Low-level radiation measuring system using magnetically levitated electrode ionization chamber

An automatic measuring system using an ionization chamber having a magnetic levitation electrode has been developed. To check the system performance, environmental radiations and natural ⁴⁰K γ-rays have been measured. Results of measurements of environmental radiations confirm the system sensitivity to be high and stable, and those of ⁴⁰K γ-rays show possibility of measurement of ultra-low level radiation even with an ionization chamber. Minimum detectable ionization current is 2.3 × 10^-17 A. It corresponds to 2.4n Gy/h and 0.0024 μ Sv/h, respectively in the absorbed dose and the dose equivalent rates. The developed system is useful for the monitor to measure the environmental dose rate.