Band reject filtration of the excitation spectrum at energy dispersive X-ray spectroscopy of weak signals

The possibility of the efficient band reject filtration of the continuous X-ray excitation spectrum in the energy range $E\geqslant8$ keV is demonstrated. This makes it possible to strongly increase the sensitivity of energy dispersive X-ray spectroscopy at detecting of weak fluorescence lines. Spectral rejection is implemented by transmitting a primary beam through highly oriented pyrolytic graphite with given structural parameters. Diffraction extinction in pyrolytic graphite ensures the possibility of reducing the intensity by more than $20$ dB and rejecting the spectral band with a width of $\sim1$ keV. The reduction of statistical fluctuations of the background of elastically scattered radiation is achieved when the bottom of the formed spectral valley is adjusted to the analyzed fluorescence line. The proposed scheme of band reject filtration also allows the suppression of intense characteristic lines in the primary and scattered radiation spectra.