Attosecond, hundred-MeV electron beams from vacuum-based direct laser acceleration with structured Bessel light

Area of Science:

• * Plasma Physics and Laser Science
• * Accelerator Physics

Background:

• * Generating high-energy electron beams typically requires large facilities.
• * Existing methods often involve plasma, which can introduce instabilities.
• * There is a need for compact, stable, and efficient electron beam sources.

Purpose of the Study:

• * To propose and demonstrate a novel vacuum-based direct laser acceleration (VDLA) scheme.
• * To generate attosecond-scale, hundred-MeV electron beams without plasma.
• * To investigate the acceleration and focusing dynamics of relativistic electrons.

Main Methods:

• * Numerical demonstration using particle-in-cell simulations.
• * Employing an ultra-intense, radially polarized first-order Bessel beam.
• * Injecting relativistic electrons off-axis into the structured laser field.

Main Results:

• * Achieved attosecond-scale electron micro-bunches with durations down to 90 attoseconds.
• * Demonstrated MeV-level electron energies exceeding 400 MeV.
• * Observed efficient electron trapping, phase-locking, and compression.
• * Identified a transverse-stratified acceleration mechanism with optimal energy gain and collimation.

Conclusions:

• * The proposed VDLA scheme is a viable plasma-free method for generating high-quality electron beams.
• * This all-optical approach offers a promising route to compact and stable attosecond electron sources.
• * Potential applications include ultrafast imaging, coherent radiation generation, and advanced accelerator development.