X-ray crystal devices for measuring compression and stability of laser fusion targets. Final report.

摘要

The major goals of this investigation were: (a) the development of a method for two-dimensional imaging of x-rays using simultaneous n-beam diffraction within crystals, and (b) the application of the above to the study of the stability of laser irradiated spherical targets by imaging x-ray line emission from thin metallic layers imbedded within plastic shell targets. To date, we have completed part (a) by identifying and characterizing n-beam maxima diffracted by a perfect Germanium crystal. We have used such diffraction to image test objects and to demonstrate the possibility of achieving satisfactory spatial resolution; these techniques will be used to image target emission. Part (b) will be completed in the near future. An x-ray camera which utilizes a Germanium crystal for monochromatic imaging is being fabricated. The camera is small (largest dimension approximately 7 cm) to enable us to position it approximately 5 cm from the target. As explained below, the finite spectral bandwidth of the crystal, and increasing the distance from the target, both lead to degradation of spatial resolution. Results of those studies are summarized. In addition to imaging, simultaneous diffraction of x-rays within crystals makes possible other applications, some of which are described below. One involves the substantial reduction of absorption of x-rays along directions which satisfy diffraction conditions with respect to several sets of crystal planes. We have demonstrated such reduction in absorption for various cases of simultaneous diffraction in Germanium. These are summarized.