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Title: Study of Z scaling of runaway electron plateau final loss energy deposition into wall of DIII-D

Here, controlled runaway electron (RE) plateau-wall strikes with different initial impurity levels are used to study the effect of background plasma ion charge Z (resistivity) on RE-­wall loss dynamics. It is found that Joule heating (magnetic to kinetic energy conversion) during the final loss does not go up monotonically with increasing Z, but peaks at intermediate Z ~ 6. Joule heating and overall time scales of the RE final loss are found to be reasonably well-described by a basic 0D coupled-circuit model, with only the loss time as a free parameter. This loss time is found to be fairly well correlated with the avalanche time, possibly suggesting that the RE final loss rate is limited by the avalanche rate. First attempts at measuring total energy deposition to the vessel walls by REs during the final loss are made. At higher plasma impurity levels Z > 5, energy deposition to the wall appears be consistent with modeling, at least within the large uncertainties of the measurement. At low impurity levels Z < 5, however, local energy deposition appears around 5-­20× less than expected, suggesting that the RE energy dissipation at low Z is not fully understood.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [1] ;  [2] ;  [5] ;  [6] ;  [3] ;  [3]
  1. Univ. of California - San Diego, La Jolla, CA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  6. Univ. Carlos III de Madrid, Madrid (Spain)
Publication Date:
Report Number(s):
LLNL-JRNL-738293
Journal ID: ISSN 1070-664X; TRN: US1800744
Grant/Contract Number:
FC02-04ER54698; AC05-00OR22725; AC05-06OR23100; AC52-07NA27344; FG02-07ER54917
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 24; Journal Issue: 6; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, 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
OSTI Identifier:
1414925
Alternate Identifier(s):
OSTI ID: 1363702; OSTI ID: 1458691