| Summary: | Aiming at the requirement of nuclear radiation spectrum and positron annihilation coincidence Doppler broadening spectrum measurement, an all digital dual channel coincidence Doppler broadening system based on FPGA is designed. In this system, the analog signal collected by the high purity germanium detector is converted into digital signal by the front-end of 16 bit analog-to-digital conversion chip AD9269-80. The digital signal enters the FPGA chip at the back-end of the system for digital processing. FPGA realizes the processing of nuclear pulse signal through moving average window, ping-pong operation, custom IP core, etc., including waveform noise reduction, trapezoid filtering, baseline recovery, stack recognition, threshold judgment, data cache, etc., so as to obtain the amplitude information and time information of nuclear pulse. Then, the communication between the network port module and the upper computer is carried out, and the amplitude and time information are transmitted by UDP protocol to obtain the energy spectrum of the nuclear signal. The system uses two channels to measure the broadening spectrum of positron coincidence Doppler and obtains two-dimensional coincidence spectrum.
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