Johann crystal diffraction spectrometer for measuring small chemical shifts of soft X-ray lines

A new crystal diffraction spectrometer constructed at the St. Petersburg Nuclear Physics Institute (NPI) according to the Johann scheme is described. The instrument is intended for studying the electron structure of light elements, in particular, 3$d$ metals (beginning with scandium) in their compounds. The working energy range is 4–15 keV. A specific feature of this Johann spectrometer is that this instrument (like the Cauchois spectrometers also available at the PNPI) is capable of simultaneously measuring chemical shifts and the other parameters of X-ray lines of the same element in two compounds possessing specific physical properties (valence, magnetoresistance, etc.). With the proposed spectrometer, it is possible to study the electron structure of elements from Sc to Br using lines of the K series and from Ba to Pb using lines of the L series. Extensive investigations in this field of solid-state physics are important in both experimental and theoretical aspects.