GAMMA RAY DETECTOR CALIBRATION TO MEASURE LOCAL ENVIRONMENT RADIATION

In a recent article the authors describe the origin of gamma radiation or low energy gamma rays up to 10 MeV (Millions of electron Volt). A type of high frequency electromagnetic radiation usually produced by radioactive elements and electrical discharges present in the environment where we live. The intensity of this radiation may vary with each location on the planet. Measurements of gamma radiation from 200 keV to 10.0 MeV were taken at the campus of the Technological Institute of Aeronautics - ITA - in São José dos Campos, SP, Brazil. The detector set plus the associated electronics was previously calibrated in the laboratory using the radioactive sources of Cesium - (Cs-137), Polonium- (Po-210) and Strontium- (Sr-90). These sources provide gamma ray energies at (0.662 keV, 1.17 MeV), alpha particles at 5.4 MeV and electrons at 0.90 keV, respectively. The detector consists of a height-by-diameter (3x 3) inches, Thallium Activated Sodium Iodide [NaI (Tl)] scintillator, associated with a photomultiplier (PM) and associated electronics and data acquisition. Measurements were taken within 10 minutes, in the environment, with each radioactive source and with all radioactive sources placed on the scintillator. The generation of the spectra as a function of energy is always studied at the same time interval. It was thus possible to determine for this location the presence of natural gamma radiation present at the ground-air interface for this energy range using a minimum measurement time interval of 10 minutes