Anomalous transport in high-temperature plasmas with applications to solenoidal fusion systems

Abstract

The linear, non-linear, and anomalous transport properties associated with various microinstabilities driven by cross-field currents in high-temperature plasmas are reviewed. Particular emphasis is placed on instabilities pertinent to the implosion and post-implosion phases of theta-pinch plasmas, e.g. Buneman (electron-ion two-stream), ion acoustic, lower-hybrid-drift, electromagnetic ion cyclotron, and ion-ion cross-field instabilities. Analytic studies of the non-linear and quasi-linear evolution of these instabilities are presented, together with a detailed comparison with computer simulation experiments to test the validity of the various theoretical models and non-linear saturation mechanisms. A general theoretical formalism is presented which describes, in a self-consistent manner, the macroscopic transport produced by the (shortwave-length) turbulence associated with the microinstabilities enumerated above. The experimental evidence that such a self-consistent anomalous transport model is required for describing the implosion behaviour (characterized by diffuse current sheaths) in rapidly pulsed theta pinches is reviewed, together with the early attempts at modelling these implosions numerically with a one-fluid (MHD) model including artificial viscosity. It is shown that fluid-numerical simulations that include (at each space and time step) the effects of anomalous transport in a fully self-consistent manner, explain several features of the experimental observations. The relevance of reflected ions to sheath structure and implosion dynamics is also discussed, and state-of-the-art hybrid-numerical studies (Vlasov ions and fluid electrons) of pinch implosions are presented, which include reflected ion dynamics as well as the anomalous transport associated with cross-field instabilities. Finally, instability mechanisms for producing long-time interpenetration of plasma and magnetic field in post-implosion theta pinches are discussed, together with estimates of the anomalous resistivity.

Implicit Collisional Three-Fluid Simulation of the Plasma Erosion Opening Switch

“…This is ev- appears that some additional mechanism is needed to explain the NRL experimental measurements. We have therefore considered the possibility that some form of anomalous collisionality [29] The total flux plots show strong emission at the cathode associated with the sharp Bz gradients there. They also show a broadened current channel crossing the center of the switch, and pronounced magnetic insulation of the electrons seeking entry to the anode.…”

The physics of fast Z pinches

“…The "natural" frequency of the lower-hybrid oscillations is (see, for example, Davidson and Krall, 1977): where inp is the proton mass. In "practical" units, w , (~-' ) = 4.5. io9 B(T) -.…”

Anomalous transport in discrete arcs and simulation of double layers in a model auroral circuit

“…Owing to momentum conservation, there is a wave-modulated friction between the electrons and ions, which may be described by an anomalous collision frequency (Davidson and Krall, 1977) v, "--_o_Ltt, where e = W/nMU_i 2. Thus, the electron and ion fluids are acted on by volume forces Fy i = -Fye, leading to an F x B drift velocity in the x-direction, i.e., opposite to Ex (the coordinate system is defined by Fig.…”