Fusion Science and Technology / Volume 60 / Number 1T / July 2011 / Pages 34-39
The paper concerns experimental investigations of metallic material erosion under the plasma heat loads expected in ITER divertor during transient events such as the type I edge-localized modes and the disruptions. Primary attention is focused on the erosion due to melt layer movement and splashing. The targets of tungsten and other metals were repeatedly exposed to hydrogen plasma flow of 0.5 ms duration in the heat load range of 0.2-4.5 MJ/m2 at the TRINITI plasma gun QSPA-T. The ejection of liquid droplets was observed during plasma exposure by special recoded system and onset conditions of droplets ejection were defined. Between some of the plasma pulses the eroded surface was analyzed with profilometry and microscopy. The mass loss and exposed surface profile were measured as a function of heat load and number of pulses. Experimentally measured target thinning due to melt layer removal from the exposed area to periphery was compared with erosion due to mass loss as a result of droplets ejection and evaporation. The obtained surface profile was compared with the result of numerical calculations which based on simultaneous solving of the 2-D heat conductivity equation and hydrodynamics equations of “shallow water” approximation.