FRC Simulations using the NIMROD Code

The Plasma Science and Innovation Center (PSI-Center) is benchmarking and refining the NIMROD code for simulations of field-reversed configurations (FRCs). The NIMROD code can resolve highly anisotropic heat conduction and viscosity (Sovinec et al., JCP 195:355, 2004). This combined with its ability to include two-fluid effects, allows us to capture more detailed physics than previous calculations. Recent modifications to the radial boundary conditions capture most of the effects of multiple discrete coils found in many FRC experiments. When the tangential electric field on the end boundaries (open field lines) is set to zero and the Hall term is included in the calculation, the open field-line plasma spins up due to end-shorting effects, which in turn couples to the main FRC plasma through shear viscosity. The spin-up rate is found to be sensitive to the open field-line plasma profile. We are also investigating recent observations (Guo et al., Phys. Rev. Lett. 95:175001, 2005] that imply that a small toroidal field could help stabilize the n = 2 rotational instability. We find that a combination of a relatively weak toroidal magnetic field and the inclusion of the Hall term in the calculation can lead to a change in the character of the mode and a dramatic reduction to its growth rate.     

High-Beta Steady-State FRC Plasma Sustained by Rotating Magnetic Field with Spatial High-Harmonic Components

Field-reversed configurations (FRCs) driven by rotating magnetic fields (RMFs) with spatial high-harmonic components have been studied in the metal flux conserver of the FRC injection experiment (FIX). The high-harmonic RMF method has some unique features; (1) field lines of the RMF do not penetrate or cross the vessel wall, (2) selective penetration/exclusion of the fundamental/high-harmonic RMF component will result in a generation of effective magnetic pressure near the separatrix, which helps to keep the separatrix away from the vessel wall, (3) strong azimuthal non-uniformity of the RMF will cause the n = 4 deformation of the core FRC plasma, which will eliminate the destructive modes caused by the rotation of the plasma column. The RMF method with high harmonics will provide quasi-steady current drive of high-beta FRC plasmas without destructive n = 2 rotational mode and will be helpful in reducing the particle loss and thermal load when applied to the fusion core plasma.     

Internal Magnetic Configuration Measured by ECE Imaging on EAST Tokamak

ECE imaging （electron cyclotron emission imaging） is an important diagnostic which can give 2D imaging of temperature fluctuation in the core of tokamak. A method based on ECE imaging is introduced which can give the information of the position of magnetic axis and the structure of internal magnetic surface for EAST tokamak. The EFIT equilibrium reconstruction is not reliable due to the absence of important core diagnostic at the initial phase for EAST, so the information given by ECE imaging could help to improve the accuracy of EFIT equilibrium reconstruction.     

Simulations of Reversed Shear Configuration in EAST

The reversed shear （RS） mode is one of the advanced configurations being considered in EAST. Predictive simulations of EAST reversed shear configuration are carried out using an 1.5D equilibrium evolution code. In order to have the desired monotonic q-profile during a tokamak discharge, a successful preparation phase is required. In our simulation, the plasma current is ramped up from 100 kA to a fiat-top maximum of 1.0 MA for four seconds. An ICRH power of 1 MW is applied until the plasma shape is formed at the moment of 4 s, and then the power is raised to 3 MW. A LHCD power of 3.5 MW is applied from ls to optimize the plasma current density profile. A series of simulations are performed to study the influence of the time of applying the auxiliary heating on the plasma parameters. Based on these simulations, a scheme is proposed and tested for the control of the safety factor profile, which is very useful in real time profile control in tokamak experiments.     

Preliminary Analysis of Advanced Equilibrium Configuration for the Fusion-Driven Subcritical System

The Fusion-Driven Subcritical System (FDS) is a subcritical nuclear energy system drived by fusion neutron source. In this paper, an advanced plasma configuration for FDS system has been proposed, which aims at high beta, high bootstrap current and good confinement. A fixed-boundary equilibrium code has been used to obtain ideal equilibrium configuration. In order to determine the feasibility of FDS operation, a two-dimensional time-dependent free boundary simulation code has been adopted to simulate time-scale evolution of plasma current profile and boundary position. By analyses, the Reversed Shear mode as the most attractive one has been recommended for the FDS equilibrium configuration design.     

三层熔池结构IVR分析程序开发及验证

目前对熔融物堆内滞留（IVR）进行分析时,主要采用两层熔池模型进行点估算分析。然而随着研究的深入,已有IVR分析程序不能准确模拟三层熔池模型。为此,本文采用三层熔池模型开发了模块化IVR分析程序SPIRE,并对计算结果进行了验证。结果表明,SPIRE程序的计算结果与文献结果吻合较好,适用于IVR分析。利用SPIRE程序进行分析可知,与两层熔池相比,三层熔池结构下压力容器底部和轻金属层热流密度均会有明显增强。敏感性分析结果表明,铀氧化份额和不锈钢总质量会显著影响热流密度分布及最大临界热流密度比。     

Linear and Nonlinear Development of the <Emphasis Type="Italic">m</Emphasis> = 0 Instability in Z-Pinch Equilibria with Axial Sheared Flows

The effect of sheared flows on the m = 0 instability development in a z-pinch is numerically investigated using a 2D magnetohydrodynamic (MHD) code. The behavior of both internal and free-boundary modes is studied by using two types of initial configurations: a diffuse Bennett equilibrium and a free-boundary parabolic equilibrium. It was found that sheared flows change the m = 0 development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. Full stability can be obtained for supersonic plasma flows, but a larger shear is needed to obtain stabilization of free-boundary modes.     

Investigation of ion fishbone stability on HL-2A using NIMROD

Numerical calculations of resistive internal kink mode with effects of energetic particles (EPs) on HL-2A have been performed using the hybrid kinetic-MHD model inplemented in the NIMROD code. The m/n=1/1 resistive internal kink mode is unstable in MHD limit. However, with kinetic effects of energetic ions, a fishbone mode is excited with mode frequency around 10 kHz. We calculate the impact of resistivity on the growth rate and frequency of ion fishbone mode, and the results are in good agreement with the analytic solutions, which are obtained by solving the fishbone dispertion relation including resistivity effect. The effects of β_frac and cut off velocity of EP on fishbone mode are calculated in detail, where β_frac is the ratio of EP pressure to background plasma pressure. This work presents a clear explanation of the stabilizing effect of ECRH on ion fishbone, which is first observed on HL-2A.     

技术状态项目和技术状态基线在核电设计项目中的确定

采用技术状态管理（CM ）可有效减少变更，控制项目成本。本文对技术状态项目和技术状态基线在红沿河二期项目上的确定进行了详细阐述，为实施技术状态管理奠定了基础。     

The Spatial Effects of Antenna Configuration in a Large Area Inductively Coupled Plasma System for Flat Panel Displays

Spatial distributions of plasma parameters such as electron density, electron temperature and electric potential were investigated using a commercial simulation software （COMSOLTM） to predict the effects of antenna configuration in a large area inductively cou- pled plasma （ICP） system for flat panel displays. Nine planar antenna sets were evenly placed above a ceramic window. While the electron density was influenced by both the input current and gas pressure, the electron temperature and electric potential were dominantly affected by the gas pressure.     

三维电场计算软件RELAX3D的前处理软件开发

针对电场计算软件RELAX3D的解场需要，用Fortran90如Visual Basic编写了前处理程序，实现了从中心区结构图到数据信息的自动生成。     

Benchmarks of 3D Laplace Equation Solvers in a Cubic Configuration for Streamer Simulation

The aim of this paper is to test a developed SOR R&B method using the Chebyshev accelerator algorithm to solve the Laplace equation in a cubic 3D configuration.Comparisons are made in terms of precision and computing time with other elliptic equation solvers proposed in the open source LIS library.The first results,obtained by using a single core on a HPC,show that the developed SOR R&B method is efficient when the spectral radius needed for the Chebyshev acceleration is carefully pre-estimated.Preliminary results obtained with a parallelized code using the MPI library are also discussed when the calculation is distributed over one hundred cores.     

等离子体电流反向平衡位形中带电粒子运动的数值模拟研究

本文采用数值方法求解Grad-Shafranov方程获得CT-6B交流放电实验总电流过零时的平衡位形和磁场分布,进而结合粒子在磁场中的运动方程,模拟氘离子在该平衡位形中的运动轨迹,统计氘离子的损失率与损失位置。结果表明：总电流过零时刻的平衡位形为内外两侧电流反向平衡位形,在强、弱场侧各存在1个磁岛,电流在磁岛附近取极值;位于强场侧的粒子几乎不损失,弱场侧的粒子在径向位置很大时存在损失,越靠近边界损失率越高;损失位置基本上位于赤道面以下并在最底部达到极值;随初始角变大,氘离子轨迹由通行轨迹变成损失轨迹再向香蕉轨迹演变。     

速度选择器电极结构的优化

速度选择器是束流传输的重要元件,电场的均匀性对速度选择器的性能有重要影响。本文利用有限元计算程序,对速度选择器的电极结构进行了优化。计算结果表明,通过对电极边缘区的优化,在不增大电极尺寸的情况下,可使优化后的均匀场区与具有均压结构的均匀场区范围接近。在速度选择器的设计中,利用优化的电极结构取代均压结构,可大幅简化速度选择器结构。     

The Influence of Magnetic Permeability on the Configuration of magnetic Field in Helimak Device

The Helimak of USA is a plasma physics experimental device designed and built by CASIPP.Its configuration of magnetic field is of very importance during the operation of this device.In this paper,the influence of magnetic permeability on configuration of magnetic field will be discussed due to the effect of weld metal in the vacuum vessel of Helimak,and some conclusion is useful for some engineering designs of the fusion experimental device.     

Simulation of Vacuum Arc Characteristics Under Four Kinds of Axial Magnetic Fields and Comparison with Experimental Results

Based on a two-dimensional axisymmetric magnetohydrodynamic （MHD） model, the vacuum arc characteristics under four kinds of axial magnetic fields （AMFs） are ana...     

ASTEC程序中反应堆熔池结构对压力容器下封头换热计算的影响

反应堆严重事故工况下堆内环境复杂,针对下腔室内熔融物行为的试验非常有限,因此通常采用假设的熔池结构模型进行事故评价。本文使用ASTEC程序中的3种熔池结构模型,评价典型严重事故工况下不同熔池结构对下封头内壁换热及压力容器完整性的影响。计算结果表明:在外壁绝热且下封头失效仅使用温度限值的条件下,两层熔池结构导致下封头失效时间最短,且由于顶部金属层集热效应,失效位置位于熔池上部;三层熔池结构由于底层金属层的出现,使下封头下部温度持续升高而发生失效,但其失效时间长于两层熔池结构的情况。     

运用MC3D程序计算分析堆坑内堆芯熔融物与冷却剂反应

简要介绍了国际上用于计算分析反应堆堆芯熔融物与冷却剂反应（FCI）的主要程序及其差异。随后,介绍了法国FCI计算分析程序MC3D的特点、验证和使用情况,以及运用MC3D程序计算分析反应堆压力容器外FCI的过程和结果,并总结了在MC3D程序使用过程中遇到的问题和解决办法。     

Numerical Simulation and Experimental Identification of Divertor Configuration in the HL-2A Tokamak

Single- and double-null divertor configurations in HL-2A are simulated by SWEQU equilibrium code. Lower divertor discharges in the first physics campaign have been achieved by two kinds of power supply method of multipole-field coils. Single-null divertor configuration has been identified by visible photography, target probe arrays and the reconstructed magnetic surface. Magnetic separatrix and minor radius of plasma column are obtained by a reconstructed code of multiple current filaments using 18 Mirnov signals.     

Simulations of H-Mode Plasmas in Tokamak Using a Complete Core-Edge Modeling in the BALDUR Code

A theory-based model for predicting the pedestal formation in both ion and electron temperatures,and hydrogenic and impurity density is developed and implemented in the 1.5D BALDUR codes for self-consistently simulating H-mode plasma in tokamak.In the simulation,the transports around pedestal,including the electron and ion thermal,hydrogenic and impurity particle transports are calculated using an anomalous semi-empirical mixed Bohm/gyro-Bohm (Mixed B/gB) model,which is modified to include the effects of ω E×B flow shear and magnetic shear.Because of the reduction of transport,the pedestal can be formed.For a preliminary test,this core-edge model is used to simulate the temporal evolution of plasma current,temperature,and density profiles for DIII-D discharges.It is found that the simulations successfully reproduce the experimental results.A statistical analysis,including RMSE and offset,is used to quantify the agreement between the prediction and the corresponding experimental results.The simulation results show an agreement with average RMSE of 11.87%,14.53%,7.59% and 12.21% for electron temperature,ion temperature,electron density,and deuterium density profiles,respectively.In addition,it is found that the suppression function developed is effective only in the edge region.