GEANT4 calibration of gamma spectrometry efficiency for measurements of airborne radioactivity on filter paper.A simple method of efficiency calibration for gamma spectrometry was performed.  This method, which focused on measuring airborne radioactivity collected on filter paper, was based on Monte Carlo simulations using the toolkit GEANT4. 
GEANT4
Experimentally, the efficiency values of an HPGe detector were calculated for a multi-gamma disk source. 
HPGe