Nona Semana Integrada do Instituto de Física de São Carlos

Magnetic island bifurcation due to resonant magnetic perturbations

Não agendado

20m

Iniciação Científica

Palestrante

Yuri Asnis

Descrição

Fusing atoms together in a controlled way releases nearly four million times more energy than a chemical reaction such as the burning of coal, oil or gas, and four times as much as nuclear fission reactions, with the advantage of not emitting harmful toxins like carbon dioxide or other greenhouse gases into the atmosphere. Therefore, the potential of nuclear fusion to provide a practically inexhaustible source of clean and renewable energy has motivated scientists for many decades to work toward developing nuclear fusion power plants. Among many concepts, the so-called tokamak concept is, at present, the most promising approach for exploiting thermonuclear fusion. Although the tokamak device is the most prominent candidate, several scientific and technological challenges impose severe constraints on the path towards a self-sustained fusion burning plasma. (1) To become economically attractive, tokamaks will have to operate in the so-called high confinement mode, whose ubiquitous feature are repetitive instabilities known as edge localized modes (ELM). These instabilities release unacceptably high fractions of the thermal energy of the plasma to the first wall of the device thus driving the need for ELM control strategies. Studies worldwide have demonstrated that the presence of relatively small non-axisymmetric resonant magnetic perturbations (RMP) can be used to suppress ELMs. Recent calculations using the resistive MHD code M3D-C1 of the linear response of spherical tokamak plasmas to RMP fields revealed a new class of magnetic field line bifurcations that do not fit into the well-accepted magnetic reconnection theory. (2) These results not only challenge reconnection theory in tokamak plasmas but are particularly important for understanding the underlying physics of self-organization in toroidal fusion plasmas. Depending on the plasma conditions, instabilities can develop when the plasma pressure is increased for better performance. The model most widely used to predict plasma stability is the so-called magnetohydrodynamic model. (3)

Referências

1 FERRARO, N. M. et al. Role of plasma response in displacements of the tokamak edge due to applied non-axisymmetric fields. Nuclear Fusion, v. 53, n. 7, p. 073042-1-073042-8, June 2013.
2 FITZPATRICK, R. Bifurcated states of a rotating tokamak plasma in the presence of a static error-field. Physics of Plasmas, v. 5, n. 9, p. 3325-3341, Sept. 1998.
3 EVANS, T. E. et al. Resonant magnetic perturbations of edge-plasmas in toroidal confinement devices. Plasma Physics and Controlled Fusion, v. 57, n. 12, p. 123001-1-123001-42, Nov. 2015.