The spatial coherence of a nanosecond pulsed germanium collisionally excited x-ray laser is measured experimentally for three target configurations. The diagnostic is based on Young’s slit interference fringes with a dispersing element to resolve the 23.2- and 23.6-nm spectral lines. Target configurations include a double-slab target, known as the injector, and geometries in which the injector image is image relayed to seed either an additional single-slab target or a second double-slab target. A special feature of this study is the observation of the change in the apparent source size with angle of refraction across the diverging laser beam. Source sizes derived with a Gaussian source model decrease from 44 μm for the injector target by a variable factor of as much as 2, according to target configuration, for beams leaving the additional amplifiers after strong refraction in the plasma.
© 1998 Optical Society of America
R. E. Burge, G. E. Slark, M. T. Browne, X.-C. Yuan, P. Charalambous, X.-H. Cheng, C. L. S. Lewis, G. F. Cairns, A. G. MacPhee, and D. Neely, "Dependence of spatial coherence of 23.2–23.6-nm radiation on the geometry of a multielement germanium x-ray laser target," J. Opt. Soc. Am. B 15, 2515-2523 (1998)