April 15-17

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Author: Roscoe White
Requested Type: Pre-Selected Invited
Submitted: 2019-01-02 10:29:04

Co-authors: V.N. Duarte, N.N. Gorelenkov, G. Meng

Contact Info:
Princeton Plasma Physics Laboratory
Princeton University
Princeton, NJ   08543
US

Abstract Text:
The phase-space structure of resonances between fast ions and an Alfvenic mode
and the associated modification of density profiles in tokamaks
are studied as a function of particle collisions. Guiding-center simulations
in a realistic tokamak equilibrium are employed to address the resonance
broadening parametric dependencies with respect to changes in the
pitch-angle scattering rate. The rate of collisional replenishment,
along with resonance strength, given by the combination of eigenmode and resonance structures and equilibrium parameters, determine saturation amplitudes for a given damping rate. As seen from the distribution function flattening, collisions have an effect of broadening the resonances while the absolute value of delta f decreases with increasing collisionality. It is observed that the collisional broadening can be
comparable to the collisionless resonance width due to the mode
amplitude alone. The resonance broadening coefficients are compared with the existing theory based on analytically expected saturation levels, showing fair agreement. The results can be useful in assisting reduced kinetic
models, such as quasilinear models, when prescribing the effective resonance phase-space width i.e., the mode-particle interaction platform, due to collisional or turbulent processes.

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