Characteristics of a 4-fold segmented clover detectore

Four high-purity germanium 4-fold segmented Clover detectors have been applied in the experiment of neutron-rich nucleus 21N. The performance of those four Clovers have been tested with radioactive sources and in-beam experiments, and the main results including energy resolution, peak-to-total ratios, the variation of the hit pattern distribution in different crystals of one Clover detector with the energy of γ ray, and absolute full energy peak detection effciency curve, were presented.     

CuS@Au纳米粒子组装的二维异质表面增强拉曼光谱基底用于结晶紫的快速检测北大核心CSCD

本文以自组装的中空CuS纳米粒子为模板,通过循环生长法,制得致密且有间隙的金包CuS纳米粒子二维团簇结构(CuS@Au),CuS核与Au壳,以及相邻Au壳之间的等离激元耦合效应,赋予此二维异质基底两种优越性能:电磁场增强表面增强拉曼光谱(SERS)“热点”,即“电磁热点”;光热作用促进固-液界面传质,诱导物质微区富集,即“光热热点”。该“双热”二维异质基底可用于水中有机污染物结晶紫的检测,结果显示在1616 cm^(-1)处结晶紫浓度范围为10~300 nmol/L时,测得拉曼信号强度与结晶紫浓度的对数呈良好的线性关系,决定系数R^(2)=0.98。方法检出限为8.55 nmol/L,从样品富集到检测完成仅需10 min。     

An empirical formula for scattered neutron components in fast neutron radiography

Scattering neutrons are one of the key factors that may affect the images of fast neutron radiography. In this paper, a mathematical model for scattered neutrons is developed on a cylinder sample, and an empirical formula for scattered neutrons is obtained. According to the results given by Monte Carlo methods, the parameters in the empirical formula are obtained with curve fitting, which confirms the logicality of the empirical formula. The curve-fitted parameters of common materials such as ⁶LiD are given.     

A TOF-PET prototype with position sensitive PMT readout

A prototype of time-of-flight positron emission computed tomography (TOF-PET) has been developed for acquiring the coincident detection of 511 keV γ-rays produced from positron annihilation. It consists of two 80.5 mm×80.5 mm LYSO scintillator arrays (composed of 35×35 pixel finger crystals) with the position sensitive photomultiplier tubes R2487 as the readout. Each array is composed of 2 mm×2 mm×15 mm finger crystals and the average pixel pitch is 2.30 mm. The measured results indicate that the TOF information has the potential to significantly enhance the image quality by improving the noise variance in the image reconstruction. The best spatial resolution (FWHM) of the prototype for the pairs of 511 keV γ-rays is 1.98 mm and 2.16 mm in the x and y directions, respectively, which are smaller than the average pixel pitch of 2.30 mm.     

基于2×2光开关的光交换系统研究

本文详细描述了基于光信元（ｐｈｏｔｏｎｉｃｃｅｌ）进行交换的光交换系统模型，讨论了光信元的帧结构方法，并完成了２×２ＬｉＮｂＯ３光开关交换单元实验，其技术性能指标为：工作速率１５５Ｍｂ／ｓ；消光比优于２０ｄＢ；插入损耗小于５ｄＢ     

顶空-气相色谱法测定葡萄糖氯化钠注射液中12种溶剂残留量

建立顶空-气相色谱法测定葡萄糖氯化钠注射液中12种残留溶剂含量的方法。采用HP-INNOWAX毛细管色谱柱(60 m×320μm,0.5μm)为分离柱,检测器为氢火焰离子化检测器(FID),柱温为程序升温。12种残留溶剂乙醇、异丙醇、丙酮、丁酮、乙酸乙酯、乙酸丁酯、乙酸正丙酯、甲苯、乙苯、对二甲苯、邻二甲苯、间二甲苯均能完全分离,在考察的浓度范围内线性关系良好(r>0.995),检出限分别为0.055,0.019,0.023,0.070,0.155,0.013,0.003,0.009,0.004,0.004,0.004,0.005μg/mL。平均回收率为90.6%~109.0%,测定结果的相对标准偏差为2.2%~5.6%(n=9)。该方法专属性强,精密度、准确度和检测灵敏度高,重复性好,可用于葡萄糖氯化钠注射液中12种溶剂残留量的测定。     

基于加权总差分最小化的中子稀疏投影计算机断层重建方法

为提升高噪声稀疏角度投影条件下中子计算机断层扫描(CT)质量,提出同时迭代重建方法(SIRT)与加权总差分最小化(WTDM)相结合的迭代重建方法(SIRT-WTDM)。在有无噪声情况下比较代数重建算法、联合代数重建算法及同时迭代重建算法的重建图像,证明了SIRT迭代重建具有较高的图像重建精度与较强的抗噪声性能,因此将SIRT作为高噪声中子投影图像CT迭代重建算法的保真项。考虑到对图像梯度稀疏性与连续性的约束,中子CT迭代重建方法的正则化约束项采用WTDM方法。由Shepp-Logan模体与真实冷中子层析扫描数据验证可知,在极端稀疏角度投影条件下,SIRT-WTDM可获得较好的重建效果。     

低能中子探测的GEANT4模拟研究

研究了GEANT4蒙特卡罗模拟程序在低能中子核反应中应用的可行性, 新版的GEANT(4.9.4版本)升级了老版本在模拟6Li(n, α)3H核反应道的不足, 并且加入了最新截面数据库。 对多个核反应道进行了研究, 模拟结果显示核反应截面、 次级粒子能量和反应的分支比等是正确的; 比较了掺6Li材料热中子探测效率的实验结果与MCNP和GEANT4模拟结果, 它们基本一致。 研究表明, 利用GEANT4研究6Li(n, α)3H是可行的, 这为进一步研究闪烁体中子探测器的位置分辨率模拟提供了有力支持。 The feasible study of Monte Carlo simulation of low energy nuclear reaction was performed based on GEANT4. The reaction channel 6Li(n, α)3H, simulated insufficiently in the old version Geant4, can be given correct results in the new version (version 4.9.4). New cross section library was added into the program. The study of several nuclear reaction channels shows that the cross sections, the secondary particle energies and the branching ratios are consistent with the experimental values. For doped 6Li materials, the comparison of thermal neutrons detection efficiencies of experimental results, MCNP and GEANT4 simulations, shows that the simulations are reasonable. From the studies above, it is feasible to simulate the 6Li(n, α)3H reaction with GEANT4. It will provide helpful information for the further study of the position resolution of scintillation neutron detector.