The empirical scaling of the electron thermal diffusivity, χe, is investigated for more than 100 beam-heated discharges. These discharges include two major features: 1) high-temperature and high-density plasma (Te(0)≈Ti(0)≈2.5–3 keV at e≈(5–7) × 1013 cm−3, PNBI ⪅ 4 MW), which will be the basis for the breakeven experiments in the next-generation tokamaks, 2) three types of discharges, i.e. good and poor confinement divertor discharges and limiter discharges. – All kinds of discharges (good heating and poor heating divertor discharges, limiter discharges) have fhe same functional form in χe within ∼ 40% at 0.25 a < r < 0.65 a, where χe in the simplest expression scales as χe ∝ 1/ne. The ion thermal diffusivity, χi, is consistent with the assumption that the neoclassical χi can be applicable to our three kinds of discharges. For discharges with different heating efficiency, there is no systematic difference, in the adjustable multiplier, to the neoclassical theory by Hinton-Hazeltine for an ion collisionality of νi* = 0.02–0.5.
Simulation of transport in ASDEX divertor discharges with neutral-injection heating