Abstract
High-energy X-rays (HEX-rays) with photon energies on order of 100 keV have attractive characteristics, such as comparably low absorption, high spatial resolution and the ability to access inner-shell states of heavy atoms. These properties are advantageous for many applications ranging from studies of bulk materials to the investigation of materials in extreme conditions. Ultrafast X-ray diffraction allows the direct imaging of atomic dynamics simultaneously on its natural time and length scale. However, using HEX-rays for ultrafast studies has been limited due to the lack of sources that can generate pulses of sufficiently short (femtosecond) duration in this wavelength range. Here we show single-crystal diffraction using ultrashort ~90 keV HEX-ray pulses generated by an all-optical source based on inverse Compton scattering. We also demonstrate a method for measuring the crystal lattice spacing in a single shot that contains only ~105 photons in a spectral bandwidth of ~50% full width at half maximum (FWHM). Our approach allows us to obtain structural information from the full X-ray spectrum. As target we use a cylindrically bent Ge crystal in Laue transmission geometry. This experiment constitutes a first step towards measurements of ultrafast atomic dynamics using femtosecond HEX-ray pulses.
Highlights
The source is capable of generating up to 106 photons per shot and for this experiment was operated at a central photon energy of ~90 keV with a relative energy spread of ~50% (FWHM)
X-rays of equal energy that are diffracted by the crystal from a position close to the spectrometer axis are focused onto a circle (Rowland circle) with a diameter that is equal to the radius of curvature (ROC) of the bent crystal[16]
Single-shot Determination of Ge lattice constant. We demonstrate that this method allows us to determine the lattice constant with a high-resolution using a single shot with only ~105 photons and a comparably broad spectrum of ~50%
Summary
HEX-ray pulses with a duration of 20 ps have been generated using a more compact source that is based on inverse Compton scattering of optical photons (laser wiggler) from a relativistic electron beam[7]. We were able to demonstrate that through energy filtering of the diffraction signal, it is possible to use the full X-ray spectrum of ~50% (FWHM) for the determination of the crystal lattice spacing.
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