Isotopic scaling of confinement in deuterium-tritium plasmas

The confinement and heating of supershot plasmas are significantly enhanced with tritium beam injection relative to deuterium injection in the Tokamak Fusion Test Reactor [Plasma Phys. Controlled Fusion 26, 11 (1984)]. The global energy confinement and local thermal transport are analyzed for deuterium and tritium fueled plasmas to quantify their dependence on the average mass of the hydrogenic ions. Radial profiles of the deuterium and tritium densities are determined from the D-T fusion neutron emission profile. The inferred scalings with average isotopic mass are quite strong, with τ_E∝〈 A〉^0.85±0.20, τ_E^thermal ∝ 〈A〉^0.89±0.20, χ_i^tot ∝ 〈A〉^-2.6±0.5, and D_e∝〈A〉 ^-1.4±0.2 at fixed P_inj. For fixed local plasma parameters χ_i^tot ∝ 〈A〉 ^-1.8±0.4 is obtained. The quoted 2σ uncertainties include contributions from both diagnostic errors and shot irreproducibility, and are conservatively constructed to attribute the entire scatter in the regressed parameters to uncertainties in the exponent on plasma mass.