Injection induced by coaxial laser interference in laser wakefield accelerators

We propose a new injection scheme that can generate electron beams with simultaneously a few permille energy spread, submillimeter milliradian emittance, and more than a 100 pC charge in laser wakefield accelerators. In this scheme, a relatively loosely focused laser pulse drivesthe plasma wakefield, and a tightly focused laser pulse with similar intensity triggers an interference ring pattern that creates onion-like multisheaths in the plasma wakefield. Owing to the change in wavefront curvature after the focal position of the tightly focused laser, the innermostsheath of the wakefield expands, which slows down the effective phase velocity of the wakefield and triggers injection of plasma electrons.Both quasicylindrical and fully three-dimensional particle-in-cell simulations confirm the generation of beams with the above mentionedproperties.