An inversion decomposition method for better energy resolution of NaI(Tl) scintillation detectors based on a Gaussian response matrix

NaI(T1) scintillation detectors have been widely applied for gamma-ray spectrum measurements owing to advantages such as high detection efficiency and low price.However,the mitigation of the limited energy resolution of these detectors,which detracts from an accurate analysis of the instrument spectra obtained,remains a crucial need.Based on the physical properties and spectrum formation processes of NaI(T1) scintillation detectors,the detector response to gamma photons with different energies is represented by photopeaks that are approximately Gaussian in shape with unique full-width-at-half-maximum(FWHM) values.The FWHM is established as a detector parameter based on resolution calibrations and is used in the construction of a general Gaussian response matrix,which is employed for the inverse decomposition of gamma spectra obtained from the detector.The Gold and Boosted Gold iterative algorithms are employed to accelerate the decomposition of the measured spectrum.Tests of the inverse decomposition method on multiple simulated overlapping peaks and on experimentally obtained U and Th radionuclide series spectra verify the practicability of the method,particularly in the low-energy region of the spectrum,providing for the accurate qualitative and quantitative analysis of radionuclides.     

TMSR白光中子源能量分辨率函数的模拟研究

白光中子源及飞行时间谱仪的能量分辨率函数描述了谱仪装置测量中子能量的分辨率与所测中子的能量之间的函数关系。能量分辨率函数用于中子共振截面测量实验数据分析,对确定共振峰参数至关重要。本工作利用Geant4蒙特卡罗工具包构建了TMSR白光中子源的中子产生靶系统模型,模拟了中子在靶系统内由产生到溢出靶系统的整个物理过程,获得了不同能群中子从产生到溢出的时间分布。基于RPI能量分辨率函数形式,对时间分布进行拟合分析,获得了一套合适的参数,用于确定TMSR白光中子源飞行时间谱仪的中子能量分辨率函数。     

Tokamak fusion neutron spectrometer based on PXI bus

In order to realize on-line real-time measurement of dynamic and time-sharing neutron spectrum of HL-2A,a tokamak fusion neutron spectrometer based on PXI bus was developed.It consists of electronics system and eight thermal neutron detectors,namely SP9 3He proportional counter,embedded in eight polyethylene spheres in different diameters.Response function of the eight polyethylene spheres was the key to calculate the neutron spectrum accurately.In this paper,response function of the eight polyethylene spheres is simulated by adopting Geant4 code,and neutron counts from an 241Am-Be neutron source are measured by the eight detectors.The calculated spectrum of the Am-Be neutron is accurate in 0-2 MeV region,and is similar to the theoretical spectrum.The tokamak fusion neutron spectrometer was used in HL-2A device to monitor the dynamic neutron spectrum of HL-2A on-line and real-time.     

基于C#和DSP的核能谱模拟平台构建

针对核信号在脉冲幅度和相邻脉冲时间间隔上存在的随机性,探讨构建了一种基于C#和DSP软硬件的核能谱模拟平台。采用相关算法,产生核随机信号,并统计其涨落特性,在软硬件两方面实现对任意核能谱的精确模拟和逼真再现。可对相邻核信号产生的时间间隔作任意分布设定,还可对核能谱的刷新频率、每次刷新增加的脉冲数以及统计脉冲总数等参数进行设置。模拟结果表明,在统计的脉冲总数与原始数据量相等的情况下,谱各道相对误差可控制在0.5%以内。     

239pu alpha spectrum analysis based on PIPS detector response function and variations with vacuum and distance

Effect factors of the absorption of the source,air,entrance window,and dead layer of a detector must be considered in the measurement of monoenergetic alpha particles,along with statistical noise and other factors that collectively cause the alpha spectrum to exhibit a well-known low-energy tail.Therefore,the estabUshment of an alpha spectrum detector response function from the perspective of a signaling system must consider the various factors mentioned above.The detector response function is the convolution of an alphaparticle pulse function,two exponential functions,and a Gaussian function,followed by calculation of the parameters of the detector response function using the weighted leastsquares fitting method as proposed in this paper.In our experiment,~(239)Pu alpha spectra were measured by a highresolution,passivated implanted planar silicon(PIPS)detector at 10 levels of vacuum and 10 source-detector distances.The spectrum-fitting results were excellent as evaluated by reduced Chi-square(x~2) and correlation coefficients.Finally,the variation of parameters with vacuum level and source-detector distance was studied.Results demonstrate that σ,τ_1,and τ_2 exhibit no obvious trend of variation with vacuum in the range 2000-20,000 mTorr,and at a confidence level of 95%,the values of τ_1 and τ_2 decline in a similar fashion with source-detector distance by the power exponential function,while the value of a declines linearly.     

基于-维参数化正交小波滤波器的信号快速重建

首先用一维参数化正交小波滤波器逼近双正交小波滤波器，然后根据信号采样值用Mallat算法对信号进行了快速重建，给出了算法；最后，用一个仿真加以说明。     

NSRL储存环平面控制网的实测与平差分析

NSRL平面控制网的建立是基于准直测量方案和测量仪器,合理布设增加的磁铁基准点,使其有效反映磁铁位置变化,正确布设地标点和测量过渡点以满足多站测量所需.依据准直方案选取仪器进行实地测量,获得可靠数据.针对实测数据,结合平差理论,依据各部件基准点的理论位置,利用多种有效的平差方法处理数据,获取二极磁铁点位误差及误差参数,建立所有测量网点的数据库,结合实际分析误差来源,并对实测过程进行修正.     

应用泵血参数评价起搏器起搏效应的初步探讨

对１３例正常人，２７例心室起搏器患者进行门控心血池显像。结果表明，应用泵血参数能较好地反映也搏器的治疗效果。心室射血功率与心室每搏量和心室前后负荷的均呈明显相关；安装心室起搏器后，左室ＥＦ没有明显提高，但ＣＯＥＭＰ明显改善，在应激状态下ＶＶＩＲ的起搏效应明显优于ＶＶＩ型起搏器；应用起搏器体外抑制的方法，可保持同一条件下用门控心血池显像观察安装起的搏器后患者的起搏起非搏时心功能的变化，并能够监测安装     

T(d,n)4He强流中子发生器的中子能谱和角分布模拟计算

采用将厚靶分割成薄靶的方法对厚氚钛靶、260keV氘束流能量条件下T(d,n)⁴He反应中子源的能谱和角分布进行计算。以分割法计算得到的能谱和角分布数据为基础,建立了D-T中子源Monte-Carlo模拟抽样模型,在考虑中子发生器各元件材料及实验大厅墙壁对快中子的慢化、散射和吸收的条件下,采用MCNP程序对兰州大学3×10¹²s^-1强流中子发生器260keV氘束流能量下的中子能谱和角分布进行了模拟,给出了模拟结果。为检验模拟结果的可靠性,与实验测量能谱进行了比较,Monte-Carlo模拟谱和实验测量谱基本符合。     

基于电子直线加速器的空间电子环境地面模拟用电子源设计与实现

空间电子环境地面模拟装置由1台电子直线加速器提供能量1~5 MeV范围内的电子,后续束流传输系统将电子束进行扩束处理。较大的能量范围对加速器的设计与运行条件提出了较高要求。本文主要阐述了该加速器的设计与实现过程,综合考虑了能量开关技术和束流负载效应,通过研究不同条件下的耦合度参数特性确定了加速管耦合度,分析提出了磁控管输出参数并进行了实验研究。加速器实验测试结果表明,电子束能量参数达到指标要求,为模拟装置提供了有效可靠的电子源。     

采用对称零面积法的高统计涨落谱线峰位解析研究

峰位分析的准确性是能谱稳谱质量的基础。为了提高峰位计算准确性和稳谱质量,针对航空γ能谱谱线高噪声特征,研究应用了采用柯西函数对称零面积法分析峰位,并且对比常用的高斯函数拟合法、峰面积法寻峰效果。结果表明针对高噪声的谱线寻峰,采用柯西函数的对称零面积法峰位计算方法,分析峰位更准确。     

BEGe探测器晶体参数的蒙特卡罗计算与实验表征技术研究

利用²⁴¹Am发射的59.54 keV平行γ射线束对宽能BEGe探测器晶体进行扫描测量,通过晶体端面垂直扫描确定晶体直径,通过晶体侧面垂直扫描确定晶体高度。利用厂家提供的参数以及扫描得到的晶体参数建立蒙特卡罗计算模型,再通过点源和体源的实验测量值对晶体前端面及侧面死层厚度进行表征调节,使其与实验值符合,从而获得最佳理论计算模型。结果表明,获得的参数正确可靠,其点源探测效率的理论计算结果与实验测量值在2%内符合。该方法极大改善了蒙特卡罗计算BEGe晶体探测效率的精度,可应用于探测器的效率刻度及环境放射性调查。     

基于DSP技术的多道核脉冲幅度分析器的设计

介绍以DSP2407芯片为核心,采用专用峰值幅度采样保持电路,根据输入信号上升沿及峰值信息进行分析的多道核脉冲幅度分析器系统的原理和硬件结构.在合金分析及同位素密度成像系统中,采用本脉冲幅度分析器进行高速数据采集,取得了满意的效果.也可适用于其他核脉冲信号峰值幅度分析的场合.     

直接确定地层有机碳含量测井方法的数值模拟

非常规资源逐渐成为我国油气勘探的重要领域,其"源储一体"的特性使得对源岩特别是有机碳含量的连续定量评价成为关键。传统测井评价方法均是基于测井资料的间接评价,受多种因素影响,计算结果有一定的不确定性。本文利用快中子与地层元素原子核发生反应产生的非弹性散射伽马能谱和俘获伽马能谱,通过谱分析技术获取地层元素含量,根据与无机碳相关的钙、镁等元素含量确定无机碳含量,从总碳含量中扣除无机碳含量可直接提供高精度的有机碳含量信息。借助于蒙特卡罗数值模拟方法,建立了6种四川盆地龙马溪组和筇竹寺组页岩地层模型,模拟不同地层条件下的混合伽马能谱,并利用模拟元素的标准伽马能谱对模拟能谱进行谱解析。模拟结果表明,本文的方法可直接提供高精度的有机碳含量,有机碳含量大于2%时,其计算值相对误差小于6%。     

Generalized formulation of extended cross-section adjustment method based on minimum variance unbiased linear estimation

ABSTRACT

By introducing a new assumption of linear estimation, we derive a new formulation of the extended cross-section adjustment (EA) method, which minimizes the variance of the design target core parameters. The new formulation is derived on the basis of minimum variance unbiased estimation with no use of the assumption of normal distribution. In this formulation, we found that EA has infinitely many solutions as the adjusted cross-section set. The new formulation of EA can represent all the possible solutions minimizing the variance of the design target core parameters and includes a special case identical to the classical Bayesian EA method, which was derived on the basis of the Bayes theorem under the assumption of normal distribution. Moreover, we prove that the special case minimizes not only the variance of the design target core parameters but also the variance of the nuclear data. Meanwhile, we show that the new assumption of linear estimation is consistent with the Kalman filter and demonstrate that we can formulate similarly the extended bias factor method, the conventional cross-section adjustment method, and the regressive cross-section adjustment method with no use of the assumption of normal distribution.     

M310压水堆的改进--不调硼负荷跟随研究

对大亚湾核电站和岭澳核电站的M310压水堆进行了不调硼负荷跟随研究.使用西屋公司APA堆芯核设计软件.从分析负荷跟随运行时的反应性变化入手,根据不调硼负荷跟随的需要重新设计控制棒价值和控制棒分组,在不改变M310压水堆现有控制棒数量和位置的前提下,实现不调硼负荷跟随.通过人为引入燃耗倾斜,并改进过渡过程,使M310压水堆不仅在实施不调硼负荷跟随时轴向偏移能够满足G模式的梯形图,同时还具备良好的实时反应能力.将这种不调硼负荷跟随加G模式梯形图的运行模式称为BTP运行模式(BTP为"不调硼"的汉语拼音缩写).从原理上证明在M310压水堆上BTP运行模式是可行的.     

Simulation on control of beam halo-chaos by power function in the hackle periodic-focusing channel

The K-V beam through a hackle periodic-focusing magnetic field is studied using the particle-core model. The beam halo-chaos is found, and a power function controller is proposed based on mechanism of halo formation and strategy of controlling halo-chaos. Multiparticle simulation was performed to control the halo by using the power function control method. The results show that the halo-chaos and its regeneration can be eliminated effectively. We also find that the radial particle density evolvement is of uniformity at the beam＇s centre as long as appropriate parameters are chosen.     

基于GATE的双平板正电子发射乳腺断层成像系统的仿真研究

采用Monte Carlo法仿真软件GATE,构建专用于乳腺成像的双平板正电子发射断层成像系统PEM并研究其性能。参考NEMA NU 4–2008标准,并在试验中略作改动。研究了PEM(positron emission mammography)的灵敏度、散射分数、晶体散射、计数率、固有空间分辨率等参数。结果表明,在350–650 keV能窗、6 cm平板间距下,系统灵敏度达14.17%,固有空间分辨率约1.2 mm;乳腺仿体活度为29.6 MBq时,噪声等效计数率NECR为1.508×105/s,满足PEM系统所需。     

中子辐射损伤等效性研究进展

为建立不同辐射源损伤评价的统一标准,制定武器抗中子辐射性能考核及验收的依据,国内外确定了中子辐射损伤等效标准源,开展了大量的等效性研究工作。本文从位移损伤函数、辐射源能谱以及二者的结合关系方面梳理了理论研究进展。从基本实验方法、效应参数及场量参数的控制趋势方面总结了实验研究进展。探讨了降低实验不确定度的方法,展望了辐射损伤等效性研究工作的方向。     

冷中子非弹性散射谱仪能量分辨率的模拟研究

能量分辨率是中子散射谱仪设计中需重点模拟计算的一项指标。本文阐述了基于反应堆中子源的两种冷中子非弹性散射谱仪——三轴谱仪和广谱谱仪的基本测量原理,利用MCSTAS软件分别建立两种谱仪的中子束追踪模型,完成了不同中子入射能量和出射能量下的谱仪整体能量分辨率的定量模拟计算。通过对比发现,广谱谱仪由于其测量原理即特殊的变异散射平面的限制,较三轴谱仪具有低的能量分辨率,但这种特殊的变异散射平面的中子散射轨迹却可优化广谱谱仪的分析器和探测器空间布局。通过分析模拟计算结果给出了适用于提高广谱谱仪能量分辨率的中子准直器类型。