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Title: Phase-space dynamics of Alfvén mode chirping

Abstract

In tokamak discharges, toroidal Alfvén eigenmodes often experience complex semi-periodic frequency modulation known as chirping. These events modify the local high energy particle distribution and are expected to occur in many future fusion devices, which include energetic beams or fusion products. In this paper, we present a study of simulations of mode chirping made in order to better understand its phase-space properties in a realistic tokamak configuration. We find a mechanism that permits rapid repeated chirping with strong amplitude variation in each chirp. Each chirp is then associated with an amplitude crash to low magnitude and local manipulation of the density gradients through a shift of mode phase through π. The chirping produces high density clumps, which propagate down the fast ion density gradient and low density holes that propagate up the density gradient away from the resonance. This flow of particles across the resonance provides an energy source and local gradients for repeated chirping.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1643796
Grant/Contract Number:  
AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 27; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Frequency spectrum; dynamical systems; plasma dynamics; particle distributions; plasma waves; plasma confinement; signal processing; fusion reactors; tokamaks

Citation Formats

White, R. B., Duarte, V. N., Gorelenkov, N. N., Fredrickson, E. D., and Podesta, M. Phase-space dynamics of Alfvén mode chirping. United States: N. p., 2020. Web. https://doi.org/10.1063/5.0004610.
White, R. B., Duarte, V. N., Gorelenkov, N. N., Fredrickson, E. D., & Podesta, M. Phase-space dynamics of Alfvén mode chirping. United States. https://doi.org/10.1063/5.0004610
White, R. B., Duarte, V. N., Gorelenkov, N. N., Fredrickson, E. D., and Podesta, M. Thu . "Phase-space dynamics of Alfvén mode chirping". United States. https://doi.org/10.1063/5.0004610. https://www.osti.gov/servlets/purl/1643796.
@article{osti_1643796,
title = {Phase-space dynamics of Alfvén mode chirping},
author = {White, R. B. and Duarte, V. N. and Gorelenkov, N. N. and Fredrickson, E. D. and Podesta, M.},
abstractNote = {In tokamak discharges, toroidal Alfvén eigenmodes often experience complex semi-periodic frequency modulation known as chirping. These events modify the local high energy particle distribution and are expected to occur in many future fusion devices, which include energetic beams or fusion products. In this paper, we present a study of simulations of mode chirping made in order to better understand its phase-space properties in a realistic tokamak configuration. We find a mechanism that permits rapid repeated chirping with strong amplitude variation in each chirp. Each chirp is then associated with an amplitude crash to low magnitude and local manipulation of the density gradients through a shift of mode phase through π. The chirping produces high density clumps, which propagate down the fast ion density gradient and low density holes that propagate up the density gradient away from the resonance. This flow of particles across the resonance provides an energy source and local gradients for repeated chirping.},
doi = {10.1063/5.0004610},
journal = {Physics of Plasmas},
number = 5,
volume = 27,
place = {United States},
year = {2020},
month = {5}
}

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