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Title: The tokamak density limit: A thermo-resistive disruption mechanism

Abstract

The behavior of magnetic islands with 3D electron temperature and the corresponding 3D resistivity effects on growth are examined for islands with near-zero net heating in the island interior. We refer to the resulting class of non-linearities as thermo-resistive effects. In particular, the effects of varying impurity mix on the previously proposed local island onset threshold [Gates and Delgado-Aparicio, Phys. Rev. Lett. 108, 165004 (2012)] are examined and shown to be consistent with the well established experimental scalings for tokamaks at the density limit. A surprisingly simple semi-analytic theory is developed which imposes the effects of heating/cooling in the island interior as well as the effects of island geometry. For the class of current profiles considered, it is found that a new term that accounts for the thermal effects of island asymmetry is required in the modified Rutherford equation. The resultant model is shown to exhibit a robust onset of a rapidly growing tearing mode—consistent with the disruption mechanism observed at the density limit in tokamaks. A fully non-linear 3D cylindrical calculation is performed that simulates the effect of net island heating/cooling by raising/suppressing the temperature in the core of the island. In both the analytic theory and the numericalmore » simulation, the sudden threshold for rapid growth is found to be due to an interaction between three distinct thermal non-linearities which affect the island resistivity, thereby modifying the growth dynamics.« less

Authors:
; ; ;  [1]
  1. Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)
Publication Date:
OSTI Identifier:
22410424
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 6; Other Information: (c) 2015 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; ASYMMETRY; BEAM CURRENTS; COMPUTERIZED SIMULATION; COOLING; CYLINDRICAL CONFIGURATION; DENSITY; ELECTRON TEMPERATURE; HEATING; MAGNETIC ISLANDS; NONLINEAR PROBLEMS; PLASMA IMPURITIES; TEARING INSTABILITY; TEMPERATURE DEPENDENCE; TOKAMAK DEVICES

Citation Formats

Gates, D. A., Brennan, D. P., Delgado-Aparicio, L., and White, R. B. The tokamak density limit: A thermo-resistive disruption mechanism. United States: N. p., 2015. Web. doi:10.1063/1.4922472.
Gates, D. A., Brennan, D. P., Delgado-Aparicio, L., & White, R. B. The tokamak density limit: A thermo-resistive disruption mechanism. United States. doi:10.1063/1.4922472.
Gates, D. A., Brennan, D. P., Delgado-Aparicio, L., and White, R. B. Mon . "The tokamak density limit: A thermo-resistive disruption mechanism". United States. doi:10.1063/1.4922472.
@article{osti_22410424,
title = {The tokamak density limit: A thermo-resistive disruption mechanism},
author = {Gates, D. A. and Brennan, D. P. and Delgado-Aparicio, L. and White, R. B.},
abstractNote = {The behavior of magnetic islands with 3D electron temperature and the corresponding 3D resistivity effects on growth are examined for islands with near-zero net heating in the island interior. We refer to the resulting class of non-linearities as thermo-resistive effects. In particular, the effects of varying impurity mix on the previously proposed local island onset threshold [Gates and Delgado-Aparicio, Phys. Rev. Lett. 108, 165004 (2012)] are examined and shown to be consistent with the well established experimental scalings for tokamaks at the density limit. A surprisingly simple semi-analytic theory is developed which imposes the effects of heating/cooling in the island interior as well as the effects of island geometry. For the class of current profiles considered, it is found that a new term that accounts for the thermal effects of island asymmetry is required in the modified Rutherford equation. The resultant model is shown to exhibit a robust onset of a rapidly growing tearing mode—consistent with the disruption mechanism observed at the density limit in tokamaks. A fully non-linear 3D cylindrical calculation is performed that simulates the effect of net island heating/cooling by raising/suppressing the temperature in the core of the island. In both the analytic theory and the numerical simulation, the sudden threshold for rapid growth is found to be due to an interaction between three distinct thermal non-linearities which affect the island resistivity, thereby modifying the growth dynamics.},
doi = {10.1063/1.4922472},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 22,
place = {United States},
year = {2015},
month = {6}
}