Using short drive laser pulses to achieve net focusing forces in tailored dual grating dielectric structures

Abstract

Laser-driven grating type DLA (Dielectric Laser Accelerator) structures have been shown to produce accelerating gradients on the order of GeV/m. In simple β-matched grating structures due to the nature of the laser induced steady-state in-channel fields the per period forces on the particles are mostly in longitudinal direction. Even though strong transverse magnetic and electric fields are present, the net focusing effect over one period at maximum energy gain is negligible in the case of relativistic electrons. Stable acceleration of realistic electron beams in a DLA channel however requires the presence of significant net transverse forces. In this work we simulate and study the effect of using the transient temporal shape of short Gaussian drive laser pulses in order to achieve suitable field configurations for potentially stable acceleration of relativistic electrons in the horizontal plane. In order to achieve this, both the laser pulse and the grating geometry are optimized. Simulations conducted with the Particle-In-Cell code VSim 7.2 are shown for both the transient and steady state/long pulse case. Finally we investigate how the drive laser phase dependence of the focusing forces could affect a potential DLA-based focusing lattice.

Status and objectives of the dedicated accelerator R&D facility “SINBAD” at DESY

“…In the first stage it is foreseen to place the experiment at the location which is reserved for a third traveling wave structure (Figure 3). The required strong focusing of the external beam to the µ-scale structures is provided by the solenoids surrounding the two up-stream TWS structures [14]. Initially, a part of the photocathode laser will be split off and used to power the DLA structures.…”

Simulation of deflecting structures for dielectric laser driven accelerators

“…Due to the dependence of the deflecting force on the laser-to-electron phase and the short laser wavelength in use further investigation is necessary to study the beam dynamics in such a system. Results on that topic can be found in [5]. For use as a streaking device the maximum bunch length is limited to one quarter of the driving wavelength.…”