Monoenergetic Energy Doubling in a Hybrid Laser-Plasma Wakefield Accelerator

Abstract

An ultracompact laser-plasma-generated, fs-scale electron double bunch system can be injected into a high-density driver/witness-type plasma wakefield accelerator afterburner stage to boost the witness electrons monoenergetically to energies far beyond twice their initial energy on the GeV scale. The combination of conservation of monoenergetic phase-space structure and fs duration with radial electric plasma fields E(r)∼100 GV/m leads to dramatic transversal witness compression and unprecedented charge densities. It seems feasible to upscale and implement the scheme to future accelerator systems.

Self-mode-transition from laser wakefield accelerator to plasma wakefield accelerator of laser-driven plasma-based electron acceleration

“…Furthermore, the radial component of the electric field oscillates in the laser polarization direction due to the residual laser pulse, such that the radial compression of the trapped electron bunch seen in Ref. 17 is not significant. This result is the primary disadvantage of the single-stage LWFA/ PWFA hybrid configuration explored here.…”

“…Note that multiple quasimonoenergetic bunch trapping in the multiple cavities is the preferred condition for the PWFA scheme suggested in Ref. 17. However, electron bunches in the second and third cavities disappear during the mode transition due to destruction of the acceleration structure ͓Fig.…”

“…10 Via PIC simulations, it has recently been shown that the very short high-energy electron double-bunch, available in LWFAs and self-modulated LWFAs, can lead to a monoenergetic energy doubling by using the PWFA scheme. 17 In this method, the LWFA stage is assumed to produce two highenergy electron beams with appropriate spacing. Then, these electron beams are sent into another plasma column to accelerate the second electron bunch ͑witness͒ in a plasma wakefield driven by the first bunch ͑driver͒.…”

Hybrid modeling of relativistic underdense plasma photocathode injectors

“…Recently, hybrid plasma accelerators [32] have been described that promise to enable dramatically increased electron bunch quality by employing an underdense photocathode plasma wakefield mechanism [33]-the equivalent of a solid photocathode in radio frequency (rf) photoinjector guns [34]. In particular, this hybrid injector scheme plasma accelerator (also known as Trojan horse injection [35]) may produce bunches with normalized transverse emittance down to the % 10 À2 mm mrad level or less.…”

Summary report of working group 4: Beam-driven acceleration

“…This natural feature is a key requirement for beamdriven PWFA stages. A combined hybrid system of a laser-driven stage and a subsequent beam-driven, dephasingfree stage can be used, for instance, to realize driver/witness-type PWFA systems, as in [6], or to drive Trojan Horse underdense plasma photocathode stages, as in [7]. The latter profits from the inherent synchronization between the electron beam and the Trojan laser, in such ultimately all-optical incarnations, and from the fact that the witness bunch quality produced in this way can exceed the drive beam quality substantially, and that its generation is to a large degree decoupled from the drive beam.…”