Simulations of an energy dechirper based on dielectric lined waveguides

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 <math id="mml18" display="inline" overflow="scroll" altimg="si18.gif"><mn>3</mn><mo>.</mo><mn>0</mn><mspace width="0.33em" class="nbsp"/><mi>μ</mi><mi mathvariant="normal">m</mi></math>, 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 analysed in terms of the energy modulation and the transverse phase space. •Passive slab-symmetric DLW based energy dechirper is studied for LWFA bunch.•Typical LWFA beam parameters are adopted in CST PIC simulations.•Effect of both longitudinal and transverse wakefields on driving bunch is analysed.