Measurement of the spatial coherence of a soft-x-ray laser

The spatial coherence of a neonlike selenium x-ray laser operating at 206 and 210 {} has been measured using a technique based on partially coherent x-ray diffraction. The time-integrated spatial coherence of the selenium x-ray laser was determined to be equivalent to that of a quasimonochromatic spatially incoherent disk source whose diameter is comparable to the line focus of the visible-light laser pumping the x-ray laser. The spatial coherence was improved by narrowing the line focus width.