Simulation and Analysis of the Hybrid Operating Mode in ITER

The hybrid operating mode in ITER is examined with 0D systems analysis, 1.5D discharge scenario simulations using TSC and TRANSP, and the ideal MHD stability is discussed. The hybrid mode has the potential to provide very long pulses and significant neutron fluence if the physics regime can be produced in ITER. This paper reports progress in establishing the physics basis and engineering limitation for the hybrid mode in ITER

Mutually Penetrating Motion of Self-Organized 2D Patterns of Soliton-Like Structures

Results of numerical simulations of a recently derived most general dissipative-dispersive PDE describing evolution of a film flowing down an inclined plane are presented. They indicate that a novel complex type of spatiotemporal patterns can exist for strange attractors of nonequilibrium systems. It is suggested that real-life experiments satisfying the validity conditions of the theory are possible: the required sufficiently viscous liquids are readily available.Comment: minor corrections, 4 pages, LaTeX, 6 figures, mpeg simulations available upon or reques

Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach

Mixing fluid in a container at low Reynolds number - in an inertialess environment - is not a trivial task. Reciprocating motions merely lead to cycles of mixing and unmixing, so continuous rotation, as used in many technological applications, would appear to be necessary. However, there is another solution: movement of the walls in a cyclical fashion to introduce a geometric phase. We show using journal-bearing flow as a model that such geometric mixing is a general tool for using deformable boundaries that return to the same position to mix fluid at low Reynolds number. We then simulate a biological example: we show that mixing in the stomach functions because of the "belly phase": peristaltic movement of the walls in a cyclical fashion introduces a geometric phase that avoids unmixing.Comment: Revised, published versio

High-Harmonic Fast Wave Driven H-mode Plasmas on NSTX

The launch of High-Harmonic Fast Waves (HHFW) routinely provides auxiliary power to NSTX plasmas, where it is used to heat electrons and pursue drive current. H-mode transitions have been observed in deuterium discharges, where only HHFW and ohmic heating, and no neutral beam injection (NBI), were applied to the plasma. The usual H-mode signatures are observed. A drop of the Da light marks the start of a stored energy increase, which can double the energy content. These H-mode plasmas also have the expected kinetic profile signatures with steep edge density and electron temperature pedestal. Similar to its NBI driven counterpart--also observed on NSTX-- the HHFW H mode have density profiles that features ''ears'' in the peripheral region. These plasmas are likely candidates for long pulse operation because of the combination of bootstrap current, associated with H-mode kinetic profiles, and active current drive, which can be generated with HHFW power

Particle transport theory with ICRH and ECRh in tokamaks

Ph.D.WM Stacey, J

Effect of a poloidal electric field on neoclassical transport in a multispecies tokamak plasma

The effects of a poloidal potential variation of or der c{var_epsilon}, heating or neutral beam injection, upon neoclassical particle transport and plasma current are studied theoretically, for a realistic tokamak plasma with significant impurity content. Using an approximate collision operator, an analytic procedure is employed to calculate the transport coefficients in the low collisionality regime for a large aspect ratio tokamak. In the presence of carbon impurity, the ion diffusion coefficients are generally found to increase by a factor of {approximately} 2. Inclusion of the effects of a poloidal electric field is found to result in an increase in the bootstrap current if the potential on the outside of the tokamak is greater than that on the inside (as during ICRH or NBI) and the density profiles are more peaked than roughly the square root of the temperature profiles

Spatiotemporal Patterns in a 3-D Film Flow

Flow of an incompressible Newtonian film down an inclined plane is considered. A multiparametric perturbation approach yields the most general leading-order equation for film thickness which can quantitatively approximate film evolution for all time. The theory yields explicit expressions for velocities and pressure in terms of film thickness. Conditions of (i) local (in time) and (ii) global validity of the theory are obtained. The evolution equation contains both dissipative and dispersive terms. It is valid for smallamplitude wave regimes. Numerical simulations with periodic boundary conditions show transient spatial patterns in qualitative agreement with recent experiments. For parametric conditions with large dispersion, highly ordered unusual (non-periodic) spatial patterns are observed at large times, near dynamical system attractors. 1 Introduction Liquid films flowing on solid surfaces are readily found in nature and industry, in both single- and multifluid settings; an examp..