First-principles density limit scaling in tokamaks based on edge turbulent transport and implications for ITER

TL;DR

This paper derives a first-principles scaling law based on turbulent transport to predict the density limit in tokamaks, with implications for ITER's operational safety margin, showing better accuracy than empirical models.

Contribution

It introduces a turbulence-based density limit scaling law validated with multi-machine data, improving predictions for future tokamak performance.

Findings

The boundary turbulent transport increases with plasma collisionality.

The scaling law predicts a higher safety margin for ITER compared to empirical models.

The power dependence significantly influences the density limit predictions.

Abstract

A first-principles scaling law, based on turbulent transport considerations, and a multi-machine database of density limit discharges from the ASDEX Upgrade, JET and TCV tokamaks, show that the increase of the boundary turbulent transport with the plasma collisionality sets the maximum density achievable in tokamaks. This scaling law shows a strong dependence on the heating power, therefore predicting for ITER a significantly larger safety margin than the Greenwald empirical scaling (Greenwald et al, Nucl. Fusion, 28(12), 1988) in case of unintentional H-L transition.