Distribution of footprint marked by energetic alpha particle bombardment on the first wall

Abstract

Abstract Full orbit-following calculations for the final orbit of lost alpha particles in an ITER equilibrium are performed using a Lorentz orbit code LORBIT [M. Isobe, et al. Rev. Sci. Instrum. 70 (1999) 827] to obtain parameter dependence of the footprint of alpha particle bombardment on the first wall. Determination of the poloidal location for the footprint is dominated by the pitch angle at the starting point. Toroidal distribution of the footprint location is inhomogeneous even for equipartitioned starting points because of the shadow of the magnetic field line on the first wall surface. Due to a hopping motion of an alpha particle on the surface of the first wall, a lined footprint is generated. Energy deposition is found to be dispersed along the line.