Electron plasmas with mean densities of 5.0 x 10(6) cm(-3) have been confined for as long as 18 ms in a partially toroidal trap with a purely toroidal magnetic field (B(0)=196 G, R(o)=43 cm, a=5 cm). Confinement is limited to 2.0 ms unless feedback is employed to suppress the growth of a toroidal version of the m=1 diocotron mode. The confinement time is much longer than all characteristic single-particle drift time scales and therefore confirms the existence of an equilibrium in which the space-charge-generated E x B drift acts as an effective rotational transform.

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