118 research outputs found
Finding matched rms envelopes in rf linacs: A Hamiltonian approach
We present a new method for obtaining matched solutions of the rms envelope
equations. In this approach, the envelope equations are first expressed in
Hamiltonian form. The Hamiltonian defines a nonlinear mapping, , and
for periodic transport systems the fixed points of the one-period map are the
matched envelopes. Expanding the Hamiltonian around a fiducial trajectory one
obtains a linear map, , that describes trajectories (rms envelopes) near the
fiducial trajectory. Using and we construct a contraction mapping
that can be used to obtain the matched envelopes. The algorithm is
quadratically convergent. Using the zero-current matched parameters as starting
values, the contraction mapping typically converges in a few to several
iterations. Since our approach uses numerical integration to obtain all the
mappings, it includes the effects of nonidealized, -dependent transverse and
longitudinal focusing fields. We present numerical examples including finding a
matched beam in a quadrupole channel with rf bunchers.Comment: 10 pages, uuencoded gzipped PostScript (88K
Large-Scale Simulation of Beam Dynamics in High Intensity Ion Linacs Using Parallel Supercomputers
In this paper we present results of using parallel supercomputers to simulate
beam dynamics in next-generation high intensity ion linacs. Our approach uses a
three-dimensional space charge calculation with six types of boundary
conditions. The simulations use a hybrid approach involving transfer maps to
treat externally applied fields (including rf cavities) and parallel
particle-in-cell techniques to treat the space-charge fields. The large-scale
simulation results presented here represent a three order of magnitude
improvement in simulation capability, in terms of problem size and speed of
execution, compared with typical two-dimensional serial simulations. Specific
examples will be presented, including simulation of the spallation neutron
source (SNS) linac and the Low Energy Demonstrator Accelerator (LEDA) beam halo
experiment
Lyapunov Exponents without Rescaling and Reorthogonalization
We present a new method for the computation of Lyapunov exponents utilizing
representations of orthogonal matrices applied to decompositions of M or
MM_trans where M is the tangent map. This method uses a minimal set of
variables, does not require renormalization or reorthogonalization, can be used
to efficiently compute partial Lyapunov spectra, and does not break down when
the Lyapunov spectrum is degenerate.Comment: 4 pages, no figures, uses RevTeX plus macro (included). Phys. Rev.
Lett. (in press
On FFT-based convolutions and correlations, with application to solving Poisson's equation in an open rectangular pipe
A new method is presented for solving Poisson's equation inside an open-ended
rectangular pipe. The method uses Fast Fourier Transforms (FFTs) to perform
mixed convolutions and correlations of the charge density with the Green
function. Descriptions are provided for algorithms based on the ordinary Green
function and for an integrated Green function (IGF). Due to its similarity to
the widely used Hockney algorithm for solving Poisson's equation in free space,
this capability can be easily implemented in many existing particle-in-cell
beam dynamics codes
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Advanced Computing Tools and Models for Accelerator Physics
This paper is based on a transcript of my EPAC'08 presentation on advanced computing tools for accelerator physics. Following an introduction I present several examples, provide a history of the development of beam dynamics capabilities, and conclude with thoughts on the future of large scale computing in accelerator physics
ADVANCED COMPUTING TOOLS AND MODELS FOR ACCELERATOR PHYSICS
Abstract This paper is based on a transcript of my EPAC'08 presentation on advanced computing tools for accelerator physics. Following an introduction I present several examples, provide a history of the development of beam dynamics capabilities, and conclude with thoughts on the future of large scale computing in accelerator physics
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