3 to 1/2 of the beam currents produced with cesiated operations. ~17 mA uncesiated H⁻ current was demonstrated within the tested RF power range up to 65 kW with the internal antenna source and ~15 mA with up to 40 kW RF with the external antenna source. In Cs-free operations, the power supply for the electron dumping electrode was loaded down below its set voltage but was not too drastic to tamper the operation.
	Poster MOPLH08 [0.949 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH08
About •	paper received ※ 27 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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MOPLH23	An Analysis of Potential Compact Positron Beam Source	positron, emittance, cavity, simulation	220
	R.M. Hessami UCLA, Los Angeles, USA S.J. Gessner CERN, Geneva, Switzerland
	For positron studies in plasma wakefield accelerators such as AWAKE, the development of new, cheaper, and compact positron beam sources is necessary. Using an electrostatic trap with parameters similar to other experiments, this paper explores converting that trapped positron plasma into a usable beam. Bunching is initially accomplished by an electrostatic buncher and the beam is accelerated to 148 keV by pulsed electrostatic accelerators. This is necessary for injection into the beta-matched rf cavities operating at 600 MHz, which bring the positron beam to a transverse emittance of 1.3 pi mrad mm, a longitudinal emittance of 93.3 pi keV mm, stdz of 1.85 mm and an energy of 22 MeV. The beamline used here is far simpler and less expensive than those at many facilities, such as SLAC, allowing for a cheap source of positron beams, potentially opening up positron beam studies to many facilities that could not previously afford such a source.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH23
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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TUZBB5	Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma	emittance, electron, experiment, HOM	363
	C. Mallick, M. Bandyopadhyay, R. Kumar Institute for Plasma Research, Bhat, Gandhinagar, India
	The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth. Reference ’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’ ’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’ ’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’
	Slides TUZBB5 [5.298 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB5
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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TUPLM03	Adjoint Approach to Accelerator Lattice Design	lattice, focusing, simulation, quadrupole	376
	T.M. Antonsen, B.L. Beaudoin, L. Dovlatyan, I. Haber UMD, College Park, Maryland, USA
	Funding: Supported by USDoE DESC0010301 Accelerator lattices are designed using computer codes that solve the equations of motion for charged particles in both prescribed and self-consistent fields. These codes are run in a mode in which particles enter a lattice region, travel for a finite distance, and have their coordinates recorded to assess various figures of merit (FoMs). The lattice is then optimized by varying the positions and strengths of the focusing elements. This optimization is done in a high dimensional parameter space, requiring multiple simulations of the particle trajectories to determine the dependence of the confinement on the many parameters. Sophisticated algorithms for this optimization are being introduced. However, the process is still time consuming. We propose to alter the design process using "adjoint" techniques []. Incorporation of an "adjoint" calculation of the trajectories and self-fields can, in several runs, determine the gradient in parameter space of a given FoM with respect to all lattice parameters. It includes naturally self-fields and can be embedded in existing codes such as WARP or Vorpal. The theoretical basis for the method and several applications will be presented. T. Antonsen, D. Chernin, J. Petillo, Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian Particle Dynamics, 2018 arXiv:1807.07898, Physics of Plasmas 26, 013109 (2019).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM03
About •	paper received ※ 23 August 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019
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TUPLM07	First Experimental Observations of the Plasma-Cascade Instability in the CeC PoP Accelerator	electron, experiment, lattice, solenoid	379
	I. Petrushina SUNY SB, Stony Brook, New York, USA Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, G. Wang, Y.H. Wu BNL, Upton, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA K. Shih SBU, Stony Brook, New York, USA
	Preservation of the beam quality is important for attaining the desirable properties of the beam. Collective effects can produce an instability severely degrading beam emittance, momentum spread and creating filamentation of the beam. Microbunching instability for beams traveling along a curved trajectory, and space charge driven parametric transverse instabilities are well-known and in-depth studied. However, none of the above include a microbunching longitudinal instability driven by modulations of the transverse beam size. This phenomenon was observed for the first time during the commissioning of the CeC PoP experiment. Based on the dynamics of this instability we named it a Plasma-Cascade Instability (PCI). PCI can strongly intensify longitudinal micro-bunching originating from the beam’s shot noise, and even saturate it. Resulting random density and energy microstructures in the beam can become a serious problem for generating high quality electron beams. On the other hand, such instability can drive novel high-power sources of broadband radiation. In this paper we present our experimental observations of the PCI and the supporting results of the numerical simulations.
	Poster TUPLM07 [17.319 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM07
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEYBA3	Tolerances for Plasma Wakefield Acceleration Drivers	FEL, luminosity, emittance, acceleration	614
	G.R. White, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	Transverse jitter tolerances are considered for beam-driven plasma accelerators. A simple model for jitter transfer from the drive to witness beam was developed and con-crete examples were studied for: high-brightness witness bunch injectors; high-energy boosters for FEL’s; and future Linear Colliders. For the LC application, we con-sider a superconducting Linac designed to minimize the jitter conditions of the drive beam. We use a start-to-end tracking model to simulate expected jitter performance. The tolerances on each subsystem of the driver Linac are found to be very tight, especially for magnet vibration which must be controlled at the sub-nm level. Work supported by the Department of Energy under Contract Number: DE-AC02-76SF00515.
	Slides WEYBA3 [6.178 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA3
About •	paper received ※ 27 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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WEPLM56	Development of Helium Gas Charge Stripper with Plasma Window	vacuum, cathode, heavy-ion, experiment	720
	J. Gao, F. Marti FRIB, East Lansing, Michigan, USA A. Lajoie NSCL, East Lansing, Michigan, USA
	Funding: This work is supported by NSF Award PHY-1565546. The cascade arc discharge, also called "plasma window", was suggested to be used as an interface to provide an effective separation between atmosphere and vacuum [1]. As suggested by Thieberger and Hershcovitch at Facility for Rare Isotope Beams (FRIB) workshop in 2009, helium plasma window offers an alternative to a large pumping system used in helium gas charge stripper for high intensity heavy ion beam accelerator facilities [2]. In this report, we present the recent progress on the development of helium plasma window with both 6mm and 10 mm diameter apparatus [3]. The size dependent sealing performance of helium plasma window has been investigated. Various diagnostics tools have been developed to improve our understanding of underlying physics. Over 140 hours continuous unattended operation of helium plasma window in recirculating gas system has been achieved, which suggests our system to be a feasible charge stripper solution for heavy ion beam accelerators. We also discuss anticipated future developments of plasma window. [1] A. Hershcovitch, Phys. Plasma 5, 2130 (1998). [2] H. Imao, et al., Phys. Rev. ST Accel. Beams 15, 123501 (2012). [3] A. LaJoie, J. Gao and F. Marti, IEEE Transactions on Plasma Science (2019)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM56
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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WEPLH16	Tolerances on Energy Deviation in Microbunched Electron Cooling	electron, hadron, impedance, kicker	837
	P. Baxevanis, G. Stupakov SLAC, Menlo Park, California, USA
	The performance of microbunched electron cooling (MBEC)* is highly dependent on the quality of the hadron and cooler electron beams. As a result, understanding the influence of beam imperfections is very important from the point of view of determining the tolerances of MBEC. In this work, we incorporate a non-zero average energy offset into our 1D formalism (,), which allows us to study the impact of effects such as correlated energy spread (chirp). In particular, we use our analytical theory to calculate the cooling rate loss due to the electron beam chirp and discuss ways to minimize the influence of this effect on MBEC. D. Ratner, Phys. Rev. Lett. 111, 084802 (2013). G. Stupakov, Phys. Rev. AB, 21, 114402 (2018). * G. Stupakov and P. Baxevanis, Phys. Rev. AB, 22, 034401 (2019).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH16
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLH17	Diffusion and Nonlinear Plasma Effects in Microbunched Electron Cooling	electron, hadron, emittance, kicker	841
	P. Baxevanis, G. Stupakov SLAC, Menlo Park, California, USA
	The technique of michrobunched electron cooling (MBEC) is an attractive scheme for enhancing the brightness of hadron beams in future high-energy circular colliders (). To achieve the required cooling times for a realistic machine configuration, it is necessary to boost the bunching of the cooler electron beam through amplification sections that utilize plasma oscillations. However, these plasma sections also amplify the intrinsic noise of the electron beam, leading to additional diffusion that can be very detrimental to the cooling. Moreover, they can exhibit nonlinear gain behavior, which reduces performance and limits the applicability of theory. In this paper, we study both of these important effects analytically with the aim of quantifying their influence and keeping them under control. D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH17
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLH20	Modeling of H⁻ Ion Source at LANSCE	ion-source, experiment, operation, electron	848
	N.A. Yampolsky, I. Draganić, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	Funding: Work supported by the US Department of Energy under Contract Number DE-AC52-06NA25396 We report on the progress in modeling performance of the H⁻ ion source at LANSCE. The key aspect we address is the lifetime of the tungsten filament. The lifetime depends on multiple parameters of the ion source and can dramatically vary in different regimes of operation. We use the multiphysics approach to model the performance of the ion source. The detailed analysis has been made to recognize key physical processes, which affect the degradation of the filament. The analysis resulted in the analytical model, which includes relevant processes from the first principles. The numerical code based on this model has been developed and benchmarked. The results of the modeling show good agreement with experimental data. As a result, the developed model allows predicting the performance of the ion source in various regimes of operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH20
About •	paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLO05	Developing Criteria for Laser Transverse Instability in LWFA Simulations	laser, simulation, wakefield, electron	855
	Y. Yan, L.D. Amorim, P. Iapozzuto, V. Litvinenko, N. Vafaei-Najafabadi Stony Brook University, Stony Brook, USA M. Babzien, M.G. Fedurin, Y.C. Jing, K. Kusche, M.A. Palmer, I. Pogorelsky, M.N. Polyanskiy BNL, Upton, New York, USA M. Downer, J.R. Welch, R. Zgadzaj The University of Texas at Austin, Austin, Texas, USA C. Joshi, W.B. Mori UCLA, Los Angeles, California, USA P. Kumar, V. Samulyak SBU, Stony Brook, USA
	Funding: We acknowledge resources of NERSC facility, operated under Contract No. DE-AC02-5CH11231, and of SEAWULF at Stony Brook University as well as funding from SBU-BNL Seed Grants. Laser-driven plasma wakefield acceleration (LWFA) is considered as a potential technology for future colliders and light sources. To make the best use of a laser’s power, the laser is expected to maintain a stable propagation. A transverse instability is observed in our previous simulations when a long, intense CO₂ laser propagates inside a plasma. This unstable motion is accompanied by strong transverse diffraction of the laser power and results in the disruption of the ion channel typically used for radiation generation. We investigated the hosing-like instability using the Particle-in-Cell code OSIRIS** by modeling the laser portion where this instability is seeded and then evolves. In this proceeding, a criteria will be described that allows for the characterization of the temporal and spatial evolution of this instability. J. Yan, et al. , AAC, IEEE, 2018. * L. Nemos et al., PPCF, 58(3), 2016. ***R. A. Fonseca et al., Lecture Notes Computation Science (2331) 342, 2002.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO05
About •	paper received ※ 16 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019
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WEPLO18	Numerical Study of Coherent Radiation from Induced Plasma Dipole Oscillation by Detuned Laser Pulses	laser, radiation, dipole, simulation	874
	P.C. Castillo, S.D. Rodriguez, D.A. Wan SUNY Farmingdale State College, State University of New York, Farmingdale, New York, USA B. Gross City College of The City University of New York, New York, USA M.S. Hur, S. Kylychbekov, H.S. Song UNIST, Ulsan, Republic of Korea D.G. Lee SBU, Stony Brook, New York, USA K. Yu BNL, Upton, New York, USA
	The study of intense laser-plasma interactions is a growing field of both theoretical and applied research. This research focuses on simulating the cross/self-interactions between high-intense short laser pulses and an initial target for preliminary ionization. Unlike our previous studies of laser-matter interaction over preformed plasma, we will explore the injection of laser pulses to induce background plasma driven by the self-guided laser wakefield mechanism, which is used to perturb the plasma for induced dipole oscillations followed by radiation. Inducing a cylindrical spatial plasma column within the laser beam radius regime, it is expected that a stable spatially localized plasma channel will result and the emitted radiation from the plasma dipole oscillation (PDO) will not be affected by surrounding absorption, resulting in effective radiation. We will depict the injection of laser pulses accounting for parameters such as field intensity, profile and phase difference defining the coordinated pulses to assess the potential of enhancing the efficiency and spectral properties of the transverse emitted radiation due to the counter-propagating pulses interaction in plasma.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO18
About •	paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLO19	Probing Multiperiod Plasma Response Regimes using Single Shot Wakefield Measurements	wakefield, electron, emittance, cathode	878
	R.J. Roussel, G. Andonian, W.J. Lynn, J.B. Rosenzweig UCLA, Los Angeles, California, USA M.E. Conde, D.S. Doran, G. Ha, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA J. Seok UNIST, Ulsan, Republic of Korea
	Funding: DE-SC0017648 Systematic differences between the linear and nonlinear regimes of plasma wakefield acceleration from electron beams are manifested in the plasma response. Typically, the ratio of peak beam density to nominal plasma density determines operation in the linear or nonlinear regime. Previous reports have shown that a the cross-over into the nonlinear regime is associated with an increase in the wakefield amplitude, as well as sawtooth-like shape. In this paper, we present preliminary measurements of quasi-nonlinear wakefields driven by a linearly ramped beam, with a maximum charge close to the unperturbed plasma density. We also demonstrate nonlinear wakefield behavior in a probe bunch using a single shot, multi-period wakefield measurement and its dependency on plasma density.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO19
About •	paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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WEPLE02	Integrated Accelerator Simulation with Electromagnetics and Beam Physics Codes	simulation, cavity, electron, emittance	885
	L. Ge, Z. Li, C.-K. Ng, L. Xiao SLAC, Menlo Park, California, USA D.A. Bizzozero, J. Qiang, J.-L. Vay LBNL, Berkeley, California, USA D.P. Grote LLNL, Livermore, California, USA
	Funding: Work supported by US Department of Energy under contracts AC02-76SF00515, DE-AC02-05CH11231 and DE-AC52-07NA27344. Used resources of the National Energy Research Scientific Computing Center. This paper presents an integrated simulation capability for accelerators including electromagnetic field and beam dynamics effects. The integrated codes include the parallel finite-element code suite ACE3P for electromagnetic field calculation of beamline components, the parallel particle-in-cell (PIC) code IMPACT for beamline particle tracking with space-charge effects, and the parallel self-consistent PIC code Warp for beam and plasma simulations. The common data format OpenPMD has been adopted for efficient field and particle I/O data transfer between codes. One application is to employ ACE3P and IMPACT for studying beam qualities in accelerator beamlines. Another is to combine ACE3P and Warp for investigating plasma processing for operational performance of RF cavities. A module for mapping the CAD geometry used in ACE3P to Warp Cartesian grid representation has been developed. Furthermore, a workflow has been implemented that enables the execution of integrated simulation on HPC systems. Examples for simulation of the LCLS-II injector using ACE3P-IMPACT and plasma ignition in SRF cavities using ACE3P-Warp will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE02
About •	paper received ※ 20 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019
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Paper

Title

Other Keywords

Page

MOYBB2

Recent Advance in ECR Ion Sources

ECR, ion-source, operation, electron

31

G. Machicoane, N.K. Bultman, P. Morrison, M. Omelayenko, X. Rao
FRIB, East Lansing, Michigan, USA
D. Arbelaez, R.R. Hafalia, P. Pan, S. Prestemon
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661, the State of Michigan and Michigan State University.
High continuous wave (cw) current of highly charged ion beams are required for several heavy ion accelerator facilities including the Facility for Rare Isotope Beams (FRIB). In most cases, Electron-Cyclotron-Resonance (ECR) ion sources remain the only ion source capable to meet the beam intensity requirement for these facilities. Performances of ECR ion source have increased by several order of magnitude since their inception in the 1970s mostly driven by increasing the resonance frequency with today current state of the art ECR ion source operating from 24 to 28 GHz. This paper provides an overview of recent advance in the design and operation of ECR ion source including plans to develop the next generation of ion source capable of operating above 40 GHz. A detailed account of the design and status of the new superconducting ECR ion source in construction for FRIB will also be reported.

Slides MOYBB2 [9.483 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB2

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paper received ※ 02 September 2019 paper accepted ※ 16 November 2020 issue date ※ 08 October 2019

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MOYBB5

Characterization and Performance of Plasma Window for Gas Flow Restriction in Different Geometries

electron, cathode, target, diagnostics

44

A. Lajoie
NSCL, East Lansing, Michigan, USA
J. Gao, F. Marti
FRIB, East Lansing, Michigan, USA

Funding: This work is supported by NSF Award PHY-1565546.
The plasma window is a DC cascaded arc whose function is to restrict gas flow from a high pressure region to a low pressure region without the use of any solid separation*. As a result, the plasma window allows a greater pressure to be maintained than otherwise possible. This is a beneficial characteristic for gas charge strippers for ion accelerators, since the higher pressures enable the stripper to be shorter and allow the same amount of stripping interactions**. The flow rate reduction is established by the increase in gas temperature from the power deposited into the plasma via the cathodes, resulting in a dramatically increased viscosity. The flow rate reduction, depends on the properties of the plasma, including the electron density and temperature, pressure, and electrical conductivity. Understanding these properties in multiple arc geometries - in this work having either 6 mm or 10 mm channel diameter - provides a means optimizing the plasma window for a given design. Determinations of the properties for different conditions are shown, and results are compared with a PLASIMO simulation, which has been shown to yield comparable properties to measurements in an argon arc***.
*A. Hershcovitch, Phys. Plasma 5, 2130 (1998).
**J. A. Nolen and F. Marti, Rev. Accel. Sci. Tech. 6, 221 (2013).
***G. M. W. Kroesen et al., Plas. Chem. and Plas. Proc. 10, 531 (1990).

Slides MOYBB5 [4.132 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBB5

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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MOPLH08

Tests of Cs-Free Operation of the SNS RF H⁻ Ion Sources

operation, ion-source, neutron, power-supply

184

B. Han, S.M. Cousineau, S.N. Murray, T.R. Pennisi, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA
T.M. Sarmento, O.A. Tarvainen
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
C. Stinson
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was performed at Oak Ridge National Laboratory, which is managed by UT-Battelle, LLC, under contract number DE-AC05-00OR22725 for the United States Department of Energy.
Tests were performed at SNS in collaboration with visiting colleagues from ISIS, UK to evaluate the uncesiated beam performance of the SNS RF H⁻ ion sources. Two spare experimental sources, one with internal antenna and one with external antenna were used for the tests. The beam currents achieved with Cs-free operations accounted for about 1/3 to 1/2 of the beam currents produced with cesiated operations. ~17 mA uncesiated H⁻ current was demonstrated within the tested RF power range up to 65 kW with the internal antenna source and ~15 mA with up to 40 kW RF with the external antenna source. In Cs-free operations, the power supply for the electron dumping electrode was loaded down below its set voltage but was not too drastic to tamper the operation.

Poster MOPLH08 [0.949 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH08

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paper received ※ 27 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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MOPLH23

An Analysis of Potential Compact Positron Beam Source

positron, emittance, cavity, simulation

220

R.M. Hessami
UCLA, Los Angeles, USA
S.J. Gessner
CERN, Geneva, Switzerland

For positron studies in plasma wakefield accelerators such as AWAKE, the development of new, cheaper, and compact positron beam sources is necessary. Using an electrostatic trap with parameters similar to other experiments, this paper explores converting that trapped positron plasma into a usable beam. Bunching is initially accomplished by an electrostatic buncher and the beam is accelerated to 148 keV by pulsed electrostatic accelerators. This is necessary for injection into the beta-matched rf cavities operating at 600 MHz, which bring the positron beam to a transverse emittance of 1.3 pi mrad mm, a longitudinal emittance of 93.3 pi keV mm, stdz of 1.85 mm and an energy of 22 MeV. The beamline used here is far simpler and less expensive than those at many facilities, such as SLAC, allowing for a cheap source of positron beams, potentially opening up positron beam studies to many facilities that could not previously afford such a source.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH23

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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TUZBB5

Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma

emittance, electron, experiment, HOM

363

C. Mallick, M. Bandyopadhyay, R. Kumar
Institute for Plasma Research, Bhat, Gandhinagar, India

The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth.
Reference
’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’
’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’
’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’

Slides TUZBB5 [5.298 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB5

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paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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TUPLM03

Adjoint Approach to Accelerator Lattice Design

lattice, focusing, simulation, quadrupole

376

T.M. Antonsen, B.L. Beaudoin, L. Dovlatyan, I. Haber
UMD, College Park, Maryland, USA

Funding: Supported by USDoE DESC0010301
Accelerator lattices are designed using computer codes that solve the equations of motion for charged particles in both prescribed and self-consistent fields. These codes are run in a mode in which particles enter a lattice region, travel for a finite distance, and have their coordinates recorded to assess various figures of merit (FoMs). The lattice is then optimized by varying the positions and strengths of the focusing elements. This optimization is done in a high dimensional parameter space, requiring multiple simulations of the particle trajectories to determine the dependence of the confinement on the many parameters. Sophisticated algorithms for this optimization are being introduced. However, the process is still time consuming. We propose to alter the design process using "adjoint" techniques [*]. Incorporation of an "adjoint" calculation of the trajectories and self-fields can, in several runs, determine the gradient in parameter space of a given FoM with respect to all lattice parameters. It includes naturally self-fields and can be embedded in existing codes such as WARP or Vorpal. The theoretical basis for the method and several applications will be presented.
* T. Antonsen, D. Chernin, J. Petillo, Adjoint Approach to Beam Optics Sensitivity Based on Hamiltonian Particle Dynamics, 2018 arXiv:1807.07898, Physics of Plasmas 26, 013109 (2019).

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paper received ※ 23 August 2019 paper accepted ※ 13 September 2019 issue date ※ 08 October 2019

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TUPLM07

First Experimental Observations of the Plasma-Cascade Instability in the CeC PoP Accelerator

electron, experiment, lattice, solenoid

379

I. Petrushina
SUNY SB, Stony Brook, New York, USA
Y.C. Jing, V. Litvinenko, J. Ma, I. Pinayev, G. Wang, Y.H. Wu
BNL, Upton, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA
K. Shih
SBU, Stony Brook, New York, USA

Preservation of the beam quality is important for attaining the desirable properties of the beam. Collective effects can produce an instability severely degrading beam emittance, momentum spread and creating filamentation of the beam. Microbunching instability for beams traveling along a curved trajectory, and space charge driven parametric transverse instabilities are well-known and in-depth studied. However, none of the above include a microbunching longitudinal instability driven by modulations of the transverse beam size. This phenomenon was observed for the first time during the commissioning of the CeC PoP experiment. Based on the dynamics of this instability we named it a Plasma-Cascade Instability (PCI). PCI can strongly intensify longitudinal micro-bunching originating from the beam’s shot noise, and even saturate it. Resulting random density and energy microstructures in the beam can become a serious problem for generating high quality electron beams. On the other hand, such instability can drive novel high-power sources of broadband radiation. In this paper we present our experimental observations of the PCI and the supporting results of the numerical simulations.

Poster TUPLM07 [17.319 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM07

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEYBA3

Tolerances for Plasma Wakefield Acceleration Drivers

FEL, luminosity, emittance, acceleration

614

G.R. White, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Transverse jitter tolerances are considered for beam-driven plasma accelerators. A simple model for jitter transfer from the drive to witness beam was developed and con-crete examples were studied for: high-brightness witness bunch injectors; high-energy boosters for FEL’s; and future Linear Colliders. For the LC application, we con-sider a superconducting Linac designed to minimize the jitter conditions of the drive beam. We use a start-to-end tracking model to simulate expected jitter performance. The tolerances on each subsystem of the driver Linac are found to be very tight, especially for magnet vibration which must be controlled at the sub-nm level.
Work supported by the Department of Energy under Contract Number: DE-AC02-76SF00515.

Slides WEYBA3 [6.178 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEYBA3

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paper received ※ 27 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

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WEPLM56

Development of Helium Gas Charge Stripper with Plasma Window

vacuum, cathode, heavy-ion, experiment

720

J. Gao, F. Marti
FRIB, East Lansing, Michigan, USA
A. Lajoie
NSCL, East Lansing, Michigan, USA

Funding: This work is supported by NSF Award PHY-1565546.
The cascade arc discharge, also called "plasma window", was suggested to be used as an interface to provide an effective separation between atmosphere and vacuum [1]. As suggested by Thieberger and Hershcovitch at Facility for Rare Isotope Beams (FRIB) workshop in 2009, helium plasma window offers an alternative to a large pumping system used in helium gas charge stripper for high intensity heavy ion beam accelerator facilities [2]. In this report, we present the recent progress on the development of helium plasma window with both 6mm and 10 mm diameter apparatus [3]. The size dependent sealing performance of helium plasma window has been investigated. Various diagnostics tools have been developed to improve our understanding of underlying physics. Over 140 hours continuous unattended operation of helium plasma window in recirculating gas system has been achieved, which suggests our system to be a feasible charge stripper solution for heavy ion beam accelerators. We also discuss anticipated future developments of plasma window.
[1] A. Hershcovitch, Phys. Plasma 5, 2130 (1998).
[2] H. Imao, et al., Phys. Rev. ST Accel. Beams 15, 123501 (2012).
[3] A. LaJoie, J. Gao and F. Marti, IEEE Transactions on Plasma Science (2019)

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM56

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paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLH16

Tolerances on Energy Deviation in Microbunched Electron Cooling

electron, hadron, impedance, kicker

837

P. Baxevanis, G. Stupakov
SLAC, Menlo Park, California, USA

The performance of microbunched electron cooling (MBEC)* is highly dependent on the quality of the hadron and cooler electron beams. As a result, understanding the influence of beam imperfections is very important from the point of view of determining the tolerances of MBEC. In this work, we incorporate a non-zero average energy offset into our 1D formalism (**,***), which allows us to study the impact of effects such as correlated energy spread (chirp). In particular, we use our analytical theory to calculate the cooling rate loss due to the electron beam chirp and discuss ways to minimize the influence of this effect on MBEC.
* D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).
** G. Stupakov, Phys. Rev. AB, 21, 114402 (2018).
*** G. Stupakov and P. Baxevanis, Phys. Rev. AB, 22, 034401 (2019).

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH16

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH17

Diffusion and Nonlinear Plasma Effects in Microbunched Electron Cooling

electron, hadron, emittance, kicker

841

P. Baxevanis, G. Stupakov
SLAC, Menlo Park, California, USA

The technique of michrobunched electron cooling (MBEC) is an attractive scheme for enhancing the brightness of hadron beams in future high-energy circular colliders (*). To achieve the required cooling times for a realistic machine configuration, it is necessary to boost the bunching of the cooler electron beam through amplification sections that utilize plasma oscillations. However, these plasma sections also amplify the intrinsic noise of the electron beam, leading to additional diffusion that can be very detrimental to the cooling. Moreover, they can exhibit nonlinear gain behavior, which reduces performance and limits the applicability of theory. In this paper, we study both of these important effects analytically with the aim of quantifying their influence and keeping them under control.
* D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).

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paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLH20

Modeling of H⁻ Ion Source at LANSCE

ion-source, experiment, operation, electron

848

N.A. Yampolsky, I. Draganić, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the US Department of Energy under Contract Number DE-AC52-06NA25396
We report on the progress in modeling performance of the H⁻ ion source at LANSCE. The key aspect we address is the lifetime of the tungsten filament. The lifetime depends on multiple parameters of the ion source and can dramatically vary in different regimes of operation. We use the multiphysics approach to model the performance of the ion source. The detailed analysis has been made to recognize key physical processes, which affect the degradation of the filament. The analysis resulted in the analytical model, which includes relevant processes from the first principles. The numerical code based on this model has been developed and benchmarked. The results of the modeling show good agreement with experimental data. As a result, the developed model allows predicting the performance of the ion source in various regimes of operation.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH20

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paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLO05

Developing Criteria for Laser Transverse Instability in LWFA Simulations

laser, simulation, wakefield, electron

855

Y. Yan, L.D. Amorim, P. Iapozzuto, V. Litvinenko, N. Vafaei-Najafabadi
Stony Brook University, Stony Brook, USA
M. Babzien, M.G. Fedurin, Y.C. Jing, K. Kusche, M.A. Palmer, I. Pogorelsky, M.N. Polyanskiy
BNL, Upton, New York, USA
M. Downer, J.R. Welch, R. Zgadzaj
The University of Texas at Austin, Austin, Texas, USA
C. Joshi, W.B. Mori
UCLA, Los Angeles, California, USA
P. Kumar, V. Samulyak
SBU, Stony Brook, USA

Funding: We acknowledge resources of NERSC facility, operated under Contract No. DE-AC02-5CH11231, and of SEAWULF at Stony Brook University as well as funding from SBU-BNL Seed Grants.
Laser-driven plasma wakefield acceleration (LWFA) is considered as a potential technology for future colliders and light sources. To make the best use of a laser’s power, the laser is expected to maintain a stable propagation. A transverse instability is observed in our previous simulations when a long, intense CO₂ laser propagates inside a plasma*. This unstable motion is accompanied by strong transverse diffraction of the laser power and results in the disruption of the ion channel typically used for radiation generation**. We investigated the hosing-like instability using the Particle-in-Cell code OSIRIS*** by modeling the laser portion where this instability is seeded and then evolves. In this proceeding, a criteria will be described that allows for the characterization of the temporal and spatial evolution of this instability.
*J. Yan, et al. , AAC, IEEE, 2018.
** L. Nemos et al., PPCF, 58(3), 2016.
***R. A. Fonseca et al., Lecture Notes Computation Science (2331) 342, 2002.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO05

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paper received ※ 16 September 2019 paper accepted ※ 04 December 2019 issue date ※ 08 October 2019

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WEPLO18

Numerical Study of Coherent Radiation from Induced Plasma Dipole Oscillation by Detuned Laser Pulses

laser, radiation, dipole, simulation

874

P.C. Castillo, S.D. Rodriguez, D.A. Wan
SUNY Farmingdale State College, State University of New York, Farmingdale, New York, USA
B. Gross
City College of The City University of New York, New York, USA
M.S. Hur, S. Kylychbekov, H.S. Song
UNIST, Ulsan, Republic of Korea
D.G. Lee
SBU, Stony Brook, New York, USA
K. Yu
BNL, Upton, New York, USA

The study of intense laser-plasma interactions is a growing field of both theoretical and applied research. This research focuses on simulating the cross/self-interactions between high-intense short laser pulses and an initial target for preliminary ionization. Unlike our previous studies of laser-matter interaction over preformed plasma, we will explore the injection of laser pulses to induce background plasma driven by the self-guided laser wakefield mechanism, which is used to perturb the plasma for induced dipole oscillations followed by radiation. Inducing a cylindrical spatial plasma column within the laser beam radius regime, it is expected that a stable spatially localized plasma channel will result and the emitted radiation from the plasma dipole oscillation (PDO) will not be affected by surrounding absorption, resulting in effective radiation. We will depict the injection of laser pulses accounting for parameters such as field intensity, profile and phase difference defining the coordinated pulses to assess the potential of enhancing the efficiency and spectral properties of the transverse emitted radiation due to the counter-propagating pulses interaction in plasma.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO18

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paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLO19

Probing Multiperiod Plasma Response Regimes using Single Shot Wakefield Measurements

wakefield, electron, emittance, cathode

878

R.J. Roussel, G. Andonian, W.J. Lynn, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
M.E. Conde, D.S. Doran, G. Ha, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
J. Seok
UNIST, Ulsan, Republic of Korea

Funding: DE-SC0017648
Systematic differences between the linear and nonlinear regimes of plasma wakefield acceleration from electron beams are manifested in the plasma response. Typically, the ratio of peak beam density to nominal plasma density determines operation in the linear or nonlinear regime. Previous reports have shown that a the cross-over into the nonlinear regime is associated with an increase in the wakefield amplitude, as well as sawtooth-like shape. In this paper, we present preliminary measurements of quasi-nonlinear wakefields driven by a linearly ramped beam, with a maximum charge close to the unperturbed plasma density. We also demonstrate nonlinear wakefield behavior in a probe bunch using a single shot, multi-period wakefield measurement and its dependency on plasma density.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO19

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paper received ※ 31 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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WEPLE02

Integrated Accelerator Simulation with Electromagnetics and Beam Physics Codes

simulation, cavity, electron, emittance

885

L. Ge, Z. Li, C.-K. Ng, L. Xiao
SLAC, Menlo Park, California, USA
D.A. Bizzozero, J. Qiang, J.-L. Vay
LBNL, Berkeley, California, USA
D.P. Grote
LLNL, Livermore, California, USA

Funding: Work supported by US Department of Energy under contracts AC02-76SF00515, DE-AC02-05CH11231 and DE-AC52-07NA27344. Used resources of the National Energy Research Scientific Computing Center.
This paper presents an integrated simulation capability for accelerators including electromagnetic field and beam dynamics effects. The integrated codes include the parallel finite-element code suite ACE3P for electromagnetic field calculation of beamline components, the parallel particle-in-cell (PIC) code IMPACT for beamline particle tracking with space-charge effects, and the parallel self-consistent PIC code Warp for beam and plasma simulations. The common data format OpenPMD has been adopted for efficient field and particle I/O data transfer between codes. One application is to employ ACE3P and IMPACT for studying beam qualities in accelerator beamlines. Another is to combine ACE3P and Warp for investigating plasma processing for operational performance of RF cavities. A module for mapping the CAD geometry used in ACE3P to Warp Cartesian grid representation has been developed. Furthermore, a workflow has been implemented that enables the execution of integrated simulation on HPC systems. Examples for simulation of the LCLS-II injector using ACE3P-IMPACT and plasma ignition in SRF cavities using ACE3P-Warp will be presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE02

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paper received ※ 20 August 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019

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