PARALLEL FINITE ELEMENT MODELING TOOLS FOR ERL DESIGN AND ANALYSIS

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PARALLEL FINITE ELEMENT MODELING TOOLS FOR ERL
DESIGN AND ANALYSIS
Liling Xiao, Volkan Akcelik, Arno Candel, Lixin
Ge, Andreas Kabel, Kwok Ko, Lie-Quan Lee, Zenghai
Li, Cho Ng, Greg Schussman SLAC, Menlo Park, CA
94025, USA
With support from SLACs accelerator program and
the DOE SciDAC project, the Advanced Computations
Department has developed a suite of 3D parallel
finite element electromagnetic codes aimed at
high-accuracy, high-fidelity simulations that can
help address the design issues and analysis
challenges in ERLs which include SRF gun design,
cavity HOM damping, beam heating, and
multipacting.

HOM Damping Evaluation with Omega3P (Eigensolver)
SLAC Parallel Finite Element Codes
TESLA TDR Cavity

• Omega3P results based on an ideal
• cavity (in black)
• Measurements from 8 cavities in TTF
• module 5 (in color), showing cavity
• imperfections
• Cavity imperfection is studied to
• identify critical dimensions affecting Qe.

• For accelerator modeling requiring
• Complexity Disparate length scales
  (unstructured mesh for model fidelity)
• Problem size Multiple cavities (large memory
  of supercomputers needed)
• Accuracy Resolve close mode spacing (higher
  order curved elements)
• Speed Fast turn around time to impact design
  (code scalability important)

0.5 mm gap
.
Beam Heating Study with T3P (Transients
wakefields)
SRF Gun Simulation with Pic3P (Particle-in-Cell)

• High current and short bunch will generate large
  amount of HOM heating
• Broadband power spectrum computed for realistic
  3D structure and bunch
• size to study the beamline absorber efficiency.

BNL Polarized SRF Gun (Design by J. Kewisch) ½
cell, 350 MHz, 24.5 MV/m, 5 MeV, solenoid (18
Gauss), recessed GaAs cathode at T70K inserted
via choke joint, cathode spot size 6.5 mm, Q3.2
nC, 0.4eV initial energy
Mode Spectrum in 2-cavity Structure
XFEL (DESY)
ERL (Cornell)
Multipacting Analysis with Track3P

• SNS SRF cavity HOM coupler
• RF heating observed at HOM coupler
• 3D simulations showed MP barriers close to
  measurements

Scattered self-fields as calculated with Pic3P -
retardation and wakefields are included from
first principles
Mesh model near cathode
Pic3P shows fast convergence of transverse
emittance (DOFs field degrees of freedom)
Bunch at gun exit, colored by energy
Work supported by the US DOE under contract
DE-AC02-76SF00515. This research used resources
of the National Energy Research Scientific
Computing Center and the National Center for
Computational Sciences at Oak Ridge National
Laboratory, which are supported by the Office of
science of the U.S. Department of Energy under
Contract No. DE-AC02-05CH11231 and DE-AC05-00OR227
25, respectively.