Scaling of Electron and Ion Transport in the High-Power Spherical Torus NSTX

Dedicated H-mode parameter scans in the high-power National Spherical Torus Experiment have been used to establish the confinement scaling and underlying transport trends at low aspect ratio (R/a1.3). These scans indicate a strong dependence of the global and thermal energy confinement times on the toroidal field, BT0.9, while their dependence on plasma current is weaker, Iₚ0.4. Local transport analysis indicates that the electrons control the BT scaling, whereas the ions control the Iₚ scaling, with χᵢ outside $r/a=0.5$ at the neoclassical level.