Observation of an improved energy-confinement regime in neutral-beam<i>–</i>heated divertor discharges in the DIII-D tokamak

TLDR

The DIII‑D tokamak with an expanded boundary divertor achieves H‑mode confinement. Neutral‑beam heating up to 6 MW maintains energy confinement comparable to Ohmic levels at 1 MA, independent of density and toroidal field, increases with plasma current, and demonstrates that H‑mode can be achieved in a reactor‑compatible open divertor.

Abstract

Tokamak discharges using the expanded boundary divertor in the DIII-D device exhibit H-mode confinement. With neutral-beam power up to 6 MW, energy confinement remains comparable to the Ohmic value at a plasma current of 1 MA. Confinement is also independent of plasma density and toroidal field. Confinement increases with plasma current, but the exact functional dependence is, as yet, uncertain. These results show that the H mode can be achieved in a reactor-compatible open divertor configuration.