Plasma loss in the levitated toroidal octupole

A detailed experimental investigation of plasma loss to the rings and walls of the levitated octupole has been made. The region around the internal rings of the octupole was of special interest, since this region can have absolute magnetohydrodynamic (MHD) stability when the plasma density gradient is directed away from the ring. Loss to the ring can be measured without supports or obstacles near the ring obscuring details of plasma behavior. Loss to the walls of the octupole was measured with 40 cm2 striped collector patches distributed around the machine, and with collectors mounted on a moveable cart. Loss to the rings was measured by 320 cm2 striped collector bands wrapped around the minor circumference of a ring. Loss information could be telemetered from the rings via a modulated light beam, with all wires, probes and supports removed from the vicinity of the ring