# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1907.05078