Electron acceleration in perpendicularly crossed laser beams with following injection in the laser wakefield accelerator

摘要

Introduction Electrons are accelerated by the plasma wave dragged by a short, intense laser pulse propagating in plasma [1]. The advantage of plasmas is in their ability to sustain an accelerating gradient much larger than in a conventional radiofrequency accelerator. Currently, the most efficient mechanism to accelerate electrons in a plasma by a laser pulse is the cavitated wakefield regime (bubble regime), i.e. electron acceleration in an ion cavity propagating behind the laser pulse in plasmas. Electrons can be trapped at the back of the ion cavity (the bubble) and they form a bunch which is accelerated by the high electric field of the plasma wave (the space-charge force). The electron bunch can be either formed from plasma by the self-injection, or by other mechanisms, e.g. by optical injection [1, 2, 3] during a collision with another additional (injection) laser pulse. In this proceeding, electron acceleration in a main laser beam (MB) colliding in plasma with an additional laser beam (ALB) which propagates perpendicularly to the MB [2] is explored by numerical modelling. In contrast to the cases of counter-propagating beams and other schemes with perpendicularly crossed beams [2], the scheme where low intensity ALB is polarized perpendicularly to the MB polarization is proposed. MB intensity in terms of normalized vector potential α_0,mb may be even greater than 2 in this configuration opposed to standard self-injection avoiding schemes. All the numerical simulations were performed by EPOCH 2D PIC code [4].