The Experimental Study On Measurement Of Radon Isotopes²²⁰Rn By Time Interval Analysis Method

Radon and its daughters are one of the main materials to cause cancer,The inhalantradiation dose of the population mainly comes from the short life decay products ofradon indoor and outdoor. Although222Rn decay products are the main source, thedose caused by220Rn decay products also cannot be ignored.Meanwhile,Inoceanography research,222Rn,220Rn,219Rn are the commonly used tracer nucildes toindirectly measure the concentration of radium isotope226Ra,224Ra,223Ra, and themeasurement of radium isotopes (226Ra/224Ra/223Ra) is an important method and keytechnology in the isotope oceanographic research. It is a hot spot at present.This paper introduces a measurement method of low concentration220Rn---Timeinterval analysis method(TIA). After the alpha particle emitted at the decay of a220Rnatom will, in a short time(0.145s), be followed by an alpha particle from the decay of216Po. The multiple time analysis method is based on the analysis of the emitting timeinterval between two successive alpha particle, which can discriminate the220Rn from222Rn. This experiment used a Lucas cell(FD-125) to flow-through measure10Bqstandard220Rn source. Through ARM-860experiment case records of alpha particlesarriving time, form a time data sequence, and then use multi-time interval analysismethod to get a distribution curve and exponential part representative radioactivenuclide, constant part representative the background or random events.When the220Rnconcentration is equal to or less than222Rn,or around220Rn concentration is more than10times the220Rn concentration, count rate control within60cpm, the time resolutionis set to1ms, and the measuring time is10h, the relative error of the results is within9%.This paper describes how to design the multi-time interval measurement softwarebased on uC/OS-II operating system, Current sensitive preamplifier, Power supply module and amplifying waveshaping circuit，and how to establish the relevant multitime interval distinguish measuring low concentration220Rn experiment system. Thesystem adopts the EL-ARM-860-S3C2410core board made by Da Sheng corporationas control core. In the first,The detector output signal is amplificatted by preamplifieramplification, then shaped to rectangular pulse sequence through amplifier shapingcircuit, afterwards sent to EL-ARM-860-S3C2410external interrupt pin, and the timeinformation of pulse rising edge are stored by the core board timer, and sent to the PCthrough a serial port. These information are been processed using matlab, then call theCftool function to calculate the theoretical value of220Rn decay in Scintillationchamber. This study reached the purpose to measure low concentration220Rn in mixedfield, and move forward a single step to improve the radon isotope measurementmethod. At the same time, it is of great significance to the following research tomeasure radon isotope by Time Interval Analysis Method.