Compact toroid formation, compression, and acceleration

Degnan, J. H.; Peterkin, R. E.; Baca, G. P.; Beason, J. D.; Bell, D. E.; Dearborn, M. E.; Dietz, D.; Douglas, M. R.; Englert, S. E.; Englert, T. J.; Hackett, K. E.; Holmes, J. H.; Hussey, T. W.; Kiuttu, G. F.; Lehr, F. M.; Marklin, G. J.; Mullins, B. W.; Price, D. W.; Roderick, N. F.; Ruden, E. L.; Sovinec, C. R.; Turchi, P. J.; Bird, G.; Coffey, S. K.; Seiler, S. W.; Chen, Y. G.; Gale, D.; Graham, J. D.; Scott, M.; Sommars, W.

doi:doi:10.1063/1.860681

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Effect of rigid toroidal rotation on the stability of a high‐beta tokamak to external kink modes

The effect of rigid toroidal rotation on the stability of a tokamak to external kink modes is examined. For simplicity a surface current model is assumed. For a high‐β tokamak it is shown that to leading order the equations governing stability in the presence of rotation are identical to those for a static plasma with β replaced by β+S, where β is the plasma beta and S is a parameter which provides a measure of the rotation rate. For a circular cross‐section tokamak the critical beta for stabili...

Shear flow effects on the nonlinear evolution of thermal instabilities

In the weak radiation drive regime, the coupling between the thermal instability driven by impurity radiation and the self‐consistent flow profile modification leads to a simple dynamical system that can be approximated by the Volterra–Lotka equations. In this system the shear flow acts as a predator and the temperature fluctuations act as prey. The solutions are oscillatory, and their behavior resembles that of edge‐localized modes (ELM’s). The solutions of the simplified model are compared wit...

Research on forming, compressing, and accelerating milligram‐range compact toroids using a meter diameter, two‐stage, puffed gas, magnetic field embedded coaxial plasma gun is described. The compact toroids that are studied are similar to spheromaks, but they are threaded by an inner conductor. This research effort, named marauder (Magnetically Accelerated Ring to Achieve Ultra‐high Directed Energy and Radiation), is not a magnetic confinement fusion program like most spheromak efforts. Rather, the ultimate goal of the present program is to compress toroids to high mass density and magnetic field intensity, and to accelerate the toroids to high speed. There are a variety of applications for compressed, accelerated toroids including fast opening switches, x‐radiation production, radio frequency (rf) compression, as well as charge‐neutral ion beam and inertial confinement fusion studies. Experiments performed to date to form and accelerate toroids have been diagnosed with magnetic probe arrays, laser interferometry, time and space resolved optical spectroscopy, and fast photography. Parts of the experiment have been designed by, and experimental results are interpreted with, the help of two‐dimensional (2‐D), time‐dependent magnetohydrodynamic (MHD) numerical simulations. When not driven by a second discharge, the toroids relax to a Woltjer–Taylor equilibrium state that compares favorably to the results of 2‐D equilibrium calculations and to 2‐D time‐dependent MHD simulations. Current, voltage, and magnetic probe data from toroids that are driven by an acceleration discharge are compared to 2‐D MHD and to circuit solver/slug model predictions. Results suggest that compact toroids are formed in 7–15 μsec, and can be accelerated intact with material species the same as injected gas species and entrained mass ≥1/2 the injected mass.

KEYWORDS and PACS

Keywords

PLASMA CONFINEMENT, TOROIDAL CONFIGURATION, SPHEROMAK DEVICES, PLASMA GUNS, ACCELERATION, COMPRESSION, MAGNETOHYDRODYNAMICS, NUMERICAL SOLUTION, COMPACT TORUS

PACS

52.55.Jd

Magnetic mirrors, gas dynamic traps
52.30.Cv

Magnetohydrodynamics (including electron magnetohydrodynamics)
52.65.-y

Plasma simulation
41.20.Gz

Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems