Experimental verification of gamma-efficiency calculations for scintillation detectors in ANGLE 4 software

ANGLE software for semiconductor detector efficiency calculations - long existing and widely accepted tool in quantitative gamma spectrometry - has been recently extended to scintillation NaI detectors. The extension features in the latest edition (ANGLE 4) and it is briefly outlined. Discretization of reference efficiency curve, meaning possibility of using ANGLE 4 for particular gamma energies without constructing the complete reference efficiency curve, is particularly emphasized. This yields both in enhanced practicality and higher accuracy, while reducing the potential for systematic errors. The present work is primarily focussed on experimental verification of ANGLE 4 for NaI detectors. Two detectors (2 ´ 2 and 3 x 3 inches) were employed in the experiment. Commercially calibrated gamma sources (in the forms of quasi point and cylinder) and homemade solutions (diluted from calibrated ones) were measured at various distances from the detector(s), ranging 0 cm to 50 cm. Energy range observed was 59 keV to 1408 keV. Versatility of counting conditions, in terms of detectors and sources used, gamma energies observed, source detector separations, etc., was aimed at creating as large experimental evidence as possible for verification purposes. Experimentally obtained efficiencies are compared with those calculated by ANGLE 4. Very good agreement is obtained - well within the experimental uncertainties - thus proving the reliability of the software

Calibration of 4π NaI(Tl) detectors with coincidence summing correction using new numerical procedure and ANGLE4 software

The 4π NaI(Tl) γ-ray detectors are consisted of the well cavity with cylindrical cross section, and the enclosing geometry of measurements with large detection angle. This leads to exceptionally high efficiency level and a significant coincidence summing effect, much more than a single cylindrical or coaxial detector especially in very low activity measurements. In the present work, the detection effective solid angle in addition to both full-energy peak and total efficiencies of well-type detectors, were mainly calculated by the new numerical simulation method (NSM) and ANGLE4 software. To obtain the coincidence summing correction factors through the previously mentioned methods, the simulation of the coincident emission of photons was modeled mathematically, based on the analytical equations and complex integrations over the radioactive volumetric sources including the self-attenuation factor. The measured full-energy peak efficiencies and correction factors were done by using 152Eu, where an exact adjustment is required for the detector efficiency curve, because neglecting the coincidence summing effect can make the results inconsistent with the whole. These phenomena, in general due to the efficiency calibration process and the coincidence summing corrections, appear jointly. The full-energy peak and the total efficiencies from the two methods typically agree with discrepancy 10%. The discrepancy between the simulation, ANGLE4 and measured full-energy peak after corrections for the coincidence summing effect was on the average, while not exceeding 14%. Therefore, this technique can be easily applied in establishing the efficiency calibration curves of well-type detectors