Madison Symmetric Torus

The features of a new reversed-field pinch (RFP) called the Madison Symmetric Torus (MST) are described. The device was designed for the dual purpose of exploring the basic physics of the RFP boundary configuration and of functioning as a key support experiment for the ZTH (1992) and RFX (1990) pinches. Its moderately large size for present day RFPs (R = 1.5 m, a = 0.52 m) and expected plasma parameter ranges were selected to ensure relevance to programmatic studies. Key design features focused on flexibility and low magnetic field error. The aluminum vessel functions as vacuum wall as well as conducting shell and carries the poloidal current needed for establishing the toroidal field, while the iron core bears the coils for exciting the polodial field. Thus, no external windings obscure diagnostic access. There are single poloidal and toroidal gaps, and the machine is split at the midplane. The top half of the device can be easily lifted for access into the vacuum chamber and modification of the boundary, limiters, or first wall features. A major unconventional feature, initial operation without a resistive liner, necessitated a voltage gap within the plasma region.