We report a successful quantitative account of the experimentally determined electron thermal conductivity chi(e) in a beam-heated H mode plasma by the magnetic fluctuations from microtearing instabilities. The calculated chi(e) based on existing nonlinear theory agrees with the result from transport analysis of the experimental data. Without using any adjustable parameter, the good agreement s...

In overdense plasma for which the plasma frequency exceeds the cyclotron frequency, X-mode, nearperpendicular cyclotron emission does not propagate to the outboard plasma edge. However, under these conditions it remains possible for electron Bernstein waves (EBWs) to transmit emitted radiation from central plasma to the plasma exterior via a mode conversion to electromagnetic waves near the pla...

A novel diagnostic design seeks to enhance the capability of multienergy soft x-ray (SXR) detection by using an image intensifier to amplify the signals from a larger set of filtered x-ray profiles. The increased number of profiles and simplified detection system provides a compact diagnostic device for measuring T(e) in addition to contributions from density and impurities. A single-energy pro...

The National Spherical Torus Experiment (NSTX) [Ono, M., et al., Nucl. Fusion, 44, (2004), 452.] is targeting long pulse high performance, non-inductive sustained operations at low aspect ratio, and the demonstration of non-solenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulat...

Motivated by experimental observations of apparently triggerless tearing modes, we have performed linear and nonlinear MHD analysis showing that a non-resonant mode with toroidal mode number n = 1 can develop in the National Spherical Torus eXperiment (NSTX) at moderate normalized βN when the shear is low and the central safety factor q0 is close to but greater than one. This mode, which is rel...

The three-dimensional plasma boundary displacement induced by long-lasting core magnetohydrodynamic (MHD) instabilities has been measured in JET, MAST and NSTX. Only saturated instabilities are considered here since transient rapidly growing modes which degrade confinement and act as potential triggers for disruptions bring more fundamental concerns than boundary displacements. The measured dis...

The high-β operating regime of spherical tokamaks (ST), such as in NSTX and MAST, make them attractive fusion devices. For access to such high β regimes, it is necessary to heat and to drive currents in ST plasmas. While such plasmas are overdense to conventional electron cyclotron waves, electron Bernstein waves (EBW) offer an attractive means toward this purpose. The applications of EBWs in S...

We present a new analytic expression for turbulent equipartition (TEP) pinch of toroidal angular momentum originating from magnetic field inhomogeneity of spherical torus (ST) plasmas. Starting from a conservative modern nonlinear gyrokinetic equation [Hahm et al., 1988 Phys. Fluids 31, 2670], we derive an expression for pinch to momentum diffusivity ratio without using a usual tokamak approxim...