Patent ID: 7279676
Filing Date: 2007-10-09
Classification: G01T,G01V

Abstract:
1. A method for identifying, quantifying, and locating an unknown source of gamma-ray emissions with little loss of detector efficiency, said method comprising the steps of: (a) recording a first calibration spectrum using a first detector with a calibration source located at a first source position, said calibration source having a known set of characteristic energies; (b) recording a second calibration spectrum using a second detector with the calibration source located at the first source position; (c) recording a third calibration spectrum using said first detector with the calibration source located at a second source position; (d) recording a fourth calibration spectrum using said second detector with the calibration source located at the second source position; (e) calculating a first set of detector efficiency values, said first set of detector efficiency values comprising an efficiency value at a selected energy for said first detector from each of said first calibration spectrum and said third calibration spectrum; (f) calculating a second set of detector efficiency values, said second set of detector efficiency values comprising an efficiency value at said selected energy for said second detector from each of said second calibration spectrum and said fourth calibration spectrum; (g) recording a first assay spectrum using said first detector to measure an unknown source; (h) recording a second assay spectrum using said second detector to measure the unknown source; (i) determining a first count total at said selected energy from said first assay spectrum; (j) determining a second count total at said selected energy from said second assay spectrum; (k) calculating a first activity value and a second activity value using said first set of detector efficiency values, said second set of detector efficiency values, said first count total, and said second count total; (l) identifying an isotope in said unknown source based upon said first assay spectrum and said second assay spectrum, the isotope having a characteristic energy equal to said selected energy; (m) quantifying an isotope in said unknown source based upon said first activity value and said second activity value; and (n) estimating a position of an isotope in said unknown source based upon a ratio of said first activity value and said second activity value.