A slit grating spectrograph for quantitative soft x-ray spectroscopy

In this article we describe a new slit grating spectrograph which is based on an e-beam written 10 000 linepairs/mm freestanding transmission diffraction grating. In combination with a thinned, back-illuminated charge coupled device (CCD), the spectrograph allows for real-time spectroscopy of laser-produced plasma x-ray sources within the wavelength region lambda = 1-20 nm. Calibration of grating and CCD allow for the possibility to measure absolute photon fluxes, currently within the wavelength region lambda = 1-6 nm. The compact spectrograph is easy to align and flexible in its use. Absolutely calibrated spectra were obtained from a liquid-jet laser- plasma source in the water window, with a spectral resolution lambda/Delta lambda greater than or equal to 330 at lambda = 3.37 nm. A simple change in experimental geometry allowed single-shot spectra to be recorded with lambda/Delta lambda greater than or equal to 60 at the same wavelength. In addition, spectra from this laser- plasma source were measured within the range lambda = 9-20 nm. (C) 1999 American Institute of Physics. [S0034-6748(99)02203-0].