NAPAC2019 - List of Keywords (wakefield)

Paper	Title	Other Keywords	Page
MOZBA6	The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project	impedance, simulation, cavity, vacuum	74
	D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini LBNL, Berkeley, California, USA K.L.F. Bane SLAC, Menlo Park, California, USA
	Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.
	Slides MOZBA6 [8.926 MB]
	Poster MOZBA6 [3.542 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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MOZBB2	Experiments with Metamaterial-Based Metallic Accelerating Structures	experiment, acceleration, radiation, GUI	78
	X. Lu SLAC, Menlo Park, California, USA M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA X. Lu, I. Mastovsky, J.F. Picard, M.A. Shapiro, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA M.M. Peng AAI/ANL, Lemont, Illinois, USA J. Seok UNIST, Ulsan, Republic of Korea
	Funding: U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award No. DE-SC0015566 at MIT and No. DE-AC02-06CH11357 at ANL We present experimental studies of metamaterial (MTM) structures for wakefield acceleration. The MTM structure is an all-metal periodic structure with its period much smaller than the wavelength at X-band. The fundamental TM mode has a negative group velocity, so an electron beam traveling through the structure radiates by reversed Cherenkov radiation. Two experiments have been completed at the Argonne Wakefield Accelerator (AWA), namely the Stage-I and Stage-II experiments. Differences between the two experiments include: (1) Structure length (Stage-I 8 cm, Stage-II 20 cm); (2) Bunch number used to excite the structure (Stage-I up to 2 bunches, Stage-II up to 8 bunches). In the Stage-I experiment, two bunches with a total charge of 85 nC generated 80 MW of RF power in a 2 ns long pulse. In the Stage-II experiment, the highest peak power reached 380 MW in a 10 ns long pulse from a train of 8 bunches with a total charge of 224 nC. Acceleration of a witness bunch has not been demonstrated yet, but the extracted power can be transferred to a separate accelerator for two-beam acceleration or directly applied to a trailing witness bunch in the same structure for collinear acceleration.
	Slides MOZBB2 [8.172 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB2
About •	paper received ※ 27 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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MOPLH26	Design of a Compact Wakefield Accelerator Based on a Corrugated Waveguide	GUI, coupling, simulation, electron	232
	A.E. Siy UW-Madison/PD, Madison, Wisconsin, USA G.J. Waldschmidt, A. Zholents ANL, Lemont, Illinois, USA
	A compact wakefield accelerator is being developed at the Argonne National Laboratory for a future multiuser x-ray free electron laser facility. A cylindrical structure with a 2 mm internal diameter and fine corrugations on the wall will be used to create Čerenkov radiation. A "drive" bunch producing radiation at 180 GHz will create accelerating gradients on the order of 100 MV/m for the "witness" bunch. The corrugated structure will be approximately half meter long with the entire accelerator spanning a few tens of meters. An ultra-compact transition region between each corrugated structure has been designed to accommodate an output coupler, a notch filter, an integrated offset monitor, bellows, pumping and water cooling ports. The output coupler will extract on the order of a kilowatt of power from the Čerenkov radiation unused by the witness bunch. The integrated offset monitor is a novel diagnostic which will measure the cumulative offset of the electron beam in the corrugated structure upstream of the monitor. The specific details of the rf design will be presented here.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH26
About •	paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019
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MOPLO23	Investigation of Various Fabrication Methods to Produce a 180GHz Corrugated Waveguide Structure in 2mm Diameter 0.5m Long Copper Tube for the Compact Wakefield Accelerator for FEL Facility	GUI, laser, electron, FEL	286
	K.J. Suthar, D.S. Doran, W.G. Jansma, S.S. Sorsher, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents ANL, Lemont, Illinois, USA A.E. Siy UW-Madison/PD, Madison, Wisconsin, USA
	Funding: This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated by the Argonne National Laboratory under Contract No. DEAC0206CH11357. Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail. [1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO23
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
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TUPLM09	A Fast Method to Evaluate Transverse Coupled-Bunch Stability at Non-Zero Chromaticity	synchrotron, dipole, betatron, simulation	387
	R.R. Lindberg ANL, Lemont, Illinois, USA
	Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 We present a dispersion relation that gives the complex growth rate for coupled-bunch instabilities at arbitrary chromaticity in terms of its value at zero chromaticity. We compare predictions of the theory to elegant tracking simulations, and show that there are two distinct regimes to stability depending upon whether the zero chromaticity growth rate is smaller or larger than the chromatic tune shift over the bunch. We derive an approximate expression that is easily solved numerically, and furthermore indicate how the formalism can be extended to describe arbitrary longitudinal potentials.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM09
About •	paper received ※ 25 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019
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TUPLH07	High-Gradient Short Pulse Accelerating Structures	electron, experiment, impedance, acceleration	500
	S.V. Kuzikov, S.P. Antipov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.
	Poster TUPLH07 [0.999 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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WEPLM68	Design of a Dielectric-Loaded Accelerator for Short Pulse High Gradient Research	acceleration, simulation, accelerating-gradient, experiment	751
	M.M. Peng, J. Shi TUB, Beijing, People’s Republic of China M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA
	The short-pulse two-beam acceleration approach is a promising candidate to meet the cost and luminosity requirements for future linear colliders. Dielectric-loaded structure has been intensely investigated for this approach because of its low fabrication cost, low RF loss, and potential to withstand GV/m gradient. An X-band 11.7~GHz dielectric-loaded accelerator (DLA) has been designed for high power test with short RF pulses (3~ns) generated from a power extractor driven by high charge bunches at Argonne Wakefield Accelerator (AWA) facility. The gradient is expected to be over 100~MV/m with the maximum input power of 400~MW.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM68
About •	paper received ※ 05 September 2019 paper accepted ※ 27 November 2019 issue date ※ 08 October 2019
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WEPLS09	Fast Two-Dimensional Calculation of Coherent Synchrotron Radiation in Relativistic Beams	radiation, synchrotron, electron, synchrotron-radiation	783
	J. Tang, G. Stupakov SLAC, Menlo Park, California, USA
	Coherent Synchrotron Radiation(CSR) in a relavistic beam during compression can lead to longitudinal modulation of the bunch with wavelength smaller than bunch length and is regarded as one of the main sources of emittance growth in the bunch compressor. Current simulations containing CSR wake fields often utilize one-dimensional model assuming a line beam. Despite its good computation efficiency, 1D CSR model can be inaccurate in many cases because it ignores the so-called ’compression effect’. On the other hand, the existing 3D codes are often slow and have high demands on computational resources. In this paper we propose a new method for calculation of the three-dimensional CSR wakefields in relativistic beams with integrals of retarded potentials. It generalizes the 1D model and includes the transient effects at the entrance and the exit from the magnet. Within given magnetic lattice and initial beam distributions, the formalism reduces to 2D or 3D integration along the trajectory and therefore allows fast numerical calculations using 2D or 3D matrices.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS09
About •	paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
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WEPLO05	Developing Criteria for Laser Transverse Instability in LWFA Simulations	laser, plasma, simulation, 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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WEPLO06	Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration	laser, simulation, electron, linac	858
	W.H. Tan, P. Piot Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA A. Zholents, A. Zholents ANL, Lemont, Illinois, USA
	Funding: This work is supported by the U.S. Department of Energy, Office of Science under contracts No. DE-AC02-06CH11357 (via a laboratory- directed R&D program at ANL) and No. DE-SC0018656 at NIU. Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser . Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability. A. Zholents et al., "A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility"*
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO06
About •	paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
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WEPLO19	Probing Multiperiod Plasma Response Regimes using Single Shot Wakefield Measurements	plasma, 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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FRXBA3	Applications and Opportunities for the Emittance Exchange Beamline	emittance, controls, electron, wiggler	981
	G. Ha, M.E. Conde, J.G. Power ANL, Lemont, Illinois, USA M. Chung, J. Seok UNIST, Ulsan, Republic of Korea
	Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357. Emittance exchange (EEX) provides a powerful method of controlling the longitudinal phase space using the relatively simpler methods of transverse control. An EEX beamline was installed at the Argonne Wakefield Accelerator (AWA) facility in 2015. Several experiments important to the wakefield acceleration, such as a high transformer ratio from shaped bunches, have already been demonstrated. We are currently developing several applications of the EEX beamline including temporal profile shaping, THz radiation generation, time-energy correlation control, diagnostic uses of EEX etc. We will present the on-going EEX program for longitudinal phase space control taking place at the AWA facility, and discuss recently discovered new opportunities.
	Slides FRXBA3 [6.814 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA3
About •	paper received ※ 02 September 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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Paper

Title

Other Keywords

Page

MOZBA6

The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project

impedance, simulation, cavity, vacuum

74

D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini
LBNL, Berkeley, California, USA
K.L.F. Bane
SLAC, Menlo Park, California, USA

Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.

Slides MOZBA6 [8.926 MB]

Poster MOZBA6 [3.542 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6

About •

paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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MOZBB2

Experiments with Metamaterial-Based Metallic Accelerating Structures

experiment, acceleration, radiation, GUI

78

X. Lu
SLAC, Menlo Park, California, USA
M.E. Conde, D.S. Doran, G. Ha, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
X. Lu, I. Mastovsky, J.F. Picard, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
M.M. Peng
AAI/ANL, Lemont, Illinois, USA
J. Seok
UNIST, Ulsan, Republic of Korea

Funding: U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award No. DE-SC0015566 at MIT and No. DE-AC02-06CH11357 at ANL
We present experimental studies of metamaterial (MTM) structures for wakefield acceleration. The MTM structure is an all-metal periodic structure with its period much smaller than the wavelength at X-band. The fundamental TM mode has a negative group velocity, so an electron beam traveling through the structure radiates by reversed Cherenkov radiation. Two experiments have been completed at the Argonne Wakefield Accelerator (AWA), namely the Stage-I and Stage-II experiments. Differences between the two experiments include: (1) Structure length (Stage-I 8 cm, Stage-II 20 cm); (2) Bunch number used to excite the structure (Stage-I up to 2 bunches, Stage-II up to 8 bunches). In the Stage-I experiment, two bunches with a total charge of 85 nC generated 80 MW of RF power in a 2 ns long pulse. In the Stage-II experiment, the highest peak power reached 380 MW in a 10 ns long pulse from a train of 8 bunches with a total charge of 224 nC. Acceleration of a witness bunch has not been demonstrated yet, but the extracted power can be transferred to a separate accelerator for two-beam acceleration or directly applied to a trailing witness bunch in the same structure for collinear acceleration.

Slides MOZBB2 [8.172 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBB2

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

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MOPLH26

Design of a Compact Wakefield Accelerator Based on a Corrugated Waveguide

GUI, coupling, simulation, electron

232

A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA
G.J. Waldschmidt, A. Zholents
ANL, Lemont, Illinois, USA

A compact wakefield accelerator is being developed at the Argonne National Laboratory for a future multiuser x-ray free electron laser facility. A cylindrical structure with a 2 mm internal diameter and fine corrugations on the wall will be used to create Čerenkov radiation. A "drive" bunch producing radiation at 180 GHz will create accelerating gradients on the order of 100 MV/m for the "witness" bunch. The corrugated structure will be approximately half meter long with the entire accelerator spanning a few tens of meters. An ultra-compact transition region between each corrugated structure has been designed to accommodate an output coupler, a notch filter, an integrated offset monitor, bellows, pumping and water cooling ports. The output coupler will extract on the order of a kilowatt of power from the Čerenkov radiation unused by the witness bunch. The integrated offset monitor is a novel diagnostic which will measure the cumulative offset of the electron beam in the corrugated structure upstream of the monitor. The specific details of the rf design will be presented here.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLH26

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paper received ※ 27 August 2019 paper accepted ※ 12 September 2019 issue date ※ 08 October 2019

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MOPLO23

Investigation of Various Fabrication Methods to Produce a 180GHz Corrugated Waveguide Structure in 2mm Diameter 0.5m Long Copper Tube for the Compact Wakefield Accelerator for FEL Facility

GUI, laser, electron, FEL

286

K.J. Suthar, D.S. Doran, W.G. Jansma, S.S. Sorsher, E. Trakhtenberg, G.J. Waldschmidt, A. Zholents
ANL, Lemont, Illinois, USA
A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA

Funding: This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated by the Argonne National Laboratory under Contract No. DEAC0206CH11357.
Argonne National Laboratory is developing a 180 GHz wakefield structure that will house in a co-linear array of accelerators to produce free-electron laser-based X-rays. The proposed corrugated waveguide structure will be fabricated on the internal wall of 0.5m long and 2mm nominal diameter copper tube. The estimated dimensions of these parallel corrugations are 200 µm in pitch with 100 µm side length (height and width). The length scale of the structure and requirements of the magnetic field-driven dimensional tolerances have made the structure challenging to produce. We have employed several method such as optical lithography, electroforming, electron discharge machining, laser ablation, and stamping to produce the initial structure from a sheet form. The successive fabrication steps, such as bending, brazing, and welding, were performed to achieve the long tubular-structure. This paper discusses various fabrication techniques, characterization, and associated technical challenges in detail.
[1] A. Zholents et al., Proc. 9-th Intern. Part. Acc. Conf., IPAC2018, Vancouver, BC, Canada, p. 1266, (2018)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLO23

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paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

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TUPLM09

A Fast Method to Evaluate Transverse Coupled-Bunch Stability at Non-Zero Chromaticity

synchrotron, dipole, betatron, simulation

387

R.R. Lindberg
ANL, Lemont, Illinois, USA

Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
We present a dispersion relation that gives the complex growth rate for coupled-bunch instabilities at arbitrary chromaticity in terms of its value at zero chromaticity. We compare predictions of the theory to elegant tracking simulations, and show that there are two distinct regimes to stability depending upon whether the zero chromaticity growth rate is smaller or larger than the chromatic tune shift over the bunch. We derive an approximate expression that is easily solved numerically, and furthermore indicate how the formalism can be extended to describe arbitrary longitudinal potentials.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM09

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paper received ※ 25 August 2019 paper accepted ※ 01 September 2019 issue date ※ 08 October 2019

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TUPLH07

High-Gradient Short Pulse Accelerating Structures

electron, experiment, impedance, acceleration

500

S.V. Kuzikov, S.P. Antipov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.

Poster TUPLH07 [0.999 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07

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paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

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WEPLM68

Design of a Dielectric-Loaded Accelerator for Short Pulse High Gradient Research

acceleration, simulation, accelerating-gradient, experiment

751

M.M. Peng, J. Shi
TUB, Beijing, People’s Republic of China
M.E. Conde, G. Ha, C.-J. Jing, W. Liu, J.G. Power, J. Seok, J.H. Shao, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

The short-pulse two-beam acceleration approach is a promising candidate to meet the cost and luminosity requirements for future linear colliders. Dielectric-loaded structure has been intensely investigated for this approach because of its low fabrication cost, low RF loss, and potential to withstand GV/m gradient. An X-band 11.7~GHz dielectric-loaded accelerator (DLA) has been designed for high power test with short RF pulses (3~ns) generated from a power extractor driven by high charge bunches at Argonne Wakefield Accelerator (AWA) facility. The gradient is expected to be over 100~MV/m with the maximum input power of 400~MW.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM68

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

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WEPLS09

Fast Two-Dimensional Calculation of Coherent Synchrotron Radiation in Relativistic Beams

radiation, synchrotron, electron, synchrotron-radiation

783

J. Tang, G. Stupakov
SLAC, Menlo Park, California, USA

Coherent Synchrotron Radiation(CSR) in a relavistic beam during compression can lead to longitudinal modulation of the bunch with wavelength smaller than bunch length and is regarded as one of the main sources of emittance growth in the bunch compressor. Current simulations containing CSR wake fields often utilize one-dimensional model assuming a line beam. Despite its good computation efficiency, 1D CSR model can be inaccurate in many cases because it ignores the so-called ’compression effect’. On the other hand, the existing 3D codes are often slow and have high demands on computational resources. In this paper we propose a new method for calculation of the three-dimensional CSR wakefields in relativistic beams with integrals of retarded potentials. It generalizes the 1D model and includes the transient effects at the entrance and the exit from the magnet. Within given magnetic lattice and initial beam distributions, the formalism reduces to 2D or 3D integration along the trajectory and therefore allows fast numerical calculations using 2D or 3D matrices.

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLS09

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paper received ※ 28 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

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WEPLO05

Developing Criteria for Laser Transverse Instability in LWFA Simulations

laser, plasma, simulation, 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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WEPLO06

Start-to-End Simulation of the Drive-Beam Longitudinal Dynamics for Beam-Driven Wakefield Acceleration

laser, simulation, electron, linac

858

W.H. Tan, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA
A. Zholents, A. Zholents
ANL, Lemont, Illinois, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science under contracts No. DE-AC02-06CH11357 (via a laboratory- directed R&D program at ANL) and No. DE-SC0018656 at NIU.
Collinear beam-driven wakefield acceleration (WFA) relies on shaped driver beam to provide higher accelerating gradient at a smaller cost and physical footprint. This acceleration scheme is currently envisioned to accelerate electron beams capable of driving free-electron laser *. Start-to-end simulation of drive-bunch beam dynamics is crucial for the evaluation of the design of accelerators built upon WFA. We report the start-to-end longitudinal beam dynamics simulations of an accelerator beamline capable of producing high charge drive beam. The generated wakefield when it passes through a corrugated waveguide results in a transformer ratio of 5. This paper especially discusses the challenges and criteria associated with the generation of temporally-shaped driver beam, including the beam formation in the photoinjector, and the influence of energy chirp control on beam transport stability.
A. Zholents et al., "A Conceptual Design of a Compact Wakefield Accelerator for a High Repetition Rate Multi User X-ray Free-Electron Laser Facility"

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLO06

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paper received ※ 27 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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WEPLO19

Probing Multiperiod Plasma Response Regimes using Single Shot Wakefield Measurements

plasma, 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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FRXBA3

Applications and Opportunities for the Emittance Exchange Beamline

emittance, controls, electron, wiggler

981

G. Ha, M.E. Conde, J.G. Power
ANL, Lemont, Illinois, USA
M. Chung, J. Seok
UNIST, Ulsan, Republic of Korea

Funding: This work is supported by the U.S. Department of Energy, Offices of HEP and BES, under Contract No. DE-AC02-06CH11357.
Emittance exchange (EEX) provides a powerful method of controlling the longitudinal phase space using the relatively simpler methods of transverse control. An EEX beamline was installed at the Argonne Wakefield Accelerator (AWA) facility in 2015. Several experiments important to the wakefield acceleration, such as a high transformer ratio from shaped bunches, have already been demonstrated. We are currently developing several applications of the EEX beamline including temporal profile shaping, THz radiation generation, time-energy correlation control, diagnostic uses of EEX etc. We will present the on-going EEX program for longitudinal phase space control taking place at the AWA facility, and discuss recently discovered new opportunities.

Slides FRXBA3 [6.814 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-FRXBA3

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

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