Research Of Related Problems In²²²Rn/²²⁰Rn Absolute Measurement Using Small Scintillation Cells

In order to implement²²²Rn/²²⁰RnRnabsolute measurement with small scintillationchamber delay method, the ZnS （Ag） coating thickness on the inner wall of the smallscintillation cell influence was studied and the thickness parameter of making the ZnS（Ag） coating was optimized in order to ensure the²²²Rn/²²⁰RnRndetection efficiencyof the small scintillation chamber is100%. The α intrinsic detection efficiencies ofdifferent ZnS （Ag） coating thickness were measured using241Am, an α referencesource used to simulate the radon radioactive particles. The results indicate the αintrinsic detection efficiency of10mg/cm2thickness ZnS （Ag） coating layer can beclose to100%. The small scintillation chambers were made using10mg/cm2thicknessZnS （Ag） coating layer and their²²²Rn/²²⁰RnRndetection efficiency experiment wasrepeated to verify the above result.The response factors between²²²Rn and²²⁰Rn concentration and its count value atcurrent state and static state were deduced. And the condition that during the currentprocess the count rate increased with time due to the wall effect of²²²Rn’s daughterswas considered and correction method was put forward as well. In the Radonlaboratory of University of South China, the response factors between²²²Rn and²²⁰Rnconcentration and its count rate at current state and the correction method toward thewall effect of²²²Rn’s daughters was verified by experiment in the²²⁰Rn room. Smallscintillation chamber delay method and current static method to implement²²²Rn/²²⁰RnRnabsolute measurement in mixted field were tested and verified as well. Inthe current static method of²²²Rn/²²⁰RnRnabsolute measurement, the static backgroundcounts introduced by the wall effect of²²²Rn ’s daughters at current state wereconsiderd, and the static waiting time was optimized as well. Test results show thatthe response factors deduced from this work is reliable, and this kind of responsefactors derivation method considering with the wall effect of²²²Rn’s daughters and static place time optimization were used to small scintillation chamber current delaymethod and the current static method to implement²²²Rn/²²⁰Rnabsolute measurementare feasible as well when the²²²Rn/²²⁰Rn concentrations are high.Thus, a²²²Rn/²²⁰Rnabsolute measurement method based on current delay of doublegas roads and double small scintillation chambers was put forward. Compared withcurrent delay method,the method based on current delay of double gas roads anddouble small scintillation chambers has a smaller delay device, and the measure timeis shortened. It needs no static waiting time, its measure time is more shorter and thebackground of the small scintillation chamber using next time is also reduced whencompared with the current static method, making it more convenient for reuse in ashort time. This method is a new method, can facilitate to the realization of theportable²²²Rn/²²⁰Rnabsolute measurement instrument.In the Radon laboratory of University of South China, the²²²Rn/²²⁰Rnabsolutemeasurement method based on current delay of double gas roads and double smallscintillation chambers was tested in the²²²Rn room. The test results show that thismethod basically shares the same result as current delay method has.