基于大学核物理实验的数字化MCA的研制

The Development of a Digital Multi-channel Pulse Height Analysis

介绍了一种用于大学核物理教学实验的基于FPGA全数字化多道脉冲幅度分析器(MCA)的研制。系统采用全数字化方法对输入的脉冲信号高速数字化,然后送入FPGA进行数字寻峰、记录、谱处理,并在主机上显示。给出了数字寻峰的原理,利用双甄别阈值提高系统的抗干扰能力;针对ADC的非线性对系统造成的影响,研究修正算法,保证数据采样的道宽均匀性;鉴于MCA采样存储的数据量大的特点,采用双RAM并行工作方式,将传输数据和计数存储分开处理,减少死时间及数据的溢出;在终端显示方面,主机通过USB总线实现了系统实时监控和能谱数据传输。通过实验对比了该系统与商用MCA的性能,取得了很好的测试效果。

A kind of digital multi-channel analyzer which was developed for Nuclear and Particle Experiment of Undergraduate Student in university was introduced.The input pulse signal is digitalized with a high speed ADC,and feed to a FPGA for seeking peak,recording,spectrometer processing and displaying automatically.The principle of digital searching peak was given in the paper.In order to improve the capability of anti-noise,a dual digital thresholds and dual buffer memories was designed.Aiming at the influence of nonlinear of ADC to the system,a revised algorithm was designed to ensure the channel width uniformity.Since the huge sampling and storaging data of MCA,a method of parallel work of double memory was used,just separated empty transmit data and stored count,reduced the dead time and data overflowing.The host computer can set up and monitor MCA real-time,read and write data from MCA by an USB interface.Contrasts commercial MCA,the MCA has a good result in function and price.