Measurements of the spatial and temporal coherence of single, femtosecond x-ray pulses generated by the first hard x-ray free-electron laser (FEL), the Linac Coherent Light Source (LCLS), are presented. Single shot measurements were performed at 780 eV x-ray photon energy using apertures containing double pinholes in "diffract and destroy" mode. We determined a coherence length of 17 µm in the vertical direction, which is approximately the size of the focused LCLS beam in the same direction. The analysis of the diffraction patterns produced by the pinholes with the largest separation yields an estimate of the temporal coherence time of 0.6 fs. We find that the total degree of transverse coherence is 56% and that the x-ray pulses are adequately described by two transverse coherent modes in each direction. This leads us to the conclusion that 78% of the total power is contained in the dominant mode.

X-ray zone plates are diffractive focusing optics composed of concentric rings of phase-shifting material with a changing period along their radii. Hard x-ray zone plates operate primarily in a range of photon energies from 3 to 30 keV. In order to achieve needed resolution and efficiency, high-aspect-ratio structures are typically patterned and fabricated by gold electroforming into a dielectric mold. Ideally, the molds would be mechanically stable and radiation resistant. Ultrananocrystalline diamond offers a solution with a set of physical properties that suggests that the material can be fabricated to desired requirements. The authors present here the first results for the fabrication of hard x-ray zone plates using an ultrananocrystalline diamond mold for electroforming gold and discuss future developments for creating an optimized focusing optic.

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