EFFECTS OF RUNAWAY ELECTRONS ON PLASMA-FACING COMPONENTS

The electron gamma shower code EGS4 was applied to the simulation of e nergy deposition due to runaway electrons in the plasma facing compone nts of tokamaks. By taking into account the magnetic field. we calcula ted the energy deposition in the layers of carbon and molybdenum irrad iated by electrons with energies from 10 to 300 MeV and an incident an gle from 0.5-degrees to 25-degrees. For a simplified model, the influe nce of the magnetic field was reduced with increase of the incident en ergies and angles of the runaway electrons. The energy deposition in t he materials was observed to be independent on the incident angles and energies over 100 MeV. Moreover, we found no effects of the inclinati on of the magnetic field on the energy deposition in the substrate. Fo r the proposed ITER divertor models, we found the energy deposition in side the water and coolant tube was high due to the magnetic fields. B ecause of the deep penetration of the runaway electrons due to the mag netic field, the deposited energy in the copper structure was increase d. The present results suggest that the divertor materials and its str ucture need to be modified against the impacts of the runaway election s.