Speaker
Description
Laser-plasma accelerators enable compact, high-gradient charged particle acceleration with broad potential applications. Despite significant progress in improving beam quality and control, the stability of accelerated electron beams remains significantly lower than that of the driving laser pulses. In this work, we investigate a previously underappreciated source of transverse beam instability originating from optical-field ionization (OFI), a fundamental mechanism in laser-driven plasma formation. We show that OFI leads to inherently asymmetric initial plasma density profiles, caused by position-dependent electron drift velocities that are highly sensitive to laser polarization, wavelength, pulse duration, and gas species. Using three-dimensional particle-in-cell simulations, we demonstrate that these asymmetries give rise to nonuniform plasma structures and axial magnetic fields, which amplify transverse hosing-like instabilities. Furthermore, we propose and validate a mitigation strategy using pre-ionization of the gas target with a secondary laser pulse, which effectively suppresses the instability by reducing initial plasma asymmetries.
