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

Texto completo
Autor(es):
Ciro, D. [1] ; Caldas, I. L. [1]
Número total de Autores: 2
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Dept Fis Aplicada, BR-05508090 Sao Paulo - Brazil
Número total de Afiliações: 1
Tipo de documento: Artigo Científico
Fonte: Physics of Plasmas; v. 20, n. 10 OCT 2013.
Citações Web of Science: 2
Resumo

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. (C) 2013 AIP Publishing LLC. (AU)

Processo FAPESP: 11/19296-1 - Dinâmica não linear
Beneficiário:Iberê Luiz Caldas
Linha de fomento: Auxílio à Pesquisa - Temático
Processo FAPESP: 12/18073-1 - Transporte simplético em plasmas de fusão com divertor
Beneficiário:David Ciro Taborda
Linha de fomento: Bolsas no Brasil - Doutorado