Scaling law for effective heat diffusivity in ELMy H-mode plasmas

Transport simulations of high density scenarios of ITER and other reactor-grade devices require a scaling law for the effective heat diffusivity, chi, in the ELMy H-mode regime. A comprehensive empirical scaling, chi(H98), compatible with the ITER reference scaling, ITERH-98P(y, 2), for the thermal energy confinement time has been set up. It follows from a power law ansatz for chi and integration of the single-fluid energy equation and recovers all the exponents of the global confinement law. The dependences on temperature and temperature gradient are consistent with the power degradation of confinement and the experimental chi profiles. The chi(H98) scaling is validated by JET, DIII-D, ASDEX Upgrade and ASDEX discharges covering a wide parameter range. Simulations of the inductive scenario of ITER with chi(H98) yield an energy confinement time which agrees with the global scaling prediction.