EFFECTS OF RUNAWAY ELECTRONS ON PLASMA-FACING COMPONENTS

The electron gamma shower code EGS4 was applied to the simulation of energy deposition due to runaway electrons in the plasma facing components of tokamaks. By taking into account the magnetic field. we calculated the energy deposition in the layers of carbon and molybdenum irradiated by electrons with energies from 10 to 300 MeV and an incident angle from 0.5-degrees to 25-degrees. For a simplified model, the influence of the magnetic field was reduced with increase of the incident energies and angles of the runaway electrons. The energy deposition in the materials was observed to be independent on the incident angles and energies over 100 MeV. Moreover, we found no effects of the inclination of the magnetic field on the energy deposition in the substrate. For the proposed ITER divertor models, we found the energy deposition inside the water and coolant tube was high due to the magnetic fields. Because of the deep penetration of the runaway electrons due to the magnetic field, the deposited energy in the copper structure was increased. The present results suggest that the divertor materials and its structure need to be modified against the impacts of the runaway elections.