Isotope effect on gyro-fluid edge turbulence and zonal flows

TL;DR

This study investigates how ion mass differences influence turbulence and flows in tokamak edges, revealing that heavier isotopes reduce transport and that finite Larmor radius effects are significant, with limited impact from zonal flows.

Contribution

It provides the first detailed gyro-fluid simulation analysis of isotope effects on edge turbulence, highlighting the roles of ion polarisation and finite Larmor radius effects.

Findings

Transport decreases with increasing plasma mass for different isotopes.

Finite Larmor radius and polarisation effects significantly influence isotope effects.

Zonal flows have a minor role in isotope-related confinement improvements.

Abstract

The role of ion polarisation and finite Larmor radius on the isotope effect on turbulent tokamak edge transport and flows is investigated by means of local electromagnetic multi-species gyro-fluid computations. Transport is found to be reduced with the effective plasma mass for protium, deuterium and tritium mixtures. This isotope effect is found for both cold and warm ion models, but significant influence of finite Larmor radius and polarisation effects are identified. Sheared flow reduction of transport through self generated turbulent zonal flows and geodesic acoustic modes in the present model (not including neoclassical flows) is found to play only a minor role on regulating isotopically improved confinement.