Characteristics and Stability of OH Plasma in the Pegasus Toroidal Experiment
Abstract
Present experimental campaigns on the Pegasus Toroidal Experiment are concerned with accessing q- and beta-limits in an ultra-low aspect ratio plasma. To date, Pegasus plasmas are heated with an OH solenoid, but an additional HHFW heating system is scheduled for operation in the near future. For A =1.15-1.4, Ro = 0.2-0.4 m, kappa = 1.5-2, Ip < = 0.15 MA, and Bt < = 0.07 T, plasmas appear limited by a global m/n = 2/1 mode, as observed on both external and internal diagnostics. The mode exists over a large, low-shear area of the plasma. Magnetic equilibrium reconstructions of these plasmas show betat < = 25 % with no instabilities due to beta yet evident. Efforts to suppress the 2/1 mode include; 1) Increasing Te, by raising the plasma current density, adding volt-seconds to the OH power supply, and RF heating; and 2) Raising the plasma q-profile with increased toroidal magnetic field. Preliminary auxiliary heating with a HHFW RF system has begun. This system supplies bulk Te heating with < = 0.5 MW of power.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2001
- Bibcode:
- 2001APS..DPPRP1033U