Session GP1 - Poster Session IV.
POSTER session, Tuesday afternoon, October 30
Exhibit Hall B,
An n=1 mode global motion on FRC plasma can be easily controlled by a multi pole field, though the deviation of the plasma center from the coil axis reaches about 20-40% of a separatrix radius on the onset of the n=2 rotational mode. The critical field strength is about 15% of the confinement one and the n=2 mode can also be stabilized by the same strength. The origin of the motion hasn't yet been clarified. An azimuthal asymmetry of a radial pinch may be triggered by an asymmetrical magnetic field reconnection at the formation phase and transferred to the n=1 motion by the axial contraction. By the enhancement of the asymmetry, the motion occurs earlier and the amplitude of the deviation increases. To avoid the asymmetry, the non-tearing formation method is introduced. Preliminary experimental data indicate that the deviation of the n=1 motion decreases within a factor of two. We'll measure the behavior of the n=1 motion at the non-tearing formation quantitatively by optical detectors and a magnetic probe array. The behavior will be compared with simulations derived by a 2-D snowplow model.