Impact of target density and field mode structure in direct laser acceleration using hollow core tubes.

Direct Laser Acceleration (DLA) enables electrons to accelerate to relativistic energies through direct interaction with high-intensity laser fields. The use of hollow-core tubes makes it possible to engage the longitudinal component of the laser electric field — rather than the transverse field — resulting in ultra-relativistic electron beams with significantly lower divergence [1]. Using Particle-in-Cell (PIC) simulations, we examine the role of target wall density in enhancing electron energy gain: We find that changing the wall density, while keeping it overcritical, can double the final electron energy. We also analyze the evolution of the laser’s field mode structure within the waveguide and its effect on acceleration. Our results highlight target density and field structure as critical parameters for optimizing DLA performance.

[1] Gong, Z., Robinson, A. P. L., Yan, X. Q., & Arefiev, A. V. (2019). Highly collimated electron acceleration by longitudinal laser fields in a hollow-core target. Plasma Physics and Controlled Fusion, 61(3), 035012.