数字化核脉冲定时方法研究

定时电路是核电子学中检出时间信息的模拟电路的基本单元,包括前沿定时、过零定时、恒比定时及幅度和上升时间补偿定时;与模拟定时电路相比,数字定时电路拥有许多优点:一是输入信号的前端数字化,大幅简化了模拟电路;二是数字信号的处理分析,根据测试的目的从采样信号中提取所需要的信息(幅度、时间)。论文以MATLAB为工具,探讨数字化恒比定时和一种改进型前沿定时。     

高速有ARC定时恒比定时甄别器

介绍了一种高速的TTL输出恒比定时甄别器.该甄别器同时实现恒比定时(CFD)功能及幅度和上升时间补偿定时(ARC)功能.最小传输延迟仅为22ns,最大计数率为100 MHz,可内部调节恒比延时.适用于多种幅度和前沿时间范围的输入信号,时间分辨能力好.电路设计简单,价格低廉,便于制作使用.     

用于PET的丝室信号恒比定时器

ＰＥＴ用丝室信号的特点,设计和实现了一种恒比定时器电路,该丝室及定时电路的双光子符合时间分辨率达到１９ｎｓ。     

基于FPGA+DSP的核信号数字时间谱仪设计

针对核电子学中核脉冲信号的高速实时数字化处理,设计了基于FPGA+DSP的两通道核信号数字时间谱仪。该实验平台基于数字恒比定时(dCFD)原理,采用高速运放和ADC进行模拟信号成型采样,数字信号送入FPGA完成波形判选、数据缓冲、FIR滤波和基线恢复,利用DSP实时信号重构和函数定时,通过USB2.0接口与上位机通信。该系统的主要特点是具有模数电路的高度集成、数字信号的实时运算,接近模拟定时的精度。     

一种简单、价廉的九路恒比定时甄别器

根据宇宙线物理实验的要求,我们研制了一种双宽CAMAC插件,它装有九路恒比定时甄别器。各路的幅度一时间移动(也称时间步移)均小于±100ps,而其造价仅相当市售单路者。 所谓恒比定时,是取前沿上 高度相当于脉冲幅度固定比例的 点作为定时瞬间的定时方法。此 方法的特点是,定时瞬间几乎与 脉冲的高低无关。通常,恒比定     

μSR谱仪前端电子学原型设计

介绍了μSR谱仪前端电子学原型的设计。利用无延迟线恒比定时电路在单宽NIM插件上实现了8路恒比定时甄别器。测试结果表明:设计电路幅度时间游动不大于255 ps,不同通道间延时的标准差为19.7 ps,前端电子学定时误差约为55 ps。前端电子学原型板具有集成度高且定时误差较小的特点,可满足μSR谱仪系统的技术指标要求。     

基于DSP builder与FPGA的数字脉冲处理算法研究

研究了基于DSP builder与FPGA的数字脉冲处理算法,设计了一种基于数字脉冲处理技术的数字实时时间谱仪。谱仪数字恒比定时(dCFD)算法部分最终全部在FPGA中实现,简化了电路。并组建了一套测量22Na放射源的数字化正电子符合谱仪,对其进行测量得到该系统能量分辨达到3.90%,时间分辨达到157.6 ps,高于传统TDC测得的时间分辨率。     

nγ粒子鉴别的计算机模拟

本文介绍了ｎ和γ的两种鉴别 计算机模拟过程。一种是恒比定时（ＣＦＴ）的鉴别方法，利用ｎ和γ脉冲积分波形恒比定时点的不同来区分两种粒子。另一种是利用粒子脉冲的不同区段占总电荷量的比例不同来区分两种粒子（ΔＱ／Ｑ法）。     

电子能量损失符合谱仪前端电子学和数据获取系统

介绍了用于原子分子实验的能量损失符合谱仪的前端电子学和数据获取系统。考虑到谱仪的高计数率的特点,设计了适应高计数率的反堆积放大器和无延迟线恒比定时甄别器。该系统现已用于原子分子实验室,并取得了令人满意的实验结果。     

光电倍增管倍增极信号定时性能的研究

介绍一种从光电倍增管倍增极引出快信号的电路。分析了信号的产生机理,研究了它的定时性能。使用两支Philips XP2020Q光电倍增管,与BaF2闪烁体组成时问谱仪探头,从D9倍增极引出快信号,在使用Ortec935恒比定时和Ortec567时幅转换的条件下,测量^60Co的瞬发时间谱,在2：1能窗下得到FWHM=138ps的时间分辨。表明,此方法明显改善了谱仪的时间分辨性能。     

一种简便的快速定时甄别电路

介绍了一种快速定时甄别器的电路实现。输入可以是各种电平的正相或者负相信号,输出是多路脉冲宽度可调的负相标准NIM信号。这个电路具有较好的定时精度和极小的输出延时,输出脉冲宽度可调,一直在量子信息实验中稳定使用。     

多重快信号甄别方法与电路

提出了超高速多重快甄别器电路系统，并简要介绍了该系统的电路结构与电路设计。它主要用于快时间信号的甄别，是为多重核探测器实验系统设计研制的，可以完成多重核探测器系统中核反应事件的判选和符合关系的识别。     

光纤在合肥同步辐射装置新时序系统定时信号传输中的应用

本文讨论一种利用高速光纤传输定时精度，低重复率触发信号的方法，此方法在两相邻定地脉冲的时间间隔加入周期脉冲，在接收端剔除叠加的周期脉冲，检出定时脉冲，解决了由于光接收器低端截止频率高于定时脉冲频率的矛盾。     

Experiments on slug mixing under natural circulation conditions at the ROCOM test facility using high-resolution measurement techniques and numerical modeling

ROCOM is a four-loop test facility used for the investigation of coolant mixing in the primary circuit of pressurized water reactors. Recently, a new sensor was developed for an improved visualisation and quantification of the coolant mixing in the downcomer. This new sensor array spans a dense measuring grid and covers nearly the whole downcomer. In the presented work, special emphasis was given to the comparison of the data of this sensor with the results of calculations using the Computational Fluid Dynamics (CFD) code ANSYS CFX. A coolant mixing experiment during natural circulation conditions has been conducted. The underlying scenario of this experiment is based on a boron dilution scenario following a SBLOCA event. The corresponding CFD code solution has been obtained using the Best Practice Guidelines. All main effects observed in the measurement are described by the calculation. The detailed comparison reveals that the calculation underestimates the coolant mixing inside the reactor pressure vessel.The measurement data, boundary conditions of the experiment and facility geometry can be made available to other CFD code users for benchmarking.     

Numerical Simulation of Gas Flow During Arcing Process for 252 kV Puffer Circuit Breakers

A numerical simulation model for 252 kV puffer circuit breaker is constructed, by using a proven commercial computational fluid dynamics （CFD） package, PHOENICS...     

Experiments at the mixing test facility ROCOM for benchmarking of CFD codes

For the validation of computational fluid dynamics (CFD) codes, experimental data on fluid flow parameters with high resolution in time and space are needed.Rossendorf Coolant Mixing Model (ROCOM) is a test facility for the investigation of coolant mixing in the primary circuit of pressurized water reactors. This facility reproduces the primary circuit of a German KONVOI-type reactor. All important details of the reactor pressure vessel are modelled at a linear scale of 1:5. The facility is characterized by flexible possibilities of operation in a wide variety of flow regimes and boundary conditions. The flow path of the coolant from the cold legs through the downcomer until the inlet into the core is equipped with high-resolution detectors, in particular, wire mesh sensors in the downcomer of the vessel with a mesh of 64 × 32 measurement positions and in the core inlet plane with one measurement position for the entry into each fuel assembly, to enable high-level CFD code validation. Two different types of experiments at the ROCOM test facility have been proposed for this purpose. The first proposal concerns the transport of a slug of hot, under-borated condensate, which has formed in the cold leg after a small break LOCA, towards the reactor core under natural circulation. The propagation of the emergency core cooling water in the test facility under natural circulation or even stagnant flow conditions should be investigated in the second type of experiment. The measured data can contribute significantly to the validation of CFD codes for complex mixing processes with high relevance for nuclear safety.     

CPLD在多路定时信号处理中的应用

本文主要介绍了CPLD在多路定时信号处理中的应用.针对大型核物理实验中的符合测量、多路时间测量系统中的门控快定时信号等应用的需要,设计了一种多路延迟/脉宽调节电路,主要功能是对输入的多路快信号进行延迟和脉宽调节,支持NIM负信号输入和输出,在系统主时钟频率为100MHz的时候,延迟和脉宽调节的最小步进精度为10ns.我们采用复杂可编程逻辑器件CPLD来构建系统的主要电路,具有较小的延迟和脉宽调节误差,和常规逻辑器件相比其特点是:元件少且成本低,功耗小,稳定性好.     

Conceptual design of helium cooling circuit for irradiation target

Small metal specimens of about 20 mm × 20 mm and 0.4 mm thick are irradiated in cyclotron facilities for radiation damage studies. Cooling of these specimens is an important factor which decides the intensity of irradiation. In this paper helium is used for the cooling of irradiation target specimen. In order to have enhanced heat removal from the specimen jet cooling is employed. The cooling scheme and the conceptual helium cooling circuit has been arrived at based on the empirical correlation available in the literature. The heat removal rate has been estimated for various jet velocities. Experiments with impinging air jets have been carried out to compare the empirical predictions. Numerical predictions have also been carried out using commercial Computational Fluid Dynamic (CFD) code. Experimental predictions are 35%–55% higher compare to empirical correlation. The empirical correlation is 30% higher compare to CFD predictions.     

Discriminator design considerations for time-interval measurement circuits in collider detector systems

An analysis of timing jitter from leading-edge discriminators (LED's) and constant-fraction discriminators (CFD's) is presented. The jitter is calculated for the cases of random white noise, coherent noise (e.g., digital switching noise or ac power-line hum), and mixed (random and coherent) noise for both discriminator architectures. A general jitter equation valid for all of these conditions is derived. It is shown that the discriminator bandwidth for minimum jitter is strongly dependent on the amount of coherent noise. This effect is shown to be more pronounced for the LED. Even though off-line walk adjustments are possible for many timing measurements, the CFD is shown to provide a major advantage by acting as a correlated double sampler that removes much of the coherent noise expected in large, multichannel collider detector systems.