JMCT程序在线多普勒展宽研究

在核反应堆堆芯物理分析中, 考虑燃料核素的多普勒效应对反应性的影响是必要的. 基于最小二乘拟合法, 在自主蒙特卡罗粒子输运程序JMCT中开发了在线多普勒展宽功能. 在300-3000 K的温度范围内, 利用核数据处理程序(NJOY)制作了系列温度点下的连续能量核数据. 在统一的能量网格上, 进行最小二乘拟合, 得到拟合参数. JMCT利用这些拟合参数, 快速计算得到任意温度的核数据, 用于输运计算. 计算结果表明, 拟合得到的核数据与NJOY制作的核数据符合很好, 满足精度要求. JMCT临界模型计算结果表明, 拟合参数计算有效增殖因数k_eff与直接采用NJOY加工得到核数据的计算结果吻合.     

热防护层覆盖弹体目标雷达散射截面的修正的等效电流近似法和图形计算电磁学法分析

将修正的等效电流近似法与图形计算电磁学法相结合引入到热防护层覆盖弹体目标的电磁散射问题的研究中.应用修正的等效电流近似法对介质和有耗表面进行散射计算,结合图形计算电磁学法,借助于计算机显示技术,将三维目标图形在计算机屏幕上投影,由图形加速卡完成遮挡和消隐工作,利用图形计算电磁学的积分公式,把三维空间的计算转化为二维空间的计算,大大降低了计算时间和复杂度.计算结果表明:当入射波频率较低时,热防护层的厚度不会影响弹体雷达截面值的大小,当频率升高,随着热防护层厚度的增加,弹体雷达截面值不断减小,说明热防护涂层为有耗介质,介电常数的虚部越大其消耗能量的能力越强,弹体雷达截面变化越明显;当热防护层中存在孔隙,热防护层厚度一定,孔隙率越大,雷达截面值越大,孔隙率为零时,雷达截面值最小.当孔隙率相同,热防护层越薄,其雷达截面值越大;当弹体在高空中出现脱粘现象,对弹体的雷达截面值影响不大.     

H-在矩形腔中的光剥离截面

根据半经典闭合轨道理论研究了矩形腔对氢负离子的光剥离进程的影响,利用反射定律分析矩形腔中与光剥离截面相联系的剥离电子运动的闭合轨道,推导出该体系下的光剥离截面公式,在线性极化光的作用下,研究了腔的尺寸对光剥离截面的影响,并将其与麻志君等用量子力学方法研究的结果进行对比.结果表明:矩形腔的存在及其大小对光剥离截面中由闭合轨道相联系的返回波与波源函数发生干涉引起的振荡有很大影响,且振荡曲线随着矩形腔的尺寸变化明显;当激光极化方向沿着x轴或者y轴时,半经典方法与量子力学方法的结果一致,当激光极化方向沿着Z轴时,由于矩形腔在z轴上对光剥离截面不作用,采用半经典方法光剥离截面与无场的情况相同,但是采用量子力学方法,其结果中却出现振荡,表明半经典方法研究此体系结果更准确.研究结果可对研究负离子光剥离以及外腔中的电子输运问题提供参考.     

Model differential cross section of elastic scattering of electrons by atoms in the Monte Carlo simulation of the passage of electrons in a substance

A new model differential cross section is proposed for describing elastic scattering of electrons in simulating the passage of electrons through a substance by the Monte Carlo method. This differential cross section correctly describes the first and second transport scattering cross sections, but is characterized by the total elastic scattering cross section much smaller than the actual value of the total elastic scattering cross section. The application of this differential cross section makes it possible to considerably reduce the number of elastic collisions in the Monte Carlo simulation of passage of electrons in a substance and to model the passage of high-energy electrons using the individual collision model.     

Alq+(q=0—12)的光电离截面和Bethe系数

使用Hartree-Fock加相对论修正(HFR)近似计算Al^q+(q=0—12)的光电离截面和Bethe系数,其中Bethe系数将光电离截面与电子碰撞电离截面联系起来,并且决定电子碰撞电离截面的高能行为.分析了光电离截面和Bethe系数随电离度q的变化规律,还与其他数据进行比较,结果表明其数据是可靠的 关键词： 光电离 截面 Bethe系数     

用圆对称截面波导逼近正多边形截面波导的方法

求解各类截面波导的本征方程,一直是导波光学研究的焦点问题。提出用内切圆和外接圆截面波导逼近正多边形截面波导的方法,把正多边形截面分为三个部分：内切圆以内,外接圆以外,以及介于它们之间的第三部分。根据各边界处电磁场切向分量相等的条件,得到了正多边形截面波导的传播方程和TE0n各模式的截止条件,在所给定的截面条件下,得出可以容纳的TE波模式数为22个。     

氢负离子在电介质球面附近的光剥离研究

利用镜像法结合半经典闭合轨道理论,对氢负离子在电介质球面附近的光剥离进行了研究.首先利用镜像法分析了剥离电子在电介质球内的镜像电荷分布情况,然后给出了体系的哈密顿量.通过求解哈密顿正则方程,找到了剥离电子在电介质球面附近运动时的闭合轨道.借助于半经典闭合轨道理论,推导出了体系的光剥离截面,并且对光剥离截面进行了计算和分析.计算结果表明,氢负离子在电介质球面附近的光剥离截面不仅与入射光子的能量有关,而且还与电介质球面的介电常数有关.对于给定的电介质球面,随着入射光子的能量增加,光剥离截面的振荡振幅减小、振荡频率增加.当入射光子的能量增加到某一临界值时,光剥离截面的振荡结构消失.除此之外,随着电介质球面介电常数的增大,光剥离截面的振荡结构变得更加复杂.当电介质常数增大到无穷大时,体系的光剥离截面和氢负离子在金属球面附近的光剥离截面一致.因此,可以通过改变入射光子的能量及电介质球面的介电常数对氢负离子在电介质球面附近的光剥离截面进行调控研究.研究结果对负离子体系在电介质球面附近的光剥离的实验研究可以提供一定的理论指导和参考价值.     

纳米碳纤维导电性对红外消光性能的影响

纳米碳纤维是一种新型吸波材料。为探讨烟幕粒子的红外消光特性,利用矩量法建立了纳米碳纤维感应电流和散射场的计算模型,在此基础上得出了纳米碳纤维吸收、散射和消光截面的计算表达式。通过Matlab编程计算分析了纳米碳纤维红外消光截面与电导率的关系。结果表明,纳米碳纤维红外消光特性与电导率密切相关,随着电导率的增加,消光截面迅速增加,当波长大于纤维本身长度时,消光截面随电导率的变化出现峰值,峰值电导率与波长有关。     

纳米DDR SRAM器件重离子单粒子效应试验研究

针对90 nm和65 nm DDR（双倍数率）SRAM器件,开展与纳米尺度SRAM单粒子效应相关性的试验研究。分析了特征尺寸、测试图形、离子入射角度、工作电压等不同试验条件对单粒子翻转（SEU）的影响和效应规律,并对现有试验方法的可行性进行了分析。研究表明:特征尺寸减小导致翻转截面降低,测试图形和工作电压对器件单粒子翻转截面影响不大;随着入射角度增加,多位翻转的增加导致器件SEU截面有所增大;余弦倾角的试验方法对于纳米器件的适用性与离子种类和线性能量转移（LET）值相关,具有很大的局限性。     

Electron scattering studies of DMS,DMDS and DMSO homologous series

The present paper reports ionisation, elastic and total cross section for the first three members of dimethyl sulphide, dimethyl disulphide and dimethyl sulphoxide family of molecules. The multi-scattering centre spherical complex optical potential formalism is applied for integral elastic and inelastic cross section calculations. From the inelastic part, ionisation cross section is derived using complex scattering potential-ionisation contribution method. The total cross section is then obtained from the sum of elastic and inelastic contributions. A reasonably good agreement is obtained for elastic cross section, wherever comparison is available. The ionisation and total cross section calculation for the complete set of molecules has been performed for the first time.     

低能电子在水中的弹性散射

基于平均散射截面概念,结合Mott截面,计算E≤10 keV范围低能电子在水中弹性散射的微分散射截面、总散射截面及弹性散射角概率分布,与应用Rutherford模型的计算结果及实验结果符合较好.在此基础上,给出一个低能电子在水中弹性散射的模拟方法,既严格可靠,又能够方便地应用于低能电子在水中径迹结构的模拟.     

On evaporation residue cross sections producing nuclei with Z=104−120

A phenomenological method to predict the evaporation residue cross section in the superheavy mass region is presented. It makes us possible to understand what are the main contributors to the cross section and to perform a systematic analysis for understanding the fusion-fission mechanism by finding a deviation from the average property by means of this method.     

掺镱硼酸盐激光玻璃的光谱性质

测试了掺镱硼酸盐玻璃的吸收光谱和荧光光谱;计算了掺镱硼酸盐玻璃光谱参数;计论了网络修饰体种类、Ｂ２Ｏ３含量和高价离子Ｌａ＾３＋、Ｔｉ＾４＋、Ｎｂ＾５＋、Ｔａ＾５＋氧化物的引入对掺镱硼酸盐玻璃光谱性质的影响,通过两种不同的方法对其受激发射截面进行计算,对结果进行了比较和分析。     

氢及其同位素分子的电子碰撞解离反应截面研究

在边界等离子体中氢及其同位素分子与电子碰撞可以发生解离反应。对于尚无反应截面的氢及其同位素分子电子碰撞激发到三重态然后发生解离反应,作者基于莫尔斯函数、弗兰克－康登原理,采用半经典的Gryzinski方法计算了这一反应截面。得到了解离反应截面的影响因素、反应截面随电子能量的变化情况以及分子的振动能级对反应截面的影响。通过比较表明到排斥态的激发然后发生解离反应的反应截面占据主导地位,比激发到其它三重态激发然后发生解离的反应截面要大一个量级。     

Two-photon absorption and laser photolysis of trans-stilbene substitutes

The measured the two-photon absorption (TPA) cross sections of ethanol solution of trans-stilbene and its two substitutes excited by nanosecond radiation of the 2nd harmonic of a Nd:YAG laser (532 nm) are presented. To determine the TPA cross section, a method based on measurements of photochemical decomposition of molecules of the examined compounds having low photostability is suggested. The measured value of the TPA cross section of trans-stilbene in ethanol is found to be 25 GM, and the TPA cross sections of the trans-stilbene substitutes are found to be 60 and 70 GM. The TPA cross section of trans-stilbene substitutes obtained in the present paper is compared with the experimental and theoretical data obtained by other authors. The results of investigations demonstrate that the photochemical decomposition method can be successfully used to determine experimentally the two-photon absorption cross section of the compounds unstable under photoexcitation, including photochromatic molecules, biological objects, and radical photoinitiators.     

Measurement of the laser beam intensity distribution using optical tomography

Optical tomography is proposed as a method for studying the intensity distribution in the laser beam cross section. The tomographic projection of the beam cross section is obtained with the help of an optical fiber possessing a high radiation resistance, which makes it possible to employ this technique for studying high-power laser radiation. The results of tomographic reconstruction of the bean cross section from experimental projections are compared with the results of reconstruction from model projections.     

On the calculation of scattering cross sections from absorption cross sections

A dispersion-type relation between photon scattering and absorption cross sections is derived. It is shown that the relation gives the correct scattering cross section in the low and high frequency limits, and is consistent with the Kramers-Heisenberg formula in the vicinity of a resonance. The practical application of the relation is illustrated by calculations of the scattering cross section and refractive index of He and Ne at STP and dry air at 1200°K from known absorption cross section data. The method is useful for obtaining scattering cross sections, polarizabilities, and refractive indices at elevated temperatures.     

间接测量中重放射性核中子俘获截面——替代比率法

s过程中的放射性核素中子俘获截面对天体核合成和核素丰度有重大影响, 在直接测量异常困难的情况下, 替代比率法是获得放射性核素中子俘获截面数据的一种间接新方法。 简单介绍了替代比率法理论, 并简要论述了用替代比率法推导中重核区放射性核素中子俘获截面的可行性。 The radioactive nuclei neutron capture cross section is very important to nuclearsynthesis and nuclide abundance in s process, but it is difficult to be measured directly because of the target production. A new method, surrogate ratio method which is developed from surrogate method, could be used to determine the cross section of radioactive nuclei neutron capture. In this paper, the surrogate ratio method was introduced and the feasibility was discussed to deduce the desired neutron capture cross sections with surrogate ratio method.     

类硼离子N^2＋的电子碰撞电离—单通道截面的共振增加

使用Ｒ－矩阵方法，在库仑－玻恩非交换近似下（ＤＣＢＮＸ）采用三态密耦图象，计算了类硼离子Ｎ２＋的电子碰撞电离截面，并给出了总的能量微分截面及分波能量微分截面。计算结果揭示了明显的Ｒｙｄｂｅｒｇ系列共振，并指出共振对截面的贡献大于直接电离过程对截面的贡献，这与Ｃｈｉｄｉｃｈｉｍｏ的结论一致。     

Viscoplastic flows in channels with variable cross section and deformable walls

A longitudinal axially symmetric Shvedov-Bingham medium flow in a deformable vessel is studied. A formulation of the problem in terms of the integral characteristics of the channel cross section (radius, flow rate, rigid core radius in the cross section, core velocity, and average pressure in the cross section) is pro- posed. The problem of a steady flow in a confuser and the problem of medium acceleration in a cylinder are solved using the integral method.