Browsing by Subject "Plasma confinement"

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Evolution equations for magnetic islands in a reversed field pinch
(2001-08) Yu, Edmund Po-ning, 1972-; Fitzpatrick, Richard, 1963-
Megagauss 2.0 : a 10 capacitor system for production of megagauss fields for laser plasma experiments
(2013-05) Lewis, Sean Matthew; Bengtson, Roger D.
High magnetic fields greater than 100 Tesla applied to laser generated plasmas can generate unique and interesting conditions. High power laser systems at the University of Texas in the Center for Higher Energy Density Sciences readily produce short lived fusion plasmas in cluster targets. A strong magnetic field could increase fusion neutron yield and plasma confinement while providing a unique plasma physics environment. For this purpose, Sandia National Laboratories in collaboration with the University of Texas designed and constructed a pulsed power device to produce more than 2 megaamperes. This current produces strong magnetic fields in small coils with duration on the order of microseconds. At the University of Texas, tests with this device determined the operational characteristics. I will describe the behavior of this device with currents of approximately a megaamp and magnetic fields of more than 60 Tesla. Emphasis is placed on understanding the behavior of the fields and coils.
Turbulent electron thermal transport in fusion plasmas
(2008-05) Kim, Juhyung, 1978-; Horton, C. W. (Claude Wendell), 1942-
Electron heat transport at the scale of electron gyroradius are investigated via numerical simulation of a fluid model and a role of E x B shear flow with intermediate E x B shearing rate is explored in Euler's equation. The anomalous transport, enhanced transport due to turbulent electro-magnetic fields caused by plasma instabilities, has been a focus of the inter-national fusion research communities. Among the instabilities, the drift-type instabilities from the pressure-gradient universal in magnetic fusion devicesare considered responsible for the anomalous transport. In the current status of wide use of wave heating on electrons and subsequent high core electron temperature, the turbulent heat loss through electrons has one of the most important science element in preventing the large fusion tokamaks from reaching breakeven in the past decade. The Electron Temperature Gradient fluid model consists of electrostatic potential, toroidal magnetic flux function and electron temperature (or pressure) describing electron drift waves. The fluid model proves to be highly useful to electron heat flux analysis in fusion machines. We analyze the discharges in National Spherical Tokamak eXperiment(NSTX) and Tokamak Configuration Variable (TCV) and found that the electron thermal diffusivities can be explained in terms of the mixing length argument based on electron gyroradius, linear theory and our nonlinear fluid simulation. The nonlinear fluid model predicts reasonable heat flux observed in the experiments. Based on the analysis, we investigate the dependences of the dynamics on the ratio of electron and ion temperature T[subscript e]/T[subscript i] and plasma beta [beta subscript e-]. The nonlinear dynamics such as saturation mechanism of the ETG turbulence and the electromagnetic dynamics in terms of micro-tearing at the scale of electron gyroradius are discussed briegly. In most of plasma confinement devices, the equilibrium radial electric field exists and the turbulence-generated electric field is observed. The coherent structure, called as zonal flow, has been know to be effective to suppress the micro-turbulence. But at intermediate E x B shear, where the vortex eddy turn-over time is comparable to E x B shearing rate, the suppression is weak and the flow shear can leads to vortex amplification through interaction of nonlinear dynamics and shear flow.