Research Of Integrated Nuclear Spectrum Acquisition Based On LaBr₃

Nuclear logging is widely used in the exploration and development of various geological minerals such as petroleum,coal,and metal minerals.It has rapidly developed into one of the most sophisticated well logging technologies with the development of modern nuclear detection and electronic technologies.In oil exploration,nuclear logging is mainly used in the fields of lithology,porosity,content of oil gas and water,sedimentary environment analysis,production logging,and so on.Nuclear logging uses the principle of interaction between radiation and matter to detect.The instrument can be divided into three major modules:radioactive source,detector,and acquisition circuit.This paper focuses on the improvement of the detector and the acquisition circuit,and proposes an integrated nuclear energy spectrum acquisition circuit based on the LaBr₃ scintillation crystal detector.For the detector,the specific performance of the LaBr₃ scintillation crystal was tested and its application in the nuclear logging instrument was studied.For the acquisition circuit,the design was based on FPGA and high-speed ADC full waveform acquisition circuit.The main work included chip selection.Hardware circuit design,FPGA programming,PCB des ign.The hardware part of the circuit includes:the pulse signal shaping module,which specifically inc ludes a preamplifier module,a zero-zero cancellation module,a baseline recovery module,a bandpass filter module;a digital chip and its peripheral circuits,Mainly include ADC and its predistortion amplifier,clock drive module,FPGA,programming socket,and their power module.FPGA internal functional modules include:phase-locked loop module,receive distribution module,data buffer module,pulse amplitude analysis module,serial communication module.Based on the above work,a PCB circuit board is drawn and the circuit is tested and debugged.The test results show that the design has excellent energy linearity,resolution less than 5%at the potassium peak,dead time is less than 1us,detection efficiency is similar to that of BGO.Compared with the traditional acquisition system,the design has the advantage of performance.