Deuterium-tritium simulations of the enhanced reversed shear mode in the Tokamak Fusion Test Reactor

Abstract

The potential performance, in deuterium-tritium plasmas, of a new enhanced confinement regime with reversed magnetic shear [enhanced reversed shear (ERS) mode] is assessed. The equilibrium conditions for an ERS mode plasma are estimated by solving the plasma transport equations using the thermal and particle diffusivities measured in a short duration ERS mode discharge in the Tokamak Fusion Test Reactor [F. M. Levinton et al., Phys. Rev. Lett. 75, 4417 (1995)]. The plasma performance depends strongly on Zeff and neutral beam penetration to the core. The steady-state projections typically have a central electron density of ∼2.5×1020 m−3 and nearly equal central electron and ion temperatures of ∼10 keV. In time-dependent simulations the peak fusion power, ∼ 25 MW, is twice the steady-state level. Peak performance occurs during the density rise when the central ion temperature is close to the optimal value of ∼15 keV. The simulated pressure profiles can be stable to ideal magnetohydrodynamic instabilities with toroidal mode number n=1,2,3,4 and ∞ for βnorm up to 2.5; the simulations have βnorm⩽2.1. The enhanced reversed shear mode may thus provide an opportunity to conduct alpha physics experiments in conditions similar to those proposed for advanced tokamak reactors.