Application of a newly developed CCD for spectral-width measurements of a 53 eV germanium laser

We report the application of a soft X-ray CCD for X-ray laser experiments. A newly developed CCD which has a thinned protection layer (SiO₂) of about 0.2 m was attached to a grazing incidence spectrometer with a resolving power of 16000 in order to measure high-resolution spectra of a germanium soft X-ray laser. Clear spectra have been recorded with a high sensitivity in the energy range between 51 eV (240 Å) and 55 eV (225 Å). In addition to the two strong lasing lines at 236 Å and 232 Å, more than 20 weak spontaneous emission lines have been recorded in this energy range. The spectral width of the 236 Å lasing line is approximately 20.5 mÅ at the full width at half maximum. It is shown that this direct X-ray detection system has a spatial resolution of about 1/10 of the CCD pixel size in this spectral measurement.