ICAP2018 - List of Keywords (emittance)

Paper	Title	Other Keywords	Page
SAPLG01	Advances in Simulation of High Brightness/High Intensity Beams	simulation, controls, linac, electron	1
	J. Qiang LBNL, Berkeley, California, USA
	High brightness/high intensity beams play an important role in accelerator based applications by driving x-ray free electron laser (FEL) radiation, producing spallation neutrons and neutrinos, and generating new particles in high energy colliders. In this paper, we report on recent advances in modeling the high brightness electron beam with application to the next generation FEL light sources and in modeling space-charge effects in high intensity proton accelerators.
	Slides SAPLG01 [3.914 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPLG01
About •	paper received ※ 02 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)

SAPAF02	Optimization of Heavy-Ion Synchrotrons Using Nature-Inspired Algorithms and Machine Learning	injection, simulation, synchrotron, space-charge	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)

SUPAF10	Reconstruction of Particle Distributions at RFQ Exit at SNS Beam Test Facility	quadrupole, rfq, simulation, lattice	76
	Z.L. Zhang ORNL RAD, Oak Ridge, Tennessee, USA A.V. Aleksandrov, S.M. Cousineau ORNL, Oak Ridge, Tennessee, USA
	Fluctuations of beam parameters and uncertainties of quadrupole gradients during measurements have effects on the reconstruction of initial particle distributions. To evaluate these effects, the concept of a distribution discrepancy is proposed. Results suggest effects of fluctuations of beam parameters are small, while uncertainties of quadrupole gradients are the main factors that affect the reconstructed distributions. By comparing the measured distributions with distributions produced by tracking the reconstructed initial distributions, it is proved that the real or quasi-real (closest to real) initial distribution can be obtained as long as the minimum distribution discrepancy is found.
	Slides SUPAF10 [8.261 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF10
About •	paper received ※ 18 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)

MOPAF05	Approaches to Optimizing Spin Transmission in Lattice Design	resonance, lattice, polarization, optics	151
	V.H. Ranjbar BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. We present our experiences in optimizing the proposed Rapid Cycling Synchrotron (RCS) injector for the eRHIC Storage ring and the RHIC 2017 lattice. We have develop python code to drive lattice calculations in MADX which are then used to calculate spin resonances using the DEPOL algorithm. This approach has been used to minimize intrinsic spin resonances during the RCS acceleration cycle while controlling lattice parameters such as dispersion and beta functions. This approach has also been used to construct localized imperfection bumps using a spin response matrix and SVD. This approach has also been used to reduce interfering intrinsic spin resonances during the RHIC acceleration ramp.
	Slides MOPAF05 [1.333 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-MOPAF05
About •	paper received ※ 17 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)

TUPAF06	Simulations of Longitudinal Beam Stabilisation in the CERN SPS With BLonD	simulation, impedance, synchrotron, flattop	179
	J. Repond, K. Iliakis, M. Schwarz, E.N. Shaposhnikova CERN, Meyrin, Switzerland
	The Super Proton Synchrotron (SPS) at CERN, the Large Hadron Collider (LHC) injector, will be pushed to its limits for the production of the High Luminosity LHC proton beam while beam quality and stability in the longitudinal plane are influenced by many effects. Particle simulation codes are an essential tool to study the beam instabilities. BLonD, developed at CERN, is a 2D particle-tracking simulation code, modelling the longitudinal phase space motion of single and multi-bunch beams in multi-harmonic RF systems. Computation of collective effects due to the machine impedance and space charge is done on a multi-turn basis. Various beam and cavity control loops of the RF system are implemented (phase, frequency and synchro-loops, and one-turn delay feedback) as well as RF phase noise injection used for controlled emittance blow-up. The longitudinal beam stability simulations during long SPS acceleration cycle (~ 20 s) include a variety of effects (beam loading, particle losses, controlled blow-up, double RF system operation, low-level RF control, injected bunch distribution, etc.). Simulations for the large number of bunches in the nominal LHC batch (288) use the longitudinal SPS impedance model containing broad and narrow-band resonances between 50 MHz and 4 GHz. This paper presents a study of beam stabilisation in the double harmonic RF system of the SPS system with results substantiated, where possible, by beam measurements.
	Slides TUPAF06 [1.518 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF06
About •	paper received ※ 18 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)

TUPAF20	Mean-Field Density Evolution of Bunched Particles With Non-Zero Initial Velocity	electron, simulation, distributed, space-charge	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)

TUPAF23	Start-to-End Simulations of THz SASE FEL Proof-of-Principle Experiment at PITZ	undulator, electron, simulation, FEL	246
	M. Krasilnikov, P. Boonpornprasert, F. Stephan DESY Zeuthen, Zeuthen, Germany H.-D. Nuhn SLAC, Menlo Park, California, USA E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	The Photo Injector Test facility at DESY in Zeuthen (PITZ) develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator has been proposed as a prototype for a tunable, high power THz source for pump and probe experiments at the European XFEL. A Self-Amplified Spontaneous Emission (SASE) FEL is considered to generate the THz pulses. High radiation power can be achieved by utilizing high charge (4 nC) shaped electron bunches from the PITZ photo injector. THz pulse energy of up to several mJ is expected from preliminary simulations for 100 um radiation wavelength. For the proof-of-principle experiments a re-usage of LCLS-I undulators at the end of the PITZ beamline is under studies. One of the challenges for this setup is transport and matching of the space charge dominated electron beam through the narrow vacuum chamber. Start-to-end simulations for the entire experimental setup - from the photocathode to the SASE THz generation in the undulator section - have been performed by combination of several codes: ASTRA, SC and GENESIS-1.3. The space charge effect and its impact onto the output THz radiation have been studied. The results of these simulations will be presented and discussed.
	Slides TUPAF23 [2.534 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF23
About •	paper received ※ 18 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)

TUPAG02	First Steps Towards a New Finite Element Solver for MOEVE PIC Tracking	electron, FEM, simulation, vacuum	260
	U. van Rienen, C.R. Bahls, J. Heller, D. Zheng Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany U. van Rienen University of Rostock, Rostock, Germany
	Funding: This work has been supported by the German Federal Ministry for Research and Education BMBF under contract 015K16HRA. A relevant task in designing high-brilliance light sources based on high-current linear accelerators (e.g. Energy Recovery Linacs (ERLs)) consists in systematic investigations of ion dynamics in the vacuum chamber of such machines. This is of high importance since the parasitic ions generated by the electron beam turned out to be a current-limiting factor for many synchrotron radiation sources. In particular, the planned high current operation at ERL facilities requires a precise analysis and an accurate development of appropriate measures for the suppression of ion-induced beam instabilities. The longitudinal transport of ions through the whole accelerator plays a key role for the establishment of the ion concentration in the machine. Using the Particle-in-Cell (PIC) method, we started redesigning our code MOEVE PIC Tracking in order to allow for the fast estimation of the effects of ions on the beam dynamics. For that, we exchanged the previously used Finite Difference (FD) method for the solution of Poisson’s equation within the PIC solver by a solver based on the Finite Element Method (FEM). Employing higher order FEM, we expect to gain improved convergence rates and thus lower computational times. We chose the Open Source Framework FEniCS for our new implementation.
	Slides TUPAG02 [0.924 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG02
About •	paper received ※ 21 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)

TUPAG20	Computational Beam Dynamics Requirements for FRIB	linac, ECR, simulation, controls	303
	P.N. Ostroumov, Y. Hao, T. Maruta, A.S. Plastun, T. Yoshimoto, T. Zhang, Q. Zhao FRIB, East Lansing, USA
	Funding: Work supported by the U.S. DOE of Science under Cooperative Agreement DE-SC0000661 and the NSF under Cooperative Agreement PHY-1102511, the State of Michigan and Michigan State University. The Facility for Rare Isotope Beams (FRIB) being built at Michigan State University moved to the commissioned stage in the summer of 2017. There were extensive beam dynamics simulations in the FRIB driver linac during the design stage. Recently, we have used TRACK and IMPACT simulation codes to study dynamics of ion beam contaminants extracted from the ECR together with main ion beam. The contaminant ion species can produce significant losses after the stripping. These studies resulted in development of beam collimation system at relatively low energy of 16 MeV/u and room temperature bunchers instead of originally planned SC cavities. Commissioning of the Front End and the first 3 cryomodules enabled detailed beam dynamics studies experimentally which were accompanied with the simulations using above-mentioned beam dynamics codes and optimization code FLAME. There are significant challenges in understanding of beam dynamics in the FRIB linac. The most computational challenges are in the following areas: (1) Simulation of the ion beam formation and extraction from the ECR; (2) Development of the virtual accelerator model available on-line both for optimization and multi-particle simulations. The virtual model should include realistic accelerator parameters including device misalignments; (3) Large scale simulations to support high-power ramp up of the linac with minimized beam losses; (4) Interaction of the beam with the gas stripper which is the backup option for high power operation of the linac.
	Slides TUPAG20 [5.721 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG20
About •	paper received ※ 02 November 2018 paper accepted ※ 10 December 2018 issue date ※ 26 January 2019
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WEPAF04	Longitudinal Beam Dynamics in FRIB and ReA Linacs	rfq, cavity, simulation, linac	330
	A.S. Plastun, P.N. Ostroumov, A.C.C. Villari, Q. Zhao FRIB, East Lansing, USA
	The Front-End and first three cryomodules of the Facility for Rare Isotope Beam (FRIB) at Michigan State University (MSU) commissioned in July, 2018. The paper describes the online tuning procedures of the longitudinal beam dynamics through the FRIB linac. These procedures include tuning of the accelerating field phases and amplitudes in the cavities. We developed an automated simulation-based tuning procedure for the multi-harmonic buncher. In order to tune the radio-frequency quadrupole (RFQ) we measured and calculated its threshold voltage and scanned its longitudinal acceptance. Tuning of the rebunchers and superconducting accelerating cavities is per-formed by means of the phase scans and Time-Of-Flight (TOF) beam energy measurements with beam position and phase monitors. While FRIB is being commissioned, the re-accelerator (ReA3) for rare isotope beams (RIBs) is being upgraded. We redesigned the ReA3 RFQ to improve its cooling system and provide reliable operation with 16.1 MHz prebunched ion beams with A/Q = 5. In order to provide matching of any ReA3 beam both to the following upgrade cryomodules and physics experiments’ requirements, room temperature rebuncher/debuncher is being designed. The design procedure includes the beam dynamics, electromagnetic, thermal and mechanical simulations and optimizations.
	Slides WEPAF04 [2.406 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPAF04
About •	paper received ※ 19 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
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WEPLG01	Analysis of Emittance Growth in a Gridless Spectral Poisson Solver for Fully Symplectic Multiparticle Tracking	space-charge, 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

SAPLG01

Advances in Simulation of High Brightness/High Intensity Beams

simulation, controls, linac, electron

1

J. Qiang
LBNL, Berkeley, California, USA

High brightness/high intensity beams play an important role in accelerator based applications by driving x-ray free electron laser (FEL) radiation, producing spallation neutrons and neutrinos, and generating new particles in high energy colliders. In this paper, we report on recent advances in modeling the high brightness electron beam with application to the next generation FEL light sources and in modeling space-charge effects in high intensity proton accelerators.

Slides SAPLG01 [3.914 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SAPLG01

About •

paper received ※ 02 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)

SAPAF02

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

injection, simulation, synchrotron, space-charge

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

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SUPAF10

Reconstruction of Particle Distributions at RFQ Exit at SNS Beam Test Facility

quadrupole, rfq, simulation, lattice

76

Z.L. Zhang
ORNL RAD, Oak Ridge, Tennessee, USA
A.V. Aleksandrov, S.M. Cousineau
ORNL, Oak Ridge, Tennessee, USA

Fluctuations of beam parameters and uncertainties of quadrupole gradients during measurements have effects on the reconstruction of initial particle distributions. To evaluate these effects, the concept of a distribution discrepancy is proposed. Results suggest effects of fluctuations of beam parameters are small, while uncertainties of quadrupole gradients are the main factors that affect the reconstructed distributions. By comparing the measured distributions with distributions produced by tracking the reconstructed initial distributions, it is proved that the real or quasi-real (closest to real) initial distribution can be obtained as long as the minimum distribution discrepancy is found.

Slides SUPAF10 [8.261 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAF10

About •

paper received ※ 18 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)

MOPAF05

Approaches to Optimizing Spin Transmission in Lattice Design

resonance, lattice, polarization, optics

151

V.H. Ranjbar
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
We present our experiences in optimizing the proposed Rapid Cycling Synchrotron (RCS) injector for the eRHIC Storage ring and the RHIC 2017 lattice. We have develop python code to drive lattice calculations in MADX which are then used to calculate spin resonances using the DEPOL algorithm. This approach has been used to minimize intrinsic spin resonances during the RCS acceleration cycle while controlling lattice parameters such as dispersion and beta functions. This approach has also been used to construct localized imperfection bumps using a spin response matrix and SVD. This approach has also been used to reduce interfering intrinsic spin resonances during the RHIC acceleration ramp.

Slides MOPAF05 [1.333 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-MOPAF05

About •

paper received ※ 17 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)

TUPAF06

Simulations of Longitudinal Beam Stabilisation in the CERN SPS With BLonD

simulation, impedance, synchrotron, flattop

179

J. Repond, K. Iliakis, M. Schwarz, E.N. Shaposhnikova
CERN, Meyrin, Switzerland

The Super Proton Synchrotron (SPS) at CERN, the Large Hadron Collider (LHC) injector, will be pushed to its limits for the production of the High Luminosity LHC proton beam while beam quality and stability in the longitudinal plane are influenced by many effects. Particle simulation codes are an essential tool to study the beam instabilities. BLonD, developed at CERN, is a 2D particle-tracking simulation code, modelling the longitudinal phase space motion of single and multi-bunch beams in multi-harmonic RF systems. Computation of collective effects due to the machine impedance and space charge is done on a multi-turn basis. Various beam and cavity control loops of the RF system are implemented (phase, frequency and synchro-loops, and one-turn delay feedback) as well as RF phase noise injection used for controlled emittance blow-up. The longitudinal beam stability simulations during long SPS acceleration cycle (~ 20 s) include a variety of effects (beam loading, particle losses, controlled blow-up, double RF system operation, low-level RF control, injected bunch distribution, etc.). Simulations for the large number of bunches in the nominal LHC batch (288) use the longitudinal SPS impedance model containing broad and narrow-band resonances between 50 MHz and 4 GHz. This paper presents a study of beam stabilisation in the double harmonic RF system of the SPS system with results substantiated, where possible, by beam measurements.

Slides TUPAF06 [1.518 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF06

About •

paper received ※ 18 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)

TUPAF20

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

electron, simulation, distributed, space-charge

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)

TUPAF23

Start-to-End Simulations of THz SASE FEL Proof-of-Principle Experiment at PITZ

undulator, electron, simulation, FEL

246

M. Krasilnikov, P. Boonpornprasert, F. Stephan
DESY Zeuthen, Zeuthen, Germany
H.-D. Nuhn
SLAC, Menlo Park, California, USA
E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

The Photo Injector Test facility at DESY in Zeuthen (PITZ) develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator has been proposed as a prototype for a tunable, high power THz source for pump and probe experiments at the European XFEL. A Self-Amplified Spontaneous Emission (SASE) FEL is considered to generate the THz pulses. High radiation power can be achieved by utilizing high charge (4 nC) shaped electron bunches from the PITZ photo injector. THz pulse energy of up to several mJ is expected from preliminary simulations for 100 um radiation wavelength. For the proof-of-principle experiments a re-usage of LCLS-I undulators at the end of the PITZ beamline is under studies. One of the challenges for this setup is transport and matching of the space charge dominated electron beam through the narrow vacuum chamber. Start-to-end simulations for the entire experimental setup - from the photocathode to the SASE THz generation in the undulator section - have been performed by combination of several codes: ASTRA, SC and GENESIS-1.3. The space charge effect and its impact onto the output THz radiation have been studied. The results of these simulations will be presented and discussed.

Slides TUPAF23 [2.534 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF23

About •

paper received ※ 18 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)

TUPAG02

First Steps Towards a New Finite Element Solver for MOEVE PIC Tracking

electron, FEM, simulation, vacuum

260

U. van Rienen, C.R. Bahls, J. Heller, D. Zheng
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
U. van Rienen
University of Rostock, Rostock, Germany

Funding: This work has been supported by the German Federal Ministry for Research and Education BMBF under contract 015K16HRA.
A relevant task in designing high-brilliance light sources based on high-current linear accelerators (e.g. Energy Recovery Linacs (ERLs)) consists in systematic investigations of ion dynamics in the vacuum chamber of such machines. This is of high importance since the parasitic ions generated by the electron beam turned out to be a current-limiting factor for many synchrotron radiation sources. In particular, the planned high current operation at ERL facilities requires a precise analysis and an accurate development of appropriate measures for the suppression of ion-induced beam instabilities. The longitudinal transport of ions through the whole accelerator plays a key role for the establishment of the ion concentration in the machine. Using the Particle-in-Cell (PIC) method, we started redesigning our code MOEVE PIC Tracking in order to allow for the fast estimation of the effects of ions on the beam dynamics. For that, we exchanged the previously used Finite Difference (FD) method for the solution of Poisson’s equation within the PIC solver by a solver based on the Finite Element Method (FEM). Employing higher order FEM, we expect to gain improved convergence rates and thus lower computational times. We chose the Open Source Framework FEniCS for our new implementation.

Slides TUPAG02 [0.924 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG02

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paper received ※ 21 October 2018 paper accepted ※ 24 October 2018 issue date ※ 26 January 2019

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TUPAG20

Computational Beam Dynamics Requirements for FRIB

linac, ECR, simulation, controls

303

P.N. Ostroumov, Y. Hao, T. Maruta, A.S. Plastun, T. Yoshimoto, T. Zhang, Q. Zhao
FRIB, East Lansing, USA

Funding: Work supported by the U.S. DOE of Science under Cooperative Agreement DE-SC0000661 and the NSF under Cooperative Agreement PHY-1102511, the State of Michigan and Michigan State University.
The Facility for Rare Isotope Beams (FRIB) being built at Michigan State University moved to the commissioned stage in the summer of 2017. There were extensive beam dynamics simulations in the FRIB driver linac during the design stage. Recently, we have used TRACK and IMPACT simulation codes to study dynamics of ion beam contaminants extracted from the ECR together with main ion beam. The contaminant ion species can produce significant losses after the stripping. These studies resulted in development of beam collimation system at relatively low energy of 16 MeV/u and room temperature bunchers instead of originally planned SC cavities. Commissioning of the Front End and the first 3 cryomodules enabled detailed beam dynamics studies experimentally which were accompanied with the simulations using above-mentioned beam dynamics codes and optimization code FLAME. There are significant challenges in understanding of beam dynamics in the FRIB linac. The most computational challenges are in the following areas: (1) Simulation of the ion beam formation and extraction from the ECR; (2) Development of the virtual accelerator model available on-line both for optimization and multi-particle simulations. The virtual model should include realistic accelerator parameters including device misalignments; (3) Large scale simulations to support high-power ramp up of the linac with minimized beam losses; (4) Interaction of the beam with the gas stripper which is the backup option for high power operation of the linac.

Slides TUPAG20 [5.721 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG20

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paper received ※ 02 November 2018 paper accepted ※ 10 December 2018 issue date ※ 26 January 2019

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WEPAF04

Longitudinal Beam Dynamics in FRIB and ReA Linacs

rfq, cavity, simulation, linac

330

A.S. Plastun, P.N. Ostroumov, A.C.C. Villari, Q. Zhao
FRIB, East Lansing, USA

The Front-End and first three cryomodules of the Facility for Rare Isotope Beam (FRIB) at Michigan State University (MSU) commissioned in July, 2018. The paper describes the online tuning procedures of the longitudinal beam dynamics through the FRIB linac. These procedures include tuning of the accelerating field phases and amplitudes in the cavities. We developed an automated simulation-based tuning procedure for the multi-harmonic buncher. In order to tune the radio-frequency quadrupole (RFQ) we measured and calculated its threshold voltage and scanned its longitudinal acceptance. Tuning of the rebunchers and superconducting accelerating cavities is per-formed by means of the phase scans and Time-Of-Flight (TOF) beam energy measurements with beam position and phase monitors. While FRIB is being commissioned, the re-accelerator (ReA3) for rare isotope beams (RIBs) is being upgraded. We redesigned the ReA3 RFQ to improve its cooling system and provide reliable operation with 16.1 MHz prebunched ion beams with A/Q = 5. In order to provide matching of any ReA3 beam both to the following upgrade cryomodules and physics experiments’ requirements, room temperature rebuncher/debuncher is being designed. The design procedure includes the beam dynamics, electromagnetic, thermal and mechanical simulations and optimizations.

Slides WEPAF04 [2.406 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPAF04

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paper received ※ 19 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

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WEPLG01

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

space-charge, 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]

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

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

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