基于实时数字恒比定时技术的数字时间谱仪研究
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摘要
核事件的许多信息以时间信息的方式存在于核辐射探测器输出信号中,例如粒子激发态寿命表现为相继两信号的时间间隔分布,中子能量可以表现为中子飞越一定距离所需的飞行时间,粒子入射的空间位置可表现为位置灵敏探测器输出信号的时间信息,入射粒子的种类也可反映在信号电荷的时间分布。为了探测核事件的性质、发生时间和位置,需要获取核脉冲信号的时间信息并进行处理。
恒比定时(Constant Fraction Timing, CFD)是核物理和粒子物理实验中用于准确确定粒子入射时间的一种重要定时技术。恒比定时的原理是采用恒定幅度触发比来检测核脉冲前沿到达的时刻,能够修正脉冲幅度变化对定时的影响。传统的恒比定时方法采用模拟定时甄别电路给出定时信号,再由时间数字化芯片TDC量化,通过计算机对时间信息进行统计,可以获得所需要的时间谱波形。其模拟电路结构较为复杂,系统设备庞大。
数字恒比定时(digital Constant Fraction Timing, dCFD)方法是采用数字信号处理技术分析和处理核脉冲信号,由模数转换芯片ADC直接对脉冲信号全波形采样,以数值计算取代模拟定时电路。此设计方法优点在于以全数字化手段完整保留核事件的全部现场信息,能够一次测量从脉冲序列中获取幅度、时间、粒子类型等整套信息,系统结构简单,算法调整方便。
基于数字恒比定时原理,本论文设计了一套通用硬件电路系统来完成实时核脉冲数字恒比定时计算。该系统的设计主要采用如下的技术路线：使用高速ADC数字量化,使用MATLAB信号模型并设计合适的滤波、定时算法,利用高性能的FPGA (Field Programmable Gate Array)和DSP (Digital Signal Processor)器件硬件实时处理,实现高精度的幅度和时间测量,使用USB2.0高速数据接口与主机通信。
本论文的主要工作和创新点如下：
1、采用MATLAB进行信号建模和算法设计,实现数字滤波器设计、定时算法优化、离线数据处理、系统性能ENOB/SNR和DNL/INL测试、物理数据统计等系统功能,并集成到一个GUI工程。
2、基于数字恒比定时原理,研制了国内首台以FPGA和DSP为并行处理核心的双通道数字恒比定时电子学系统原型机,系统的主要功能集成在NIM插件电路上实现,能够实现两路信号实时量化、滤波、幅度计算、时间计算工作;
目前,本论文所设计的电子学系统原型机已经完成,并经过了一系列电子学测试,测试结果表明数字恒比定时电子学系统接近模拟定时的精度,在功能集成和算法灵活上有较突出优点。
Much of the nuclear incident time information exists in the nuclear radiation detectors output signals.For example,excited particle lifetime performance with two successive time interval distribution of the signals,Neutron energy can be expressed as the neutron flight time over the distance,the spatial location of incident particles can be expressed as time information of position sensitive detectors output signals,the type of incident particles also can be expressed in the time distribution of the signal charge.In order to detect the nature of the nuclear incident and the occurrence time and position information,we need to obtain and process nuclear pulse signal time information.
Constant Fraction Timing Discriminator (CFD) is an effective timing method used to obtain particles experiment incident time in Nuclear Physics and Particle Physics.CFD triggered by a constant fraction of signals amplitude to detect the arrival time of the nuclear pulse leading edge,it is possible to correct timing accuracy in pulse amplitude fluctuations.The traditional CFD method use analog circuit to given timing signals,then use Time-to-Digital Converter (TDC) chip to quantify timing signal. Time spectral waveform of the time information through computer statistics time data.The disadvantage is analog circuit complex and system equipment is huge.
Digital Constant Fraction Timing Discriminator (dCFD) is a digital timing method with using Digital Signal Processing technology to analysis nuclear pulse signals.Nuclear pulse signal quantified directly by high speed Analog-to-Digital Converters (ADC),replaced analog timing circuit by numerical simulation. Advantage of this method is using digital over-sampling keep all the nuclear incident scene information,nuclear signals amplitude,time,particle type and the other information can obtained form one measurement.System structure simpler than the analog system,the algorithm is easy to adjust for different experiment environment.
According to the dCFD timing method above,a timing calculating system,which is a hardware circuit,is designed and implemented as a solution. The main technical features of the system are:using high-speed analog-digital converters convert the pulse voltage into digital signals,using MATLAB designed the appropriate filter coefficients and timing algorithm model based on the characteristic relationship between the pulse voltage and the noise voltage,using a high performance FPGA (Field Programmable Gate Array) device and a DSP (Digital Signal Processor) device parallel process of amplitude and time calculating for double-channels pulse signal.USB2.0high-speed data interface used for host communication.
The innovations of this thesis are shown as follows:
1、 Using MATLAB established signal noise model for dCFD offline simulation, realized Digital filter design, Optimized timing process algorithm,and developed a experiment GUI user system for online digital timing measurement, analyzed system performance, given nuclear pulse signal time histogram.
2、 Designed a dCFD prototype for double-channels nuclear pulse signal measurement, based on FPGA and DSP digital processing. The mainly function of the electronics system is integrated in one NIM plug-in module, which implement real-time sampling two channel signals,filtering,incident energy calculation,incident time calculation.
Presently, the prototype of electronics system has been produced. After a series of electronics test, the result show that digital electronics system prototype timing accuracy close to traditional analog electronics system, and digital System has more prominent advantages in functional integration and algorithm flexibility.
恒比定时(Constant Fraction Timing, CFD)是核物理和粒子物理实验中用于准确确定粒子入射时间的一种重要定时技术。恒比定时的原理是采用恒定幅度触发比来检测核脉冲前沿到达的时刻,能够修正脉冲幅度变化对定时的影响。传统的恒比定时方法采用模拟定时甄别电路给出定时信号,再由时间数字化芯片TDC量化,通过计算机对时间信息进行统计,可以获得所需要的时间谱波形。其模拟电路结构较为复杂,系统设备庞大。
数字恒比定时(digital Constant Fraction Timing, dCFD)方法是采用数字信号处理技术分析和处理核脉冲信号,由模数转换芯片ADC直接对脉冲信号全波形采样,以数值计算取代模拟定时电路。此设计方法优点在于以全数字化手段完整保留核事件的全部现场信息,能够一次测量从脉冲序列中获取幅度、时间、粒子类型等整套信息,系统结构简单,算法调整方便。
基于数字恒比定时原理,本论文设计了一套通用硬件电路系统来完成实时核脉冲数字恒比定时计算。该系统的设计主要采用如下的技术路线：使用高速ADC数字量化,使用MATLAB信号模型并设计合适的滤波、定时算法,利用高性能的FPGA (Field Programmable Gate Array)和DSP (Digital Signal Processor)器件硬件实时处理,实现高精度的幅度和时间测量,使用USB2.0高速数据接口与主机通信。
本论文的主要工作和创新点如下：
1、采用MATLAB进行信号建模和算法设计,实现数字滤波器设计、定时算法优化、离线数据处理、系统性能ENOB/SNR和DNL/INL测试、物理数据统计等系统功能,并集成到一个GUI工程。
2、基于数字恒比定时原理,研制了国内首台以FPGA和DSP为并行处理核心的双通道数字恒比定时电子学系统原型机,系统的主要功能集成在NIM插件电路上实现,能够实现两路信号实时量化、滤波、幅度计算、时间计算工作;
目前,本论文所设计的电子学系统原型机已经完成,并经过了一系列电子学测试,测试结果表明数字恒比定时电子学系统接近模拟定时的精度,在功能集成和算法灵活上有较突出优点。
Much of the nuclear incident time information exists in the nuclear radiation detectors output signals.For example,excited particle lifetime performance with two successive time interval distribution of the signals,Neutron energy can be expressed as the neutron flight time over the distance,the spatial location of incident particles can be expressed as time information of position sensitive detectors output signals,the type of incident particles also can be expressed in the time distribution of the signal charge.In order to detect the nature of the nuclear incident and the occurrence time and position information,we need to obtain and process nuclear pulse signal time information.
Constant Fraction Timing Discriminator (CFD) is an effective timing method used to obtain particles experiment incident time in Nuclear Physics and Particle Physics.CFD triggered by a constant fraction of signals amplitude to detect the arrival time of the nuclear pulse leading edge,it is possible to correct timing accuracy in pulse amplitude fluctuations.The traditional CFD method use analog circuit to given timing signals,then use Time-to-Digital Converter (TDC) chip to quantify timing signal. Time spectral waveform of the time information through computer statistics time data.The disadvantage is analog circuit complex and system equipment is huge.
Digital Constant Fraction Timing Discriminator (dCFD) is a digital timing method with using Digital Signal Processing technology to analysis nuclear pulse signals.Nuclear pulse signal quantified directly by high speed Analog-to-Digital Converters (ADC),replaced analog timing circuit by numerical simulation. Advantage of this method is using digital over-sampling keep all the nuclear incident scene information,nuclear signals amplitude,time,particle type and the other information can obtained form one measurement.System structure simpler than the analog system,the algorithm is easy to adjust for different experiment environment.
According to the dCFD timing method above,a timing calculating system,which is a hardware circuit,is designed and implemented as a solution. The main technical features of the system are:using high-speed analog-digital converters convert the pulse voltage into digital signals,using MATLAB designed the appropriate filter coefficients and timing algorithm model based on the characteristic relationship between the pulse voltage and the noise voltage,using a high performance FPGA (Field Programmable Gate Array) device and a DSP (Digital Signal Processor) device parallel process of amplitude and time calculating for double-channels pulse signal.USB2.0high-speed data interface used for host communication.
The innovations of this thesis are shown as follows:
1、 Using MATLAB established signal noise model for dCFD offline simulation, realized Digital filter design, Optimized timing process algorithm,and developed a experiment GUI user system for online digital timing measurement, analyzed system performance, given nuclear pulse signal time histogram.
2、 Designed a dCFD prototype for double-channels nuclear pulse signal measurement, based on FPGA and DSP digital processing. The mainly function of the electronics system is integrated in one NIM plug-in module, which implement real-time sampling two channel signals,filtering,incident energy calculation,incident time calculation.
Presently, the prototype of electronics system has been produced. After a series of electronics test, the result show that digital electronics system prototype timing accuracy close to traditional analog electronics system, and digital System has more prominent advantages in functional integration and algorithm flexibility.
引文
[1]虞孝麒.核电子学方法,中国科技大学讲义
[2]王经瑾.核电子学,原子能出版社,1983
[3]王永纲.基于DSP的核信号处理方法研究,核电子学与探测技术,2004,Vo1.24 No.5
[4]Basilio Simoed J,et al. Nuclear Spectroscopy Pulse Height Analysis Based on Digital Signal Processing Techniques [J]. IEEE Nucl Sci,1995,42(4)
[5]Meyassar N Ai-Hadded,et al. Development and Testing of a flash Analog-To-Digital Converter Based system for pulse shape Discrimination of Nuclear Radiation Pulses[J]. IEEE Trans Nucl Sci,1994,41(5)
[6]Xie ShuXin,et al. A digital energy spectroscopy based on FIR filter[J]. Science China Technological Sciences,2011,54
[7]L.Bardelli,et al. Time measurements by means of digital sampling techniques:a study case of 100ps FWHM time resolution with a 100 MSample/s,12 bit digitizer[J]. Nuclear Instruments and Methods in Physics Research A,2004
[8]G.Pasquali,et al. A DSP equipped digitizer for online analysis of nuclear detector signals [J]. Nuclear Instruments and Methods in Physics Research A,2007
[9]孔伟,正电子湮没多参数测量系统研制,中国科技大学博士学位论文,2004
[10]郭建华,北京谱仪(BesⅢ)飞行时间电子学系统设计与实现,中国科技大学博士学位论文,2007
[11]A.Geraci,et al. A new on-line digital solution for event timing setups[J]. Nuclear Instruments and Methods in Physics Research A,1999
112] D.G. Cussans,et al. Optimization of the pulse arrival time determination in the ZEUS central tracking detector FADC system[J]. Nuclear Instruments and Methods in Physics Research A,1995
[13]Antonio Codino. The Pulse digitization for measuring the time of flight of ionizing particles[J]. Nuclear Instruments and Methods in Physics Research A,2000
[14]Mark A.Nelson,et al. Analysis of digital timing methods with BaF2 scintillators.[J] Nuclear Instruments and Methods in Physics Research A,2003
[15]胡广书,数字信号处理-理论、算法与实现,清华大学出版社,2003
[16]Fundamentals of Sampled Data Systems, Analog Devices AN-282
[17]John Ardizzoni,Jonathan pearson,高速差分 ADC 驱动器设计指南, Analog Devices
[18]Rob Reeder,Jim Caserta. Transformer Vs Amp.Analog Devices
[19]John Ardizzoni. A Practical Guide to High-speed Printed-Circuit-Board Layout,Analog Devices
[20]AD8045 Analog Devices,Datasheet
[21]AD8139 Analog Devices,Datasheet
[22]AD9445 Analog Devices,Datasheet
[23]Cyclone Ⅲ Device Handbook, CⅢ5Ⅴ1-2.0,2008Altera Corporation
[24]Quartus Ⅱ Handbook QⅡ5Ⅴ1-6.1, Altera Corporation, November 2006
[25]Configuration Handbook, CF5Ⅴ1-2.2, Altera Corporation, August 2005
[26]TMS320VC5416 Texas Instrument,Datasheet
[27]DSP技术及应用,北京大学出版社,2006
[28]TMS320C54X DSP Reference Set.Volume 1:CPU and Peripherals. Texas Instrument
[29]TMS320C54X DSP Reference Set.Volume 2:Mnemonic Instruction Set. Texas Instrument
[30]TMS320C54X DSP Reference Set.Volume 3:Algebraic Instruction Set. Texas Instrument
[31]TMS320C54X DSP Reference Set.Volume 4:Application Guide. Texas Instrument
[32]TMS320C54X DSP Reference Set.Volume 5:Enhanced Peripherals. Texas Instrument
[33]25X40AVA Microchip Datasheet
[34]TMS320VC5416 Bootloader. Application Report. Texas Instrument
[35]CY7C68013 Cypress Semiconductor Corporation,Datasheet
[36]USB Bus Datasheet
[37]EZ-USB FX2 Technical Reference Manual,Cypress Semiconductor Corporation,2008
[38]EZ-Loader Design Notes,Cypress Semiconductor Corporation,1998
[39]TMS320C54X DSP硬件开发教程,机械工业出版社,2003
[40]C/C++语言硬件程序设计,西安电子科技大学出版社,2003
[41]数值计算方法和算法,科学出版社,2002
[42]MATLAB 7基础与提高,电子工业出版社,2005
[43]MATLAB宝典,电子工业出版社,2008
[44]数字信号处理的FPGA实现,清华大学出版社,2003
[45]DSP Builder User Guide,Rev.6.1,Altera Corporation,2006
[46]INL/DNL Measurements for High-speed Analog-to-Digital Converters(ADCs), Maxim Application Note 283,2000
[47]许弟建,基于DSP的高速模数转换器动态测试技术研究,重庆大学硕士论文,2007
[48]IEEE Standard for Terminology and Test Methods for Analog-to-Digital Converters.2000
[49]高鑫,白雪宁,陈宜保,何元金,LaCl3：Ce3+闪烁体正电子湮没寿命谱仪,核电子学与探测技术,Vol.2007 No.2
[50]Luigi Bardelli, Development of sampling and digital signal processing techniques with application to Nuclear Physics detectors.2005
[2]王经瑾.核电子学,原子能出版社,1983
[3]王永纲.基于DSP的核信号处理方法研究,核电子学与探测技术,2004,Vo1.24 No.5
[4]Basilio Simoed J,et al. Nuclear Spectroscopy Pulse Height Analysis Based on Digital Signal Processing Techniques [J]. IEEE Nucl Sci,1995,42(4)
[5]Meyassar N Ai-Hadded,et al. Development and Testing of a flash Analog-To-Digital Converter Based system for pulse shape Discrimination of Nuclear Radiation Pulses[J]. IEEE Trans Nucl Sci,1994,41(5)
[6]Xie ShuXin,et al. A digital energy spectroscopy based on FIR filter[J]. Science China Technological Sciences,2011,54
[7]L.Bardelli,et al. Time measurements by means of digital sampling techniques:a study case of 100ps FWHM time resolution with a 100 MSample/s,12 bit digitizer[J]. Nuclear Instruments and Methods in Physics Research A,2004
[8]G.Pasquali,et al. A DSP equipped digitizer for online analysis of nuclear detector signals [J]. Nuclear Instruments and Methods in Physics Research A,2007
[9]孔伟,正电子湮没多参数测量系统研制,中国科技大学博士学位论文,2004
[10]郭建华,北京谱仪(BesⅢ)飞行时间电子学系统设计与实现,中国科技大学博士学位论文,2007
[11]A.Geraci,et al. A new on-line digital solution for event timing setups[J]. Nuclear Instruments and Methods in Physics Research A,1999
112] D.G. Cussans,et al. Optimization of the pulse arrival time determination in the ZEUS central tracking detector FADC system[J]. Nuclear Instruments and Methods in Physics Research A,1995
[13]Antonio Codino. The Pulse digitization for measuring the time of flight of ionizing particles[J]. Nuclear Instruments and Methods in Physics Research A,2000
[14]Mark A.Nelson,et al. Analysis of digital timing methods with BaF2 scintillators.[J] Nuclear Instruments and Methods in Physics Research A,2003
[15]胡广书,数字信号处理-理论、算法与实现,清华大学出版社,2003
[16]Fundamentals of Sampled Data Systems, Analog Devices AN-282
[17]John Ardizzoni,Jonathan pearson,高速差分 ADC 驱动器设计指南, Analog Devices
[18]Rob Reeder,Jim Caserta. Transformer Vs Amp.Analog Devices
[19]John Ardizzoni. A Practical Guide to High-speed Printed-Circuit-Board Layout,Analog Devices
[20]AD8045 Analog Devices,Datasheet
[21]AD8139 Analog Devices,Datasheet
[22]AD9445 Analog Devices,Datasheet
[23]Cyclone Ⅲ Device Handbook, CⅢ5Ⅴ1-2.0,2008Altera Corporation
[24]Quartus Ⅱ Handbook QⅡ5Ⅴ1-6.1, Altera Corporation, November 2006
[25]Configuration Handbook, CF5Ⅴ1-2.2, Altera Corporation, August 2005
[26]TMS320VC5416 Texas Instrument,Datasheet
[27]DSP技术及应用,北京大学出版社,2006
[28]TMS320C54X DSP Reference Set.Volume 1:CPU and Peripherals. Texas Instrument
[29]TMS320C54X DSP Reference Set.Volume 2:Mnemonic Instruction Set. Texas Instrument
[30]TMS320C54X DSP Reference Set.Volume 3:Algebraic Instruction Set. Texas Instrument
[31]TMS320C54X DSP Reference Set.Volume 4:Application Guide. Texas Instrument
[32]TMS320C54X DSP Reference Set.Volume 5:Enhanced Peripherals. Texas Instrument
[33]25X40AVA Microchip Datasheet
[34]TMS320VC5416 Bootloader. Application Report. Texas Instrument
[35]CY7C68013 Cypress Semiconductor Corporation,Datasheet
[36]USB Bus Datasheet
[37]EZ-USB FX2 Technical Reference Manual,Cypress Semiconductor Corporation,2008
[38]EZ-Loader Design Notes,Cypress Semiconductor Corporation,1998
[39]TMS320C54X DSP硬件开发教程,机械工业出版社,2003
[40]C/C++语言硬件程序设计,西安电子科技大学出版社,2003
[41]数值计算方法和算法,科学出版社,2002
[42]MATLAB 7基础与提高,电子工业出版社,2005
[43]MATLAB宝典,电子工业出版社,2008
[44]数字信号处理的FPGA实现,清华大学出版社,2003
[45]DSP Builder User Guide,Rev.6.1,Altera Corporation,2006
[46]INL/DNL Measurements for High-speed Analog-to-Digital Converters(ADCs), Maxim Application Note 283,2000
[47]许弟建,基于DSP的高速模数转换器动态测试技术研究,重庆大学硕士论文,2007
[48]IEEE Standard for Terminology and Test Methods for Analog-to-Digital Converters.2000
[49]高鑫,白雪宁,陈宜保,何元金,LaCl3：Ce3+闪烁体正电子湮没寿命谱仪,核电子学与探测技术,Vol.2007 No.2
[50]Luigi Bardelli, Development of sampling and digital signal processing techniques with application to Nuclear Physics detectors.2005