Efficiency enhancement in regenerative amplifier free-electron lasers using a tapered undulator

TL;DR

This paper analyzes how using a tapered undulator in a regenerative amplifier free-electron laser (RAFEL) can significantly improve efficiency, especially for high-power EUV and x-ray applications, surpassing traditional single-pass FELs.

Contribution

It presents the first analysis demonstrating efficiency enhancement in a RAFEL with a long, tapered undulator line for high-power EUV and x-ray FELs.

Findings

Efficiency exceeds that of single-pass tapered SASE FELs.

Performance demonstrated at 13.5 nm wavelength.

Potential for high-power tapered undulator x-ray RAFELs.

Abstract

Recent progress in short wavelength free-electron lasers extending from the extreme ultraviolet through the x-ray regime have opened new avenues for industrial and research applications. A high-gain/low-Q oscillator, i.e., a regenerative amplifier free-electron laser (RAFEL), is one possible concept. In this paper, we present the first analysis of efficiency enhancement in a RAFEL with a long, tapered undulator line. For the present analysis, we consider a high average power EUV RAFEL at 13.5 nm and show that the performance exceeds that of single-pass, tapered self-amplified spontaneous emission. This points the way to high power tapered undulator x-ray RAFELs.