Effect of the Dosimeter Size on the Absorbed Dose to Al_2O_3 Dosimeter in ~(60)Coγ Beams

The effect of the dosimeter size on the absorbed dose to the Al2O3 dosimeter in a water phantom irradiated by 60Co γ beams was simulated using EGSnrc /DOSRZnrc code.Simulation results reveal that the effect of the dosimeter size on the absorbed dose ratio factor is obvious.The absorbed ratio factor can be different with different radius or thickness of the dosimeter,and the maximum difference can be up to 6%.But for dosimeter with a certain size,all the absorbed ratio factors are nearly a constant at various depths of 0.5~8.0 cm in the water phantom,and the maximum discrepancy of those the absorbed ratio factors to the average value is not more than 1%.