Development Of The Digital ? Spectrometer Based On LaBr₃?Ce? Detector

LaBr₃?Ce? detector has high energy resolution and high detection efficiency,and has wide application prospect in?-ray spectrum measurement.But the self-generated background gives great interference to the gamma spectrum analysis of U,Th,K.In this paper,a digital multi-channel gamma spectrometer based on La Br₃?Ce?detector was developed for the application of natural radioactive?-ray spectroscopy.The methods of analyzing the contents of U,Th and K in natural radioactivity were discussed.Achievements and innovations have the following aspects:?1?Using a voltage-controlled gain amplifier plus DAC architecture,to design the program control input amplifier,to achieve the input signal of the flexible regulation,the adjustment range of-4d B²0d B.?2?Designed a sampling rate of 80MSPS analog/digital conversion circuit.In the differential input mode and adding anti-aliasing circuit,effectively suppress the input signal common mode noise and high frequency noise,improve the system signal to noise ratio.?3?The energy filter of trapezoidal shape based on FPGA is designed,and the optimal filtering parameters are tested.For the selected detector,taking into account the energy resolution and the counting rate,the best rise time for trapezoidal forming is 5?s.?4?The method of analyzing the natural radioactive U,Th and K contents by the characteristic peak method of mid-energy spectrum is tested.The self-background of the calibration of the La Br₃?Ce?detector is proposed,and the analytical accuracy of U,Th and K is achieved to meet the requirement of ground gamma-ray spectrometry.?5?The experimental energy spectrometer?The detector is a La Br₃?Ce?crystal with a size of?50mm×75mm?has an energy resolution of 2.44%(662ke V radiation for ¹³⁷Cs point source),and the energy linear correlation coefficient is 0.999.