Determination of hybrid and direct laser acceleration dominated regimes in a 55fs laser driven plasma accelerator with ionization induced injection

TL;DR

This study experimentally and computationally investigates the dominant acceleration mechanisms in a 55fs laser-driven plasma accelerator, revealing how plasma density influences the transition between direct laser acceleration and wakefield acceleration regimes.

Contribution

It provides new insights into the density-dependent transition between DLA and wakefield acceleration in laser-driven plasma accelerators, supported by experimental data and 2D PIC simulations.

Findings

Lower density favors DLA with ionization injection

Higher density leads to hybrid DLA-wakefield regime

Simulations show surface wave generation as pre-acceleration mechanism

Abstract

An experimental study on 55fs laser driven plasma accelerator using mixed gas-jet target with varying plasma density is used to identify the role of different acceleration mechanisms, viz. Direct Laser Acceleration (DLA) and wakefield. At lower electron density electron acceleration could be attributed mainly to DLA with ionization induced injection. With increase in density, increasing role of wakefield was observed leading to hybrid regime, and at densities higher than self-injection threshold, observed experimentally for He target contribution of DLA and wakefield was found to be comparable. Dominant DLA mechanism was also observed in case of pure nitrogen target. 2D PIC simulations performed using the EPOCH code corroborate the above scenario, and also showed generation of surface waves, considered as a potential mechanism of pre-acceleration to DLA.