Simulations of an energy dechirper based on dielectric lined waveguides

TL;DR

This paper investigates a dielectric lined waveguide-based passive dechirper to reduce energy spread in electron bunches from laser plasma accelerators, using simulations to optimize its design and analyze wakefield effects.

Contribution

It introduces a tunable rectangular waveguide dechirper design for LPA bunches and provides simulation-based optimization and analysis of its wakefield effects.

Findings

Effective energy spread compensation demonstrated in simulations.

Tunable gap allows optimization of wakefield effects.

Analysis of self-wake impacts on bunch energy and phase space.

Abstract

Terahertz frequency wakefields can be excited by ultra-short relativistic electron bunches travelling through dielectric lined waveguide (DLW) structures. These wakefields can either accelerate a witness bunch with high gradient, or modulate the energy of the driving bunch. In this paper, we study a passive dechirper based on the DLW to compensate the correlated energy spread of the bunches accelerated by the laser plasma wakefield accelerator (LWFA). A rectangular waveguide structure was employed taking advantage of its continuously tunable gap during operation. The assumed 200 MeV driving bunch had a Gaussian distribution with a bunch length of 3.0 {\mu}m, a relative correlated energy spread of 1%, and a total charge of 10 pC. Both of the CST Wakefield Solver and PIC Solver were used to simulate and optimize such a dechirper. Effect of the time-dependent self-wake on the driving bunch was analyzed in terms of the energy modulation and the transverse phase space.