Studies On Absolute Measurement Of ²²²Rn Using Defined Solid Angle Counting Method

Radon gas,especially the ²²²Rn,exists widely in human society for a long time and has a great harm to human beings,which lead the radon activity measurement a inevitable problem in many situation.However,the radon activity measurement in China has a much lower level than that of international,the main reason is that the domestic radon activity measurements are based on relative measurement methods,which has a natural disadvantage compared to various absolute measurement methods of international.In this research thinking,based on the similar device in the world,the device for absolute measurement of ²²²Rn,which uses defined solid angle counting method,has been primarily established.The device can be used not only to build a radon standard source with high-precision,but also to provides the basis for the establishment of radon primary standard.Besides,the successful establishment of the device filled the blank of the field of domestic high-precision absolute measurement of ²²²Rn,this is a big step of domestic radon activity measurement,which has extremely important significance and prospect.This paper mainly completed the following work:?1?The device for absolute measurement of ²²²Rn activity,which uses defined solid angle counting method,has been primarily established,and the experiment results show that the device has good performance to provide the vacuum and cryogenic environment that required for radon activity measurement,and the environment that the device provided is considered to be stable in a acceptable range for a long time.?2?An electronic system for the measurement of radon activity was established,the alpha energy spectrum with high energy resolution was successfully collected.Based on the theory of radioactive equilibrium,the algorithm of ²²²Rn activity in the solid angle under different energy spectrum characteristics is established.?3?According to the algorithm established,analysis and calculation haveadoptedtothe?spectrumthatacquiredfrom long-time-measurement?>5h?,the result shows that:in the beginning,the resolution of spectrum is good,²²²Rn activity in the solid angle can be directly obtained by choosing some suitable channels.With the time of the measurement goes by,foreign gases introduced and make the energy of?particle lose or condensate on the cold point to hinder the emission of?particle,these all make the resolution of spectrum worse,and the way choosing some suitable channels to obtained ²²²Rn activity in the solid angle directly doesn't work anymore.In this situation ²²²Rn activity in the solid angle can be calculated by the algorithm established before,by comparing the decay curve of the theoretical value and the calculated value,the result is the they are virtually identical.?4?The repeatability of the experiment was investigated,the result shows the repeatability of the experiment is less than 0.45%,it is considered as a good value.?5?In this paper,the parameters of the solid angle which limited by the condensing chamber are measured accurately.According to the calculation formula of the solid angle,the solid angle of the device can be calculated,the result is?=0.01583sr.In summary,the absolute measurement of ²²²Rn activity,which uses defined solid angle counting method,has been primarily realized,the realization has important significance in the domestic radon activity measurement and in transfer of the value of radon activity.