Field analysis of a dielectric-loaded rectangular waveguide accelerating structure

Abstract

In this paper, we present a detailed analysis of the modes of a dielectric-loaded rectangular waveguide accelerating structure. In general, the acceleration field in a synchronous acceleration mode is non-uniform in the two transverse dimensions. However, we could use an array of these structures rotated alternatively by 90 degrees to get a focusing-defocusing force continuously as a simple FODO lattice, while maintaining uniform energy gain. The expressions of characteristic parameters such as R/Q, group velocity and attenuation constant are given. The longitudinal wake field experienced by a relativistic charged particle beam in the structure is also presented. These analytical results are also compared with numerical calculations using the MAFIA code suite demonstrating the validity of our analytic approach.

Transverse operator method for wakefields in a rectangular dielectric loaded accelerating structure

“…This is not obvious for the solution obtained by the impedance method [25,26] and requires additional analysis and proof.…”

“…Finally, (i) the proposed method does not require any assumptions on the form of the beam's Coulomb field (in contrast to the impedance method [25,26], where it is often assumed that the field of the beam is essentially flat, an assumption that is valid only at ultrarelativistic energies); (ii) we also did not use the mode decomposition for the problem formulation and its subsequent solution; the mode series obtained as a solution emerges in a natural way as a result of solving the problem; (iii) as a consequence of (ii), and the use of the transverse operator formalism the series of modes of the solution is uniformly convergent. This is not obvious for the solution obtained by the impedance method [25,26] and requires additional analysis and proof.…”

“…Theoretical analyses of dielectric accelerating structures with rectangular geometries have been reported in a number of publications [23,[25][26][27][28][29][30][31]. To determine the amplitudes of individual Cherenkov radiation modes excited in a rectangular waveguide with dielectric slabs, the impedance matching technique was used in the earlier papers [23,25,26].…”

“…To determine the amplitudes of individual Cherenkov radiation modes excited in a rectangular waveguide with dielectric slabs, the impedance matching technique was used in the earlier papers [23,25,26]. When that formalism is used instead of the direct solution of the nonhomogeneous system of Maxwell equations (the standard analytic approach in analysis of wakefields in cylindrical structures [20,21]), the amplitudes of the wakefields needs to be expressed in terms of the shunt impedance (or integrated loss factor) for each mode of the structure [23,25,26]. The approach involves certain approximations, while the direct solution of the inhomogeneous system of Maxwell's equations without intermediate approximations is always preferable for analyzing the wakefield generation problem in DWA structures.…”

Three-dimensional analysis of wakefields generated by flat electron beams in planar dielectric-loaded structures

“…Therefore, the design of the DLW structures must compromise between a small transverse size to maximize the intensity of the wakefield, and a longer interaction length to maximize the energy gain of the test charge. An appealing solution consists of using flat electron beams passing through slab-geometry DLWs [14,[23][24][25]. This possibility has become more attractive since the recent advances toward generating flat beams directly in photoinjectors [26,27].…”