Abstract
The sensitivities of two types of β-ray ionization chambers to measure the dose-equivalent were evaluated by a tissue equivalent extrapolation ionization chamber. Seven kinds of β-ray sources; 90Sr-90Y, 210Pb-210Bi, 204Tl, 137Cs, 60Co, 147Pm, and 14C with intensities of several MBq were utilized for the evaluation. The measured values were corrected to maximum dose-equivalents at the position of the extrapolation chamber by the multiplying correction factors of the spatial dose distribution to remove the characteristics of the extrapolation ionization chamber.
The variation of the sensitivities of one type ionization chamber at the distance between 50 mm and 200 mm from the β source was within ±50% for seven kinds of sources and that of another type ionization chamber was within ±50% for six sources except 14C. The variation was also compared with the inverse square characteristic of the absorption dose.
