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Title: Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

Abstract

The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode(ELM) crashes and the consistent collisionality scaling of ELMenergy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELMenergy losses vs collisionality via a density scan. Moreover, the linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. For nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELMenergy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. Finally, the critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality withmore » decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Univ. of Texas, Austin, TX (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chinese Academy of Sciences, Hefei (China)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1258542
Alternate Identifier(s):
OSTI ID: 1226641
Report Number(s):
LLNL-JRNL-656259
Journal ID: ISSN 1070-664X; PHPAEN
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 12; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION

Citation Formats

Xu, X. Q., Ma, J. F., and Li, G. Q. Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling. United States: N. p., 2014. Web. doi:10.1063/1.4905070.
Xu, X. Q., Ma, J. F., & Li, G. Q. Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling. United States. doi:10.1063/1.4905070.
Xu, X. Q., Ma, J. F., and Li, G. Q. Mon . "Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling". United States. doi:10.1063/1.4905070. https://www.osti.gov/servlets/purl/1258542.
@article{osti_1258542,
title = {Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling},
author = {Xu, X. Q. and Ma, J. F. and Li, G. Q.},
abstractNote = {The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode(ELM) crashes and the consistent collisionality scaling of ELMenergy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELMenergy losses vs collisionality via a density scan. Moreover, the linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. For nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELMenergy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. Finally, the critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.},
doi = {10.1063/1.4905070},
journal = {Physics of Plasmas},
number = 12,
volume = 21,
place = {United States},
year = {Mon Dec 29 00:00:00 EST 2014},
month = {Mon Dec 29 00:00:00 EST 2014}
}

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