Analyses of Transport and Stability in Tokamaks with Hollow Current Profile

1.输运模型的改进将等离子体旋转效应引入到电流扩散气球模型的湍流输运模型中。使用这个新模型的输运模拟成功地再现了延迟过渡的内部输运势垒的形成，正如在实验中观察到的那样，我们还进行了包括粒子输运的输运模拟，以描述具有中空电流分布的内部输运势垒的形成。密度、温度和安全系数随时间的演化与实验观测结果吻合较好.电子回旋电流驱动的并行计算分析为了以更少的计算时间和更大的内存容量来模拟托卡马克等离子体的时间演化，我们开发了一个并行计算程序，该程序运行在由8台计算机组成的高速网络机群上。特别是对电子回旋加速器电流驱动程序（ASK/EC）进行了并行化 ...更多信息 D和用于研究维持空心电流分布所需的电流驱动。该程序包括磁流体平衡分析、波的传播分析和速度分布分析。离轴电流驱动是有效的，以维持空心电流分布和电流驱动效率进行了评估。在电子速度分布分析中，八处理器的计算时间减少到单处理器的1/5以下.本文用三维全波程序（ASK/WM）研究了空心电流分布托卡马克中Alfven本征模的线性稳定性。结果发现，除了环形诱导的阿尔芬本征模，全球阿尔芬本征模也有一个显着的作用，在一个反向的磁剪切配置。本征频率对电流分布的细节很敏感。这段代码也被并行化，用于分布式内存计算机集群。计算时间大大减少，存储空间大大增加。少

1. Improvement of Transport ModelThe effect of plasma rotation was introduced into the turbulent transport model of the current-diffusive ballooning mode. Transport simulations using this new model successfully reproduced the formation of internal transport barriers with delayed transition, as was observed in experiments, We have also carried out transport simulations including particle transport in order to describe the formation of internal transport barrier with a hollow current profile. Time evolution of density, temperature and safety factor is in good agreement with experimental observation.2. Analysis of Electron Cyclotron Current Drive with Parallel ProcessingIn order to simulate the time evolution of tokamak plasmas with less computation time and more memory size, we have developed a parallel computation code which runs on a computer cluster composed of 8 computers connected with high-speed network. Especially the electron cyclotron current drive code (TASK/EC) was parallelize … More d and employed to study the current drive required for maintaining the hollow current profile. The code includes the analyses of MHD equilibrium, wave propagation and velocity distribution. Off-axis current drive is effective to sustain the hollow current profile and the current drive efficiency was evaluated. In the analysis of electron velocity distribution, the computation time with 8 processors was reduced to less than 1/5 of that with single processor.3. Stability Analysis of Alfven EigenmodeLinear stability of Alfven eigenmodes in a tokamak with a hollow current profile was studied by the use of three-dimensional full wave code (TASK/WM). It was found that, in addition to the toroidicity-induced Alfven eigenmode, the global Alfven eigenmode has also a significant role in a reversed magnetic shear configuration. The eigen frequency is sensitive to the detail of the current profile. This code was also parallelized for a distributed-memory computer cluster. Considerable reduction of computation time and enlargement of memory space were achieved. Less