基于Geant4的反应堆临界及动态计算方法

Geant4是一款基于C++面向对象技术的蒙特卡罗开发程序包,可以模拟各种已知粒子与物质之间的相互作用。然而该程序包没有提供临界源功能,无法直接用于反应堆物理计算。因此,利用Geant4提供的基础物理模型和粒子跟踪控制等功能,用两种不同方法实现了临界源的设置,实现了基于Geant4的反应堆静态计算程序G4-RSM和反应堆动态计算程序G4-RDM。两个程序均可用于反应堆临界计算,与MCNP计算结果相对误差在5%以内。G4-RDM程序除可用于临界计算外,还可用于模拟堆内事故工况下的中子学瞬态变化。     

高温反应堆瞬发中子代时间计算

高温核反应堆在磁流体发电和核火箭等领域有良好的应用前景。高温反应堆具有堆芯温度高、结构复杂等特点,其中子物理性能参数的计算难度较大。研究了高温核反应堆瞬发中子代时间的计算方法,介绍了多种方法的计算原理和一种新型高温核反应堆的计算结果。研究表明,对于相同的反应堆模型,几种方法的计算结果符合较好,计算结果可信。     

高温反应堆瞬发中子代时间计算

高温核反应堆在磁流体发电和核火箭等领域有良好的应用前景。高温反应堆具有堆芯温度高、结构复杂等特点,其中子物理性能参数的计算难度较大。研究了高温核反应堆瞬发中子代时间的计算方法,介绍了多种方法的计算原理和一种新型高温核反应堆的计算结果。研究表明,对于相同的反应堆模型,几种方法的计算结果符合较好,计算结果可信。     

用Geant4对相对论电子的动能与动量关系测量实验的模拟与拓展

基于蒙特卡罗方法的Geant4计算机模拟软件平台,对传统的相对论实验进行模拟,实验直观而形象,数据精准可信,有助于学生加深理论知识和实验内容的理解.     

基于Geant 4的介质深层充电电场计算

基于Geant4模拟了电子在Teflon介质中的电荷输运过程,获得了其内部的电流密度、剂量率和电荷沉积量沿深度的分布曲线,进而利用电荷连续性方程、泊松方程和深层俘获方程求解出Teflon中高能量、小束流电子辐照下的电场分布. 将介质平板充电过程简化为屏蔽铝板与分层介质组成的Geant4模型,电子源为1.0MeV,0.1pA/cm²的平面源. 通过记录经过各层介质的电子电量和各层介质内沉积能量和电子数目,用统计平均的方法获得了介质内电流密度、剂量率和电荷沉积量沿深度的分布规律. 介质内 关键词： 卫星 介质深层充电 Geant4 电场     

400~1500 MeV质子轰击铅靶和钨靶的出射中子能谱的FLUKA和Geant4模拟研究

在ADS散裂靶系统的优化设计中,蒙特卡罗方法结合可靠的散裂反应理论模型进行中子学计算具有重要的作用。本工作利用Geant4程序中的INCLXX模型、BIC模型以及BERT模型和FLUKA程序分别模拟了597 MeV和1 500 MeV质子轰击薄铅靶不同出射角度的中子双微分截面,500,1 500 MeV质子轰击厚铅靶不同出射角度的中子双微分产额,以及400,600,800,1 000和1 200 MeV质子轰击厚钨靶在反角方向（175 °）的中子双微分产额,并与实验数据进行比较。研究表明,对于薄铅靶,Geant4程序的INCLXX模型和FLUKA程序模拟结果与实验符合得更好。能量在10～40 MeV范围内,BIC模型模拟结果明显高于实验数据,而BERT模型模拟结果略微低于实验数据。对于厚铅靶,在40 MeV左右所有的模拟结果都低于实验数据。对于厚钨靶,Geant4程序的BIC模型和FLUKA程序与实验数据符合得较好,INCLXX模型在能量高于60 MeV时模拟结果低于实验数据,BERT模型与实验数据差异较大。总体来看,Geant4程序的INCLXX模型和FLUKA程序进行ADS散裂靶相关的中子学的计算是合理和可靠的。The reliable Monte Carlo simulation codes coupled with nuclear reaction models play an important role in the neutronic calculation for the design and optimization of the ADS spallation target. In this work, the double differential cross sections at different angles produced from a thin lead target bombarded with 597 and 1 500 MeV protons, the neutron energy spectra at different angles produced from a thick lead target bombarded with 500 and 1 500 MeV protons, and the neutron energy spectra in the backward direction(175°) produced from a thick tungsten target bombarded with 400, 600, 800, 1 000 and 1 200 MeV protons are calculated with the Geant4 code coupled INCLXX, BIC and BERT models and the FLUKA code. The calculations are compared with the available experimental data. The results show that, for the thin lead target, the calculations with the Geant4 coupled INCLXX model and FLUKA code well reproduce the experimental results. In a energy range from 10 to 40 MeV, BIC model obviously overestimates the experimental results, and BERT model slightly underestimates the experimental results. For the thick lead target, all of the calculations underestimate the experimental results around 40MeV. For the thick tungsten target, the Geant4 coupled BIC model and FLUKA code well reproduce the experimental results. INCLXX model underestimates the experimental results above 60 MeV. BERT model bad reproduces the experimental results. Overall, the neutronic calculations with the Geant4 code coupled INCLXX model and FLUKA code for the ADS spallation target is reasonable and reliable.     

基于Geant4的回旋加速器束流动力学计算

针对回旋加速器的束流动力学设计,基于Geant4模拟研究,提供一种可行的数值模拟方法。通过电磁场仿真软件Opera建立相应的电磁场数据导入到Geant4中进行插值计算,利用Geant4自带的电磁场微分方程与微分方程求解器计算粒子的平衡轨道,振荡频率以及加速轨道。其结果表明:对于横向运动而言,Geant4的计算结果与传统数值方法计算结果趋于一致;对于轴向运动而言,由于磁场插值方法的差异性,二者有一定的区别,对于在加速过程中的非平衡粒子,其能量变化围绕平衡粒子振荡。对于束损,通过限制粒子的运动时间,轴向位移加快计算效率,加入电极碰撞的判定使模拟更趋近实际情况。     

多物理耦合计算中动态输运问题高效蒙特卡罗模拟方法

多物理耦合计算在众多领域都有重要应用.如果其包含粒子输运过程,用蒙特卡罗方法模拟粒子输运常占据大部分的计算时间,因此多物理耦合计算中动态输运问题的高效蒙特卡罗模拟方法意义重大,其不可避免地依赖于大规模并行.基于动态输运问题的特点,本文提出了两种新方法:一是针对输运燃耗耦合计算的新型计数规约算法;二是动态输运计算样本数自适应算法.两种算法都能在保持计算结果基本不变的前提下使计算时间大幅减少,从而提高了效率.     

基于Geant4的卢瑟福散射计算机模拟

利用Geant4对卢瑟福散射实验进行仿真模拟,改变模拟过程中的相关参数以达到不同实验条件的要求。对模拟过程中收集的数据进行分析得到的结果符合卢瑟福散射关系式。这说明利用计算机模拟卢瑟福散射实验是可行的。本文中的实验对大学物理实验教学的开展有很大的意义。     

基于MCNP计算结果的快速物理插值方法（英）

在核辐射科学研究中经常使用MCNP蒙卡计算程序,但其计算结果只是给定位置的物理量。为了快速获得计算点附近的感兴趣位置处的值,本研究建立了一种3点插值计算方法。首先分析了粒子在材料中输运的物理规律,给出了满足3点插值的空间范围,建立了插值计算模型。然后利用距离平方反比权重法,结合粒子衰减规律,推导了插值计算公式。最后设计了计算机程序,并用X射线屏蔽后注量的MCNP计算结果进行验证。通过和直接采用的距离平方反比权重法和克里金插值法对比,考虑物理作用机制的该计算方法精度更高,且误差在10%以内。     

Iterative methods for solving nonlinear problems of nuclear reactor criticality

The paper presents iterative methods for calculating the neutron flux distribution in nonlinear problems of nuclear reactor criticality. Algorithms for solving equations for variations in the neutron flux are considered. Convergence of the iterative processes is studied for two nonlinear problems in which macroscopic interaction cross sections are functionals of the spatial neutron distribution. In the first problem, the neutron flux distribution depends on the water coolant density, and in the second one, it depends on the fuel temperature. Simple relationships connecting the vapor content and the temperature with the neutron flux are used.     

临界-燃耗耦合计算方法

基于蒙特卡罗模拟方法,采用MCNP的多群计算程序模拟中子输运方程,并与栅元均匀化程序WIMS耦合,实现了临界-燃耗耦合计算。具体过程是：首先扩展MCNP的多群功能,将其能群扩展为69群;然后,由接口程序将WIMS程序产生69群共振、自屏宏观中子截面转化为ACE格式的多群截面;其次,将新产生的多群截面提供给MCNP,完成临界-燃耗计算;最后,利用此耦合程序进行了基准题校核计算以及实验对比。计算结果表明,此耦合程序是可靠和正确的。     

临界-燃耗耦合计算方法

基于蒙特卡罗模拟方法,采用MCNP的多群计算程序模拟中子输运方程,并与栅元均匀化程序WIMS耦合,实现了临界-燃耗耦合计算。具体过程是:首先扩展MCNP的多群功能,将其能群扩展为69群;然后,由接口程序将WIMS程序产生69群共振、自屏宏观中子截面转化为ACE格式的多群截面;其次,将新产生的多群截面提供给MCNP,完成临界-燃耗计算;最后,利用此耦合程序进行了基准题校核计算以及实验对比。计算结果表明,此耦合程序是可靠和正确的。     

Monte Carlo simulation based on Geant4 of single event upset induced by heavy ions

The present work is a computational simulation of single event upset(SEU) induced by heavy ions passing through the device with Geant4-tool based on Monte Carlo transport code.Key parameters affecting SEU occurrence are examined,and related geometrical construction and critical charge are quantified.The MUlti-Functional Package for SEU Analysis(MUFPSA) has been successfully programmed and applied for SEU occurrence after the completion of device geometrical construction,critical charge,and SEU cross section calculation.The proposed MUFPSA has yielded a good agreement with MRED.Specifically,the results show that higher LET incident ions lead to increased SEU vulnerability due to more diffusion and higher energy deposition.In addition,the analytical method of radial ionization profile provides a good complementary interpretation.     

Experimental spectra analysis in THM with the help of simulation based on the Geant4 framework

The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles at astrophysical energies. The Trojan-horse method (THM) has been introduced to solve the difficulties as a powerful indirect tool. In order to understand experimental spectra better, Geant4 is employed to simulate the method. Validity and reliability of simulation data are examined by comparing the experimental data with simulated results. The Geant4 simulation of THM improves data analysis and is beneficial to the design for future related experiments.     

Integration of Geant4 with the Gaudi Framework

The GAUDI software framework is to be used for all event-processing applications in the LHCb experiment.The GEANT4 toolkit has been integrated into GAUDI to form the basis of the LHCb simulation program GAUSS.The benefits of this approach are that it permits re-use of basic services,such as persistency,interactivity and data visualization,as well as physics algorithms that were originally developed in the context of the reconstruction and analysis programs.Following the GAUDI philosophy,the integration has been achieved by developing a number of services with abstract interfaces that can be plugged in at run-time.We describe the overall design and details of the components for interfacing the detector geometry,the primary interaction and the output from tracking particles through the detector.