The APS SASE FEL : modeling and code comparison. Page: 1 of 5
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THE APS SASE FEL: MODELING AND CODE COMPARISON
S.G Biedron', Y.C. Chae, R.J. Dejus, B. Faatz', H.P. Freund*, S.V. Milton, H-D. Nuhn", Re
Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 $
tDeutsches Elektronen Synchrotron, Notkestrasse 85, 22603 Hamburg GermaQ )
"Stanford Linear Accelerator Center, Stanford, California 94309 USA
Abstract undulator period. For non-waveguide simulations,
A self-amplified spontaneous emission (SASE) free- GINGER uses a nonlinear, expanding radial grid,
electron laser (FEL) is under construction at the proportional to the square of the radius near the axis, and
Advanced Photon Source (APS). Five FEL simulation expands exponentially for large distances from the axis.
codes were used in the design phase: GENESIS, The outer grid boundary, the number of radial grid zones,
GINGER, MEDUSA, RON, and TDA3D). Initial as well as the region over which the grid is linear are
comparisons between each of these independent controlled by input parameters. GINGER is able to
formulations show good agreement for the parameters of simulate a single segment of undulator as well as lumped,
the APS SASE FEL. quadruple focusing.
1 INTRODUCTION 2.3 MEDUSA
The Advanced Photon Source (APS) at Argonne National MEDUSA is a 3D multi-frequency, nonlinear simulation
Laboratory (ANL) is currently commissioning a free- code where the electromagnetic field is represented as a
electron laser (FEL) based on the self-amplified superposition of Gauss-Hermite modes and where a
spontaneous emission (SASE) process [1]. The design source-dependent expansion is used to determine the
parameters were based on capabilities of the existing APS of the optical mode radius. The field equations
linear accelerator, the linear theory [2], and simulations. are integrated simultaneously with the 3D Lorentz force
The codes used in the design include GENESIS [3], equations. As such, MEDUSA differs from the other
GINGER [4j, MEDUSA [5], RON [6], and TDA3D [7,8]. nonlinear simulation codes in that no undulator-period
Comparative simulations were performed using a specific average is imposed on the electron dynamics. It is capable
set of input parameters for the APS SASE FEL. of treating quadrupole and corrector fields, magnet errors,
and multiple segment undulators.
2 CODE DESCRIPTIONS 2.4 RON2.1 GENESIS
GENESIS has its origin in TDA3D, a steady-state
simulation code, which has been extended to perform
multi-frequency simulations. The radiation field is
discretized on a Cartesian grid and solved by the
alternating direction implicit (ADI) integration scheme.
The transverse motion of the electron beam, described by
macroparticles, is calculated analytically, whereas the
energy and phase are found by Runge-Kutta integration.
In addition to the standard internal generation, an external
seeding radiation field, undulator field, and longitudinal
variation of the electron beam parameters can be supplied
in input files.
2.2 GINGER
GINGER is a 3D multi-frequency particle tracking code
with a 2D, axisymmetric representation of the radiation
field. The equations of motion are averaged over an
Work supported by U.S. Department of Energy, Office of Basic
Energy Sciences, under Contract No. W-31-109-ENG-38.
' Email: biedron@aps.anl.gov
'Permanent Address: Science Applications International CorporationRON is a linear, single-frequency code intended for
design optimization of high-gain, short wavelength FELs,
with features for multiple-segment undulators, field
errors, and distributed focusing elements. The electron
motion is along precalculated, period-averaged
trajectories and the radiation field and the bunched beam
current density are calculated at these trajectories from a
set of linear integral equations. Explicit calculation of the
radiation field (on an arbitrary grid) and the capability to
use a measured magnetic field profile as input has been
added recently. Although the linearity does not provide
the saturated state, it does allow for fast run times.
2.5 TDA3D
TDA3D has been publicly available for over a decade.
The latest official release is still a paraxial, single-
frequency code. Extensions include non-axisymmetric
radiation modes, wiggler errors, a strong quadrupole
FODO lattice with arbitrary misalignments, as well as
multi-segment undulators. In "expert" mode, arbitrary
quadrupole focusing can be simulated.te submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory ("Argonne") under Contract No. W-31-109-ENG-38
with the U.S. Department of Energy. he U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said
article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.k N .f sr.-
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Biedron, S. G. The APS SASE FEL : modeling and code comparison., article, April 20, 1999; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc625482/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.