Magnetic aspects of the passive stabilizing structure in TPX

The advanced operating modes of TPX require both passive stabilization and active control of critical magneto hydrodynamic (MHD) modes. TPX contains a inner passive stabilizer, an outer passive stabilizer, and a set of active fast position control coils inside the TPX vacuum vessel. The passive structure is placed close to the plasma surface and covers enough of the plasma surface area in appropriate locations to provide good inductive coupling to the unstable modes. Access requirements for heating systems, diagnostics, divertors, and planned maintenance operations constrain the area available for the conductor coverage. This paper describes the TPX passive stabilizing structure. This includes the special analysis techniques developed to (1) assess kink stabilizing performance, (2) approximate these structures as simple axisymmetric structures for startup, disruption, and position control analysis, and (3) estimate the field errors produced by the eddy currents in these structures.