β-Suppression of AlfvÊn Cascade Modes in the National Spherical Torus Experiment

Fredrickson, E D ; Gorelenkov, N N ; Heidbrink, W W ; Kubota, S ; Levinton, F M ; Yuh, H ; Menard, J E

关键词: ACOUSTICS;    ELECTRONS;    FORECASTING;    GEODESICS;    REVERSED SHEAR;    SHEAR NSTX;   

DOI  :  10.2172/962716
RP-ID  :  PPPL-4253
PID  :  OSTI ID: 962716
Others  :  TRN: US0903676

学科分类：原子、分子光学和等离子物理

美国|英语

来源: SciTech Connect

【 摘 要 】

The coupling of AlfvÊn Cascade (AC) modes or reversed-shear AlfvÊn eigenmodes (rsAE) to Geodesic Acoustic Modes (GAM) implies that the range of the AC frequency sweep is reduced as the electron β is increased. This model provides an explanation for the otherwise surprising absence of AC modes in reverse shear NSTX plasmas, given the rich spectrum of beam-driven instabilities typically seen in NSTX. In experiments done at very low β to investigate this prediction, AC modes were seen, and as the βe was increased from shot to shot, the range of the AC frequency sweep was reduced, in agreement with this theoretical prediction.