Single and multi-pulse based X-ray photon correlation spectroscopy.

The ability of pulsed nature of synchrotron radiation opens up the possibility of studying microsecond dynamics in complex materials via speckle-based techniques. Here, we present the study of measuring the dynamics of a colloidal system by combining single and multiple X-ray pulses of a storage ring. In addition, we apply speckle correlation techniques at various pulse patterns to collect correlation functions from nanoseconds to milliseconds. The obtained sample dynamics from all correlation techniques at different pulse patterns are in very good agreement with the expected dynamics of Brownian motions of silica nanoparticles in water. Our study will pave the way for future pulsed X-ray investigations at various synchrotron X-ray sources using individual X-ray pulse patterns.

Demonstration of 3D photon correlation spectroscopy in the hard X-ray regime.

Three-dimensional photon correlation spectroscopy (3D PCS) is a well-known technique developed to suppress multiple scattering contributions in correlation functions, which are inevitably involved when an optical laser is employed to investigate dynamics in a turbid system. Here, we demonstrate a proof-of-principle study of 3D PCS in the hard X-ray regime. We employ an X-ray optical cross-correlator to measure the dynamics of silica colloidal nanoparticles dispersed in polypropylene glycol. The obtained cross correlation functions show very good agreement with auto-correlation measurements. This demonstration provides the foundation for X-ray speckle-based studies of very densely packed soft matter systems.

Compact hard X-ray split-and-delay line for studying ultrafast dynamics at free-electron laser sources.

A compact hard X-ray split-and-delay line for studying ultrafast dynamics at free-electron laser sources is presented. The device is capable of splitting a single X-ray pulse into two fractions to introduce time delays from -5 to 815 ps with femtosecond resolution. The split-and-delay line can operate in a wide and continuous energy range between 7 and 16 keV. Compact dimensions of 60 × 60 × 30 cm with a total weight of about 60 kg make it portable and suitable for direct installation in an experimental hutch. The concept of the device is based on crystal diffraction. The piezo-driven stages utilized in the device give nanometre positioning accuracy. On-line monitoring systems based on X-ray cameras and intensity monitors are implemented to provide active alignment feedback. Performance estimates of the system are also presented.

Hard X-ray Fourier transform holography at free electron lasers source.

We report on the feasibility of Fourier transform holography in the hard X-ray regime using a Free Electron Laser source. Our study shows successful single and multi-pulse holographic reconstructions of the nanostructures. We observe beam-induced heating of the sample exposed to the intense X-ray pulses leading to reduced visibility of the holographic reconstructions. Furthermore, we extended our study exploring the feasibility of recording holographic reconstructions with hard X-ray split-and-delay optics. Our study paves the way towards studying dynamics at sub-nanosecond timescales and atomic lengthscales.

Nanosecond X-ray photon correlation spectroscopy using pulse time structure of a storage-ring source.

X-ray photon correlation spectroscopy (XPCS) is a routine technique to study slow dynamics in complex systems at storage-ring sources. Achieving nanosecond time resolution with the conventional XPCS technique is, however, still an experimentally challenging task requiring fast detectors and sufficient photon flux. Here, the result of a nanosecond XPCS study of fast colloidal dynamics is shown by employing an adaptive gain integrating pixel detector (AGIPD) operated at frame rates of the intrinsic pulse structure of the storage ring. Correlation functions from single-pulse speckle patterns with the shortest correlation time of 192 ns have been calculated. These studies provide an important step towards routine fast XPCS studies at storage rings.

Double-pulse speckle contrast correlations with near Fourier transform limited free-electron laser light using hard X-ray split-and-delay.

The ability to deliver two coherent X-ray pulses with precise time-delays ranging from a few femtoseconds to nanoseconds enables critical capabilities of probing ultra-fast phenomena in condensed matter systems at X-ray free electron laser (FEL) sources. Recent progress made in the hard X-ray split-and-delay optics developments now brings a very promising prospect for resolving atomic-scale motions that were not accessible by previous time-resolved techniques. Here, we report on characterizing the spatial and temporal coherence properties of the hard X-ray FEL beam after propagating through split-and-delay optics. Speckle contrast analysis of small-angle scattering measurements from nanoparticles reveals well-preserved transverse coherence of the beam. Measuring intensity fluctuations from successive X-ray pulses also reveals that only single or double temporal modes remain in the transmitted beam, corresponding to nearly Fourier transform limited pulses.