This Invention describes two optical schemes, which have immediate applications to the x-ray spectroscopy and diagnosis of high-density, laser-produced plasmas. The underlying concepts are, however, applicable to a broad spectrum of the electromagnetic radiation, so that the two schemes may have additional applications in EUV lithography, medicine, industrial manufacturing and biological, chemical, and pharmaceutical research. The first scheme makes use of a convex spherically bent crystal to image the radiation of different wavelengths from a laser-produced plasma of small dimensions (point source), as physical lines across the strips of a gated multichannel strip detector. Here, the strips of the detector are activated sequentially of obtain fast (sub-ns) time resolution. The second scheme consists of a combination of one convex and one concave spherically bent crystal, where the 2d-spacings and radii of curvature of the two crystals are properly matched to eliminate the astigmatism for one particular wavelength.