Research On Two-probe ? Cascaded Conformal Measurement Method

In recent years,with the sustained and rapid development of the national economy,people's demands for physical and mental safety and property safety have become higher.Radon in water can cause lung cancer and stomach cancer,which will have a tremendous impact on the body and mind.At the same time,Radon in water can be applied to the prediction of earthquakes.Accurate and timely measurement of radon concentrations in water may ensure people's physical and mental safety and property safety.At present,the measurement method of radon concentration in water has failed to meet the new requirements of real-time and accuracy.Therefore,the dual probe?-ray coincidence method is of great significance as a new method for measuring radon concentration in water.In this study,the dual probe?-ray coincidence measurement method was determined based on the theoretical knowledge of radioactive decay of ²²²Rn and its daughters.Then a measurement system was built in the laboratory and a NaI?Tl?detector was chosen as the experimental?probe.The parameters of the linear amplifier and the single-channel pulse amplitude analyzer in the measurement system were set and optimized.Calibration of the coincidence with the measurement system's optimal pulse width that is resolving time of coincidences,through experiments to prove that different measurement systems must be carried on the best pulse width before measurement,the calibration method are obtained by calculation in the radiation source activity A?5×106Bq is feasible.Investigate the accuracy of the ⁶⁰Co source measured by the measurement system to achieve the purpose of performance test.Before using the dual probe?-ray coincidence method to measure the concentration of radon in water,a NaI?Tl?energy spectrometer was constructed.The spectrometer was calibrated with energy scale,and the left and right boundaries of the?-ray all-energy peak with an energy of609.32 keV were marked.The No.1 standard liquid source radium scale coincidence measurement system conforms to the track detection efficiency,and was verified with No.2 standard liquid radium source,and measured with the No.3 unknown liquid radium source.The experiments show that the dual probe?-ray coincidence method can measure the concentration of ²²²Rn in water,and the measurement accuracy is high.Compared with the traditional relative measurement method,the coincidence method can improve the signal-to-noise ratio of measurement.The lower limit of detection of radon concentration in water by the dual probe?-ray coincidence method was calculated,Which can achieve the purpose of rapid measurement of radon concentration in water.Finally,the concentration of ²²²Rn in the No.3 liquid radium source was measured with a RAD7,and the comparison with the dual probe?-ray coincidence method was consistent within the error range.