Magnetic field effects on runway electron energy deposition in plasma facing materials and components

Magnetic field effects on runaway electron energy deposition in plasma facing materials and components have been investigated using the Integrated TIGER Series. A 3D computational model of 100-MeV electrons incident on a graphite block was used to simulate runaway electrons striking a plasma facing component at the edge of a tokamak. An embedded magnetic field of 1, 3, and 5 T intersecting the front face of the graphite block at 1° and 5° was studied. Analysis shows that a plasma facing component in the presence of a magnetic field will have more energy deposited in it than it would in no field. Most of the increased energy is deposited near the surface with a higher energy density. This is due primarily to a reduction in the reflection of electrons from the surface, resulting in a substantial increase in surface energy deposition. A second, but smaller effect is that knock-on electrons born in the material attempt to orbit the embedded magnetic field lines, resulting in a localized energy deposition (closer to the surface). The higher energy deposition and higher energy density will cause higher temperatures which are expected to increase material damage