Method for measuring counting rates or measured variables dependent on the counting rates and apparatus for measuring counting rates or measured variables dependent on the counting rates

An apparatus for measuring counting rates or measured variables dependent on the counting rates for determining a density profile of at least two substances with different densities arranged within a container, the apparatus comprising:

• a plurality of radiation sources, wherein each of the plurality of radiation sources is configured to emit respective gamma rays with a discrete isotope gamma energy into at least one of the substances, a Compton energy value being less than the isotope gamma energy;
• a plurality of detectors, wherein each of the plurality of detectors is configured to record the respective gamma rays which have penetrated at least partially through at least one of the substances, and
• a plurality of generating devices, wherein each of the plurality of generating devices is configured to generate a respective counting rate or a respective measured variable dependent on the counting rate only on the basis of respectively recorded gamma rays of which the respective gamma energy is greater than or equal to an energy threshold value, the energy threshold value being a minimum of 0.5 times the Compton energy value of a Compton gap of the gamma rays.