Temporal and lateral electron pulse compression by a compact spherical electrostatic capacitor

• We propose a new method for spatial and temporal compression of ultrafast electron pulses.
• Compact in-line construction is based on the idea of the spherical electrostatic capacitor (α-SDA).
• It is free of chromatic, geometrical and temporal aberrations after 2π deflection.
• Contrary to other methods it enables time reversal of the pulse with static electric fields only.
• Spatial and temporal focus can be independently fine-adjusted at the target position.

A novel solution for high intensity electron pulse compression in both space and time is proposed in this paper. Based on the unique properties of the central-force electrostatic field of a spherical electrostatic capacitor, the newly developed α-Spherical Deflector Analyzer (α-SDA) with 2π total deflection is utilized for the practical realization of femtosecond electron pulse compression. The mirror symmetry of the system at π deflection causes not only the cancellation of the geometrical and chromatic aberrations at 2π, but also leads to aberration-free time reversal of the electron pulse in the exit plane. As a consequence, the time-divergent electrons at the input are transformed to a time-convergent pulse at the output. In the symmetric case with the first time compression exactly at π, the shortest electron pulse behind the α-SDA analyzer is a mirror symmetric to the original electron pulse at the photocathode. It results in extremely short final electron pulses that are limited only by the duration of the laser pulse, the emittance of the electron bunch, and by imperfections of the real system.