X-ray Free Electron Laser based Dark-Field X-ray Microscopy

TL;DR

This paper explores the potential of using X-ray free electron lasers for dark-field X-ray microscopy at picosecond time scales, enabling dynamic imaging of phonon-induced strain in crystals.

Contribution

It demonstrates the feasibility of ultrafast DFXM at the picosecond scale through simulations combining thermomechanical and optical models.

Findings

Simulated DFXM images show strain wave propagation in diamond.

The approach suggests potential for real-time imaging of phonon dynamics.

Feasibility established for ultrafast DFXM using LCLS specifications.

Abstract

Dark-field X-ray microscopy (DFXM) is a nondestructive full-field imaging technique providing three dimensional mapping of microstructure and local strain fields in deeply embedded crystalline elements. This is achieved by placing an objective lens in the diffracted beam, giving a magnified projection image. So far, the method has been applied with a time resolution of milliseconds to hours. In this work, we consider the feasibility of DFXM at the picosecond time scale using an X-ray free electron laser source and a pump-probe scheme. We combine thermomechanical strain wave simulations with geometrical optics and wavefront propagation optics to simulate DFXM images of phonon dynamics in a diamond single crystal. Using the specifications of the XCS instrument at the Linac Coherent Light Source (LCLS) as an example results in simulated DFXM images clearly showing the propagation of a strain wave.