Isotope and plasma size scaling in ion temperature gradient driven turbulence

Abstract

This Letter presents the impacts of the hydrogen isotope mass and the normalized gyroradius ρ* on L-mode like hydrogen (H) and deuterium (D) plasmas dominated by ion temperature gradient driven (ITG) turbulence using global full-f gyrokinetic simulations. In ion heated numerical experiments with adiabatic electrons, the energy confinement time shows almost no isotope mass dependency and is determined by Bohm like ρ* scaling. Electron heated numerical experiments with kinetic electrons show clear isotope mass dependency caused by the isotope effect on the collisional energy transfer from electrons to ions, and the H and D plasmas show similar ion and electron temperature profiles at an H to D heating power ratio of ∼1.4. The normalized collisionless ion gyrokinetic equations for H and D plasmas become identical at the same ρ*, and collisions weakly affect ITG turbulence. Therefore, the isotope mass dependency is mainly contributed by the ρ* scaling and the heating sources.