Wall-locking and phase-locking modes are studied in detail in a reversed-fi
eld pinch device, TPE-RX [Y. Yagi , Fusion Eng. Design 45, 409 (1999)]. The
se mode-locking phenomena arise from tearing instabilities. Wall locking me
ans the stopping of mode rotations, and phase locking means the locking of
the phases of multiple modes. Phase locking induces a toroidally localized
enhanced magnetic amplitude. There are two types of mode-locking states in
TPE-RX. One of them exhibits a clear phase-locked structure, while the othe
r exhibits a weak toroidal localization. Both types show finite toroidal ro
tation during the current-rising phase of the discharge, and are eventually
wall locked during the current flat-top phase. However, the rotation speed
s are clearly different between the two types. Confinement properties are c
ompared between the two types of mode-locking states. It is shown that the
threshold for the mode amplitude necessary to wall lock the toroidal rotati
on, as well as the bifurcation of phase-locked structures, agrees with theo
retical predictions [R. Fitzpatrick , Phys. Plasmas 6, 1168, 3878 (1999)].
(C) 2001 American Institute of Physics.