Deconvolution Based Measurement Of Gammaray Attenuation Coefficients With Validation Using Standard Absorbers

During the measurement of attenuation parameters, the recorded gamma ray spectra are often significantly influenced by multiple factors, including the presence of multi-gamma emitting radio-nuclides, broadening of photo-peaks due to poor detector resolution and additional contributions from Compton scattered photons originating from the collimator walls. To overcome these limitations, the present work employs the Maximum Likelihood Expectation Maximization (MLEM) deconvolution technique to unfold experimentally measured NaI (Tl) gamma ray spectra in the energy range of 123–1330 keV. The detector response is modelled under the assumption that the scintillator and photomultiplier coupling controls the Gaussian broadening of the photopeak. Response-based deconvolution is used to retrieve the genuine photo-peak counts from Monte Carlo-generated spectra, which by their very nature have poor resolution. By comparing the experimentally determined mass attenuation coefficients (µ/ρ) for aluminium absorbers with the conventional theoretical values given by Hubbell and Seltzer1 over the energy range of 123–1330 keV, the efficacy of this method is confirmed, showing good agreement.