Investigation of the Way of Phase Synchronization of a Self-Injected Bunch and an Accelerating Wakefield in Solid-State Plasma

Abstract

The electron acceleration, in a laser wakefield accelerator, controlled through plasma density inhomogeneity is studied on a basis of 2.5-dimensional particle-in-cell simulation. The acceleration requires a concordance of the density scale length and shift of the accelerated electron bunch relative to wake bubble during electron acceleration. This paper considers the excitation of a wakefield in plasma with a density equal to the density of free electrons in metals, solid-state plasma (the original idea of Prof. T. Tajima), in the context of studying the wakefield process. As is known in the wake process, as the wake bubble moves through the plasma, the self-injected electron bunch shifts along the wake bubble. Then, the self-injected bunch falls into the phase of deceleration of the wake wave. In this paper, support of the acceleration process by maintaining the position of the self-injected electron bunch using an inhomogeneous plasma is proposed. It is confirmed that the method of maintaining phase synchronization proposed in the article by using a nonuniform plasma leads to an increase in the accelerating gradient and energy of the accelerated electron bunch in comparison with the case of self-injection and acceleration in a homogeneous plasma.

On Wakefield Acceleration in Inhomogeneous Plasma

“…Comparing the results of the current study with previous studies [27,28], it can be concluded that the current study provides the process of formation and subsequent retention of a self-injected bunch at laser amplitudes 2.0 [27] and 3.33 [28] times smaller, which brings the research topics closer to experimental realization. In the current study, a 10 4 times lower plasma density is considered.…”

“…In addition, in the current study, compared to [27,28] an increase in the bunch charge from 0.56 to 20 pC (by a factor of 35.7) is observed. Also, an energy increase of 7.67 times compared to 3.67 times [28] for the observed time intervals is observed.…”

“…It was previously shown that in an inhomogeneous plasma, including when using profiling, retention of a self-injected bunch in the acceleration phase of the wakefield is observed. The longitudinal inhomogeneity of the plasma was considered [27,28].…”

Improving Stability of the Self-Injected Bunch by Variation of a Sequence of Two Laser Pulses Parameters at Wakefield Excitation in a Metal Density Plasma

“…Synchronization of self-injected bunches with an accelerating field in a metal-density plasma was also studied [13,14].…”