Results of high heat flux tests of tungsten divertor targets under plasma heat loads expected in ITER and tokamaks (review)

Abstract

Heat loads on the tungsten divertor targets in the ITER and the tokamak power reactors reach ~10MW m⁻² in the steady state of DT discharges, increasing to ~0.6–3.5 GW m⁻² under disruptions and ELMs. The results of high heat flux tests (HHFTs) of tungsten under such transient plasma heat loads are reviewed in the paper. The main attention is paid to description of the surface microstructure, recrystallization, and the morphology of the cracks on the target. Effects of melting, cracking of tungsten, drop erosion of the surface, and formation of corrugated and porous layers are observed. Production of submicron-sized tungsten dust and the effects of the inhomogeneous surface of tungsten on the plasma–wall interaction are discussed. In conclusion, the necessity of further HHFTs and investigations of the durability of tungsten under high pulsed plasma loads on the ITER divertor plates, including disruptions and ELMs, is stressed.