Simulation of radon detection efficiency with small pulse ionization chamber based on Geant4

Radon measurement is crucial in assessing the damage to the human body caused by natural radiation. Pulsed ionization chambers are effective for real-time radon measurement and have widespread applications in other radiation techniques. However, due to practical constraints such as limited space and portability concerns, it becomes imperative to consider not only the detection efficiency but also their ease of transportation. This work utilizes the Geant4 Monte Carlo simulation toolkit to characterize the detection models of small cylindrical and flat plate-type pulsed ionization chambers, and carry out a simulation study to analyze the three crucial factors that influence detection efficiency, including the geometry of the chamber, electrode size, and operating temperature. The results indicate that the cylindrical pulse ionization chamber, with a length of 8 cm and radius of 2 cm, has the best detection efficiency and portability in terms of geometric dimensions, achieving a detection efficiency of (58 ± 4)%. Meanwhile, the flat plate pulse ionization chamber, with dimensions of 7 cm in length and 3 cm in width, achieves the best detection efficiency and portability, with a detection efficiency of (54 ± 3)%. In terms of electrode wire size, the cylindrical ionization chamber electrode wire with a length of 7 cm and a radius of 2.5 mm was optimal with a detection efficiency of (59 ± 4)%. In terms of operating temperature, the detection efficiency of the flat-plate pulsed ionization chamber was the highest at 30 °C, which was (58 ± 4)%, and that of the cylindrical pulsed ionization chamber was the highest at 20 °C, which was (63 ± 4)%. By analyzing the influencing factors of the detection efficiency of the pulsed ionization chamber, it has a certain reference value and guiding significance for the research and design of small pulsed ionization chamber detectors for radon measuring instruments.