Two-dimensional spatial imaging of the multiple-pulse-driven 196-angstrom neonlike germanium x-ray laser

W present two-dimensional, high-resolution, spatial images of the 196-Angstrom laser emission from the output aperture of a neonlike germanium laser which is created by illuminating a slab target with a series of short 100-ps pulses from the Nova laser. Simulations of the gain which are propagated through the plasma density gradients to calculate the spatial distribution of the laser intensity are compared with the experiments and show good agreement. The importance of refraction in the propagation calculation manifests itself in the laser intensity peaking 150 mu m from the target surface, even though the gain peaks 50 to 60 mu m from the target surface.