In this research, Geiger-Muller counter tube detector (Type ABG, hi-energy), have been used together with cobalt-60 radioactive gamma source to calculate buildup factor using lead and aluminum materials. Effect of material atomic number and thickness of the shield material on buildup factor value of gamma rays has been studied.
Five types of shields were studied as follow:
· Two single-layer shields of both lead and aluminum.
· Two dual-layers shields composed of (Pb-Al) and (Al-Pb) · Multi-layers shield (Pb-Al) have been used which composed of successive layers of lead and aluminum, respectively, with thickness of (0.5cm) for each layer.
The study showed that the buildup factor value increases with decreasing the atomic number of the shield material. While buildup factor values of the dual-layers shields ((Pb-Al) & (Al-Pb)) and multi-layers shield (Pb-Al) are found to be smaller than the buildup factor values of lead shield. Also it is found that the dual[1]layers shield (Al-Pb) give the best results in this work where it gives smaller and acceptable buildup factor.
