Change of Paradigm for the Reversed Field Pinch

Journal Article · Tue Nov 23 00:00:00 EST 2010 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3526166· OSTI ID:21506924

Escande, D F ^[1]

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1. Physique des Interactions Ioniques et Moleculaires, UMR 6633-CNRS / Aix-Marseille Universite, Case 321, Av. Normandie Niemen, 13397 MARSEILLE Cedex 20 (France)

The reversed field pinch (RFP) is a magnetic configuration germane to the tokamak, but it produces most of its magnetic field by the currents flowing inside the plasma; external coils provide only a small edge toroidal field whose sign is reversed with respect to the central one, whence the name of the configuration. Because of the presence of magnetic turbulence and chaos, the RFP had been considered for a long period as a terrible confinement configuration. However, recently a change of paradigm occurred for this device. Indeed, when the toroidal current is increased in the RFX-mod RFP in Padua (Italy), a self-organized helical state with an internal transport barrier (ITB) develops, and a broad zone of the plasma becomes hot (above 1 keV for a magnetic field above 0.8 T). The present theoretical picture of the RFP mainly comes from three-dimensional nonlinear visco-resistive MHD simulations whose dynamics has strong similarities with the experimental one, and triggered the experimental search for RFP states with improved confinement. The RFP ohmic state involves a helical electrostatic potential generating, as an electric drift, the so-called dynamo velocity field. The magnetic topology can bifurcate from a magnetic island to kink-like magnetic surfaces with higher resilience to magnetic chaos. This theoretical scenario was found to be relevant when ITB's enclosing a broad hot domain were discovered. The ITBs occur in the vicinity of the maximum of the safety factor. The new paradigm for the RFP supports its reappraisal as a low-external field, non-disruptive, ohmically heated approach to magnetic fusion, exploiting both self-organization and technological simplicity. Furthermore the RFP has the same Greenwald density limit as the tokamak, and it is an excellent test bed for the efficient control of multiple resistive wall modes. Its helical magnetic structure makes it germane to the stellarator too. As a result the RFP is also useful to bring support to the present two main lines of magnetic confinement.

• OSTI ID: 21506924
• Journal Information: AIP Conference Proceedings, Vol. 1308, Issue 1; Conference: International symposium on waves, coherent structures and turbulence in plasmas, Gandhinagar (India), 12-15 Jan 2010; Other Information: DOI: 10.1063/1.3526166; (c) 2010 American Institute of Physics; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHAOS THEORY
CHARGED-PARTICLE TRANSPORT
CONFIGURATION
DENSITY
KEV RANGE 01-10
MAGNETIC CONFINEMENT
MAGNETIC FIELDS
MAGNETIC ISLANDS
MAGNETIC SURFACES
MAGNETOHYDRODYNAMICS
NONLINEAR PROBLEMS
PLASMA
REVERSE-FIELD PINCH
SAFETY
SIMULATION
THERMAL BARRIERS
THREE-DIMENSIONAL CALCULATIONS
TOKAMAK DEVICES
TURBULENCE
VELOCITY
CLOSED PLASMA DEVICES
CONFINEMENT
ENERGY RANGE
FLUID MECHANICS
HYDRODYNAMICS
KEV RANGE
MAGNETIC FIELD CONFIGURATIONS
MATHEMATICS
MECHANICS
PHYSICAL PROPERTIES
PINCH EFFECT
PLASMA CONFINEMENT
RADIATION TRANSPORT
THERMONUCLEAR DEVICES