An absolutely calibrated spectrograph based on a new single x-ray optical element, namely, an elliptical off-axis reflection zone plate, has been used for brilliance measurements of a laser-produced plasma of solid carbon and boron nitride. The spectral range investigated, λ≈2.1–4.3 nm, covers the emission from excited H- and He-like carbon states to the ground state. The plasma was generated by a subpicosecond high-intensity KrF<sup>*</sup>-laser pulse at an intensity of 2×10<sup>16</sup> W/cm<sup>2</sup>. Under these conditions more than 10<sup>11</sup> photons/sr per pulse were emitted in the strongest lines, demonstrating that this plasma can serve as an intense x-ray source. The measured spectra were in good agreement with a simulation that used the radiation program RATION for an electron density of n<sub>e</sub>=4×10<sup>22</sup> cm<sup>3</sup> and an electron temperature of T<sub>e</sub>=90 eV. Measurements of spectral changes at different angles of incidence of the laser beam confirmed theoretical predictions for line intensities.
© 1998 Optical Society of America
T. Wilhein, D. Altenbernd, U. Teubner, E. Förster, R. Hässner, W. Theobald, and R. Sauerbrey, "X-ray brilliance measurements of a subpicosecond laser plasma using an elliptical off-axis reflection zone plate," J. Opt. Soc. Am. B 15, 1235-1241 (1998)