Spatially resolved soft X-ray spectrometry from single-image diffraction

High-harmonic generation (HHG) offers better coherence, shorter pulse durations and far greater accessibility than synchrotron sources. These factors make HHG an increasingly important source of soft X-rays and an excellent resource in many emerging areas, for example, the time-resolved study of conformational changes in single biological molecules. Here, we demonstrate a novel technique that enables us to reconstruct spectral information spatially across an X-ray beam. As only a single diffraction image is required per measurement, this technique is well suited to time-resolved studies. This technique is applicable to many types of X-ray source and can be adapted for different spectral regions. Here, results are obtained using a capillary high-harmonic source, revealing detailed information that brings new insight into the physical processes occurring inside the source and enabling us to show the first measurement of radial variation of harmonic order in the emission from an HHG capillary