阵列式反中微子探测系统模拟信号发生器设计

使用阵列式塑料闪烁体探测器结合多通道电子学系统对反中微子进行探测是目前较为流行的探测方法,其以多路信号之间的能量-时间符合关系来甄别中微子事件,其电子学系统建立后,需要有符合理论算法关系的多通道随机模拟信号对系统进行测试,以验证系统是否具有预期的探测效果。介绍了一种符合式多通道模拟信号发生器的设计,可以产生满足要求的模拟信号,下位机部分利用高速FPGA作为主控制单元,控制32路DAC通道对外输出信号;上位机部分使用直接抽样方法对蒙特卡洛算法得出的数据生成信号的输出通道、输出幅度和预期输出时间,通过USB传输给FPGA,由FPGA对信号进行精确控制,以达到在多个通道上输出满足要求的信号的目的。测试表明,本系统产生的符合式多通道模拟信号满足反中微子探测的能量-时间符合要求,为复杂的多路仿核信号模拟发生器的研制与改进提供了新的思路。     

GRM复合晶体探测器读出系统设计

针对SVOM卫星中的γ暴监视仪的叠成闪烁体探测器,设计了一套混合信号读出系统,用于获取GRM复合晶体探测器输出电压脉冲幅度与信号宽度,并根据脉冲的宽度对信号进行甄别分类。在系统设计中采用FPGA对系统进行时序控制,使用高速峰值保持电路对复合晶体输出信号进行峰值保持,利用RS232数据接口完成测试系统与PC机的数据交换。测试结果表明,本工作所设计的系统可稳定可靠地实现对复合晶体输出信号的获取与甄别分类。     

任意形状的脉冲信号发生器的研制

上海光源增强器引出系统中有三块凸轨磁铁,需要一台带外触发的信号发生器产生励磁电流脉冲波形.该信号发生器要求三路输出独立可调,包括幅度和通断可调,还能读取各通道的当前状态,包括通断状态和幅度值.本文介绍了一种基于FPGA和DAC的脉冲信号发生器,利用FPGA可编程灵活、IO资源丰富和可配置的特点,选用了四路输出的16 b...     

基于Flash ADC的闪烁探测信号测量装置研制

介绍了一种基于Flash ADC和FPGA的探测器信号测量装置,此装置基于高速ADC对信号波形进行数字化采样,通过FPGA逻辑对波形进行缓冲存储和数字化分析,获得探测信号的幅度、时间、脉冲形状等信息,应用USB接口或光纤接口实现与计算机的数据通讯。该装置可实现对多种常规探测器输出信号进行采集,并实现脉冲形状分析功能。文中首先对装置的硬件组成和软件设计进行了详细描述,之后给出了测量装置实物照片,并通过一个测试实例展示了它的脉冲信号测量和波形甄别功能。     

基于采样定理的核信号数字高斯滤波成形研究

核能谱分析仪中,常采用模拟滤波成形电路处理探测器的输出信号,以满足后级电路对信号波形的需要并滤除噪声。由模拟电路实现的高斯成形系统,改变成形参数必须对硬件进行调整,灵活性及稳定性均不理想。为实现数字滤波成形,根据模拟Sallen-Key高斯滤波成形电路,推导出模拟高斯成形系统的冲激响应;再根据采样定理推导出了数字高斯成形系统的冲激响应。用该数字高斯成形系统对实测核脉冲信号进行处理的结果显示,数字核脉冲信号被滤波成形为准高斯信号,为核脉冲信号数字滤波成形的实现提供了一种新的实现方法。     

新型随机核脉冲信号发生器设计

本文设计了一种基于FPGA和C#程序的随机核脉冲信号发生器。该脉冲信号发生器以高斯脉冲为基础,利用线性反馈移位寄存器产生均匀分布随机数,并根据核素特征谱线进行抽样,使输出高斯脉冲信号的幅度满足特征谱线的概率密度分布函数。系统具有电路简单,分辨率高,抗干扰能力强等优点。利用多道分析系统对241Am、109Cd、188Re、60Co四种放射性核素的模拟信号进行测试,结果表明:该信号发生器能够产生模拟核素特征谱线的高斯脉冲,并具有较高的稳定性和可靠性。     

基于Sallen-Key滤波器的主成形放大电路的研究

主成形放大器的作用在于将前置放大器输出的降指数信号变成准高斯信号。一级的Sallen-Key滤波电路相当于一个二阶的RC低通滤波器,采用两级的Sallen-Key级联滤波就可以实现四级RC滤波的效果,得到准高斯波形的输出。文中从基本的电路设计与分析开始,用C++模拟了主放大器的功能并分析了相关特性。最后用AD827双路运放实现了该电路,并对此电路性能进行了测试与验证。     

宽量程中子通量密度测量数字化处理系统设计

实时准确地测量反应堆的中子通量变化状况,对于确保反应堆的安全运行有着重要意义。基于模拟测量系统存在的一些不足,设计一种数字化的宽量程裂变室输出信号处理系统。该数字化信号处理系统将裂变室的脉冲和坎贝尔两种工作模式相结合,利用高速ADC对裂变室输出脉冲信号数字化,在FPGA中运用数字信号处理算法实现两种工作模式的信号处理,并仿真了裂变室的输出脉冲信号导入任意波形信号发生器模拟中子信号源,用于对处理算法的初步验证。测试结果表明数字化处理系统线性度和性能良好。     

基于FPGA的核信号高速采集系统的设计

对核信号高速采集系统的研究可实现数字核信号处理方法的改进与算法的验证,以及对数字化核能谱测量系统性能指标的提升具有重要意义。研发一套核信号高速采集系统,通过高速ADC将信号调理电路输出核脉冲信号进行采样,同时在FPGA系统中实现FIFO、USB接口传输功能,将采样后的数据经过FIFO缓存,再通过USB接口传送给后续计算机系统进行保存、显示与进一步处理。在搭建的核信号采集系统上进行测试,通过对5、10、20与33.3 MHz采样率下得到的核信号进行分析与讨论,表明该系统可有效地实现核信号的高速采集。     

低功耗海洋地震勘探数据采集系统设计

针对海洋地震勘探,设计了一种低功耗数据采集系统。该系统以FPGA为控制核心,采用低功耗24位□-型AD7779模数转换芯片完成多路信号采集,通过USB总线与上位机进行数据交换。同时,系统使用高精度DAC芯片设计了自检电路,用于采集通道性能与质量检测。测试结果表明:系统性能指标与功耗水平均达到了设计目标,满足海洋地震勘探的需求。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation.Due to the variations in the results during storage,the eggs of ostrich,duck,hen,and quail were irradiated to doses of 0,1,2,and 3 kGy.Most of the samples were incorrectly identified during storage after four months of irradiation.Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs.TL glow curves were recorded between the temperatures 50℃to 400℃at the rate of 5°/s for all the control and irradiated samples.On the basis of integrated areas of first glow curves (TL1),the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed.Furthermore,the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.     

数字射线扫描成像系统MTF的测试分析

为有效实现数字射线扫描成像检测系统性能的定量分析评价,据此进行检测工艺参数的优化,对数字射线扫描成像检测系统调制传递函数(Modulation transfer function,MTF)进行了测试分析。采用刀口工具、双线型像质计、分辨率测试卡,对系统在不同焦点大小、放大倍数、运动方向的检测情况,分别进行了MTF的测试并进行了比较。结果表明,双线型像质计与分辨率测试卡的测试结果基本一致,但双线型像质计更便于对比度的定量计算;双线型像质计的对比度传递函数近似符合二次曲线,经转换得到的调制传递函数值高于刀口法的测试值,刀口法计算数值偏低的原因在于运动不平稳所带来的不利影响。分析表明,数字射线扫描成像系统性能受到多个因素的共同影响,MTF测试结果可较全面地对影响因素进行定量评价,可用于确定最佳的检测参数或找出等价的参数组合。     

基于物理体模CT图像的1岁儿童体素体模构建

本文介绍了基于1岁儿童物理体模（Model 704-D）的CT图像和中国成年男性参考人体素体模(CRAM)的1岁儿童体素体模（CPP01）的构建,包括通过对物理体模扫描得到OCP01体模（基于儿童物理体模的CT图像建立的一粗略的体素体模）,进而构建和优化CPP01。该体素体模的各器官组织的质量与GBZ/T 200.2-2007所给数据的相对偏差约在5%以内,且其外部轮廓和主要器官的位置与Model 704-D相匹配。     

Activity level of gross α and gross β in airborne aerosol samples around the Qinshan NPP

The monitoring results of gross α and gross β activity from 2001 to 2005 for environmental airborne aerosol samples around the Qinshan NPP base are presented in this paper. A total of 170 aerosol samples were collected from monitoring sites of Caichenmen village, Qinlian village, Xiajiawan village and Yangliucun village around the Qinshan NPP base. The measured specific activity of gross α and gross β are in the range of 0.02 ～ 0.38 mBq/m3 and 0.10 ～ 1.81 mBq/m3, respectively, with an average of 0.11 mBq/m3 and 0.45mBq/m3, respectively. They are lower than the average of 0.15 mBq/m3 and 0.52mBq/m3, of reference site at Hangzhou City. It is indicated that the specific activity of gross α and gross β for environmental aerosol samples around the Qinshan NPP base had not been increased in normal operating conditions of the NPP.     

Simulation of the mixing process in FCIs with hydrodynamic fragmentation model

Fuel Coolant Interactions (FCIs) are important issues in nuclear reactor severe accident analysis. In FCIs, fragmentation model of molten droplets is a key factor to estimate degree of possible damage. In this paper, the mixing process in FCIs is studied by the simulation of MIXA experiment with hydrodynamic fragmentation model. The result shows that hydrodynamic fragmentation model underestimates the fragmentation rate of high temperature molten droplets under the condition of low Weber numbers. It is concluded that models based on thermal fragmentation mechanism should be adopted to analyze the FCI process and its consequence.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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NUCLEAR SCIENCE AND TECHNIQUES Volume 25,2014

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The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

Probing stray surface electric patch fields using Rydberg atoms

The stray electric “patch” fields present at a Au(1 1 1) surface are investigated by studying the ionization of Rydberg atoms incident at near-grazing angles. Measurements of the threshold conditions required to observe the resulting ions are used to estimate how large such stray fields can be. The data show that the stray fields can be sizeable, as large as ∼10³ V cm⁻¹ 100 nm from the surface and ∼20 V cm⁻¹ 500 nm from the surface, and illustrate the potential of Rydberg atoms for detecting and characterizing surface electric fields.