【作者】 谢广利；

【导师】 常青； 田小林；

【作者基本信息】 华东理工大学 ， 电子与通信工程， 2011， 硕士

【摘要】 多道脉冲幅度分析器(简称MCA)是X、γ射线能谱分析仪的最重要部件。它的主要作用是将核辐射探测器输出一串脉冲信号的幅度转换成数字量,通过数据处理获得X、γ射线的能谱数据,为能谱分析应用提供有力支持。随着A/D转换器和专用集成电路的快速发展,数字化的多道脉冲幅度分析器(DMCA)已逐步替代了传统的模拟MCA。采用高性能器件设计的数字化MCA有许多优势,它能提高测量速度,降低成本、功耗和体积,并容易拓展新功能等。本课题以Actel公司的FPGA芯片A3P1500为开发平台来实现MCA的数字化设计。外部采用高速A/D转换器LTC2248I对核脉冲信号进行持续采样,采样周期为25MHz。在FPGA中运用Verilog HDL语言设计均衡器、梯形滤波器、基线恢复器、堆积排除、峰值检测、数据存储和传输等功能模块对核脉冲采样信号进行处理。USB接口设计采用FT245BL芯片,实现外部设备和DMCA之间的数据快速传输。采用DC到DC电源转换电路,将USB总线提供的5V电源变换成低噪声的1.5V,3.3V及3.3VA等系统所需电源,解决了系统供电问题。测试结果表明,该DMCA能够满足X荧光分析仪和γ能谱分析仪的技术指标要求。更多还原

【Abstract】 Multi-channel pulse height analyzer (MCA) is the primary part for X and gamma ray energy spectrum analysis technology. It can digital the pulse signal of nuclear detector output. So that we can get the pulse-height spectra of the X and gamma ray, i.e. the pulse counting distribution of each channel for the different height pulse. It can strongly support the spectrum analysis technology at lots of fields. As the developing of A/D converter and ASIC, the traditional analog MCA has been replaced gradually by digital MCA. Designing with the advanced chips, it can enhance strongly the performance of DMCA, such as improving data processing rate, reducing material costs, PCB volume and dissipation power, and easy to modify or add new function, etc.This thesis describes a solution of DMCA design based on A3P1500 control development platform of Actel ProASIC3 Flash FPGA. With high-speed A/D converter LTC2248I, DMCA system can sampling the pulse signal of unclear detector output continuously, the sample cycle is 25MHz. By using Verilog HDL language, all of data processing function modules, such as equalizer filter, trapezoidal filter, baseline restorer, pulse pileup rejection, peak value hold, data storage and communication etc, had been realized in one FPGA chip to process the digital sampling signal of nuclear analogy pulse. The IC of FT245BL was applied to the interface of USB communication, it supply higher speed data transfer between the external devices and DMCA system. The interface of USB can supply 5V power with the maximal 500mA current. Via DC to DC circuits, high noise 5V power can be switched to low noise and stable power supply, such as 1.5V,3.3V and 3.4V, which needed by this system. This DMCA module will be used to X-ray fluorescence spectrometer and gamma-ray spectrometric analyzer.更多还原