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Title: Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

Excitation of Alfvén modes is commonly viewed as a concern for energetic particle confinement in burning plasmas. The 3.5 MeValpha particles produced by fusion may be affected as well as other fast ions in both present and future devices. Continuum damping of such modes is one of the key factors that determine their excitation thresholds and saturation levels. This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is largely motivated by the need to describe the continuum absorption in the frequency sweeping events. Akey element of this problem is the negative interference of the two closely spaced continuum crossing points.Weexplain why the lower and upper edges of the gap can have very different continuum absorption features. Lastly, the difference is associated with an eigenmode whose frequency can be arbitrarily close to the upper edge of the gap whereas the lower edge of the gap is always a finite distance away from the closest eigenmode.
Authors:
 [1] ;  [1] ;  [1] ;  [2]
  1. Univ. of Texas, Austin, TX (United States)
  2. DecisionNext Inc., San Francisco, CA (United States)
Publication Date:
OSTI Identifier:
1240265
Grant/Contract Number:
FG02-04ER54742
Type:
Accepted Manuscript
Journal Name:
New Journal of Physics
Additional Journal Information:
Journal Volume: 17; Journal Issue: 12; Journal ID: ISSN 1367-2630
Publisher:
IOP Publishing
Research Org:
Univ. of Texas at Austin, Austin, TX (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY