Numerical Modeling of a Magnetic Flux Compression Experiment

A possible plasma target for Magnetized Target Fusion (MTF) is a stable diffuse z-pinch in a toroidal cavity, like that in MAGO experiments. To examine key phenomena of such MTF systems, a magnetic flux compression experiment with this geometry is under design. The experiment is modeled with 3 codes: a slug model, the 1D Lagrangian RAVEN code, and the 1D or 2D Eulerian Magneto-Hydro-Radiative-Dynamics-Research (MHRDR) MHD simulation. Even without injection of plasma, high-Z wall plasma is generated by eddy-current Ohmic heating from MG fields. A significant fraction of the available liner kinetic energy goes into Ohmic heating and compression of liner and central-core material. Despite these losses, efficiency of liner compression, expressed as compressed magnetic energy relative to liner kinetic energy, can be close to 50%. With initial fluctuations (1%) imposed on the liner and central conductor density, 2D modeling manifests liner intrusions, caused by the m = 0 Rayleigh-Taylor instability during liner deceleration, and central conductor distortions, caused by the m = 0 curvature-driven MHD instability. At many locations, these modes reduce the gap between the liner and the central core by about a factor of two, to of order 1 mm, at the time of peak magnetic field.     

Magnetic Field and Inductance Calculations in Theta-Pinch and Z-Pinch Geometries

Two codes have been developed to model solid metal or wire-wound conductors. The calculations are based on the decomposition of the conductors into arrays of thin wires. The first code, EDDY, models cylindrically symmetric conductors with currents in the theta direction. This code accurately models eddy current induction and magnetic diffusion. It was created in order to aid the design of magnetic-field shields in the FRX-L experiment for Magnetized Target Fusion (MTF). EDDY uses fast, accurate elliptic integral subroutines from MATLAB to solve for the time-dependent current flowing through each wire loop and the resultant magnetic field configuration. The second code, INDIV, models arbitrarily shaped conductors with current flow in the z direction. It was designed to model current division in an inductive divider that would inject current into a liner cavity, for magnetic flux and magnetized-plasma compression experiments. An experiment has been performed to test the INDIV code and the inductive division concept. The numerical results compare well with those of the experiment.     

Tendency of MHD Forces to Create Localized, Collimated Plasma-filled Flux Tubes & Ion Orbit Instability in a Flux Tube

Electrostatic helicity injection involves the injection of new azimuthal magnetic flux to link the existing axial flux of an open magnetic field. Since magnetic flux is frozen into plasma, this injection of new flux requires the injection of new plasma as well. This associated plasma injection means that helicity injection involves an increase of the density in the flux tube comprised by the initial open magnetic field lines. The injection of plasma and its embedded magnetic flux results in a collimation of the open flux tube when the embedded magnetic flux becomes compressed due to flow stagnation. Plasma injection occurs in the form of jets originating from biased electrodes having plasma sources. These jets can originate from both cathodes and anodes. An ion orbit instability may occur for cathode-originating jets. In cathode-originating jets the ions move opposite to the direction of the conventional current and so experience an anti-pinch force which can be strong enough to overwhelm the usual magnetic force responsible for cyclotron orbit motion.     

临界热流密度实验研究进展

临界热流密度是重要的限制性热工参数，它的大小直接影响反应堆的安全性和经济性。本文介绍了我国核电站临界热流密度实验研究进展，比较了国外核电站临界热流密度研究发展状况，文章认为，我国临界热流密度实验研究的发展方向是进行全长棒束非均匀加热临界热流密度的实验研究。     

The Pulsed High Density Experiment: Concept, Design, and Initial Results

An experimental program has been initiated that will explore the very compact, high energy density regime of fusion based on the magneto-kinetic compression of the FRC. Of all fusion reactor embodiments, only the FRC has the simply-connected closed field, linear confinement geometry, and intrinsic high β required for magnetic fusion at high energy density. PHD takes advantage of the linear confining geometry by incorporating a traveling, burning plasmoid, significantly reducing the wall loading as well as keeping the formation well separated from the burn chamber. Being small, compact, and at high β greatly improves the exposed surface to reacting volume ratio. Being pulsed eliminates the need for flux sustainment, and provides for regulation of the average wall loading. A wide range of reactor scenarios are compatible with PHD including liquid metal walls with the prospect of direct energy conversion through cyclical wall compression/expansion.     

Nonlinear Simulations of Coalescence Instability Using a Flux Difference Splitting Method

A flux difference splitting numerical scheme based on the finite volume method is applied to study ideal/resistive magnetohydrodynamics. The ideal/resistive MHD equations are cast as a set of hyperbolic conservation laws, and we develop a numerical capability to solve the weak solutions of these hyperbolic conservation laws by combining a multi-state Harten-Lax-Van Leer approximate Riemann solver with the hyperbolic divergence cleaning technique, high order shock-capturing reconstruction schemes, and a third order total variance diminishing Runge-Kutta time evolving scheme. The developed simulation code is applied to study the long time nonlinear evolution of the coalescence instability. It is verified that small structures in the instability oscillate with time and then merge into medium structures in a coherent manner. The medium structures then evolve and merge into large structures, and this trend continues through all scale-lengths.The physics of this interesting nonlinear dynamics is numerically analyzed.     

脉冲中子测量中的准直器设计

为满足脉冲中子探测系统对辐射屏蔽的要求,在利用MCNP程序模拟计算准直孔分别为圆柱形直孔和锥形孔的屏蔽效果基础上,设计了圆柱形直孔+锥形孔的准直器结构,准直器采用铁35cm厚+聚乙烯20 cm厚+铅15 cm厚的组合材料。理论计算表明:该准直器用于反冲质子探测系统时,探测系统输出信号与干扰信号的比值大于10。     

脉冲堆快中子实验装置设计

本文利用蒙特卡罗方法和离散坐标法设计了满足器件辐照效应研究的脉冲堆快中子实验装置.采用SAND-Ⅱ多箔活化法和热释光剂量片法对装置参数进行了测试分析,验证了装置设计参数与实验测量值符合一致.     

卧式V型管管壁温度特性及临界热负荷的研究

本文对卧式Ｖ型管高压汽水两相流的传热特性进行了试验研究。根据试验得到了计算临界热负荷的关系式。该式可用来预测卧式Ｖ型管弯头上、下游部分的传热恶化条件，为沸腾燃烧锅炉中卧式Ｖ型坦管、锅炉炉膛出口凝渣管等的设计与运行提供了可靠依据。     

池式夹带高速区试验研究

发生失水事故后的压水堆内会产生池式夹带现象,这一现象将造成反应堆进一步失水,进而发生堆芯裸露或堆芯熔化等严重事故。Kataoka和Ishii于1983年开发的池式夹带模型在反应堆安全分析中被广泛使用,但十分保守。其中一个重要原因是模型中高速夹带区的试验数据极为有限且不确定性较大,导致该区的模型并不完善。本文介绍空气-水的池式夹带高速区试验,试验本体参考AP1000原型参数,本体内径为380 mm,高为2.2 m,由透明材料制作,供气流速为0.98~5.41 m/s。试验过程中的两相混合液位和夹带液体质量的测量分别使用导波雷达液位计和称重模块。本试验为夹带模型的高速区补充了数据,发展了现有的池式夹带高速区模型,并发现了在夹带高速区出现的夹带饱和现象。     

磁约束聚变“点火”装置中聚变中子测量

概述了大、中型托卡马克在D-D和D-T运行条件下聚变中子能谱和强度的测量的最新方法;推介了几种最新的聚变中子探测器和能谱仪及活化分析方法;评估了各种聚变中子探测器和能谱仪的优势,适用的范围和技术方面的局限性。对即将建成的HL-2A(中环流器二号A型)托卡马克的聚变中子的泄漏能谱和辐射强度的时、空分辨测量以及研究聚变中子在通过中子倍增剂过程中的能谱变化,在探测器方面提供了几种可供选择的技术方案。     

单棒垂直方形通道临界热流密度实验研究

采用R134a作为流体工质,对单棒垂直方形通道临界热流密度（CHF）进行了实验研究。流道横截面为19 mm×19 mm的方形通道,内置外径为9.5 mm的单根加热棒,用来模拟压水堆中典型栅元通道。实验工况通过流体模化方法覆盖了压水堆典型运行工况。实验结果表明,R134a在方形通道内的CHF参数趋势与圆管中水的CHF参数趋势相同,R134a可以替代水作为模化工质;通过对圆管Bowring关系式和Katto & Ohno关系式进行冷壁因子修正,可用于预测带有冷壁的方形通道的CHF;Katto的流体模化方法适用于带有冷壁的方形通道。      

暗物质实验网络读出数据获取软件设计

在ATLAS TDAQ框架的基础上,为暗物质实验开发了基于网络读出的数据获取软件。软件实现了高速数据读出,事例组装,数据波形零压缩和存盘等功能。论文最后对软件的运行情况进行了稳定性测试,软件的读出带宽可达到240MB/s,波形压缩比可达到150倍。     

不同流道间隙下矩形通道临界热流密度的实验研究

在氟利昂工质条件下,进行1~3 mm间隙的矩形通道临界热流密度(CHF)的实验研究。研究发现,在1~3 mm间隙的矩形通道内,随着压力的升高,CHF稍有下降;质量流速对CHF的影响呈非单调关系,在低含汽率区随着质量流速的增大,CHF增大;在高含汽率区,随着质量流速的增大,CHF减小;临界含汽量的增加导致CHF明显降低。综合分析表明,在本实验工况参数范围内,流道间隙范围为1~3 mm的矩形通道在相同的工况参数条件下,其CHF基本不受流道间隙的影响。     

冷冻靶封装套中辅助热流密度的优化

为研究达到控温要求的冷冻靶封装套辅助加热量,建立了带有屏蔽罩和暴风窗的冷冻靶的二维轴对称模型。考虑封装套外屏蔽罩辐射强度和封装套内填充气体压力对冷冻靶温度场的影响,利用FLUENT软件对冷冻靶温度场进行了数值模拟计算。结果表明：合理选择上、下辅助加热带的热流密度及其差值,可使靶丸外表面最大温差降至0.1 mK以下;辐射强度越强,气体压力越大,靶丸表面最大温差越大,为实现靶丸外表面温度均匀性要求所施加的上、下辅助热流密度的差值就应越大。     

Erosion of Pyrolytic Graphite and Ti-doped Graphite due to High Flux Irradiation

The erosion of pyrolytic graphite and titanium doped graphite RG-Ti above 1,780K was investigated by 5keV Ar beam irradiation with the flux from 4x10¹⁹ to 1x10²¹ m^?2·s^?1. The total erosion yields were significantly reduced with the flux. This reduction would be attributed to the reduction of RES (radiation enhanced sublimation) yield, which was observed in the case of isotropic graphite with the flux dependence of RES yield of φ^?0.26 (φ: flux) obtained in our previous work. The yield of pyrolytic graphite was roughly 30% higher than that of isotropic graphite below the flux of 10²⁰ m^?2·s^?1 whereas each yield approached to very close value at the highest flux of 1x10²¹ m^?2·s^?1. This result indicated that the effect of graphite structure on the RES yield, which was apparent in the low flux region, would disappear in the high flux region probably due to the disordering of crystal structure.

In the case of irradiation to RG-Ti at 1,780K, the surface undulations evolved with a mean height of about 3μm at 1.2×10²⁰ m^?2·s^?1, while at higher flux of 8.0×10²⁰ m^?2·s^?1 they were unrecognizable. These phenomena can be explained by the reduction of RES of graphite parts excluding Tic grains.     

水基磁性流体竖直加热棒下的池沸腾传热实验研究

研究了磁性微粒浓度、外加磁场对水基磁性流体在竖直加热棒加热情况下的沸腾传热影响;实验结果显示,磁性微粒浓度和外加磁场对磁性流体的沸腾换热有很大影响：对于中低浓度的磁性流体,存在一个最优的磁粒浓度,在该浓度下沸腾传热的强化效果最显著,施加磁场时,该结论仍然成立。施加磁场能强化磁性流体的沸腾传热。     

Design of Magnetic Measurement System on SUNIST Spherical Tokamak

A magnetic measurement system consisting of magnetic probes and flux loops for spherical tokamak SUNIST, is uniquely designed due to the strongly shaped plasma cross section and the narrow space near the central solenoid. Plasma equilibrium reconstruction with the current filament method is performed to determine the number and positions of the magnetic probes and flux loops, as well as their design precision required.     

中子反照效应实验理论设计

为深化中子反照效应的认识,获得宏观测量数据,本文开展了中子反照效应实验的理论设计,给出了反照效应分析的理论公式。采用两组不同的实验状态分别给出了直照能谱和反照能谱下两种核素反应率的测量结果,再通过某测点这两种核素反应率的测量实现反照影响的定量分析。分析认为,给出的理论公式和实验布局方案是有效的,获得实验测量数据后可给出中子反照效应的定量信息。     

聚变实验增殖堆氚系统设计研究(英文)

介绍了核工业西南物理研究院聚变实验增殖堆工程概要设计(FEB-E)中的氚系统设计研究。第一部分介绍包层氚增殖区的划分、几何尺寸、装料特征和用蒙特卡罗程序计算得到的液态锂中的氚浓度分布;第二部分描述根据聚变堆氚物理基础构造的氚循环系统,共分成 10 个子系统及它们之间氚的流程图。运用研制的程序SWITRIM 计算了各个子系统中的氚投料量随时间的变化,满功率运行一年后各个子系统中的氚投料量。研究结果表明起动 143 MW 聚变功率 FEB-E 堆所需要的初始氚投料量大约为 319 g。第三部分对不同的运行状态下的氚泄漏问题进行了分析。潜在的氚泄漏危险可能来自于偏滤器系统从等离子体中抽出的气体。得到的结论是提高FEB-E 堆芯等离子体的燃耗份额从而减少氚的通过量对降低氚的泄漏危险是重要的。