Plasma Behavior in a Toroidal High-β Device

Abstract

The stability of a cusp magnetic field has been combined with the low loss rate of a closed field configuration in a series of three small toroidal devices designed for plasma containment. In operation, a pinch partly stabilized by an axial magnetic field, is produced prior to application of the containing cusp field. The axial stabilizing field of the pinch is then trapped by the plasma so that closed field lines are maintained within the plasma while the cusp is excluded from the plasma. There is no evidence of turbulence and the device exhibits a loss rate an order of magnitude below that to be expected from the same device operated as a minimum-B configuration without field trapping. Containment time is dependent on the decay rate of the applied cusp field. Maximum value of β within the plasma exceeds 2 and β remains above 1 for 15 μsec. Electron densities and temperatures exceed 1016 cm−3 and 105 °K, respectively.

Plasma containment in cusp-shaped magnetic fields

“…Ring cusp losses are expected at the magnetic field zeros in these regions, offsetting the advantages of a favourable curvature toroidal equilibrium. The toroidal line cusp or Tormak [14] is a toroidal version of the cross-field line cusp [9], and provides adiabatic particle trajectories, but retains line cusp losses. Questions are posed concerning the effect of the toroidal magnetic field curvature and gradient on particle trajectories, how the azimuthal current which contains the toroidal field within the sheath crosses the line cusps, and whether it leads to rotation of the plasma about the minor axis of the torus through the Hall effect [15].…”

“…-H (16) qA -. -( p y -~^) " 2mq*| F(H,p y )dHdp y < + (14) where the range of integration is given by Eq. ( 14).…”

Study of ion line broadening in the Tormac discharge

“…The T IV-c experiment is the smaller of the two considered nere. 7,21,33,34,35 The vacuim vessel is a glass torold of rectangular cross section ( The rise time is -10 usee, giving an inductance of -1.0 uH and a resistance of -lOmrt. The bank is crrwbarred by 7703-type ignitrons mounted directly on the windings at the vessel, 8 ignitrons for each of the three sections.…”

Transient evolution and steady-state emission from passively mode-locked lasers

“…Spine [18] (Federal Republic of Germany) is a toroidal theta pinch with a superimposed hexapole field. Other devices, such as Tormac [19][20][21] (USA), use toroidal line cusps and multipole magnetic fields.…”