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Theory of continuum damping of toroidal Alfven Eigenmodes in finite-{beta} tokamaks

Technical Report ·
DOI:https://doi.org/10.2172/10160858· OSTI ID:10160858

We have formulated a general theoretical approach for analyzing two-dimensional structures of high-n Toroidal Alfven Eigenmodes (TAE) in large aspect-ratio, finite-{beta} tokamaks. Here, n is the toroidal wave number and {beta} is the ratio between plasma and magnetic pressures. The present approach generalizes the standard ballooning-mode formalism and is capable of treating eigenmodes with extended global radial structures as well as finite coupling between discrete and continuous spectra. Employing the well-known (s,{alpha}) model equilibrium and assuming a linear equilibrium profile, we have applied the present approach and calculated the corresponding resonant continuum damping rate of TAE modes. Here, s and {alpha} denote, respectively, the strengths of magnetic shear and pressure gradients. In particular, it is found that there exists a critical {alpha}{sub c}(s), such that, as {alpha} {yields} {alpha}{sub c}, the continuum damping rate is significantly enhanced and, thus, could suppress the potential TAE instability.

Research Organization:
Princeton Univ., NJ (United States). Plasma Physics Lab.
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
AC02-76CH03073
OSTI ID:
10160858
Report Number(s):
PPPL--2908; ON: DE93014598
Country of Publication:
United States
Language:
English