Indirect methods for wake potential integration

Abstract

The development of the modern accelerator and free-electron laser projects requires to consider wake fields of very short bunches in arbitrary three dimensional structures. To obtain the wake numerically by direct integration is difficult, since it takes a long time for the scattered fields to catch up to the bunch. On the other hand no general algorithm for indirect wake field integration is available in the literature so far. In this paper we review the known indirect methods to compute wake potentials in rotationally symmetric and cavity-like three dimensional structures. For arbitrary three dimensional geometries we introduce several new techniques and test them numerically.Comment: 19 pages, 6 figures, submitted to PR STA

Longitudinal wakefield for an axisymmetric collimator

“…(1). In this paper, we used the ECHO code [1,2] to carry out an extensive study of the dependence of the wakefield on the transverse geometric parameters. For a tapered collimator, we have shown that the short-range wakefield, for s=d & 0:3 and & =3, is well approximated by Eq.…”

“…Progress in understanding this subject has been achieved through both analytical and numerical studies. In this paper, using the 2D electromagnetic simulation ECHO code [1,2], we carry out an investigation of the longitudinal short-range wakefield due to an axisymmetric collimator. We consider the highly relativistic limit in which a particle traveling at the speed of light c, passes through a step function or tapered collimator illustrated in Figs.…”

Time Domain Boundary Element Analysis of Wake Fields in Long Accelerator Structures

“…To obtain the short-range wake potential of a short bunch in long accelerator structures, direct time domain calculations of wake field are commonly made with the moving window technique and indirect integration methods [8]- [11] are often used in order to dramatically reduce the calculation time in a computer code. In the following, we shall review the implementation of indirect methods for wake potential integration.…”

“…For axis-symmetric structures, the infinite integration of wake potential can be replaced by a finite range of integration with the Napoly-Chin-Zotter (NCZ) indirect integration method [11]. Especially, selecting the integration path along the boundary surface of a structure as the path (i) shown in Fig.…”

“…As is well-known in the development of wake field simulation codes, it is possible to dramatically reduce the calculation costs for a time domain wake field computation by utilizing the indirect wake potential integration [8]- [11] and the moving window technique [12]. In fact, these techniques have been applied to FIT codes.…”