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Title: Dissipation of post-disruption runaway electron plateaus by shattered pellet injection in DIII-D

Abstract

Here, we report on the first demonstration of dissipation of fully avalanched post-disruption runaway electron (RE) beams by shattered pellet injection in the DIII-D tokamak. Variation of the injected species shows that dissipation depends strongly on the species mixture, while comparisons with massive gas injection do not show a significant difference between dissipation by pellets or by gas, suggesting that the shattered pellet is rapidly ablated by the relativistic electrons before significant radial penetration into the runaway beam can occur. Pure or dominantly neon injection increases the RE current dissipation through pitch-angle scattering due to collisions with impurity ions. Deuterium injection is observed to have the opposite effect from neon, causing the background thermal plasma to completely recombine, reducing the high-Z impurity content and thus decreasing the dissipation. When injecting mixtures of the two species, deuterium levels as low as ~10% of the total injected atoms are observed to adversely affect the resulting dissipation, suggesting that complete elimination of deuterium from the injection may be important for optimizing RE mitigation schemes.

Authors:
 [1];  [1];  [1];  [2]; ORCiD logo [3];  [4];  [3];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge Associated Univ., Oak Ridge, TN (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Univ. of California, San Diego, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1432365
Grant/Contract Number:  
FC02-04ER54698; AC05-00OR22725; AC05-060R23100; FG02-07ER54917
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 5; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Shiraki, D., Commaux, N., Baylor, L. R., Cooper, C. M., Eidietis, N. W., Hollmann, E. M., Paz-Soldan, C., Combs, S. K., and Meitner, S. J.. Dissipation of post-disruption runaway electron plateaus by shattered pellet injection in DIII-D. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aab0d6.
Shiraki, D., Commaux, N., Baylor, L. R., Cooper, C. M., Eidietis, N. W., Hollmann, E. M., Paz-Soldan, C., Combs, S. K., & Meitner, S. J.. Dissipation of post-disruption runaway electron plateaus by shattered pellet injection in DIII-D. United States. doi:10.1088/1741-4326/aab0d6.
Shiraki, D., Commaux, N., Baylor, L. R., Cooper, C. M., Eidietis, N. W., Hollmann, E. M., Paz-Soldan, C., Combs, S. K., and Meitner, S. J.. Wed . "Dissipation of post-disruption runaway electron plateaus by shattered pellet injection in DIII-D". United States. doi:10.1088/1741-4326/aab0d6.
@article{osti_1432365,
title = {Dissipation of post-disruption runaway electron plateaus by shattered pellet injection in DIII-D},
author = {Shiraki, D. and Commaux, N. and Baylor, L. R. and Cooper, C. M. and Eidietis, N. W. and Hollmann, E. M. and Paz-Soldan, C. and Combs, S. K. and Meitner, S. J.},
abstractNote = {Here, we report on the first demonstration of dissipation of fully avalanched post-disruption runaway electron (RE) beams by shattered pellet injection in the DIII-D tokamak. Variation of the injected species shows that dissipation depends strongly on the species mixture, while comparisons with massive gas injection do not show a significant difference between dissipation by pellets or by gas, suggesting that the shattered pellet is rapidly ablated by the relativistic electrons before significant radial penetration into the runaway beam can occur. Pure or dominantly neon injection increases the RE current dissipation through pitch-angle scattering due to collisions with impurity ions. Deuterium injection is observed to have the opposite effect from neon, causing the background thermal plasma to completely recombine, reducing the high-Z impurity content and thus decreasing the dissipation. When injecting mixtures of the two species, deuterium levels as low as ~10% of the total injected atoms are observed to adversely affect the resulting dissipation, suggesting that complete elimination of deuterium from the injection may be important for optimizing RE mitigation schemes.},
doi = {10.1088/1741-4326/aab0d6},
journal = {Nuclear Fusion},
number = 5,
volume = 58,
place = {United States},
year = {Wed Mar 07 00:00:00 EST 2018},
month = {Wed Mar 07 00:00:00 EST 2018}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on March 7, 2019
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