High efficiency energy extraction from a relativistic electron beam in a strongly tapered undulator

TL;DR

This paper reports an experiment where a relativistic electron beam's energy was efficiently converted into coherent radiation using a strongly tapered undulator, achieving over 30% energy extraction and demonstrating high electro-optical conversion efficiency.

Contribution

The study demonstrates a novel high-efficiency energy extraction method from a relativistic electron beam using a strongly tapered undulator, advancing coherent radiation source development.

Findings

Over 30% energy extraction efficiency achieved

Decelerated electron beam from 65 MeV to 35 MeV

Demonstrates high electro-optical conversion efficiency

Abstract

We present results of an experiment where, using a 200 GW CO2 laser seed, a 65 MeV electron beam was decelerated down to 35 MeV in a 54 cm long strongly tapered helical magnetic undulator, extracting over 30$\%$ of the initial electron beam energy to coherent radiation. These results demonstrate unparalleled electro-optical conversion efficiencies for a relativistic beam in an undulator field and represent an important step in the development of high peak and average power coherent radiation sources.