Abstract
Propagation distances of intense laser pulses and high-charge electron beams through the plasma are, respectively, limited by diffraction and self-deceleration. This imposes severe constraints on the performance of the two major advanced accelerator concepts: laser and plasma wakefield accelerators. Using numerical simulations, we demonstrate that when the two beams co-propagate in the plasma, they can interact synergistically and extend each other's travel distances. The key interactions responsible for the synergy are found to be laser channeling by the electron bunch, and direct laser acceleration of the bunch electrons by the laser pulse. Remarkably, the amount of energy transferred from the laser pulse to the plasma can be increased by several times by the guiding electron bunch despite its small energy content. Implications of such synergistic interactions for the high-gradient acceleration of externally injected witness charges are discussed, and a new concept of a Laser-pulse and Electron-bunch Plasma Accelerator (LEPA) is formulated.
Highlights
Plasma-based accelerators represent one of the most exciting concepts in high-gradient particle acceleration
We show that objective (i) can be accomplished using the recently discovered phenomenon of direct laser acceleration (DLA) in a decelerating plasma wakefield [31], and objective (ii) can be accomplished via beam channeling of laser pulses by high-current electron bunches [32]
When comparing laser-pulse and electronbunch plasma accelerator (LEPA) to the more conventional plasma-based accelerator approaches, such as laser wakefield accelerator (LWFA) and plasma wakefield accelerator (PWFA), we have discovered that the propagation distances of both the electron bunch and the laser pulse are extended as the result of a synergistic interaction between the laser pulse and the bunch
Summary
Plasma-based accelerators represent one of the most exciting concepts in high-gradient particle acceleration. Limiting the single-stage energy gain of the accelerated electrons: (i) the accelerating gradient Ek, which scales with the plasma density n0 according to Ek ∝ n10=2, where the proportionality coefficient is determined by the strength of the driver, and (ii) the acceleration distance Lacc, which is subject to very different constraints for the LWFA and PWFA concepts. It would be highly advantageous to find a way of combining the LWFA and PWFA approaches to benefit from their respective advantages: long propagation distance Llparsoepr of a laser pulse and a small energy content Ubunch of an electron driver bunch. Assuming the wakefield equals to the cold plasma wave-breaking limit, i.e., ak 1⁄4 aWk B ≡ ωp=ω0, we estimate that the driver bunch electrons can gain up to several GeVs of energy in a tenuous plasma with n0 1⁄4 1017 cm−3. The electron driver bunch can be extended by the laser pulse
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