BROAD-BAND STIGMATIC SPECTROGRAPH FOR THE SOFT-X-RAY RANGE

We describe a panoramic stigmatic spectrograph comprising a grazing-in cidence toroidal mirror and a large-aperture free-standing transmissio n diffraction grating (5000 lines mm(-1)). Two spectrograph versions w ere constructed, with grazing angles of 7.6 and 4 degrees and the shor t-wavelength spectral limits near 4 and 1.5 nm. The spectrograph aberr ations were studied by numerical ray tracing. The spectrograph was use d to record line and quasi-continuous spectra (1.5-30 nm) of multiply charged ions in a plasma generated by the second-harmonic pulses of an yttrium aluminate laser (Q = 0.15 J, tau = 5 ns, lambda = 0.54 mu m, repetition rate = 0.5 Hz). In combination with a laser-produced plasma radiation source, the arrangement was used to characterise soft x-ray optical components and to generate collimated beams of polarised radi ation in the 14-20 nm range.