Subcyclotron Instability of Alfven Eigenmodes due to Energetic Ions in Low Aspect Ratio Plasmas

Gorelenko, N.N. ; Fredrickson, E. ; Belova, E. ; Cheng, C.Z. ; Gates, D. ; White, R.

Princeton University. Plasma Physics Laboratory.

关键词: Beam Plasma Interactions;    Tail Ions;    Spherical Tokamak;    Cyclotron Resonance;    70 Plasma Physics And Fusion Technology;   

DOI  :  10.2172/814748
RP-ID  :  PPPL-3857
RP-ID  :  AC02-76CH03073
RP-ID  :  814748

美国|英语

来源: UNT Digital Library

【 摘 要 】

High-frequency modes with frequencies below the fundamental cyclotron frequency of thermal ions were observed in the National Spherical Torus Experiment (NSTX). Based on the measured spectrum of high-frequency modes they are identified as Compressional Alfven Eigenmodes (CAEs) and Global Alfven Eigenmodes (GAEs). CAEs have similar time evolution as plasma parameters change, while GAEs may intersect due to q-profile relaxation. A theory has been developed to study the properties of these modes. Both types of instabilities are driven by the tangential neutral-beam injection in NSTX. Beam ions excite CAEs/GAEs through the Doppler-shifted cyclotron resonance. The main source for the drive is the velocity space anisotropy of the beam ion distribution function. Simulations of the effect CAEs/GAEs may have on plasma ions indicate that these modes may provide a channel for efficient energy transfer from fast ions directly to thermal ions.