Nonambipolar radial particle transport in a tandem mirror

Abstract

Nonambipolar transport has been measured in the tandem mirror TMX-U [Phys. Rev. Lett. 53, 783 (1984)] by applying charge conservation to the measured electron currents to the end walls. The resulting confinement time τ⊥ is found to depend upon the central-cell potential φ approximately as τ⊥(msec) =3φ(kV)−2. The transport rate, deduced from the data, agrees to within a factor of 1–5 with resonant-transport theory applied to the measured plasma parameters. Attempts to include radial effects by modeling the plasma self-consistently using resonant transport are less successful; near the axis the transport coefficients become too small to explain the equilibrium. Modeling using an ad hoc φ−2 law for the transport coefficients is more successful.

Rotation and shear control of a weakly magnetized plasma column using current injection by emissive electrodes

“…Most of these studies focused on the influence of the bias of cold limiters, concentric rings or grids on the rotation profiles and on the rotation-shear profiles of plasma columns or plasma tori (Hooper et al. 1985; Tsushima et al. 1986; Severn et al.…”

Radial transport in a tandem mirror

“…Theoretically, 3 ' 4 quadrupole magnetic fields used for MHD stability enhance the radial losses because resonant ions, which drift azimuthally by an odd multiple of /r/2 each axial bounce, experience large radial geodesic curvature drifts. In TMX-U, 5 the radial loss rate v± increases with potential <j> as expected from resonant transport (RT). However, the measured magnitude and radial variation of v± are inconsistent with RT theory.…”

Neoclassical resonant plateau transport calculation in an effectively axisymmetrized tandem mirror with finite endplate resistance

“…However, the non-self-consistent analysis leads to a discrepancy with the experiments, i.e. r^A(r) scales roughly as r" 2 in the calculation while the TMX-U data indicate that r^A(r) is almost independent of r [8]. An attempt to calculate the self-consistent radial potential profile in the TMX configuration faced a bifurcation problem as well as certain difficulties in defining the boundary conditions of the potential profile [9].…”

“…It is also important to calculate the radial potential self-consistently for radial transport because the neoclassical resonant plateau transport depends sensitively on the radial electric field. In analysing the radial transport in TMX-U [8], a parabolic radial potential profile was assumed for evaluating the neoclassical resonant plateau transport. However, the non-self-consistent analysis leads to a discrepancy with the experiments, i.e.…”