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Title: Investigation of peeling-ballooning stability prior to transient outbursts accompanying transitions out of H-mode in DIII-D

The H-mode transport barrier allows confinement of roughly twice as much energy as in an L-mode plasma. Termination of H-mode necessarily requires release of this energy, and the timescale of that release is of critical importance for the lifetimes of plasma facing components in next step tokamaks such as ITER. H-L transition sequences in modern tokamaks often begin with a transient outburst which appears to be superficially similar to and has sometimes been referred to as a type-I edge localized mode (ELM). Type-I ELMs have been shown to be consistent with ideal peeling ballooning instability and are characterized by significant (up to ∼50%) reduction of pedestal height on short (∼1 ms) timescales. Knowing whether or not this type of instability is present during H-L back transitions will be important of planning for plasma ramp-down in ITER. This paper presents tests of pre-transition experimental data against ideal peeling-ballooning stability calculations with the ELITE code and supports those results with secondary experiments that together show that the transient associated with the H-L transition is not triggered by the same physics as are type-I ELMs.
Authors:
 [1] ;  [2] ; ; ; ; ; ;  [3] ; ;  [1] ;  [4] ;  [5] ;  [6]
  1. University of California San Diego, 9500 Gilman Dr., La Jolla, California 92093-0964 (United States)
  2. (United States)
  3. General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
  4. Princeton University, Princeton, New Jersey 08543 (United States)
  5. University of California Los Angeles, Los Angeles, California 90095-7099 (United States)
  6. University of York, Heslington, York YO10 5DD (United Kingdom)
Publication Date:
OSTI Identifier:
22410289
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; DOUBLET-3 DEVICE; EDGE LOCALIZED MODES; EXPERIMENTAL DATA; FIRST WALL; H-MODE PLASMA CONFINEMENT; ITER TOKAMAK; L-MODE PLASMA CONFINEMENT; SERVICE LIFE