Angular Distribution of Nonlinear Harmonic Generation in Helical Undulators: a comparison between experiments and theory

TL;DR

This paper presents a quantitative experimental analysis of the angular distribution of harmonic emission from helical undulators in free-electron lasers, comparing results with a theoretical model based on Maxwell's equations.

Contribution

It provides the first detailed experimental data on harmonic emission angular distribution in helical undulators and validates a theoretical model against these measurements.

Findings

Experimental results match theoretical predictions

Angular distribution patterns are characterized for different harmonic orders

Insights into optimizing harmonic emission in FELs

Abstract

Using harmonic emission from circularly polarized undulator is a procedure that is normally employed on synchrotron beamlines in order to extend the covered spectral range. A similar capability is likewise beneficial for next generation free-electron lasers. In this paper, we perform a first quantitative experimental analysis of the angular distribution of free-electron laser harmonic emission from helical undulators. Experimental results are compared to those obtained by means of a theoretical model based on the paraxial solution of Maxwell's equations.