Physical Design and Transport Simulation of the STOR-U Tokamak

The Saskatchewan TORus Upgraded (STOR-U) tokamak is a new spherical tokamak (ST) with tight aspect ratio = 1.7, plasma major/minor radius = 55/32 cm, plasma current 2 MA and 1.5 T toroidal field. The research scope of the STOR-U project covers ST engineering, high $\beta$ plasma confinement and transport, advanced plasma fueling by compact torus injection, helicity injection for plasma start-up and development of advanced plasma diagnostics. In this presentation, design and numerical studies on STOR-U toroidal/poloidal field systems are described. Various plasma equilibria have been obtained to meet the discharge requirements through variation in elongation, ($k \leq 3$), triangularity ($\Delta \leq 0.5$) and divertor configurations. The poloidal coil current waveforms have been determined for plasma breakdown and start-up. In addition, STOR-U plasma transport simulations have been carried out using the ASTRA code. The results reveal that, compared with purely ohmic heating, 3MW NBI heating significantly increases both $T_i$ and $T_e$ by $46\%$ and $15\%$, achieving 2.4 and 2.2 $keV$ (at center), respectively. Bootstrap current ratio, $f_{bs}$, is larger than $50\%$. Results of simulation with different transport models are also presented.