Search

X-ray Free Electron Lasers (XFELs) allow the collection of high-quality serial femtosecond crystallography data. The next generation of megahertz superconducting FELs promises to drastically reduce data collection times, enabling the capture of more structures with higher signal-to-noise ratios and facilitating more complex experiments. Currently, gas dynamic virtual nozzles (GDVNs) stand as the sole delivery method capable of best utilizing the repetition rate of megahertz sources for crystallography. However, their substantial sample consumption renders their use impractical for many protein targets in serial crystallography experiments. Here, we present a novel application of a droplet-on-demand injection method, which allowed operation at 47 kHz at the European XFEL (EuXFEL) by tailoring a multi-droplet injection scheme for each macro-pulse. We demonstrate a collection rate of 150 000 indexed patterns per hour. We show that the performance and effective data collection rate are comparable to GDVN, with a sample consumption reduction of two orders of magnitude. We present lysozyme crystallographic data using the Large Pixel Detector at the femtosecond x-ray experiment endstation. Significant improvement of the crystallographic statistics was made by correcting for a systematic drift of the photon energy in the EuXFEL macro-pulse train, which was characterized from indexing the individual frames in the pulse train. This is the highest resolution protein structure collected and reported at the EuXFEL at 1.38 Å resolution.

The continued development of synchrotron sources, especially over the previous two decades, has allowed the new field of coherent X-ray optics to flourish. Rapid advancement in the field is set to continue, with the recent completion of the new X-ray free electron laser (XFEL) source at the Stanford Linear Accelerator Centre. Unlike visible wavelength lasers, XFEL and synchrotron sources are not fully coherent, meaning that coherence based imaging techniques are not at present fully optimised for use with these sources. A pre-requisite for the optimisation of coherence based imaging techniques, is the full characterisation of the coherence properties of the incident beam used in these techniques. The task of characterising the coherence properties of an optical wavefield was first investigated by Zernicke in 1938. His use of Young’s double slit experiment remains to this day a popular means of performing a basic measurement of the coherence properties of a wavefield. A limitation of such measurement techniques arises because the coherence properties of an incident wavefield are fully described in terms of a four-dimensional correlation function. This means that a one-dimensional measurement such as a Young’s double slit type experiment fails to provide sufficient information about the wavefield to fully characterise the beam. Over the past 15 years, there has been a development of non-interferometric methods of coherence measurement which seek to obtain a full characterisation of the four-dimensional correlation function. The author develops a non-interferometric iterative method for mapping the correlation function, which is based upon the analysis of the partially coherent wavefield in terms of its coherent modes. A computational method for numerically extracting the coherent modes of a partially coherent wavefield is presented, which is followed by the development of an iterative scheme for experimentally determining the form of these modes. The iterative scheme