Numerical model for plasma electron acceleration in laser wakefield accelerators

Abstract

Summary form only given. Plasma wakefields produced by a sub-picosecond, high intensity laser pulse in a dense gas jet can accelerate plasma electrons to high energies. The acceleration is believed to be a two stage process in which plasma electrons are accelerated to moderate energies by a low phase velocity wave and then trapped and accelerated by the high phase velocity (v/sub p//spl sim/c), large amplitude wakefield. The laser wakefield accelerator (LFWA) experiment at the Naval Research Laboratory has produced up to 30 MeV electrons with no external injector when operating in the self-modulated regime. The low phase velocity wave in this case could arise from the beating of the laser pump pulse with a wave arising from the backward Raman instability. This interpretation is supported by a numerical model which follows the motion of plasma electrons in analytically-prescribed fields corresponding to the laser pump pulse, the forward-going wakefield, and the Raman waves. The accelerated electrons have a large energy spread and are trapped in several bunches.