IPAC2017 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D03 Calculations of EM Fields

Paper	Title	Page
WEPIK062	UNDUMAG - A New Computer Code to Calculate the Magnetic Properties of Undulators	3071
	M. Scheer HZB, Berlin, Germany
	A new code for the magnetic design of undulators is under development at the Helmholtz-Zentrum Berlin (BESSY). The program reads in the geometry and material properties of the undulator magnets and iron poles. Magnetic fields, forces and torques, as well as trajectories and synchrotron radiation can be calculated. The code is a stand-alone FORTRAN program, thus, only a FORTRAN compiler is needed to install it. Build-in graphic routines allows to write postscript files to visualize the geometry and the fields. Other results like 3D field maps, field integrals etc. are written to ASCII files for later use. The code will be published under the GNU general public license. First results and comparison to other codes are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK062
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK064	Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral	3074
	W. Ackermann, H. De Gersem, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK064
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK073	Three Dimensional Wake Field for an Electron Moving in Undulator	3098
	K. Ohmi KEK, Ibaraki, Japan
	Electro-magnetic field for given trajectory of an electron is calculated by Lienard-Wiechert potential. The field near the electron moving in an undulator is presented. The field is regarded as a wake field in the undulator. Motion of a bunch is studied in the wake field.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK073
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK077	Shielding of Beam Pipe on Rapidly Varying Magnetic Field	3107
	N. Wang, J. Chen, S.K. Chen, P. He, G. Xu IHEP, Beijing, People's Republic of China
	In low emittance rings, beam is quite sensitive to orbit oscillations. Fast correctors will be used to correct the beam orbit. The fast varying magnetic field will generate eddy current on the beam pipe, which will in turn change the phase and the amplitude of the magnetic field. The shielding effect of the beam pipe on a fast varying magnetic field is simulated for different frequencies. The results are also benchmarked with the measurements in the lab.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK077
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK086	Wave Propagation in a Fractal Wave Guide	3128
	V.G. Ziemann, A.K. Bhattacharyya, M. Holz, J. Ögren Uppsala University, Uppsala, Sweden
	We analyze the propagation of electro-magnetic waves in a wave guide that has the shape of Koch's snowflake, a well-known fractal.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK086
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK097	An Optimization Tool to Design a Coreless Non-Linear Injection Kicker Magnet	3170
	B. MacDonald-de Neeve ETH, Zurich, Switzerland B. MacDonald-de Neeve, M. Paraliev, Á. Saá Hernández PSI, Villigen PSI, Switzerland
	Top-up injection into low emittance light sources is challenging due to their inherent small dynamic apertures (DA). The use of a multipole-magnet injection kicker prevents disturbing the circulating beam. However, the injected bunch will be mismatched due to unwanted focusing (linear field profile) or even filamented (nonlinear field profile). Coreless nonlinear kicker magnets, using different configurations of straight conductors, can produce transverse step-like magnetic field distribution which prevent the mismatch. We explored an 8-conductor configuration and a multi-conductor approach like unipolar massless septum design. Maximizing the spatial derivative of the transverse field step function is crucial in order to kick the injected bunch inside the DA. Comparing the results of different designs a particular dependence between the smallest clear aperture and the maximum transverse field spatial derivative was observed. We have developed an optimization tool to generate arbitrary 2D magnetic fields and determine the associated current distribution. With it we obtained new design solutions for possible injection magnets that go beyond the limitations of the standard designs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK097
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK101	Novel Implementation of Quadrupole and Higher Order Fringe Fields to Accelerator Design	3184
	B.D. Muratori STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Until recently, in the initial design phase of any accelerator project, it was not possible to have an adequate description of quadrupole and higher order multipole fringe fields. We report on the latest developments in analytical fringe fields for multipoles, particularly for quadrupoles and sextupoles. We show how they can be used to improve accelerator codes and make them both faster and more precise. We also show how the analytical formulae for the fringe fields yield expressions for both the scalar and vector potentials in electromagnetism. We conclude by discussing the application of both potentials to the design of multipole magnets as well as the implementation of symplectic kick approximations for fringe fields in thin lens models that could be used in accelerator codes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK101
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK111	Derivation of a Finite Element Formulation From a Lagrangian for the Electromagnetic Potentials	3208
	A.R. Vrielink, M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Conventional electromagnetic finite element solvers typically solve a weak formulation of the Helmholtz wave equation. While mathematically this approach is correct, it does not fully reflect the fundamental physics involved. We offer an alternative variational formulation which is not derived from the Helmholtz wave equation but is more fundamentally tied to the physics of the system: a Lagrangian for the electromagnetic potentials. Solving for the potentials directly allows for a natural accounting of the beam wave interaction. It could also potentially avoid the issue of deleterious spurious modes inherent when selecting the Coulomb gauge and enforcing the subsequent divergence free condition, eliminating the need for vector basis functions. Herein we present the theory and the resulting formulation including a discussion on gauge fixing. We conclude with some numerical results demonstrating the potential of this formulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK111
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK112	A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry	3211
	A.R. Vrielink, M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK112
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK121	Computation of Synchrotron Radiation on Arbitrary Geometries in 3D with Modern GPU, Multi-Core, and Grid Computing	3238
	D.A. Hidas BNL, Upton, Long Island, New York, USA
	Funding: Supported by the U.S. Department of Energy under contract DE-SC0012704 Open Source Code for Advanced Radiation Simulation (OSCARS) is an open source project being developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary particle beams in arbitrary magnetic (and electric) fields on arbitrary geometries in 3D. OSCARS was designed with considerations for modern large scale computing infrastructure. These include the ability to use GPUs for computations, multi-threaded computations, and utilities for grid (or cloud) computing. Primary applications include, but are not limited to, the computation of spectra, photon flux densities, and notably, power density distributions on arbitrary geometries in 3D which is of interest in accelerator component study and design. This modern approach and several complex geometries will be highlighted and elaborated on. http://oscars.bnl.gov
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK121
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THOBA2	Coherent Synchrotron Radiation and Wake Fields With Discontinuous Galerkin Time Domain Methods	3649
	D. A. Bizzozero, H. De Gersem, E. Gjonaj TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: This work is supported by DESY, Hamburg. Coherent synchrotron radiation (CSR) is an essential issue in modern accelerators. We propose a new method to examine CSR in the time domain using an unstructured Discontinuous Galerkin (DG) method. The method uses a 2D spatial discretization in the longitudinal and transverse coordinates (Z,X) with a Fourier series decomposition in the transverse coordinate Y and computes the fields modally. Additionally, by alignment of mesh element interfaces along a source reference orbit, DG methods can naturally handle discontinuous or thin sources in the transverse X direction. We present an overview of the method, illustrate it by calculating wake potentials in a model problem, and in a bunch compressor.
	Slides THOBA2 [2.526 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBA2
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB023	The Influence of Initial Current Density Distribution on the Emittance Reduction	3744
SUSPSIK062	use link to see paper's listing under its alternate paper code
	H. Yamashita, T. Kii, K. Masuda, K. Nagasaki, T. Nogi, H. Ohgaki, K. Torgasin, H. Zen Kyoto University, Kyoto, Japan
	In this study, the influence of current density distribu-tion on the cathode surface on the beam emittance evolution was investigated. The emittance evolution with different beam profiles (flat-top, peak and hollow distribution) have been compared. The modification of the current profile was shown to affect the axial distance of the point of minimal emittance over wide range. The hollow profile allows extending the axial distance of the point of emittance minimum keeping its value extremely low. Further the parameters of a peak profile, which give the smallest emittance were determined. This work demonstrates the significance of initial current density distribution for the emittance evolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB023
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

UNDUMAG - A New Computer Code to Calculate the Magnetic Properties of Undulators

3071

M. Scheer
HZB, Berlin, Germany

A new code for the magnetic design of undulators is under development at the Helmholtz-Zentrum Berlin (BESSY). The program reads in the geometry and material properties of the undulator magnets and iron poles. Magnetic fields, forces and torques, as well as trajectories and synchrotron radiation can be calculated. The code is a stand-alone FORTRAN program, thus, only a FORTRAN compiler is needed to install it. Build-in graphic routines allows to write postscript files to visualize the geometry and the fields. Other results like 3D field maps, field integrals etc. are written to ASCII files for later use. The code will be published under the GNU general public license. First results and comparison to other codes are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK062

Export •

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

WEPIK064

Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral

3074

W. Ackermann, H. De Gersem, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK064

Export •

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

WEPIK073

Three Dimensional Wake Field for an Electron Moving in Undulator

3098

K. Ohmi
KEK, Ibaraki, Japan

Electro-magnetic field for given trajectory of an electron is calculated by Lienard-Wiechert potential. The field near the electron moving in an undulator is presented. The field is regarded as a wake field in the undulator. Motion of a bunch is studied in the wake field.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK073

Export •

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

WEPIK077

Shielding of Beam Pipe on Rapidly Varying Magnetic Field

3107

N. Wang, J. Chen, S.K. Chen, P. He, G. Xu
IHEP, Beijing, People's Republic of China

In low emittance rings, beam is quite sensitive to orbit oscillations. Fast correctors will be used to correct the beam orbit. The fast varying magnetic field will generate eddy current on the beam pipe, which will in turn change the phase and the amplitude of the magnetic field. The shielding effect of the beam pipe on a fast varying magnetic field is simulated for different frequencies. The results are also benchmarked with the measurements in the lab.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK077

Export •

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

WEPIK086

Wave Propagation in a Fractal Wave Guide

3128

V.G. Ziemann, A.K. Bhattacharyya, M. Holz, J. Ögren
Uppsala University, Uppsala, Sweden

We analyze the propagation of electro-magnetic waves in a wave guide that has the shape of Koch's snowflake, a well-known fractal.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK086

Export •

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

WEPIK097

An Optimization Tool to Design a Coreless Non-Linear Injection Kicker Magnet

3170

B. MacDonald-de Neeve
ETH, Zurich, Switzerland
B. MacDonald-de Neeve, M. Paraliev, Á. Saá Hernández
PSI, Villigen PSI, Switzerland

Top-up injection into low emittance light sources is challenging due to their inherent small dynamic apertures (DA). The use of a multipole-magnet injection kicker prevents disturbing the circulating beam. However, the injected bunch will be mismatched due to unwanted focusing (linear field profile) or even filamented (nonlinear field profile). Coreless nonlinear kicker magnets, using different configurations of straight conductors, can produce transverse step-like magnetic field distribution which prevent the mismatch. We explored an 8-conductor configuration and a multi-conductor approach like unipolar massless septum design. Maximizing the spatial derivative of the transverse field step function is crucial in order to kick the injected bunch inside the DA. Comparing the results of different designs a particular dependence between the smallest clear aperture and the maximum transverse field spatial derivative was observed. We have developed an optimization tool to generate arbitrary 2D magnetic fields and determine the associated current distribution. With it we obtained new design solutions for possible injection magnets that go beyond the limitations of the standard designs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK097

Export •

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

WEPIK101

Novel Implementation of Quadrupole and Higher Order Fringe Fields to Accelerator Design

3184

B.D. Muratori
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Until recently, in the initial design phase of any accelerator project, it was not possible to have an adequate description of quadrupole and higher order multipole fringe fields. We report on the latest developments in analytical fringe fields for multipoles, particularly for quadrupoles and sextupoles. We show how they can be used to improve accelerator codes and make them both faster and more precise. We also show how the analytical formulae for the fringe fields yield expressions for both the scalar and vector potentials in electromagnetism. We conclude by discussing the application of both potentials to the design of multipole magnets as well as the implementation of symplectic kick approximations for fringe fields in thin lens models that could be used in accelerator codes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK101

Export •

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

WEPIK111

Derivation of a Finite Element Formulation From a Lagrangian for the Electromagnetic Potentials

3208

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Conventional electromagnetic finite element solvers typically solve a weak formulation of the Helmholtz wave equation. While mathematically this approach is correct, it does not fully reflect the fundamental physics involved. We offer an alternative variational formulation which is not derived from the Helmholtz wave equation but is more fundamentally tied to the physics of the system: a Lagrangian for the electromagnetic potentials. Solving for the potentials directly allows for a natural accounting of the beam wave interaction. It could also potentially avoid the issue of deleterious spurious modes inherent when selecting the Coulomb gauge and enforcing the subsequent divergence free condition, eliminating the need for vector basis functions. Herein we present the theory and the resulting formulation including a discussion on gauge fixing. We conclude with some numerical results demonstrating the potential of this formulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK111

Export •

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

WEPIK112

A 2D Finite Element Solver for Electromagnetic Fields with m-fold Azimuthal Symmetry

3211

A.R. Vrielink, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Radiofrequency (RF) cavities for use in accelerators, from RF sources to accelerating and transverse cavities, often exhibit m-fold azimuthal symmetry. For cases where m>0, commercially available finite element codes used to simulate the beam-wave interaction typically require a full 3D simulation. We have derived a finite element formulation which accounts for the known azimuthal dependence of the electromagnetic fields, allowing us to solve for these problems on a 2D mesh and reducing simulation times significantly. The theory, including the construction of the local finite element matrices and the selection of appropriate basis functions, will be presented in addition to numerical results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK112

Export •

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

WEPIK121

Computation of Synchrotron Radiation on Arbitrary Geometries in 3D with Modern GPU, Multi-Core, and Grid Computing

3238

D.A. Hidas
BNL, Upton, Long Island, New York, USA

Funding: Supported by the U.S. Department of Energy under contract DE-SC0012704
Open Source Code for Advanced Radiation Simulation (OSCARS*) is an open source project being developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary particle beams in arbitrary magnetic (and electric) fields on arbitrary geometries in 3D. OSCARS was designed with considerations for modern large scale computing infrastructure. These include the ability to use GPUs for computations, multi-threaded computations, and utilities for grid (or cloud) computing. Primary applications include, but are not limited to, the computation of spectra, photon flux densities, and notably, power density distributions on arbitrary geometries in 3D which is of interest in accelerator component study and design. This modern approach and several complex geometries will be highlighted and elaborated on.
* http://oscars.bnl.gov

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK121

Export •

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

THOBA2

Coherent Synchrotron Radiation and Wake Fields With Discontinuous Galerkin Time Domain Methods

3649

D. A. Bizzozero, H. De Gersem, E. Gjonaj
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: This work is supported by DESY, Hamburg.
Coherent synchrotron radiation (CSR) is an essential issue in modern accelerators. We propose a new method to examine CSR in the time domain using an unstructured Discontinuous Galerkin (DG) method. The method uses a 2D spatial discretization in the longitudinal and transverse coordinates (Z,X) with a Fourier series decomposition in the transverse coordinate Y and computes the fields modally. Additionally, by alignment of mesh element interfaces along a source reference orbit, DG methods can naturally handle discontinuous or thin sources in the transverse X direction. We present an overview of the method, illustrate it by calculating wake potentials in a model problem, and in a bunch compressor.

Slides THOBA2 [2.526 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBA2

Export •

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

THPAB023

The Influence of Initial Current Density Distribution on the Emittance Reduction

3744

SUSPSIK062

use link to see paper's listing under its alternate paper code

H. Yamashita, T. Kii, K. Masuda, K. Nagasaki, T. Nogi, H. Ohgaki, K. Torgasin, H. Zen
Kyoto University, Kyoto, Japan

In this study, the influence of current density distribu-tion on the cathode surface on the beam emittance evolution was investigated. The emittance evolution with different beam profiles (flat-top, peak and hollow distribution) have been compared. The modification of the current profile was shown to affect the axial distance of the point of minimal emittance over wide range. The hollow profile allows extending the axial distance of the point of emittance minimum keeping its value extremely low. Further the parameters of a peak profile, which give the smallest emittance were determined. This work demonstrates the significance of initial current density distribution for the emittance evolution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB023

Export •

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