ICAP 2002 Abstracts and Posters

3D Space-charge model for GPT simulations of high-brightness electron bunches

Abstract

Applications such as SASE-FEL's require high quality electron bunches with an emittance of the order of 1 micron and a peak current of 1 kA. The standard method to create such bunches is to use a rf-photogun to produce relatively long bunches, and magnetically compress them to the required current following acceleration. The compression stage however causes Coherent Synchrotron Radiation and significantly degrades the bunch quality.

As an alternative to this route, we are studying new acceleration techniques based on pulsed DC technology. Attainable fields of 1 GV/m can keep a bunch sufficiently short to reach the target current without the need for downstream compression and thus avoiding degradation of bunch brightness.

The dynamic behavior of these short bunches is very different from the rf-gun case because the aspect ratio, defined as the radius divided by the length in the rest-frame of the bunch, varies significantly during the first stages of acceleration. For the simulation of these bunches, a new 3D space-charge model is being implemented in the General Particle Tracer (GPT) code. It is based on a non-equidistant multigrid solver, allowing smooth transitions from a high to a low-aspect ratio during a single run. The algorithm scales linearly in CPU time with the number of particles and the insensitivity to aspect-ratio ensures that it can be used for a variety of applications. Tracking examples and field comparisons with an analytical model will be shown.

S.B. van der Geer, O.J. Luiten, Eindhoven University of Technology, The Netherlands M.J. de Loos, Pulsar Physics, The Netherlands G. Poplau, U. van Rienen, Rostock University, Germany

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