Formation of spectral valleys in the hard X-ray spectrum by diffraction band reject filtering

The possibility of forming deep spectral valleys in the polychromatic spectrum of X rays with an energy of $E\geqslant15$ keV using diffraction band rejection is demonstrated. The rejection has been carried out by passing the radiation beam through plates of highly oriented pyrolytic graphite (HOPG) with a thickness of $0.73$ and $0.58$ mm at the diffraction angle $\theta$ in the interval of $3.26^\circ$–$6.98^\circ$. The average values of the mosaic spread angles $\Delta\omega$ of HOPG samples are equal to $0.72^\circ$ and $0.3^\circ$. For HOPG with $\Delta\omega= 0.72^\circ$, a five- and threefold attenuation of the radiation intensity due to diffraction extinction has been obtained upon the rejection of the spectral band with minima near $15.2$ and $22.5$ keV, respectively, and the full width at half depth of the valley is $1.4$ and $3.1$ keV. The proposed diffraction filtration scheme can be used in X-ray spectrometry and in medical diagnostics to reduce radiation loads.