On the use of multilayer Laue lenses with X-ray Free Electron Lasers

TL;DR

This paper demonstrates the first use of multilayer Laue lenses to focus X-ray Free Electron Laser beams to nanometer-scale spots, analyzing their efficiency and stability over multiple pulses at the European XFEL.

Contribution

It introduces the application of multilayer Laue lenses with XFELs, detailing their alignment, characterization, and performance under high-intensity pulse trains.

Findings

Achieved focusing to a few tens of nanometers.

Transmission increased with pulses, reaching 92% at 5 pulses.

Diffraction efficiency varied over pulse trains and was reproducible.

Abstract

Multilayer Laue lenses were used for the first time to focus x-rays from an X-ray Free Electron Laser (XFEL). In an experiment, which was performed at the European XFEL, we demonstrated focusing to a spot size of a few tens of nanometers. A series of runs in which the number of pulses per train was increased from 1 to 2, 3, 4, 5, 6, 7, 10, 20 and 30 pulses per train, all with a pulse separation of 3.55 us, was done using the same set of lenses. The increase in the number of pulses per train was accompanied with an increase of x-ray intensity (transmission) from 9% to 92% at 5 pulses per train, and then the transmission was reduced to 23.5 % when the pulses were increased further. The final working condition was 30 pulses per train and 23.5% transmission. Only at this condition we saw that the diffraction efficiency of the MLLs changed over the course of a pulse train, and this variation was reproducible from train to train. We present the procedure to align and characterize these lenses and discuss challenges working with the pulse trains from this unique x-ray source.