High-Resolution Transmission Gratings For Use In The Spectroscopy Of Laser-Produced Plasmas

Carbon transmission gratings with line densities in the range 7000-17500 lines/mm have been made, by contamina-tion lithography, on thin boron nitride (80 nm) or carbon (25-35 nm) substrates. The efficiencies of these gratings in the water-window wavelength range can be enhanced by coating with metal (preferably nickel, chromium or copper) at an angle; a model used to calculate the optimum coating angles and thicknesses is presented. Calculated optimum efficiencies (including phase effects) vary considerably over the spectral range investigated but can approach 20% in the first order. A preliminary characterisation of the gratings has been carried out in the radiometric laboratory of the PTB at BESSY, Berlin. It is intended to use the gratings in the study of laser-produced plasmas.