Linear gyrokinetic analysis of a DIII-D H-mode pedestal near the ideal ballooning threshold
Linear gyrokinetic analysis of a DIII-D H-mode pedestal near the ideal ballooning threshold
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DOI：
10.1088/0029-5515/52/10/103015
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发表时间：
2012-09
期刊：
影响因子：
3.3
通讯作者：
E.H.-J. Wang;X. Xu;Jeff Candy;R. Groebner;P. Snyder;Yang Chen;S. Parker;W. Wan;G. Lu
中科院分区：
文献类型：
--
作者：
E.H.-J. Wang;X. Xu;Jeff Candy;R. Groebner;P. Snyder;Yang Chen;S. Parker;W. Wan;G. Lu
GYRO的最新进展允许模拟以低计算成本绘制出陀螺动力学方程的许多特征值和特征向量的线性稳定性（而不是仅最不稳定的）。在这项工作中，GYRO的新的线性功能被应用到一个压力扫描的底座区域的DIII-D拍摄131997。MHD计算在无限n极限的理想气球模式，在非常成功的EPED模型预测基座的高度和宽度，表现出明显的不稳定性在70%的实验压力。GYRO结果首次表明，在基座的顶部，离子温度梯度驱动模和微撕裂模占主导地位，而在基座的峰值梯度区，一组未命名的漂移波是最不稳定的.峰值梯度模具有非常扩展的气球结构，峰值靠近内侧中平面，并且即使对于非常低的波数（kθρs <$0. 2），漂移频率也在电子抗磁漂移方向上或附近。通过证明动力气球模式（KBM）是存在的，但在DIII-D基座次主导的连接到MHD的计算，和KBM在回旋极限的开始所需的压力是在接近协议与MHD的预测。最后，GYRO与两个独立的陀螺动力学代码，GEM（初始值）和HD 7（一维特征值）的比较和分析。
Recent advances in GYRO allow simulations to map out the linear stability of many eigenvalues and eigenvectors of the gyrokinetic equation (as opposed to only the most unstable) at low computational cost. In this work, GYRO's new linear capabilities are applied to a pressure scan about the pedestal region of DIII-D shot 131997. MHD calculations in the infinite-n limit of the ideal ballooning mode, used in the very successful EPED model to predict pedestal height and width, demonstrate clear onset of the instability at 70% of the experimental pressure. Presented GYRO results first demonstrate that the ion temperature gradient driven mode and microtearing mode are dominant at the top of the pedestal, while an unnamed group of drift waves are found to be most unstable in the peak gradient region of the pedestal. The peak gradient modes have very extended ballooning structure, peak near the inboard midplane and have drift frequencies at or near the electron diamagnetic drift direction, even for very low wavenumbers (kθρs ∼ 0.2). Connection is made to the MHD calculations by demonstrating the kinetic ballooning mode (KBM) is present but subdominant in the DIII-D pedestal, and the pressure required for onset of the KBM in the gyrokinetic limit is in near agreement with MHD predictions. Finally, comparisons and analysis of GYRO with two independent gyrokinetic codes, GEM (initial value) and HD7 (1D eigenvalue), are presented.