Transportable soft X-ray flat-field spectrograph

We report fabrication and testing of a transportable version of a high-resolution flat-field spectrograph. The device uses two replaceable grazing-incidence VLS gratings with central densities of 1200 and 2400 lines mm⁻¹, producing a flat field in the wavelength ranges of 5–28 nm and 2.5–14 nm, respectively. The plate scale is about 0.56 and 0.28 nm/mm at a wavelength of 12 and 6 nm for the first and second gratings, respectively. The VLS gratings are fabricated by interference lithography. The grating efficiency at a wavelength of 12.5 nm is measured by a reflectometer with a laser-plasma source of soft X-ray radiation. During the tests of the spectrograph, line spectra of multiply charged ions in a plasma excited by nanosecond laser radiation are obtained. The spectrograph is designed to record soft X-ray radiation excited by a multiterawatt femtosecond laser in various targets.