数字高斯脉冲成形算法仿真研究

高斯脉冲具有良好的时间、频率响应和较高的信噪比,探测器输出信号通常被滤波成形为高斯波形或类高斯波形。在高斯脉冲成形算法基础上,引入截止频率和品质因子,讨论成形参数对成形脉冲幅度、宽度的影响。通过与梯形脉冲成形算法对比,研究高斯脉冲成形算法的滤波效果以及对核信号幅度谱的作用。结果表明,在相同达峰时间条件下高斯脉冲成形算法具有更好的噪声抑制能力,同时可减小核信号幅度谱的半高宽;结合使用梯形脉冲成形算法可改善高斯脉冲成形算法在处理堆积脉冲中的不足,提高核信号通过率。     

Study of time-domain digital pulse shaping algorithms for nuclear signals

With the development on high-speed integrated circuit,fast high resolution sampling ADC and digital signal processors are replacing analog shaping amplifier circuit.This paper firstly presents the numerical analysis and simulation on R-C shaping circuit model and C-R shaping circuit model.Mathematic models are established based on 1st order digital differential method and Kirchhoff Current Law in time domain,and a simulation and error evaluation experiment on an ideal digital signal are carried out with Excel VBA.A digital shaping test for a semiconductor X-ray detector in real time is also presented.Then a numerical analysis for Sallen-Key(S-K) low-pass filter circuit model is implemented based on the analysis of digital R-C and digital C-R shaping methods.By applying the 2nd order non-homogeneous differential equation,the authors implement a digital Gaussian filter model for a standard exponential-decaying signal and a nuclear pulse signal.Finally,computer simulations and experimental tests are carried out and the results show the possibility of the digital pulse processing algorithms.     

一种基于数字延迟线的新型时间数码变换电路

提出了一种基于数字延迟线的时间数码变换方法,该电路具有精度和稳定性高．扩展性强的优点。在与传统计数式时间数码变换方法结合使用后．在使用低频自激振荡器的情况下,可以对较大动态范围的脉冲宽度进行测量,实现了较小的时间道宽和较高的测量精度。     

基于FPGA+MCU的全数字式滑移脉冲信号发生器的研制

介绍了一种基于现场可编程逻辑门阵列FPGA和微控制器MCU设计的高性能全数字式滑移脉冲信号发生器的系统结构,详细说明了仪器软、硬件各部分的设计思路和实现的技术。通过对标准核能谱仪多道脉冲幅度分析器的检测试验,该仪器达到了高精度、高稳定性的技术指标,满足了用户的生产需求。     

基于FPGA脉冲幅度分析器的数字化基线估计方法

从对数字化波形基线求取的准确性、实时性、灵敏度以及算法对硬件资源占有量等方面出发,分析直方图统计法和平均值法的优劣,提出了一种动态实时提取随机信号数字化波形基线的方法,并利用基于现场可编程门阵列(Field-Programmable Gate Array,FPGA)的数字多道脉冲幅度分析器对几种方法进行了测试。直方图统计法具有较高的准确性,将其结果与动态实时提取随机信号数字化波形基线方法的实验结果进行比较,验证了该方法在占有较少硬件资源和计数率较高的条件下,同样具有较高的准确性、实时性和灵敏度,并且对能谱分辨率有所改善。     

Estimation of Gaussian overlapping nuclear pulse parameters based on a deep learning LSTM model

A long short-term memory(LSTM) neural network has excellent learning ability applicable to time series of nuclear pulse signals. It can accurately estimate parameters associated with amplitude, time, and so on, in digitally shaped nuclear pulse signals—especially signals from overlapping pulses. By learning the mapping relationship between Gaussian overlapping pulses after digital shaping and exponential pulses before shaping, the shaping parameters of the overlapping exponential nuclear pulses can be estimated using the LSTM model. Firstly, the Gaussian overlapping nuclear pulse(ONP) parameters which need to be estimated received Gaussian digital shaping treatment, after superposition by multiple exponential nuclear pulses. Secondly, a dataset containing multiple samples was produced, each containing a sequence of sample values from Gaussian ONP, after digital shaping, and a set of shaping parameters from exponential pulses before digital shaping. Thirdly, the Training Set in the dataset was used to train the LSTM model. From these datasets, the values sampled from the Gaussian ONP were used as the input data for the LSTM model, and the pulse parameters estimated by the current LSTM model were calculated by forward propagation.Next, the loss function was used to calculate the loss value between the network-estimated pulse parameters and the actual pulse parameters. Then, a gradient-based optimization algorithm was applied, to feedback the loss value and the gradient of the loss function to the neural network, to update the weight of the LSTM model, thereby achieving the purpose of training the network. Finally, the sampled value of the Gaussian ONP for which the shaping parameters needed to be estimated was used as the input data for the LSTM model. After this, the LSTM model produced the required nuclear pulse parameter set. In summary,experimental results showed that the proposed method overcame the defect of local convergence encountered in traditional methods and could accurately extract parameters from multiple, severely overlapping Gaussian pulses,to achieve optimal estimation of nuclear pulse parameters in the global sense. These results support the conclusion that this is a good method for estimating nuclear pulse parameters.     

A digital long pulse integrator for EAST Tokamak

A digital integrator has been developed to be compatible with the long pulse plasma discharges on the Experimental Advanced Superconductor Tokamak (EAST), in which the induced signal is modulated by a chopper, and a field programmable gate array (FPGA) in the 16-bit digitizer is used to realize the digital integration in real time. After rectification and integration, the drift is almost linear and stable in controlled temperature, so a period of 50 s is used to determine the linear drift rate for drift compensation. The integration data can be directly transferred to the reflective memory (RFM) card, which is installed in the same PCI eXtensions for Instrumentation (PXI) chassis, so the data transmission can be also done in real time. The test results show that the real time data transmission rate is up to 10 kHz, the integration drift is typically less than 0.4 uVs/s and drift performance is a little worse in real long pulse discharge, which can be reduced further by using more precise data acquisition.     

数字化多道脉冲幅度分析技术研究

多道脉冲幅度分析技术正在朝数字化方向发展,基于数字信号处理技术的数字化多道具有脉冲处理能力强、速度快、稳定性高和灵活性强等特点。文章分析了数字核脉冲处理关键技术,利用MATLAB完成了梯形成形、数字基线估计、数字极零零极补偿、极零点识别等核心算法的模拟。给出了数字化多道初步总体设计方案,探讨了工程没计中的关键技术问题,为研制国产数字化核谱仪打下了基础。     

一种基于实时数字图像处理的同步辐射微探针自动化扫描新方法

在上海光源硬X微聚焦及应用光束线站(BL15U1)上实现了一种基于实时数字图像处理的同步辐射微探针自动化扫描方法。该方法采用高灵敏度、高帧率的数字电荷耦合器件(Charge Coupled Device,CCD)显微镜实时成像,通过对显微镜系统和X光微米探针系统的坐标转换,使用户在图像空间直接点击到感兴趣的位置后,样品台就自动将该点移入光路。在设定好扫描时间、扫描步长等必要的实验参数后,只需要用鼠标在图像空间圈出需要扫描的区域,系统将自动生成XPS运动控制器的运动配置文件,并驱动电机运动,对该区域进行微束荧光扫描成像。结果表明,该方法不仅可以提高同步辐射机时的使用效率,而且可以满足微区研究人员快捷、方便的自动化操作需求。     

一个基于数字示波器的实验室数据采集系统

基于数字示波器的功能,通过编程实现观测信号的自动测量和数据的在线采集和处理。不需专用或标准电子学插件,方便快捷地实现实验室小型数据采集系统的功能,并将其应用于闪烁探测器的单u标定。     

用于复合晶体探测器的数字波形甄别方法研究

本文设计了-个基于DSP的数字波形甄别系统,在此基础上研究了BP神经网络法、最佳线性法、等效宽度法、脉冲前后沿宽度法等数字甄别方法,给出了NaI(Tl)和csI(Na)复合晶体探测器的甄别结果,并从甄别能力、运算速度、抗干扰能力等方面进行了比较和讨论,结果表明BP神经网络甄别方法具有最大的甄别能力和抗干扰能力,同时能够满足系统实时甄别的要求.     

A new digital beam position monitor in SSRF

The newly developed Digital Beam Position Monitor (DBPM) system is introduced. The DBPM system differs with the conventional beam position monitor system in the use of DSP chips and the digital signal processing technology. It can be programmed on-line to select operation modes through EPICS control panel, and to measure various parameters of the third generation synchrotron radiation facility. This DBPM system can be used in the pre-injector LINAC, the transfer lines, the booster synchrotron and the storage ring. The electronic parameters of the DBPM system itself have been measured also.     

基于数字延迟线的高分辨率TDC系统

介绍了采用数字延迟线集成电路芯片和微控制器结合组成的高性价比的时间数字化测量系统。在单通道工作模式下,系统的分辨率达到125ps,动态量程达到7．2μs。该系统被用于浅水环境的机载激光测深系统。     

基于CPLD的多路脉冲形状甄别电路

在前后沿甄别原理的基础上,对脉冲形状甄别电路进行了数字化设计,用高频脉冲计数方法测量信号脉宽,在CPLD内对各路信号进行甄别,实现了多路处理的集成。在信号甄别的过程中,用窗函数代替传统的单边甄别阈,解决了甄别电路处理超大信号的难题,大大降低了系统的误触发和误甄别率。此设计方案在HXMT望远镜电子学系统中得到了成功应用。     

Fast data acquisition system based on digital oscilloscopes for fluctuation measurements in a long pulse JT-60U tokamak plasma

We have developed a new data acquisition (DAQ) system with fast sampling rate for fluctuation measurements in a long pulse JT-60U tokamak plasma. This system is based on a powerful digital oscilloscope, which has a large acquisition memory up to 50 Mwords/ch, 1 MHz sampling rate and 16 bits high resolution AD convertors. The system is composed of plural digital oscilloscopes and mass storages. On this system, most of data acquisition processes are executed at each digital oscilloscope. This feature of the system leads to an advantage that the processing loads are distributed among the digital oscilloscopes. This system has been successfully employed for measurements of various fluctuations obtained through magnetic probes, beam emission spectroscopy and so on. The size of the acquired data using this system has reached up to 10 GB/shot so far. It has demonstrated that this system is very powerful for data acquisition of multi-channeled signals with high time resolution in a long pulse plasma.     

基于概率因果模型与遗传算法的船舶核动力装置故障诊断的新方法

介绍一种将概率因果模型和遗传算法相结合的核动力装置二回路凝给水系统的故障诊断方法,它将概率因果模型的似然函数作为遗传算法的适应函数,从而将复杂系统的故障诊断转化为最优问题。仿真结果表明,该方法能够适应诊断过程中出现的不确定性,并实现多故障诊断,具有较高的诊断可靠性和实用性。     

基于平稳小波变换的毛刺检测算法

核爆炸地震监测技术研究中,数据质量检测是地震数据自动处理的基本内容,毛刺是影响数据质量的主要问题数据。基于平稳小波变换和非线性能量检测算法,给出一种毛刺自动检测算法。平稳小波变换弥补了正交小波变换存在的不足,可以使尺度分解结果的长度和原始数据保持一致,具备时移不变性。非线性能量检测算法可以增强记录中的高频信号,对平稳小波变换的结果应用非线性能量检测算法,提高了记录中毛刺检测的准确性,非常适合连续地震监测数据自动处理的需要。实验结果表明,给出的这种算法特别有利于记录中小毛刺的检测,从而能够减小信号检测的误检率。     

基于脉冲激发等离子体的高速开关设计

在等离子体的基础研究中,用可调高频脉冲来激发等离子体是一种重要的研究手段.介绍了用单片机系统控制线性开关来实现可调高频激励脉冲源的电路原理和方法.     

基于FPGA的单光子脉冲信号发生器设计

针对光电倍增管(Photomultiplier Tube,PMT)批量测试实际需求和单光电子谱精确测试光源的要求,通过对光电倍增管性能测试系统进行分析,设计制造了一种多通道输出可调的脉冲信号发生器的控制板,可用于光电倍增管单光电子谱的性能测试。该脉冲信号发生器在上升时间、下降时间等参数性能方面优于目前测试系统采用的商用信号源RIGOO-DG5352 350 MHz。用此脉冲信号发生器对光电倍增管进行单光电子测试,其输出信号能满足单光子测试的基本要求,利用其多路信号输出的特点,通过性能扩展即可用于光电倍增管的批量测试。     

Laser-RF synchronization based on digital phase detector

Laser oscillator synchronization with RF reference signal is ultra-important for a modem light source based on the accelerator.For Tsinghua Thomson scattering X-ray source,we have synchronized the mode-locked laser oscillator to RF reference signal with 48.2 fs RMS relative jitter.Both fundamental and harmonic signals derived from photo diode detection are used for laser-RF synchronization in our scheme.The fundamental signal is for coarse laser-RF synchronization and multiple laser oscillator synchronization.The harmonic signal is for high precise phase locking.The digital phase detector is implemented in the synchronization scheme for less noise,replacing the mixing to DC phase detection scheme.The digital processing algorithm for synchronization is commonly used in low-level RF control field.In order to test the phase locking loop logic without damaging the real laser oscillator,a laser oscillator emulator was developed for phase locking.This paper will report the laser-RF synchronization scheme and its performance.The laser oscillator emulator system will also be introduced here.