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

Here, 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 for 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 2 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:
ORCiD logo [1] ;  [2] ;  [2] ;  [2] ;  [2] ; ORCiD logo [2] ;  [3] ;  [3] ; ORCiD logo [2] ;  [4] ;  [5] ;  [6]
  1. Univ. of California San Diego, La Jolla, CA (United States); Princeton Univ., Princeton, NJ (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Univ. of California San Diego, La Jolla, CA (United States)
  4. Princeton Univ., Princeton, NJ (United States)
  5. Univ. of California, Los Angeles, CA (United States)
  6. Univ. of York, York (United Kingdom)
Publication Date:
OSTI Identifier:
1356320
Grant/Contract Number:
FC02-04ER54698; AC02-09CH11466; FG02-07ER54917; FG02-08ER54984
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
General Atomics, San Diego, CA (United States)
Sponsoring Org:
USDOE Office of Nuclear Energy (NE)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY