Characteristics of transient plasma layers produced by irradiation of graphite targets by high power quasi-stationary plasma streams under the disruption simulation conditions

Simulation experiments to model the situation occurring at the divertor plates during disruptions and ELMy H-modes of tokamak were carried out with plasma streams generated at the Kharkov QSPA. The facility ultimate plasma parameters were as follows: plasma energy density — above 2 kJ/cm 2, proton energy — 0.9 keV, plasma density — 10 16 cm −3, pulse duration — 0.1–0.15 ms. Graphite targets of different sizes utilized in these experiments. It was shown that high density target plasma layer, with densities up to 6 · 10 17 cm −3, were formed above the target surface, when incident plasma interacted with target, and sustained during the whole pulse. Density and thickness (usually within 3 to 5 cm) increased with increasing incident plasma power and target surface. The main part of incident plasma energy (≈ 90%) is absorbed by the transient layer on the first 2–3 cm of its thickness. The average erosion coefficient of the graphite under the influence of incident plasma was of the order of 1 μm/kJ.