The Development Of Multi-channel Gamma-ray Spectrometer Of Radioactive Surveying Station

As the shortage of energy is serious,the effort of mining uranium ore is intensified in our country. The original instruments measuring the content of uranium ore are unsatisfactory. The technical specification and performance can't meet the requirement of measuring, which restricts the mining efficiency. According to the request of uranium mine, multi-channel gamma-ray spectrometer of radioactive surveying station is developed. It is composed by the following:(1) NaI(Tl) scintillation crystal gamma-ray detector is composed by NaI(Tl) crystal, photomultiplier tube, preamplifier. It convert gamma-ray to pulse signal.(2) Linear pluse amplifer: amplifying and formating pluse signal from NaI detector in order to get proper signal, including polar-zero cancellation circuit, adjustable operational amplifier, integrating circuit, baseline recovery circuit.(3) Multi-channel pluse-height analyzer: converting pluse peak amplitude to digital signal(A/D converting), including peak detector and amplitude track and hold circuit, A/D converting circuit, logic control circuit. Pluse amplitude discriminator is to eliminate the interference of noise and low energy pluse. Pluse peak detector and amplitude track and hold circuit is to detect pluse peak and hold peak amplitude ready for A/D converting. A/D converting circuit is to quantize the amplitude of pluse peak. Logic control circuit is to make circuit work harmoniously by logic signal.(4) Communication interface: transfering digital data of MCA to upper machine by DI/O card with PCI bus.(5) Application program: acquiring data, controlling measuring process, displaying spectral line, processing data, anaylsing content etc.(6) Power circuit: transforming 220V AC to operating voltage of circuit and high voltage of gamma-ray detector.The instrument performance and the technical specifications are qualified. Energy resolution is 8.6% (measured by ¹³⁷Cs 0.662MeV energy peak). The linearity of energy is qualified, the correlative coefficient of linear equation is 0.9975. The drift of spectrum is less than 2% during 8 hours. Through field testing of uranium mine, multi-channel gamma-ray spectrometer of radioactive surveying station can mesuring the content of uranium ore accurately.