ICAP2018 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
SAPAF02	Optimization of Heavy-Ion Synchrotrons Using Nature-Inspired Algorithms and Machine Learning	injection, emittance, simulation, synchrotron	15
	S. Appel, W. Geithner, S. Reimann, M. Sapinski, R. Singh, D.M. Vilsmeier GSI, Darmstadt, Germany
	The application of machine learning and nature-inspired optimization methods, like for example genetic algorithms (GA) and particle swarm optimization (PSO) can be found in various scientific/technical areas. In recent years, those approaches are finding application in accelerator physics to a greater extent. In this report, nature-inspired optimization as well as the machine learning will be shortly introduced and their application to the accelerator facility at GSI/FAIR will be presented. For the heavy-ion synchrotron SIS18 at GSI, the multi-objective GA/PSO optimization resulted in a significant improvement of multi-turn injection performance and subsequent transmission for intense beams. An automated injection optimization with genetic algorithms at the CRYRING@ESR ion storage ring has been performed. The usage of machine learning for a beam diagnostic application, where reconstruction of space-charge distorted beam profiles from ionization profile monitors is performed, will also be shown. First results and the experience gained will be presented.
	Slides SAPAF02 [2.642 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF02
About •	paper received ※ 16 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SAPAF03	Comparison of Model-Based and Heuristic Optimization Algorithms Applied to Photoinjectors Using Libensemble	simulation, cavity, gun, solenoid	22
	N.R. Neveu IIT, Chicago, Illinois, USA S. T. P. Hudson, J.M. Larson ANL, Argonne, Illinois, USA L.K. Spentzouris Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: U.S. DOE, OS, contract DE-AC02-06CH11357 and grant DE-SC0015479. Genetic algorithms are common and often used in the accelerator community. They require large amounts of computational resources and empirical adjustment of hyperparameters. Model based methods are significantly more efficient, but often labeled as unreliable for the nonlinear or unsmooth problems that can be found in accelerator physics. We investigate the behavior of both approaches using a photoinjector operated in the space charge dominated regime. All optimization runs are coordinated and managed by the Python library libEnsemble, which is developed at Argonne National Laboratory.
	Slides SAPAF03 [0.653 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF03
About •	paper received ※ 11 November 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAF04	Symplectic and Self-Consistent Algorithms for Particle Accelerator Simulation	plasma, simulation, betatron, resonance	42
	T. Planche, P. M. Jung TRIUMF, Vancouver, Canada
	This paper is a review of algorithms, applicable to particle accelerator simulation, which share the following two characteristics: (1) they preserve to machine precision the symplectic geometry of the particle dynamics, and (2) they track the evolution of the self-field consistently with the evolution of the charge distribution. This review includes, but is not limited to, algorithms using a Particle-in-Cell discretization scheme. At the end of this review we discuss to possibility to derived algorithms from an electrostatic Hamiltonian.
	Slides SUPAF04 [0.424 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF04
About •	paper received ※ 19 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAF07	High-Fidelity Three-Dimensional Simulations of Thermionic Energy Converters	simulation, electron, cathode, operation	59
	N.M. Cook, J.P. Edelen, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler RadiaSoft LLC, Boulder, Colorado, USA J.-L. Vay LBNL, Berkeley, California, USA
	Funding: This work is supported the US DOE Office of Science, Office of High Energy Physics: DE-SC0017162. Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver. We also consider self-consistent effects to model Schottky emission near the space-charge limit for arrays of shaped emitters. The efficiency of these devices is computed by modeling distinct loss channels, including kinetic losses, radiative losses, and dielectric charging. We demonstrate many of these features within an open-source, browser-based interface for running 3D electrostatic simulations with Warp, including design and analysis tools, as well as streamlined submission to HPC centers.
	Slides SUPAF07 [6.097 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF07
About •	paper received ※ 01 November 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAG01	Space Charge and Transverse Instabilities at the CERN SPS and LHC	coupling, simulation, optics, impedance	80
	E. Métral, D. Amorim, G. Arduini, H. Bartosik, E. Benedetto, H. Burkhardt, K.S.B. Li, A. Oeftiger, D. Quatraro, G. Rumolo, B. Salvant, C. Zannini CERN, Geneva, Switzerland
	At the CERN accelerator complex, it seems that only the highest energy machine in the sequence, the LHC, with space charge (SC) parameter close to one, sees the predicted beneficial effect of SC on transverse coherent instabilities. In the other circular machines of the LHC injector chain (PSB, PS and SPS), where the SC parameter is much bigger than one, SC does not seem to play a major (stabilising) role, and it is maybe the opposite in the SPS. All the measurements and simulations performed so far in both the SPS and LHC will be reviewed and analysed in detail.
	Slides SUPAG01 [37.523 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAG01
About •	paper received ※ 20 October 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPLG01	Computational Accelerator Physics: On the Road to Exascale	simulation, plasma, optics, radiation	113
	R.D. Ryne LBNL, Berkeley, USA
	The first conference in what would become the ICAP series was held in 1988. At that time the most powerful computer in the world was a Cray YMP with 8 processors and a peak performance of 2 gigaflops. Today the fastest computer in the world has more than 2 million cores and a theoretical peak performance of nearly 200 petaflops. Compared to 1988, performance has increased by a factor of 100 million, accompanied by huge advances in memory, networking, big data management and analytics. By the time of the next ICAP in 2021 we will be at the dawn of the Exascale era. In this talk I will describe the advances in Computational Accelerator Physics that brought us to this point and describe what to expect in regard to High Performance Computing in the future. This writeup as based on my presentation at ICAP’18 along with some additional comments that I did not include originally due to time constraints.
	Slides SUPLG01 [25.438 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPLG01
About •	paper received ※ 14 November 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAF20	Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity	electron, simulation, emittance, distributed	233
	B.S. Zerbe, P.M. Duxbury MSU, East Lansing, Michigan, USA
	Funding: NSF Grant 1625181 NSF Grant RC108666 MSU Col. Nat. Sci., Provost Off., Col. Comm. Art and Sci. Reed (2006) presented a 1D mean-field model of initially cold pancake-beam expansion demonstrating that the evolution of the entire spatial distribution can be solved for all time where the 1D assumption holds. This model is relevant to ultra-fast electron microscopy as it describes the evolution of the distribution within the photoelectron gun, and this model is similar to Anderson’s sheet beam density time dependence (Anderson 1987) except that Reed’s theory applies to freely expanding beams instead of beams within a focussing channel. Our recent work (Zerbe 2018) generalized Reed’s analysis to cylindrical and spherical geometries demonstrating the presence of a shock that is seen in the Coulomb explosion literature under these geometries and further discussed the absence of a shock in the 1D model. This work is relevant as it offers a mechanistic explanation of the ring-like density shock that arises in non-equilibrium pancake-beams within the photoelectron gun; moreover, this shock is coincident with a region of high-temperature electrons providing an explanation for why experimentally aperturing the electron bunch results in a greater than 10-fold improvement in beam emittance(Williams 2017), possibly even resulting in bunch emittance below the intrinsic emittance of the cathode. However, this theory has been developed for cold-bunches, i.e. bunches of electrons with 0 initial momentum. Here, we briefly review this new theory and extend the cylindrical- and spherical- symmetric distribution to ensembles that have non-zero initial momentum distributions that are symmetric but otherwise unrestricted demonstrating how initial velocity distributions couple to the shocks seen in the less general formulation. Further, we derive and demonstrate how the laminar condition may be propagated through beam foci.
	Slides TUPAF20 [1.396 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF20
About •	paper received ※ 19 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPLG01	Analysis of Emittance Growth in a Gridless Spectral Poisson Solver for Fully Symplectic Multiparticle Tracking	emittance, lattice, plasma, simulation	335
	C.E. Mitchell, J. Qiang LBNL, Berkeley, California, USA
	Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Gridless spectral methods for self-consistent symplectic space charge modeling possess several advantages over traditional momentum-conserving particle-in-cell methods, including the absence of numerical grid heating and the presence of an underlying multi-particle Hamiltonian. Nevertheless, evidence of collisional particle noise remains. For a class of such 1D and 2D algorithms, we provide analytical models of the numerical field error, the optimal choice of spectral modes, and the numerical emittance growth per timestep. We compare these results with the emittance growth models of Struckmeier, Hoffman, Kesting, and others.
	Slides WEPLG01 [11.804 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPLG01
About •	paper received ※ 18 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

SAPAF02

Optimization of Heavy-Ion Synchrotrons Using Nature-Inspired Algorithms and Machine Learning

injection, emittance, simulation, synchrotron

15

S. Appel, W. Geithner, S. Reimann, M. Sapinski, R. Singh, D.M. Vilsmeier
GSI, Darmstadt, Germany

The application of machine learning and nature-inspired optimization methods, like for example genetic algorithms (GA) and particle swarm optimization (PSO) can be found in various scientific/technical areas. In recent years, those approaches are finding application in accelerator physics to a greater extent. In this report, nature-inspired optimization as well as the machine learning will be shortly introduced and their application to the accelerator facility at GSI/FAIR will be presented. For the heavy-ion synchrotron SIS18 at GSI, the multi-objective GA/PSO optimization resulted in a significant improvement of multi-turn injection performance and subsequent transmission for intense beams. An automated injection optimization with genetic algorithms at the CRYRING@ESR ion storage ring has been performed. The usage of machine learning for a beam diagnostic application, where reconstruction of space-charge distorted beam profiles from ionization profile monitors is performed, will also be shown. First results and the experience gained will be presented.

Slides SAPAF02 [2.642 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF02

About •

paper received ※ 16 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SAPAF03

Comparison of Model-Based and Heuristic Optimization Algorithms Applied to Photoinjectors Using Libensemble

simulation, cavity, gun, solenoid

22

N.R. Neveu
IIT, Chicago, Illinois, USA
S. T. P. Hudson, J.M. Larson
ANL, Argonne, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: U.S. DOE, OS, contract DE-AC02-06CH11357 and grant DE-SC0015479.
Genetic algorithms are common and often used in the accelerator community. They require large amounts of computational resources and empirical adjustment of hyperparameters. Model based methods are significantly more efficient, but often labeled as unreliable for the nonlinear or unsmooth problems that can be found in accelerator physics. We investigate the behavior of both approaches using a photoinjector operated in the space charge dominated regime. All optimization runs are coordinated and managed by the Python library libEnsemble, which is developed at Argonne National Laboratory.

Slides SAPAF03 [0.653 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPAF03

About •

paper received ※ 11 November 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAF04

Symplectic and Self-Consistent Algorithms for Particle Accelerator Simulation

plasma, simulation, betatron, resonance

42

T. Planche, P. M. Jung
TRIUMF, Vancouver, Canada

This paper is a review of algorithms, applicable to particle accelerator simulation, which share the following two characteristics: (1) they preserve to machine precision the symplectic geometry of the particle dynamics, and (2) they track the evolution of the self-field consistently with the evolution of the charge distribution. This review includes, but is not limited to, algorithms using a Particle-in-Cell discretization scheme. At the end of this review we discuss to possibility to derived algorithms from an electrostatic Hamiltonian.

Slides SUPAF04 [0.424 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF04

About •

paper received ※ 19 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAF07

High-Fidelity Three-Dimensional Simulations of Thermionic Energy Converters

simulation, electron, cathode, operation

59

N.M. Cook, J.P. Edelen, C.C. Hall, M.V. Keilman, P. Moeller, R. Nagler
RadiaSoft LLC, Boulder, Colorado, USA
J.-L. Vay
LBNL, Berkeley, California, USA

Funding: This work is supported the US DOE Office of Science, Office of High Energy Physics: DE-SC0017162.
Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver. We also consider self-consistent effects to model Schottky emission near the space-charge limit for arrays of shaped emitters. The efficiency of these devices is computed by modeling distinct loss channels, including kinetic losses, radiative losses, and dielectric charging. We demonstrate many of these features within an open-source, browser-based interface for running 3D electrostatic simulations with Warp, including design and analysis tools, as well as streamlined submission to HPC centers.

Slides SUPAF07 [6.097 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF07

About •

paper received ※ 01 November 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPAG01

Space Charge and Transverse Instabilities at the CERN SPS and LHC

coupling, simulation, optics, impedance

80

E. Métral, D. Amorim, G. Arduini, H. Bartosik, E. Benedetto, H. Burkhardt, K.S.B. Li, A. Oeftiger, D. Quatraro, G. Rumolo, B. Salvant, C. Zannini
CERN, Geneva, Switzerland

At the CERN accelerator complex, it seems that only the highest energy machine in the sequence, the LHC, with space charge (SC) parameter close to one, sees the predicted beneficial effect of SC on transverse coherent instabilities. In the other circular machines of the LHC injector chain (PSB, PS and SPS), where the SC parameter is much bigger than one, SC does not seem to play a major (stabilising) role, and it is maybe the opposite in the SPS. All the measurements and simulations performed so far in both the SPS and LHC will be reviewed and analysed in detail.

Slides SUPAG01 [37.523 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAG01

About •

paper received ※ 20 October 2018 paper accepted ※ 19 November 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

SUPLG01

Computational Accelerator Physics: On the Road to Exascale

simulation, plasma, optics, radiation

113

R.D. Ryne
LBNL, Berkeley, USA

The first conference in what would become the ICAP series was held in 1988. At that time the most powerful computer in the world was a Cray YMP with 8 processors and a peak performance of 2 gigaflops. Today the fastest computer in the world has more than 2 million cores and a theoretical peak performance of nearly 200 petaflops. Compared to 1988, performance has increased by a factor of 100 million, accompanied by huge advances in memory, networking, big data management and analytics. By the time of the next ICAP in 2021 we will be at the dawn of the Exascale era. In this talk I will describe the advances in Computational Accelerator Physics that brought us to this point and describe what to expect in regard to High Performance Computing in the future. This writeup as based on my presentation at ICAP’18 along with some additional comments that I did not include originally due to time constraints.

Slides SUPLG01 [25.438 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPLG01

About •

paper received ※ 14 November 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPAF20

Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity

electron, simulation, emittance, distributed

233

B.S. Zerbe, P.M. Duxbury
MSU, East Lansing, Michigan, USA

Funding: NSF Grant 1625181 NSF Grant RC108666 MSU Col. Nat. Sci., Provost Off., Col. Comm. Art and Sci.
Reed (2006) presented a 1D mean-field model of initially cold pancake-beam expansion demonstrating that the evolution of the entire spatial distribution can be solved for all time where the 1D assumption holds. This model is relevant to ultra-fast electron microscopy as it describes the evolution of the distribution within the photoelectron gun, and this model is similar to Anderson’s sheet beam density time dependence (Anderson 1987) except that Reed’s theory applies to freely expanding beams instead of beams within a focussing channel. Our recent work (Zerbe 2018) generalized Reed’s analysis to cylindrical and spherical geometries demonstrating the presence of a shock that is seen in the Coulomb explosion literature under these geometries and further discussed the absence of a shock in the 1D model. This work is relevant as it offers a mechanistic explanation of the ring-like density shock that arises in non-equilibrium pancake-beams within the photoelectron gun; moreover, this shock is coincident with a region of high-temperature electrons providing an explanation for why experimentally aperturing the electron bunch results in a greater than 10-fold improvement in beam emittance(Williams 2017), possibly even resulting in bunch emittance below the intrinsic emittance of the cathode. However, this theory has been developed for cold-bunches, i.e. bunches of electrons with 0 initial momentum. Here, we briefly review this new theory and extend the cylindrical- and spherical- symmetric distribution to ensembles that have non-zero initial momentum distributions that are symmetric but otherwise unrestricted demonstrating how initial velocity distributions couple to the shocks seen in the less general formulation. Further, we derive and demonstrate how the laminar condition may be propagated through beam foci.

Slides TUPAF20 [1.396 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF20

About •

paper received ※ 19 October 2018 paper accepted ※ 15 December 2018 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPLG01

Analysis of Emittance Growth in a Gridless Spectral Poisson Solver for Fully Symplectic Multiparticle Tracking

emittance, lattice, plasma, simulation

335

C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work was supported by the Director, Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Gridless spectral methods for self-consistent symplectic space charge modeling possess several advantages over traditional momentum-conserving particle-in-cell methods, including the absence of numerical grid heating and the presence of an underlying multi-particle Hamiltonian. Nevertheless, evidence of collisional particle noise remains. For a class of such 1D and 2D algorithms, we provide analytical models of the numerical field error, the optimal choice of spectral modes, and the numerical emittance growth per timestep. We compare these results with the emittance growth models of Struckmeier, Hoffman, Kesting, and others.

Slides WEPLG01 [11.804 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPLG01

About •

paper received ※ 18 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)