Angular momentum evolution in laser-plasma accelerators

TL;DR

This paper investigates how angular momentum in electron beams from laser-plasma accelerators evolves during acceleration, identifying its growth source and providing experimental evidence of its dynamic nature.

Contribution

It is the first to experimentally demonstrate the evolution and origin of angular momentum in laser-plasma accelerated electron beams.

Findings

Angular momentum in electron beams grows during acceleration.

A specific source of angular momentum growth is identified.

Experimental results confirm the evolution of angular momentum.

Abstract

The transverse properties of an electron beam are characterized by two quantities, the emittance which indicates the electron beam extend in the phase space and the angular momentum which allows for non-planar electron trajectories. Whereas the emittance of electron beams produced in laser- plasma accelerator has been measured in several experiments, their angular momentum has been scarcely studied. It was demonstrated that electrons in laser-plasma accelerator carry some angular momentum, but its origin was not established. Here we identify one source of angular momentum growth and we present experimental results showing that the angular momentum content evolves during the acceleration.