Noninductively Driven Tokamak Plasmas at Near-Unity Toroidal Beta
AbstractAccess to and characterization of sustained, toroidally confined plasmas with a very high plasma-to-magnetic pressure ratio (βt), low internal inductance, high elongation, and nonsolenoidal current drive is a central goal of present tokamak plasma research. Stable access to this desirable parameter space is demonstrated in plasmas with ultralow aspect ratio and high elongation. Local helicity injection provides nonsolenoidal sustainment, low internal inductance, and ion heating. Equilibrium analyses indicate βt up to ∼100% with a minimum |B| well spanning up to ∼50% of the plasma volume.