Spatial coherence measurements and x‐ray holographic imaging using a laser‐generated plasma x‐ray source in the water window spectral region

The properties of a coherent x‐ray point source in the water window spectral region generated using a small commercially available KrF laser system focused onto a Mylar (essentially carbon) target have been measured. By operating the source in a low‐pressure (approximately 20 Torr) nitrogen environment, the degree of monochromaticity was improved due to the nitrogen acting as an x‐ray filter and relatively enhancing the radiation at a wavelength of 3.37 nm (C vi 1s‐2p). X‐ray pinhole camera images show a minimum source size of 12 μm. A Young’s double slit coherence measurement gave fringe visibilities of approximately 62% for a slit separation of 10.5 μm at a distance of 31.7 cm from the source. To demonstrate the viability of the laser plasma as a source for coherent imaging applications a Gabor (in‐line) hologram of two carbon fibers, of different sizes, was produced. The exposure time and the repetition rate was 2 min and 10 Hz, respectively.