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Title: Blob-hole correlation model for edge turbulence and comparisons with NSTX gas puff imaging data [Blob-hole correlation model for edge turbulence and comparisons with NSTX GPI data]

We report that gas puff imaging (GPI) observations made in NSTX have revealed two-point spatial correlations of edge and scrape-off layer turbulence in the plane perpendicular to the magnetic field. A common feature is the occurrence of dipole-like patterns with significant regions of negative correlation. In this paper, we explore the possibility that these dipole patterns may be due to blob-hole pairs. Statistical methods are applied to determine the two-point spatial correlation that results from a model of blob-hole pair formation. It is shown that the model produces dipole correlation patterns that are qualitatively similar to the GPI data in several respects. Effects of the reference location (confined surfaces or scrape-off layer), a superimposed random background, hole velocity and lifetime, and background sheared flows are explored and discussed with respect to experimental observations. Additional analysis of the experimental GPI dataset is performed to further test this blob-hole correlation model. A time delay two-point spatial correlation study did not reveal inward propagation of the negative correlation structures that were postulated to correspond to holes in the data nor did it suggest that the negative correlation structures are due to neutral shadowing. However, tracking of the highest and lowest values (extrema) ofmore » the normalized GPI fluctuations shows strong evidence for mean inward propagation of minima and outward propagation of maxima, in qualitative agreement with theoretical expectations. Finally, other properties of the experimentally observed extrema are discussed.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ;  [1]
  1. Lodestar Research Corporation, Boulder, CO (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Report Number(s):
OE-ER/54678-12; DOE-ER/54392-89; LRC-18-174
Journal ID: ISSN 0741-3335
Grant/Contract Number:
FG02-02ER54678; FG02-97ER54392; AC02-09CH11466
Type:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 60; Journal Issue: 7; Related Information: http://arks.princeton.edu/ark:/88435/dsp01x346d687k; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Research Org:
Lodestar Research Corp., Boulder, CO (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (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; fusion; tokamak; scrape-off-layer; turbulence; blob; hole; correlations; gas puff imaging
OSTI Identifier:
1440543
Alternate Identifier(s):
OSTI ID: 1460988