摘要:

Tormac (ToroidalMagneticCusp) is a plasma confinement concept combining the favorable magnetohydrodynamic stability properties of a cusp geometry with the good particle confinement inherent to closed field geometry. A conceptual Tormac plasma has two regions; an interior region in which a toroidal bias or stuffing field is embedded, and an exterior or surface region confined by mirror trapping along open field lines. The combination of these two regions is expected to lead to a configuration having confinement substantially superior to that of a mirror, and to allow the plasma to be stable to high &bgr;. The Tormac V experiment is an attempt to establish such a configuration and to investigate the characteristic behavior of the Tormac plasma. The Tormac concept, the Tormac V experimental setup, and the results are described.

ISSN:0031-9171    

DOI:10.1063/1.863631

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Zakharov and Shafranov’s method for deriving plasma displacement and averaged shape in a tokamak from magnetic probes positioned along a contour around the plasma cross section is extended in several ways. Formulas are derived which allow vertical as well as horizontal displacements with any ratio of minor contour width to major radius, asymmetric as well as symmetric multipole moments, and explicit relations for rectangular as well as circular contours. The relations in the literature for a circular contour are also re‐examined and corrected equations are given. It is shown that a rectangular contour can provide the same information.

ISSN:0031-9171    

DOI:10.1063/1.863632

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The effect of a radially bounding wall on a magnetically confined single‐species plasma near thermal equilibrium is considered. Solutions to the like‐particle collisional transport equation are obtained; the boundary conditions at the wall follow from simple physical considerations. Integral constraints on the plasma evolution imply that only a fraction of the plasma can ever be lost to the wall. Analytic estimates and numerical solutions give the scaled wall flux in terms of the unperturbed equilibrium density at the radius of the wall.

ISSN:0031-9171    

DOI:10.1063/1.863634

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A fluid model for the flow conditions necessary to form a compact torus from the plasma ejected by a coaxial plasma gun is developed. This is done by finding the conditions for which the steady‐flow equations break down. Results are found for two cases; variable external flux and variable outer‐wall radius.

ISSN:0031-9171    

DOI:10.1063/1.863608

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A finite‐difference, resistive, magnetohydrodynamic code is used to follow the long‐time evolution of decaying nonequilibrium states inside a rigid, perfectly conducting cylindrical boundary. The energy‐to‐magnetic helicity ratio decays toward a minimum, in accord with a conjecture of Taylor. The magnetic Reynolds number is considerably higher than the mechanical Reynolds number for the regime considered. The energy, which is mostly magnetic, tends to decay in bursts associated with current filamentation and magnetic reconnection.

ISSN:0031-9171    

DOI:10.1063/1.863609

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Magnetohydrodynamic stability of force‐free spheromak plasmas ton= 1 free boundary tilt and radial shift modes is studied. The exterior region of open field lines is treated either as a conducting plasma or as a vacuum. In the former case the effect of line tying of the open field lines is present and is found to improve stability greatly. The equilibria which have optimum stability properties to the tilt and shift modes have a length‐to‐diameter ratio of 0.6, and can be stable with conducting walls at a relatively large distance.

ISSN:0031-9171    

DOI:10.1063/1.863610

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Plasma equilibrium with dissipation is governed by more equations than the one used for stability problems in ideal magnetohydrodynamics. Consequently, as transport processes became more important in fusion experiments, it is necessary to determine whether an equilibrium will eventually be reached after a long time at the end of the transport processes. A study is made of a cylindrical plasma with an ohmic heating current as an approximation to a large aspect‐ratio tokamak. For comparison, both single‐fluid theory and two‐fluid theory are used. It is found that no equilibrium exists in the single‐fluid theory with a plasma temperature dropping to zero at a finite radius, while such an equilibrium does exist in two‐fluid theory provided that the electron temperature is higher than twice the ion temperature. Both the low‐pressure and high‐pressure cases are studied in the tokamak parameter range. Analytical results for the plasma behavior near its edge are also obtained.

ISSN:0031-9171    

DOI:10.1063/1.863611

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The kinetic energy principle is modified by the presence of an equilibrium electrostatic potential and the inclusion of the quasineutrality condition. By identifying terms that are fluid‐like (local) and kinetic (nonlocal), one can express the change in potential energy, &Dgr;W, in a form which is both variational and minimizing and also displays, clearly, the electrostatic effects on the various free energy sources. The kinetic energy principle determines the stability of the plasma to perturbations that grow on the time scale associated with the streaming of particles along field lines. Recently, a new variational principle has been proposed which determines the stability of the plasma to perturbations that grow on the time scale associated with the drifting of particles across field lines. The modifications of this principle due to electrostatic effects will also be considered, and cases in which necessary and sufficient conditions for instability can be found will be discussed.

ISSN:0031-9171    

DOI:10.1063/1.863612

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Ripple transport in tokamaks is discussed for the ’’banana drift’’ collisionality regime, which lies below the ripple plateau regime treated earlier. The physical mechanisms that dominate banana drift transport are found to differ from those considered in previous work on this regime, and consequently the resulting transport coefficients can differ by several orders of magnitude.

ISSN:0031-9171    

DOI:10.1063/1.863635

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Steady‐state temperature profiles in a magnetically confined tokamak type plasma are derived by balancing Ohmic power input, thermal diffusion, and radiation. A comprehensive study is presented of the impact that different electron conductivities,K⊥boundary conditions, and radiation may have on thermal stability. In particular, their influence on the bifurcation in the position of the minor radius as a function of the temperature at the centerTmis considered. Points of bifurcation correspond to marginally stable equilibria. However, it is also possible to have both branches without marginally stable equilibrium. Critical values of parameters that cause the onset of a new branch or instability are determined. Growth rates are not calculated, but domains of stabilty of all possible equilibria are determined. It is shown that Ohmically heated plasma in the classical scaling is thermally unstable to convective boundary conditions or if the plasma is cold at the edge. It is shown that a finite temperature at the edge will generate a stable, lower branch, but the upper branch will be unstable as long asp<0.5, whereK⊥(T)∼Tp.

ISSN:0031-9171    

DOI:10.1063/1.863613

出版商:AIP    

年代:1982

数据来源: AIP