Vertical variant of a double channel-cut crystal spectrometer for investigation of laser-generated plasmas

The theoretical design of multicrystal instruments which define a new class of spectrometers based on the vertical dispersion principle is reported together with experimental confirmation of design. Previous designs in the vertical-variant scheme—which have been fielded successfully in laser-produced plasma experiments—have operated with one or two crystal surfaces in a configuration that deflects the diffracted radiation back in the general direction of the source. The additional reflecting surfaces described here direct the radiation along a radial vector from the source to the detector, independent of the Bragg angle. Thus, the experimental setup is more flexible and greatly facilitates the coupling of the spectrometer to a charge-coupled device or streak camera. One of these instruments, a double channel-cut crystal spectrometer working in the vertical dispersion mode (DCCV), employs a total of four diffracting crystal surfaces. A compact design of the DCCV prototype is compatible with small bore reentrant diagnostic access tubes (e.g., the 6 in. manipulator) employed at several large-scale laser facilities. This high-dispersion spectrometer combines a high spectral resolution [R=13 500 with Si(111) crystals] with a one-dimensional spatial resolution of the order of 20 μm.