ATRAP - A 2D1 2 BEAM DYNAMICS CODE USING THE LIENARD-WIECHERTS EQUATIONS/

This paper describes ATRAP (Acceleration and TRAnsport of Particles), a numerical code simulating the beam dynamics. The first objective of this code is the beam quality optimization, in the first meters of an accelerator line, like a photo-injector, for an axi-symmetrical proble m and for a negligible weakfield. If the weakfield can be neglected, w e do not need to develop a self-consistent code. The Maxwell's equatio n solution can be obtained with the Lienard-Wiechert' equations for th e field created by the charges, and with a spatial harmonic expansion for the external fields. Another major problem in a beam dynamic code is the beam charge modelization. It has been shown [1] that the Gaussi an assignment algorithm is superior to the other techniques used. In A TRAP, different algorithms and analytical developments are used, which permit us to keep the same accuracy as that of a self consistent code , reducing the computation time.