Experimental demonstration of longitudinal beam phase space linearizer in a free-electron laser facility by corrugated structures

TL;DR

This paper demonstrates the first practical use of a corrugated structure as a beam phase space linearizer in a free-electron laser, significantly improving laser gain and bandwidth control.

Contribution

It introduces the application of corrugated structures for beam linearization in FELs, achieving substantial gain enhancement and bandwidth narrowing in a real-world setup.

Findings

Achieved a gain of ~10,000 over spontaneous emission.

Narrowed FEL bandwidth by about 50%.

Confirmed theoretical predictions with experimental results.

Abstract

Removal of residual linear energy chirp and intrinsic nonlinear energy curvature in the relativistic electron beam from radiofrequency linear accelerator is of paramount importance for efficient lasing of a high-gain free-electron laser. Recently, it was theoretically and experimentally demonstrated that the longitudinal wakefield excited by the electrons itself in the corrugated structure allows for precise control of the electron beam phase space. In this Letter, we report the first utilization of a corrugated structure as beam linearizer in the operation of a seeded free-electron laser driven by a 140 MeV linear accelerator, where a gain of ~10,000 over spontaneous emission was achieved at the second harmonic of the 1047 nm seed laser, and a free-electron laser bandwidth narrowing by about 50% was observed, in good agreement with the theoretical expectations.