High brightness fully coherent X-ray amplifier seeded by a free-electron laser oscillator

TL;DR

This paper proposes a novel scheme combining X-ray free-electron laser oscillator seeding with undulator tapering using a chirped electron beam, enabling the generation of highly coherent, high-brightness X-ray pulses with improved stability.

Contribution

It introduces a new FEL amplification method seeded by XFELO with a chirped electron beam, enhancing coherence and power beyond previous approaches.

Findings

Feasible to generate terawatt-level coherent X-ray pulses.

Utilizes natural double-horn beam current and residual energy chirp.

Achieves unprecedented shot-to-shot stability.

Abstract

X-ray free-electron laser oscillator (XFELO) is expected to be a cutting edge tool for fully coherent X-ray laser generation, and undulator taper technique is well-known for considerably increasing the efficiency of free-electron lasers (FELs). In order to combine the advantages of these two schemes, FEL amplifier seeded by XFELO is proposed by simply using a chirped electron beam. With the right choice of the beam parameters, the bunch tail is within the gain bandwidth of XFELO, and lase to saturation, which will be served as a seeding for further amplification. Meanwhile, the bunch head which is outside the gain bandwidth of XFELO, is preserved and used in the following FEL amplifier. It is found that the natural "double-horn" beam current as well as residual energy chirp from chicane compressor are quite suitable for the new scheme. Inheriting the advantages from XFELO seeding and undulator tapering, it is feasible to generate nearly terawatt level, fully coherent X-ray pulses with unprecedented shot-to-shot stability, which might open up new scientific opportunities in various research fields.