Toward a single mode Free Electron Laser for coherent hard x-ray experiments

TL;DR

This paper investigates the spectral stability of the LCLS free electron laser and proposes a scheme to produce single-mode X-ray radiation, enhancing coherence for experiments.

Contribution

It analyzes shot-to-shot spectral fluctuations of the LCLS and introduces a method to generate single-mode X-ray beams using a monochromator.

Findings

LCLS spectral fluctuations are manageable for coherent experiments.

A proposed monochromator scheme can produce single-mode X-ray radiation.

Spectral stability supports feasible coherent hard X-ray experiments.

Abstract

The fluctuations of the longitudinal coherence length expected from the world's first hard X-ray Free Electron Laser, the Linac Coherent Light Source, are investigated. We analyze, on a shot-to-shot basis, series of power spectra generated from 1D-FEL simulations. We evaluate how the intrinsic noise in the spectral profile of the X-ray beam reflects on its longitudinal coherence length. We show that the spectral stability of the LCLS beam will allow coherent X-ray experiments with a reasonable acquisition time. We also propose a scheme to deliver single-mode X-ray radiation using a narrow bandpass monochromator.