Effect of Partial Dependence of Photopeak Data on The Calculations of NaI(Tl) Detector Spectrum


Partial dependence of photopeak data of ɣ-ray energies is considering apart of peak channels after subtracting background (including Compton distribution) and obtaining symmetric Gaussian distribution, then considering this part to obtain other total data of peak. This was investigated by using NaI(Tl) detector with Eu-152, Ra-226 and Cs-137 point sources. For the isolated peaks of Eu-152, Gaussian shape is obtained, and the areas between ±σ and ±0.5σ were determined and efficiency is obtained. The calculated transformation to total data of peaks gave excellent agreement with the ordinary case. The overlap between the two peaks at 609.3 (Ra-226) and 661.6 keV (Cs-137) is studied with using σ values from data when sources are separated, and counts in peaks centroids. The data of each peak is "restored" and compared with that when sources are separated and gave a 98% agreement. Also the overlap between the two peaks at 1120 and 1238 keV (Ra-226) is studied with adopting the σ values from the shape calibration curve of Eu-152 and centroid counts in the same way as for the Ra-226 and Cs-137 case. The resultant peaks areas are compared with those obtained from efficiency calibration curve of Eu-152. However results here are of lower agreement