The Design Of Signal's Readout System Based On PSPMT

At present, various types of domestic nuclear instruments and equipment, such as X-ray fluorescence analyzer, gamma-ray spectrometer, personal meter, etc., can measure the radioactivity intensity, radionuclide species and energy spectrum of the radioactive substance, but fail to visually analyze its specific location and intensity distribution. Therefore, in view of this limitation, we carry out the related research work about the gamma camera.In this article, the multi-anode position-sensitive photomultiplier tubes(PSPMT)-H12700 A of the Hamamatsu corp is selected as the gamma-ray array imaging detector, and the detector's output channel number is 64. This paper is mainly about the design of signal's readout system based on detector, the main contents and results as following:1) According to the structure characteristics of the multi-anode position sensitive photomultiplier tubes, we make the design scheme of signal's readout system.2) Design the analog circuit and position information readout circuit of signal's readout system. The analog circuit includes two stages of simplified circuit, amplitude modulation circuit, and differential ADC drive circuit. Location location information readout circuit is designed based on ADI company's A/D conversion device AD9633. The chip integrated 4-channel ADC, will complete the multi-channel signal synchronous digital conversion work.3) Design the digital signal processing circuit. Using Xilinx company's Spartan-3E series FPGA chip designs circuit, mainly includes the SPI configuration module, LVDS input and parallel output module, FIFO read and write control module, etc. At the same time, completing the communication between the host computer and the circuit through the USB interface.4) System test. After completing the design of the signal's readout system, we verify the function of each part of the circuit and carry on the experimental test for the system.In this paper, the design of the signal's readout system based on PSPMT has been developed, in which the analog circuit and location information readout circuit simplifies the output channel number of PSPMT detector, completes the location of single photon event, realizes the synchronization acquisition of four ways location information, and etc. The digital signal processing circuit based on FPGA realizes the synchronous processing and transmission function of the four ways position information. After experimental verification, the design of signal's readout system based on PSPMT has preliminary imaging function, can determine the location of gamma rays, and display a certain area of radiation intensity distribution.