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Title: Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks

Abstract

Linear full radius gyrokinetic calculations show the existence of unstable microtearing modes (MTMs) in purely collisionless, high temperature, large aspect ratio tokamak plasmas. The present study takes into account fully gyrokinetic highly passing ions and electrons. The global 2-D structures of the collisionless mode with full radius coupling of the poloidal modes is obtained and compared with another electromagnetic mode, namely, the Alfvén Ion Temperature Gradient (AITG) mode (or Kinetic Ballooning Mode, KBM) for the same equilibrium profile. Several important characteristics of the modes are brought out and compared, such as a clear signature in the symmetry properties of the two modes, the plasma–β dependence, and radial and poloidal length scales of the electrostatic and magnetic vector potential fluctuations. Extensive parameter scans for this collisionless microtearing mode reveal the scaling of the growth rate with β and the electron temperature gradient η{sub e}. Scans at different β values show an inverse relationship between the η{sub e} threshold and β, leading to a stability diagram, and implying that the mode might exist at moderate to strong temperature gradients for finite β plasmas in large aspect ratio tokamaks. In contrast to small aspect ratio tokamaks where the trapped electron magnetic drift resonancemore » is found to be important, in large aspect ratio tokamaks, a strong destabilization due to the magnetic drift resonance of passing electrons is observed and is identified as a possible collisionless drive mechanism for the collisionless MTM.« less

Authors:
;  [1]; ; ;  [2]
  1. Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)
  2. CRPP, EPFL, 1015 Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
22303590
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 21; Journal Issue: 8; Other Information: (c) 2014 AIP Publishing LLC; 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; ELECTRON TEMPERATURE; PLASMA; STABILITY; SYMMETRY; TOKAMAK DEVICES; TRAPPED ELECTRONS

Citation Formats

Swamy, Aditya K., Ganesh, R., E-mail: ganesh@ipr.res.in, Chowdhury, J., Brunner, S., Vaclavik, J., and Villard, L. Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks. United States: N. p., 2014. Web. doi:10.1063/1.4893314.
Swamy, Aditya K., Ganesh, R., E-mail: ganesh@ipr.res.in, Chowdhury, J., Brunner, S., Vaclavik, J., & Villard, L. Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks. United States. https://doi.org/10.1063/1.4893314
Swamy, Aditya K., Ganesh, R., E-mail: ganesh@ipr.res.in, Chowdhury, J., Brunner, S., Vaclavik, J., and Villard, L. 2014. "Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks". United States. https://doi.org/10.1063/1.4893314.
@article{osti_22303590,
title = {Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks},
author = {Swamy, Aditya K. and Ganesh, R., E-mail: ganesh@ipr.res.in and Chowdhury, J. and Brunner, S. and Vaclavik, J. and Villard, L.},
abstractNote = {Linear full radius gyrokinetic calculations show the existence of unstable microtearing modes (MTMs) in purely collisionless, high temperature, large aspect ratio tokamak plasmas. The present study takes into account fully gyrokinetic highly passing ions and electrons. The global 2-D structures of the collisionless mode with full radius coupling of the poloidal modes is obtained and compared with another electromagnetic mode, namely, the Alfvén Ion Temperature Gradient (AITG) mode (or Kinetic Ballooning Mode, KBM) for the same equilibrium profile. Several important characteristics of the modes are brought out and compared, such as a clear signature in the symmetry properties of the two modes, the plasma–β dependence, and radial and poloidal length scales of the electrostatic and magnetic vector potential fluctuations. Extensive parameter scans for this collisionless microtearing mode reveal the scaling of the growth rate with β and the electron temperature gradient η{sub e}. Scans at different β values show an inverse relationship between the η{sub e} threshold and β, leading to a stability diagram, and implying that the mode might exist at moderate to strong temperature gradients for finite β plasmas in large aspect ratio tokamaks. In contrast to small aspect ratio tokamaks where the trapped electron magnetic drift resonance is found to be important, in large aspect ratio tokamaks, a strong destabilization due to the magnetic drift resonance of passing electrons is observed and is identified as a possible collisionless drive mechanism for the collisionless MTM.},
doi = {10.1063/1.4893314},
url = {https://www.osti.gov/biblio/22303590}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 8,
volume = 21,
place = {United States},
year = {Fri Aug 15 00:00:00 EDT 2014},
month = {Fri Aug 15 00:00:00 EDT 2014}
}