Rn-220及其子体是人类所受天然辐射不可忽视的来源，为准确测量与评价其辐射剂量，需建立调控能力强的钍射气室用于测量仪器的刻度或校准。由于Rn-220与其子体在半衰期、物态等方面差异较大，使得钍射气室Rn-220与其子体的调控性能难以兼顾，特别是存在钍射气室流场模式下Rn-220与其子体不能同时调控的难题。本项目拟基于Rn-220子体补充技术，采用理论分析与建模的方法开展钍射气室流场模式下Rn-220及其子体同时调控方案和理论模型的研究，建立循环流场下Rn-220子体循环损失率测量方法，着重分析循环风速与子体损失率和子体均匀性的关系，最后通过实验和数值模拟对调控方法进行优化，对调控范围、稳定性、均匀性、调控时间等性能进行测试与验证。本项目将解决钍射气室流场模式下Rn-220及其子体不能同时调控的难题，对进一步提高钍射气室调控水平和提升我国Rn-220及其子体计量水平，具有重要意义。

Thoron and its progeny are non-negligible sources of natural radiation for human. In order to ensure the quality of measurement and assessment, the standard thoron chamber which has good control ability should be established for calibration of the instruments. It is hard to concurrently achieve good control performance for thoron and its progeny in thoron chamber, particularly it is a problem to control.thoron and its progeny simultaneously, because there are large differences of half-life and state of matter between thoron and its progeny. This project propose to study plans and theory models of controlling thoron and its progeny simultaneously in air flow field of thoron chamber which are based on the thoron progeny complementary technology by using theoretical analysis and modeling method, establish a method for measuring loss rate of thoron progeny when thoron progeny go around in a cyclic flow field, emphatically analyze relationships between wind speed and the loss rate of thoron progeny and uniformity of progeny, optimize the new control method and test performances such as scope of control, stability, uniformity and response time, and contrastively verify through experiment and numerical simulation. In this project it will be truth to control thoron and its progeny simultaneously in air flow field of thoron chamber. The research will be great significance to improve the control of thoron chamber and enhance the metrology of thoron and its progeny in China.