Abstracts Brochure - CERN

WEPCH — Poster Session 28-Jun-06 16:00 - 18:00
points inside the elliptical cross-section of the beam pipe taking care of the conducting boundaries of the pipe. The
new routine will be implemented in the tracking code ASTRA. Numerical examples demonstrate the performance
of the solution strategy underling the new routine. Further tracking results with the new method are compared to
established space-charge algorithms such as the FFT-approach.
3D Space-charge Calculations for Bunches in the Tracking Code ASTRA
Precise and fast 3D space-charge calculations
for bunches of charged particles are of growing
importance in recent accelerator designs.
One of the possible approaches is the parti-
G. Pöplau, U. van Rienen (Rostock University, Faculty of Computer
Science and Electrical Engineering) K. Floettmann (DESY)
cle-mesh method computing the potential of the bunch in the rest frame by means of Poisson’s equation. In that, the
charge of the particles are distributed on a mesh. Fast methods for solving Poisson’s equation are the direct solution
applying Fast Fourier Methods (FFT) and a finite difference discretization combined with a multigrid method for
solving the resulting linear system of equations. Both approaches have been implemented in the tracking code AS-
TRA. In this paper the properties of these two algorithms are discussed. Numerical examples will demonstrate the
advantages and disadvantages of each method, respectively.
2D Wake Field Calculations of Tapered Structures with Different FDTD Discretization
Schemes
The continual performance improvement of
particle accelerators requires advanced prediction
of parasitic wake field effects, even in
structures of comparatively weak influence
like tapers. In the case of smooth tapered
C. Schmidt (Rostock University, Institute for General Electrical
Engn.) H.-W. Glock, U. van Rienen (Rostock University, Faculty
of Engineering)
components, even well established codes like MAFIA* demonstrate strong discretization dependency of the results or
solver instabilities, making them not reliable in such applications. Grid dispersion is assumed to generate this failure.
In Ref.** an alternative discretization scheme is described, using a homogeneous rotated mesh intended to eliminate
such grid dispersion effects. In order to study the dependence on the discretization applied, we use this scheme to
calculate wake fields in prototype taper structures of rotational symmetry. Furthermore a comparison is provided
with the results of a non-rotated mesh, MAFIA runs and - so far applicable - analytical approaches.
*MAFIA V4.107: CST GmbH, Bad Nauheimer Str. 19, D-64289 Darmstadt**R. Hampel et al. New discretization
scheme for wake field computation in cylindrically symmetric structure. Proc. EPAC’04, pp 2559
Implementing Wake Fields in Tracking Codes
We present a formalism for incorporating intra-bunch
wake fields into particle-by-particle
tracking codes, such as MERLIN and BD-
SIM. Higher order wake field effects are in-
R.J. Barlow (UMAN) A. Bungau, G.Yu. Kourevlev, A. Mercer (Cockcroft
Institute)
corporated in a manner which is computationally efficient. Standard formulae for geometric, resistive and dielectric
wake fields are included for various apertures, particularly those relevant for ILC collimators. Numerous examples
are given.
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