Direct visualization of shock front induced nonlinear laser wakefield dynamics

Abstract

Laser-plasma acceleration is considered to be a promising candidate for compactly delivering high-energy high-quality electron beams. One of the most common methods for injecting plasma electrons into the wakefield structure is the shock front injection. Here we present the first direct visualization of the nonlinear laser wakefield dynamics resulting from a tilted shock front using the femtosecond relativistic electron microscopy technique. Our observations reveal the occurrence of a split in the wakefield, with the formation of an on-axis laser-driven wakefield and an off-axis beam-driven wakefield just after the passage through the hydrodynamic shock. Using experimental and three-dimensional numerical evidence, we identify the mechanism of this newly observed phenomenon as an off-axis electron injection from the tilted shock, which amplified the betatron oscillations of the bunch until its breakup. These results propel our comprehension of the intricate and nonlinear laser-plasma dynamics within the widely employed shock-front injection scheme, providing crucial information for high-quality beam generation in real-time operations.