Development of a Wide Band and Compact X-Ray Crystal Spectrometer for Iron Charge State Distribution Measurement on LHD

A wide band and compact X-ray spectrometer has been developed using a Johan-type crystal and a back-illuminated CCD detector for charge state distribution measurement of highly ionized iron in LHD. In order to observe all charge states of iron ions a curved crystal of LiF(220) with a curvature of 430 mm was selected for the spectrometer. A wide energy range of 6.4-7.0 keV could be observed with use of CCD detector in a size of 26.6 × 6.7 mm2 . An energy resolution of the spectrometer was 10 eV at full width at half maximum (FWHM). Time-developed Fe Kα spectra were thus measured with a time interval of 10 ms in the full binning mode of the CCD. The charge states from Fe ions of FeXXI to FeXXV were clearly observed, but FeXXVI has not been observed. In the next step, then, the charge state distribution measurement is focused on the measurement of FeXXI-XXV and a quartz(2023) curved crystal is selected to measure the energy range of 6.40-6.75 keV. The expected energy resolution is 4 eV at 6.7 keV for the quartz crystal, which is enough for further analysis of the iron charge state distribution.