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.