Excitation of High-n Toroidicity-induced Shear Alfven Eigenmodes by Energetic Particles and Fusion Alpha Particles in Tokamaks

Download or read book Excitation of High-n Toroidicity-induced Shear Alfven Eigenmodes by Energetic Particles and Fusion Alpha Particles in Tokamaks written by and published by . This book was released on 1992 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The stability of high-n toroidicity-induced shear Alfven eigenmodes (TAE) in the presence of fusion alpha particles or energetic ions in tokamaks is investigated. The TAE modes are discrete in nature and thus can easily tap the free energy associated with energetic particle pressure gradient through wave particle resonant interaction. A quadratic form is derived for the high-n TAE modes using gyro-kinetic equation. The kinetic effects of energetic particles are calculated perturbatively using the ideal MHD solution as the lowest order eigenfunction. The finite Larmor radius (FLR) effects and the finite drift orbit width (FDW) effects are included for both circulating and trapped energetic particles. It is shown that, for circulating particles, FLR and FDW effects have two opposite influences on the stability of the high-n TAE modes. First, they have the usual stabilizing effects by reducing the wave particle interaction strength. Second, they also have destabilizing effects by allowing more particles to resonate with the TAE modes. It is found that the growth rate induced by the circulating alpha particles increase linearly with toroidal mode number n for small?{sub?}?{sub?}, and decreases as 1/n for?{sub?}?{sub?} {much gt} 1. The maximum growth rate is obtained at?{sub?}?{sub?} on the order of unity and is nearly constant for the range of 0.7