- - 1 - Disruptive MHD Activity during Plasma

During the current rise phase of the Alcator A discharge a series of disruptions occurs, related to MHD activity of poloidal periodicity m, at limiter q values approximately 1.6 m (m integral). The electron temperature profile is peaked at the-center throughout. It is shown, however, that current diffusion with the experimental T profiles typically leads to hollow current profiles and that the disruptions appear to be related to the local minimum of q inside the plasma attaining near-integral values. Disruptions may be avoided by decreasing the rate of current rise. This leads to improved plasma conditions throughout the discharge.