Damage structure in divertor armor materials exposed to multiple ITER relevant ELM loads

Abstract: The damage threshold and damage mechanisms of divertor armor materials, i.e. CFC and tungsten, were studied under the impact of ITER relevant ELM-like loads. These experiments were carried out in a Quasi-Stationary Plasma Accelerator applying repetitive pulses of 500μs up to 100 cycles. CFC showed preferential erosion of the PAN fiber-bundles above 0.6MJ/m2 and cracking of pitch fiber-bundles. Tungsten showed cracking already at 0.2MJ/m2 and melting at flat surfaces above 1MJ/m2. Cracks in tungsten were identified as primary and secondary cracks which all propagated in the vertical direction, which was considered to be less critical. At an energy density of 1.5MJ/m2, the melt-layer completely covered the surface and bridged the castellation slots. [Copyright &y& Elsevier]