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Despite the importance of rotation in fusion plasmas, our present understanding of momentum transport is inadequate. The lack of understanding is in part related to the difficulty of performing accurate rotation measurements, especially for poloidal rotation. Recently, measurements of poloidal rotation for impurity ions (Z>1) have been obtained in the core of DIII-D [J. L. Luxon, Nucl. Fusion 42, 6114 (2002)] plasmas using charge exchange recombination spectroscopy. The inferred poloidal rotation is based on careful consideration of the effective energy-dependent cross section and of the gyromotion of the ions. The rotation measurements are found to be consistent with the radial electric field determined independently from multiple impurity species as well as from motional Stark effect spectroscopic measurements. The poloidal rotation measurements have been compared with predictions based on the neoclassical theory of poloidal rotation from the code NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)]. The comparison shows that the neoclassically predicted poloidal rotation is in general significantly smaller than the actual measurements. [ABSTRACT FROM AUTHOR]

Spatially and temporally resolved toroidal rotation measurements have been made in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] discharges with no externally applied torque. The velocity measurements are made using the charge exchange recombination (CER) technique viewing emission from the intrinsic carbon impurity in deuterium discharges. Three cases have been studied: L mode and H mode with Ohmic heating and H mode with electron cyclotron heating (ECH). The ECH H mode has carbon counter-rotation in the center of the plasma, and co-rotation outside, where co- and counter- are relative to the direction of the toroidal plasma current. The Ohmic H mode has carbon rotation everywhere in the co-direction. Neoclassical theory is applied to compute the deuterium toroidal velocity and it is found that the counter-rotation measured for carbon in the core of the ECH H mode is also thus predicted for the bulk deuterium species. Short blips of neutral beams (NB) must be used for the CER technique and these blips do apply a toroidal torque. Care is taken to verify that a nonperturbative measurement is made; data from the first 2 ms of NB injection in each discharge are used for this measurement. [ABSTRACT FROM AUTHOR]

Measurements of the relative toroidal rotation velocities of low Z impurity ions have been made in DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] plasmas that have a strong core pressure gradient and reduced anomalous transport. They show that the differences in toroidal rotation velocities agree with predictions of neoclassical transport theory. The toroidal rotation velocities are measured via charge exchange recombination (CER) spectroscopy of the impurity species. Taking into account the non-negligible effect of energy dependent charge exchange cross sections, quantitative agreement is found between the measured and predicted difference in toroidal rotation velocities, including the strong Z dependence. The predicted difference between the measured impurity rotation velocity and the main ion rotation velocity can be substantial and therefore care should be taken in using quantitative results from impurity rotation measurements and applying them to the bulk plasma. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the improvement of core fuelling with high field side (HFS) pellet injection in the DIII-D tokamak. Use of HFS injected pellets for generating peaked density profile plasmas; Investigation of transport barrier physics; Modification of plasma edge conditions.

Describes a multi-species fluid model for the steady state parallel and radial force balance equations in axisymmetric tokamak plasmas. Steady state force balance model; Reduced charge state solution; Current and resistivity; Particle and heat fluxes; Local flow velocities.

The scope and detail of physics contained in computational models for fluid (density, momentum, energy) transport in toroidal plasmas have steadily increased during the past two decades. There has been considerable success in the development and verification of models for sources and sinks of particles, energy, momentum, and magnetic flux. Transport codes have collectively become very useful tools in interpreting experimental data and in providing guidance for new experiments. However, a more thorough understanding of the fundamental transport processes of magnetically confined plasmas and development of improved computational models are needed to enhance the predictive capabilities of transport codes. It is argued that fluid transport modeling by itself cannot lead to a complete understanding of transport—there must be a very strong collaboration among theory, experiment, and modeling on both the fluid and kinetic levels. [ABSTRACT FROM AUTHOR]