An experimental method for the optimization of anti-Compton spectrometer

The reduction of the Compton continuum can be achieved using a Compton suppression shield. For the first time, an experimental method is purposed for estimating the optimum dimensions of such a shield. The method can also provide information on the effect of the air gap, source geometry, gamma-ray energy, etc., on the optimum dimension of the active shield. The method employs the measurements of the Compton suppression efficiency in two dimensions using small size scintillation detectors. Two types of scintillation materials; NaI(Tl) and NE-102A plastic scintillators, were examined. The effect of γ-ray energy and source geometry were also investigated using 137Cs and 60Co sources with three geometries; point, cylindrical, and Marinelli shapes. The results indicate the importance of both NaI(Tl) and NE-102A guard detectors in surrounding the main detector rather than the distance above it. The ratio between the part of the guard detector above the surface of the main detector to that below it should be about 1:3 for NaI and 1:4 for NE-102A. The optimum dimensions for NaI(Tl) detector were found to be 12.5–20 cm for the height and 15–20 cm for the thickness. The corresponding values for NE-102A are 17.5–25 cm for the height and 25–30 cm for the thickness.