Calculation on the Electron Ion Pair Production Rate of the Radioisotope Ionizing Air

The emission of alpha decay and beta decay are widely used in industrial production for its ability of ionizing air. To evaluate the ability of radioisotope ionizing air, a method to calculate the electron ion pair production rate was established. Energy deposition of the ideal radiation source in the air could be obtained through simulating with Monte Carlo method, and then electron ion pair production rate could be calculated. The effect on ionizing air of radiation source shape, energy, activity and particle energy distribution were studied. We found that the electron ion pair production rate was mainly affected by the activity of radioactive source. However, the particle energy and energy spectrum distribution mainly affect the ionization range and the decay rate of the electron ion pair production rate. Computations for a flat surface coated with 3.7×10⁶ becquerel alpha radioisotope per square centimeter showed that the largest electron ion pair production rate could be 10¹¹ cm^-3•s^-1 to 10¹² cm^-3•s^-1, and 10⁹ cm^-3•s^-1 to 10¹⁰ cm^-3•s^-1 for beta radioisotope with the same activity. This conclusion can provide theoretical guidance for existing related application and developing new application of radioactive source.