ITER-grade tungsten limiters damage under high turbulent heat flux in the T-10 tokamak

Highlights: • The ITER-grade tungsten limiters tested in the T-10 tokamak. • Strong destruction of the limiters under the combination of the high heat and particle fluxes observed. • Intensive cracking of the tungsten tiles observed at the heat loads from 1 MW/m² up to 30 MW/m². • In the areas of highest heat loads, tungsten plates were melted and close to full destruction. • The nonambipolar flow due to the arcs and sparks can explain the observed overheating and melting of the tungsten surface. -- Abstract: The tungsten limiters were tested in the T-10 tokamak during the 2015–2017 experimental campaign. The limiters were made from the ITER-grade WMP "POLEMA" tungsten. Inspection of the tungsten limiters after experimental campaign has revealed their strong destruction due to the combination of the high heat and particle fluxes from the edge plasma toward the limiters surface. The influence of the edge tokamak plasma on tungsten limiters leads to significant cracking of the tungsten. Heat load up to 2 MW m^âˆ'² leads to micro-cracks at the grain boundaries. Heat loads exceeding 5 MW m^âˆ'² lead to macro-cracks formation. In the areas of highest heat loads, tungsten plates are melted and close to full destruction. In these zones, intensive sparking and arcing were observed. Arc craters have been scattered across the surface, and along the cracks. It is supposed that the nonambipolar flow due to the arcs and sparks can explain the observed overheating and melting of the tungsten surface. Disruptions and runaway electrons beams have driven extreme heat loads of more than 1 GW/m² causing strong melting of the tungsten on the outer board of the ring limiter.