Natural Fueling of a Tokamak Fusion Reactor

TL;DR

This paper discusses a natural inward fueling mechanism in tokamak fusion reactors driven by ion-temperature gradient turbulence, which helps maintain core fuel density and reduces turbulence growth rates.

Contribution

It introduces a natural fueling process in tokamaks driven by ITG turbulence, supported by gyrokinetic simulations and quasilinear analysis, enhancing understanding of plasma fueling.

Findings

Natural fueling causes inward pinch of cold DT ions near the edge.

It reduces linear growth rates of turbulence and energy transport.

The mechanism applies even with electron kinetic effects included.

Abstract

A natural fueling mechanism that helps to maintain the main core deuterium and tritium (DT) density profiles in a tokamak fusion reactor is discussed. In H-mode plasmas dominated by ion- temperature gradient (ITG) driven turbulence, cold DT ions near the edge will naturally pinch radially inward towards the core. This mechanism is due to the quasi-neutral heat flux dominated nature of ITG turbulence and still applies when trapped and passing kinetic electron effects are included. Fueling using shallow pellet injection or supersonic gas jets is augmented by an inward pinch of could DT fuel. The natural fueling mechanism is demonstrated using the three-dimensional toroidal electromagnetic gyrokinetic turbulence code GEM and is analyzed using quasilinear theory. Profiles similar to those used for conservative ITER transport modeling that have a completely flat density profile are examined and it is found that natural fueling actually reduces the linear growth rates and energy transport.