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Title: Magnetic topology and current channels in plasmas with toroidal current density inversions

Abstract

The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is considered. Previous works have shown that internal regions with negative current density lead to non-nested magnetic surfaces inside the plasma. Following these results, we derive a general expression relating the positive and negative currents inside the non-nested surfaces. This is done in terms of an anisotropy parameter that is model-independent and is based in very general properties of the magnetic field. We demonstrate that the positive currents in axisymmetric islands screen the negative one in the plasma center by reaching about twice its magnitude. Further, we illustrate these results by developing a family of analytical local solutions for the poloidal magnetic field in a region of interest that contains the inverted current. These local solutions exhibit non-nested magnetic surfaces with a combined current of at least twice the magnitude of the negative one, as prescribed from the topological arguments, and allow to study topological transitions driven by geometrical changes in the current profile. To conclude, we discuss the signatures of internal current density inversions in a confinement device and show that magnetic pitch measurements may be inappropriate to differentiate current reversals and small current holesmore » in plasmas.« less

Authors:
;  [1]
  1. Departamento de Física Aplicada, Universidade de São Paulo, 05508-090 São Paulo (Brazil)
Publication Date:
OSTI Identifier:
22218535
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 20; Journal Issue: 10; Other Information: (c) 2013 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; ANISOTROPY; AXIAL SYMMETRY; CURRENT DENSITY; ELECTRIC CURRENTS; EQUILIBRIUM; MAGNETIC FIELDS; MAGNETIC ISLANDS; MAGNETIC SURFACES; MAGNETOHYDRODYNAMICS; PLASMA; TOKAMAK DEVICES; TOPOLOGY

Citation Formats

Ciro, D., and Caldas, I. L. Magnetic topology and current channels in plasmas with toroidal current density inversions. United States: N. p., 2013. Web. doi:10.1063/1.4825241.
Ciro, D., & Caldas, I. L. Magnetic topology and current channels in plasmas with toroidal current density inversions. United States. https://doi.org/10.1063/1.4825241
Ciro, D., and Caldas, I. L. 2013. "Magnetic topology and current channels in plasmas with toroidal current density inversions". United States. https://doi.org/10.1063/1.4825241.
@article{osti_22218535,
title = {Magnetic topology and current channels in plasmas with toroidal current density inversions},
author = {Ciro, D. and Caldas, I. L.},
abstractNote = {The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is considered. Previous works have shown that internal regions with negative current density lead to non-nested magnetic surfaces inside the plasma. Following these results, we derive a general expression relating the positive and negative currents inside the non-nested surfaces. This is done in terms of an anisotropy parameter that is model-independent and is based in very general properties of the magnetic field. We demonstrate that the positive currents in axisymmetric islands screen the negative one in the plasma center by reaching about twice its magnitude. Further, we illustrate these results by developing a family of analytical local solutions for the poloidal magnetic field in a region of interest that contains the inverted current. These local solutions exhibit non-nested magnetic surfaces with a combined current of at least twice the magnitude of the negative one, as prescribed from the topological arguments, and allow to study topological transitions driven by geometrical changes in the current profile. To conclude, we discuss the signatures of internal current density inversions in a confinement device and show that magnetic pitch measurements may be inappropriate to differentiate current reversals and small current holes in plasmas.},
doi = {10.1063/1.4825241},
url = {https://www.osti.gov/biblio/22218535}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 10,
volume = 20,
place = {United States},
year = {Tue Oct 15 00:00:00 EDT 2013},
month = {Tue Oct 15 00:00:00 EDT 2013}
}