Toroidal studies of sawtooth oscillations in tokamaks

Tokamak sawtooth oscillations are studied with a nonreduced, fully toroidal, resistive MHD (magnetohydrodynamic) model that includes ohmic heating, and parallel and perpendicular thermal conduction. Effects of perpendicular transport in producing different types of sawteeth, varying form simple, periodic oscillations to giant sawteeth with temperature modulations of order unity, and compound sawteeth with multiple relaxations, are demonstrated. Some of the recent experimental observations from large tokamaks, such as the fast crash times and a presumed topological anomaly in the x-ray tomography pictures, thought to be inconsistent with the Kadomtsev reconnection model, are examined and possible explanations are offered. 23 refs., 17 figs