Session 1S - TFTR.
POSTER session, Monday morning, November 11
Exhibit Hall - Concourse Level, Adam's Mark
Typically, TFTR supershot plasmas evolve to a peak energy content after about 0.5 sec of neutral beam heating. Thereafter, the confinement time, energy content, and neutron emission degrade (termed rollover); about 15% of TFTR plasmas have negligibly small rollover. A data base of 1450 TFTR plasmas (from July 1993 to September 1995) has been created and the dominant MHD activity has been identified in each plasma. The magnitude of the observed MHD is sufficient to explain the observed confinement degradation in only about 15% of the plasmas. The MHD confinement degradation was described by Z. Cheng ( Z. Cheng, et al., Nucl. Fus. \bf34), 1309 (1994) for 2/1, 3/2, and 4/3 m/n islands as due to a large conductivity over the island width. Eighty percent of the plasmas do not have observable MHD but many still have rollover. The rollover of these plasmas correlated with the magnitude of deuterium influx from the TFTR limiters.