β-Suppression of Alfvén 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

Princeton University. Plasma Physics Laboratory.

关键词: Nstx;    Forecasting;    70 Plasma Physics And Fusion Technology;    Acoustics;    Geodesics;   

RP-ID  :  PPPL-4253
RP-ID  :  DE-ACO2-76CHO3073
RP-ID  :  962716

美国|英语

来源: UNT Digital Library

【 摘 要 】

The coupling of Alfvén Cascade (AC) modes or reversed-shear Alfvén 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.