Interferometric optical signature of electron microbunching in laser-driven plasma accelerators

TL;DR

This paper demonstrates the use of coherent optical transition radiation interferometry to observe and characterize electron microbunching in laser-driven plasma accelerators, revealing detailed beam properties.

Contribution

It provides the first detailed optical signature of electron microbunching in plasma accelerators using COTRI, including divergence, beam radius, and emittance measurements.

Findings

Microbunched electrons have ~6x smaller divergence than the ensemble beam.

Microbunched beam radius is less than 3 microns.

Estimated transverse normalized emittance is approximately 0.5 mm·mrad.

Abstract

We report observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched ~200-MeV electrons as they emerge from a laser-plasma accelerator. The divergence of the microbunched portion of electrons, deduced by comparison to an analytical COTRI model, is ~6x smaller than the ~3 mrad ensemble beam divergence, while the radius of the microbunched beam, obtained from COTR images on the same shot, is < 3 microns. The combined results show that the microbunched distribution has estimated transverse normalized emittance ~0.5 mm mrad.