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

WU Xiu-feng;ZHANG Li-feng;MA Jun-ping;LUO Zhi-fu

1. Department of Isotope, China Institute of Atomic Energy, Beijing 102413, China
• Online:2016-11-20 Published:2016-11-21

### 放射性核素电离空气电子离子对产生率计算

1. 中国原子能科学研究院 同位素研究所，北京102413

Abstract:

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.

α衰变核素和β衰变核素发射的射线具有电离空气能力而被广泛应用于工业生产中。为研究α或β衰变核素对空气电离能力的大小，本研究采用蒙特卡洛方法模拟理想放射源发出带电粒子在空气中的能量沉积，并结合空气电离理论，计算放射源表面不同距离处电子离子对产生率。利用此计算方法，研究放射源形状、粒子能量、活度和粒子能量分布对电子离子对产生率的影响。结果表明，放射源表面空气中电子离子对产生率的大小主要受放射源活度的影响，而粒子能量及能谱分布等主要影响电离空气范围及电子离子对产生率衰减速率； 3.7×106 Bq/cm2的α放射源最大电子离子对产生率可达1011~1012 cm-3•s-1量级， 3.7×106 Bq/cm2的β放射源最大电子离子对产生率可达109~1010 cm-3•s-1量级。研究结果可提供数据支持，为新的放射性同位素应用技术开发提供理论指导。