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The China Atomic Energy Research Institute (CIAE) has designed a fully automated extrapolation ionization chamber with variable collection area. Compared with the traditional type of extrapolation ionization chamber, it has the advantages of variable collection area, and the adjustment of the depth of the ionization chamber can be accomplished through the control system, and it can cope with the measurement requirements of different sizes of radioactive sources by providing an adjustable and selectable mode of four sizes of collection electrodes, and the fully automated measurement system is beneficial to reduce the measurement error of reference absorbed dose and improve the efficiency and accuracy of measurement results. The fully automated measurement system helps to minimize the measurement error of the reference absorbed dose and improve the efficiency and accuracy of the measurement results. In this paper, the performance parameters such as leakage current, saturation curve, ion collection efficiency, extrapolation curve, and effective collection area of this extrapolation chamber are investigated to evaluate its feasibility in β-ray dosimetry. Through experimental measurements, the leakage current of the ionization chamber is in the range of 4.2 fA~7.7 fA, which is smaller than the specified 12 fA, the ion collection efficiency is greater than 0.9999, the slopes of the extrapolation curves are 0.6417 and 1.3167 for the irradiation of the two radioactive sources, 90Sr/90Y and 85Kr, which are additionally with beam flattening filters 10 cm from the source, respectively, and the effective collection areas of the four collection poles are 28.35132 cm2 , respectively. The experiments show that the performance of this new type of extrapolation ionization chamber is qualified, and its feasibility in β-ray dosimetry is verified.
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