论文标题
球形tokamaks中的压缩和全球Alfven本征稳定性的理论和模拟
Theory and Simulations of Compressional and Global Alfven Eigenmode Stability in Spherical Tokamaks
论文作者
论文摘要
中性光束驱动的，亚周期性压缩（CAE）和全球（GAE）\ alfven eigenmodes通常会在诸如NSTX（-u）等球体tokamak中激发人们对常规的纵横倍率tokamak dokamak diiii-d-d，并且可能是在it buran buran buransmas中不稳定的。它们的存在与NSTX中远光灯功率下的电子温度曲线的异常平坦相关，可能会限制融合性能。因此，对CAE/GAE激发的详细理解对于预测（并最终控制）其对等离子体限制的影响至关重要。为此，混合动力学MHD模拟与CAES和GAE的线性稳定性特性的分析研究相辅相成。扰动，局部分析理论已被用来得出由现实中性束分布驱动的CAES/GAE的新不稳定性条件。已经为广泛的光束参数进行了一系列对NSTX样等离子体的模拟集，为球形Tokamaks中的CAE和GAE稳定性提供了丰富的信息。线性模拟表明，CAES vs Gaes的激发对快速离子注入速度和几何形状具有复杂的依赖性，这是本文中开发的分析理论的定性描述。在模拟中发现了GAE的强烈颗粒修饰，表明存在一种新型的高频能量粒子模式。理论稳定性界限，仿真结果和实验测量之间的交叉验证显示出对不稳定的CAE和GAE光谱对快速离子参数的依赖性的有利一致。该分析结果准确地解释了GAE稳定的最新实验发现，并在NSTX-U上使用少量的离轴束注射量少量，并在将来的实验中提出了对这些不稳定性控制的新技术。
Neutral-beam-driven, sub-cyclotron compressional (CAE) and global (GAE) \Alfven eigenmodes are routinely excited in spherical tokamaks such as NSTX(-U) and MAST, have been observed on the conventional aspect ratio tokamak DIII-D, and may be unstable in ITER burning plasmas. Their presence has been experimentally linked to the anomalous flattening of electron temperature profiles at high beam power in NSTX, potentially limiting fusion performance. A detailed understanding of CAE/GAE excitation, therefore, is vital to predicting (and ultimately controlling) their effects on plasma confinement. To this end, hybrid kinetic-MHD simulations are complemented with an analytic study of the linear stability properties of CAEs and GAEs. Perturbative, local analytic theory has been used to derive new instability conditions for CAEs/GAEs driven by realistic neutral beam distributions. A comprehensive set of simulations of NSTX-like plasmas has been performed for a wide range of beam parameters, providing a wealth of information on CAE and GAE stability in spherical tokamaks. Linear simulations show that the excitation of CAEs vs GAEs has a complex dependence on the fast ion injection velocity and geometry, qualitatively described by the analytic theory developed in this thesis. Strong energetic particle modifications of GAEs are found in simulations, indicating the existence of a new type of high frequency energetic particle mode. A cross validation between the theoretical stability bounds, simulation results, and experimental measurements shows favorable agreement for both the unstable CAE and GAE spectra's dependence on fast ion parameters. The analytic results accurately explain the recent experimental discovery of GAE stabilization with small amounts of off-axis beam injection on NSTX-U and suggest new techniques for control of these instabilities in future experiments.
