Monochromatic backlighting as a laser-fusion diagnostic

The case of an x-ray radiographed (backlit) image of a CH-shell laser-fusion target to be imploded by the Omega Upgrade laser system is studied. The goal is to obtain information on the conditions at peak compression, where the experimental constraints due to target self-emission and required spatial resolution are maximal. Particular attention is devoted to the problem of discriminating against the target self-emission. It is shown that a way to selectively image the target with radiation from a backlight source is to obtain a monochromatic image at a single spectral line emitted by the backlighter. Two experimental configurations are discussed: (a) an x-ray microscope with a flat crystal monochromator, and (b) pinhole imaging in conjunction with a curved crystal monochromator. Useful images are obtained with simple CH-shell targets and without the need for a short-pulse backlighter beam.