Analysis of Interaction of Disruption Induced Runaway Electrons with Plasma Facing Components in Next Generation Tokamaks.

Abstract

Runaway electrons which are accelerated during plasma disruptions may cause damage to the plasma facing components when their energy is deposited locally. In order to assess the possible damage of plasma facing components and the associated damage thresholds in a next generation tokamak, analyses have been carried out. The energy deposition by 100 and 300 MeV electrons in component materials has been calculated using a Monte Carlo code. The effect of parametric changes of carbon armor thickness, electron energy and angle of incidence has been evaluated. Subsequently the thermal response of divertor structures with carbon armor and with bare tungsten, and of a first wall structure has been analyzed and thresholds for thermally induced component damage were derived, The damage threshold under 100 MeV electron impact on a divertor structure with 10 mm carbon coverage and dispersion strengthened copper cooling tubes is about 60 MJ/m2 of incident energy, that for a divertor structure with molybdenum coolant tubes is about 115 MJ/m2, whereas the damage threshold for melting of the bare tungsten diver tor is only about 30 MJ/m2. Damage of the first wall structure would occur above 180 MJ/m2. For 300 MeV electron incidence the damage thresholds are 13 to 47% lower than the values for 100 MeV.