Attosecond electron pulses enable real-time observation of ultrafast processes in matter with unprecedented temporal resolution, while also offering a viable pathway toward high-intensity attosecond light sources. Sub-relativistic electron sources—common in university laboratories—are far more accessible than large-scale accelerator facilities, yet the micrometer-scale longitudinal focal length of attosecond pulses generated from such beams severely limits their scope of application. Here we demonstrate a compact, laser-based scheme that simultaneously modulates a sub-relativistic electron beam into attosecond pulse trains and accelerates it to relativistic energies, extending the focal length by orders of magnitude while keeping the source size and complexity compatible with table-top experiments. Particle tracking simulations confirm the generation of ∼1 attosecond pulses with a maximum Lorentz factor of 15 and a relative energy spread below 0.02%. By combining the accessibility of laboratory-scale sources with the performance of high-energy facilities, our method offers a practical and scalable route to attosecond electron pulse generation for broad applications in ultrafast microscopy and spectroscopy.
 

Attosecond electron pulse,Direct laser acceleration,Parametric resonance