Plasma toroidal

The Spheromak has been presented by Dr. M. Okaba-yashi. The toroidal plasma has an aspect ratio not much larger than 1 the complex device proposed for the production of the plasma configuration is hardly compatible with the neutronics associated with the burning phase. Thus it has been proposed to extrude the plasma toroid from the place of formation and guide it magnetically to the place of burning. 

This deleterious effect can be obviated by introducing additional components of magnetic field, causing the field lines to circumscribe the toms without ever closing on themselves. The net magnetic field is then composed of a major, or toroidal, field component produced by the current cods, plus a smaller poloidal component which gives the desired twist to the lines. Particle drifts weaken or nullify the harmful electrical field and the plasma no longer tends to move to the wads. 

ATC Adiabatic Toroidal Compiessoi Princeton Plasma Physics Laboratory (PPPL), Princeton, N.J. 

Most schemes that have been proposed to propel starships involve plasmas. Schemes differ both in the selection of matter for propulsion and the way it is energi2ed for ejection. Some proposals involve onboard storage of mass to be ejected, as in modem rockets, and others consider acquisition of matter from space or the picking up of pellets, and their momentum, which are accelerated from within the solar system (184,185). Energy acquisition from earth-based lasers also has been considered, but most interstellar propulsion ideas involve nuclear fusion energy both magnetic, ie, mirror and toroidal, and inertial, ie, laser and ion-beam, fusion schemes have been considered (186—190). 

Schematic of a fusion reactor, assuming a generally toroidal shape of the plasma and magnetic fusion. The principles emphasized are central hot core (red) at 100 million degrees, blanket and heat exchanger, shield, energy conversion, and the handling of D, T, and the "ash" He.

D. T. Young, J. A. Marshall, J. L. Burch, T. L. Booker, A. G. Ghielmetti, and E. G. Shelley. A Double-Focusing Toroidal Mass Spectrograph for Energetic Plasmas. II Experimental Results, Nucl. Instr. and Meth., A258(1987) 304. 

Early experience also showed that the induced plasma current in a tokamak generates a magnetic field that loops die minor axis nf Ihe torus. The field lines form helices along the toroidal surface the plasma must cross the lines to escape. It does so through the cumulative action of many random displacements caused by interparticle collisions, tin effect diffusing across the field lines and out of the system). Thermal energy is transported by much the same process. 

In other early, commonly explored toroidal devices, the required equilibrium w as supplied by means of externally imposed twisted multiple magnetic fields. The stelleraror design developed by the Princeton Plasma Physics Laboratory was representative of this approach. 

With this expression for B, we find that the field fines for the solution assume a key geometric relationship in addition to the previously considered axisymmetric helicoidal solutions exemplified in the vortex filaments of the plasma focus. Several researchers [43,44] have termed P the poloidal solution and T the toroidal solution. Accordingly, if the equation for B is expressed in terms of... 

The stellarators are similar to Tokamaks, both employing a closed toroidal magnetic field for basic plasma confinement. The stabilization in stellarators is, however, provided by special helical windings16. They possess some potential advantages as compared to the Tokamaks with respect to confinement properties and the possibility of steady state operation. Technical and technological limitations such as the small size of the presently available stellarators and the lack of appropriate, sufficiently intense heating systems have inhibited progress comparable to that which Tokamaks have so far achieved. 

Both the open and closed (toroidal) configurations are feasible but the latter is preferred because of the elimination of plasma losses at the ends. 

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