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Title: Interpretation of fast-ion signals during beam modulation experiments

Fast-ion signals produced by a modulated neutral beam are used to infer fast-ion transport. The measured quantity is the divergence of perturbed fast-ion flux from the phase-space volume measured by the diagnostic, ∇•$$\bar{Γ}$$. Since velocity-space transport often contributes to this divergence, the phase-space sensitivity of the diagnostic (or “weight function”) plays a crucial role in the interpretation of the signal. The source and sink make major contributions to the signal but their effects are accurately modeled by calculations that employ an exponential decay term for the sink. Recommendations for optimal design of a fast-ion transport experiment are given, illustrated by results from DIII-D measurements of fast-ion transport by Alfv´en eigenmodes. Finally, the signal-to-noise ratio of the diagnostic, systematic uncertainties in the modeling of the source and sink, and the non-linearity of the perturbation all contribute to the error in ∇•$$\bar{Γ}$$.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [2]
  1. Univ. of California, Irvine, CA (United States)
  2. General Atomics, San Diego, CA (United States)
Publication Date:
OSTI Identifier:
1354784
Grant/Contract Number:
FC02-04ER54698
Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 11; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Research Org:
Univ. of California, Irvine, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; fast-ions; transport analysis; phase-space transport; perturbative experiments; Alfvén eigenmode instabilities