Plasma-Facing Materials Erosion Under ITER-Like Transient Loads at QSPA Plasma Gun Facility

The beryllium (Be) plasma-facing components (PFCs) of the ITER first wall (FW) were tested in the plasma gun QSPA-Be under pulsed plasma heat loads of 0.5-ms duration relevant to those expected in ITER during transient plasma events (edge-localized modes and disruptions). The experiments were performed for different Be grades (Russian TGP-56FW and US S65-C). The measured Be melting threshold decreases from 0.5 MJm(-2) down to 0.4 MJm(-2) with Be initial temperature increasing in the range of 250-500 degrees C. Under plasma heat loads on the exposed surface below the melting point the Be PFC erosion was mainly due to melting of the plasma-facing and lateral edges of the Be tiles. Under plasma heat loads above the melting point the Be PFC erosion was mainly due to intense melt layer movement and splashing. The Be melt layer behavior at 0.5 and 1.0 MJm(-2) is similar to early investigated W melt layer behavior at higher heat loads of 1.0 and 1.5 MJm(-2) correspondingly. Unlike W the Be erosion rate significantly increases with initial temperature in the range of 250-500 degrees C. These experimental observations are supported by calculation of temperature dynamics and melt layer thickness dynamics.