Low-Background Method of Isotope Markers for Measuring the Efficiency of Intercalation of Graphite by Potassium Atoms

The result of low-background measurements of the gamma activity of graphite-potassium intercalated sample is presented. A germanium gamma spectrometer, used for measurements, was located in the low-background chamber of Baksan Neutrino Observatory. For 384 hours of exposure, 768 decays of K-40 isotope nuclei were registered. This activity corresponds to 85 μg/cm² potassium atoms embedded in to graphite lattice. A computer simulation of the intercalation process and the gamma-ray spectrum set is also presented. The accuracy of the potassium concentration determination can be brought to 10^–11–10^–12 g/g for mixture enriched with K-40 isotope.