2-D X-RAY LASER-PLASMA IMAGING USING BRAGG-FRESNEL MULTILAYER ZONE PLATES

Two types of Bragg Fresnel multilayer zone plates operating in the keV range have been investigated for X-ray laser-plasma imaging. Elliptic al on-axis and off-axis Bragg Fresnel multilayer zone plates were char acterised. With the on-axis zone plate all the reflection orders are s uperposed in the same plane. The image contrast is then degraded as th e zone plate focus distance is not the same for all orders. The proble m is avoided with an off-axis zone plate with which the different orde rs in the image plane are spatially separated. The Al Pie, strong emis sion line (7.757 Angstrom) of a laser produced aluminium plasma has be en selected for the imaging tests. The first order reflected intensity has been optimized by varying the Bragg and azimuthal angles. As a re sult, an X-ray image of a fine gold grid backlighted by the aluminium plasma emission has been obtained with a spatial resolution very close to the theoretical limit of the imaging mounting. (C) 1998 Elsevier S cience B.V. All rights reserved.