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Title: Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?

Abstract

Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles, this mode cannot exist, and instead, a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found, provided the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs.

Authors:
 [1]; ;  [2]
  1. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)
  2. York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom)
Publication Date:
OSTI Identifier:
22252178
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 1; Other Information: (c) 2014 EURATOM; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALLOONING INSTABILITY; CRITICAL FLOW; EDGE LOCALIZED MODES; PLASMA RADIAL PROFILES; TOKAMAK DEVICES

Citation Formats

Dickinson, D., E-mail: dd502@york.ac.uk, EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB, Roach, C. M., Skipp, J. M., and Wilson, H. R. Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?. United States: N. p., 2014. Web. doi:10.1063/1.4861628.
Dickinson, D., E-mail: dd502@york.ac.uk, EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB, Roach, C. M., Skipp, J. M., & Wilson, H. R. Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?. United States. https://doi.org/10.1063/1.4861628
Dickinson, D., E-mail: dd502@york.ac.uk, EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB, Roach, C. M., Skipp, J. M., and Wilson, H. R. 2014. "Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?". United States. https://doi.org/10.1063/1.4861628.
@article{osti_22252178,
title = {Structure of micro-instabilities in tokamak plasmas: Stiff transport or plasma eruptions?},
author = {Dickinson, D., E-mail: dd502@york.ac.uk and EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB and Roach, C. M. and Skipp, J. M. and Wilson, H. R.},
abstractNote = {Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles, this mode cannot exist, and instead, a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found, provided the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs.},
doi = {10.1063/1.4861628},
url = {https://www.osti.gov/biblio/22252178}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 1,
volume = 21,
place = {United States},
year = {Wed Jan 15 00:00:00 EST 2014},
month = {Wed Jan 15 00:00:00 EST 2014}
}