Bifurcated states of a rotating tokamak plasma in the presence of a static error-field
- Institute for Fusion Studies, Department of Physics, The University of Texas at Austin, Austin, Texas 78712 (United States)
The bifurcated states of a rotating tokamak plasma in the presence of a static, resonant, error-field are strongly analogous to the bifurcated states of a conventional induction motor. The two plasma states are the {open_quotes}unreconnected{close_quotes} state, in which the plasma rotates and error-field-driven magnetic reconnection is suppressed, and the {open_quotes}fully reconnected{close_quotes} state, in which the plasma rotation at the rational surface is arrested and driven magnetic reconnection proceeds without hindrance. The response regime of a rotating tokamak plasma in the vicinity of the rational surface to a static, resonant, error-field is determined by {ital three} parameters: the normalized plasma viscosity, {ital P}, the normalized plasma rotation, Q{sub 0}, and the normalized plasma resistivity, {ital R}. There are 11 distinguishable response regimes. The extents of these regimes are calculated in P{endash}Q{sub 0}{endash}R space. In addition, an expression for the critical error-field amplitude required to trigger a bifurcation from the {open_quotes}unreconnected{close_quotes} to the {open_quotes}fully reconnected{close_quotes} state is obtained in each regime. The appropriate response regime for low-density, ohmically heated, tokamak plasmas is found to be the nonlinear {ital constant}-{psi} regime for small tokamaks, and the linear {ital constant}-{psi} regime for large tokamaks. The critical error-field amplitude required to trigger error-field-driven magnetic reconnection in such plasmas is a rapidly decreasing function of machine size, indicating that particular care may be needed to be taken to reduce resonant error-fields in a reactor-sized tokamak. {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 641529
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 9 Vol. 5; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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