Isotope and mixture effects on neoclassical transport in the pedestal
Conference contribution, 2017

The isotope mass scaling of the energy confinement time in tokamak plasmas differs from gyro-Bohm estimates, with implications for the extrapolation from current experiments to D-T reactors. Differences in mass scaling in L-mode and various H-mode regimes suggest that the isotope effect may originate from the pedestal. In the pedestal, sharp gradients render local diffusive estimates invalid, and global effects due to orbit-width scale profile variations have to be taken into account. We calculate neoclassical cross-field fluxes from a radially global drift-kinetic equation using the PERFECT code [Landreman et al. (2014) PPCF 56, 045005], to study isotope composition effects in density pedestals. The relative reduction to the peak heat flux due to global effects as a function of the density scale length is found to saturate at an isotope-dependent value that is larger for heavier ions. We also consider D-T and H-D mixtures with a focus on isotope separation. The ability to reproduce the mixture results via single-species simulations with artificial "DT" and "HD" species has been considered. These computationally convenient single ion simulations give a good estimate of the total ion heat flux in corresponding mixtures.

transport barrier

plasma

isotope effect

radially global

neoclassical

tokamak

Author

Istvan Pusztai

Chalmers, Physics, Subatomic and Plasma Physics

Stefan Buller

Chalmers, Physics, Subatomic and Plasma Physics

John Omotani

Chalmers, Physics, Subatomic and Plasma Physics

Sarah Newton

Chalmers, Physics, Subatomic and Plasma Physics

59th Annual Meeting of the APS Division of Plasma Physics, Milwaukee WI, USA

Vol. 62 12 YO4.12-

Driving Forces

Sustainable development

Areas of Advance

Energy

Subject Categories

Fusion, Plasma and Space Physics

More information

Created

12/26/2017