Modeling uc(Pegasus) Plasmas with TSC

The operational space of the uc(Pegasus) ST will be significantly expanded by recent upgrades: shape and position control, increased and time variable toroidal field, increased ohmic flux, and V_loop control. The Tokamak Simulation Code (TSC)(S.C. Jardin, J.L. DeLucia, N. Pomphrey, J. Comput. Phys. 66), 481 (1986). is used to model plasma evolution in a number of scenarios in order to determine accessible paths to high toroidal field utilization and beta. Various startup scenarios and fast TF rampdown are under study. The focus of the startup studies is optimization of the V_loop waveform and plasma position during the startup. Fast TF rampdown is a tool that may allow access to high I_p/I_tf and β_t, but which could be destabilizing if overdriven. Initial studies show that a 50% TF rampdown in 3 ms increases β_t by a factor of 4 while keeping β_p relatively constant, and drives parallel edge current that reduces l_i and q_95.