Orbit-following fusion alpha wall load simulation for ITER scenario 4 including full orbit effects

A large population of fusion-born alphas present in ITER scenario 4 is a potential risk to the first wall elements. In this study, the ITER scenario 4 alpha wall loads are estimated using the Monte Carlo orbit-following code ASCOT. To ensure realistic wall load profiles, we have adopted three different methods to record the wall collision points: (i) pure guiding centre tracking, (ii) guiding centre tracking away from the wall and gyro-orbit following close to it and (iii) pure gyro-orbit following. It is found that pure gyro-orbit simulation produces an averaged wall load roughly three times as large as the pure guiding centre wall load while the peak power loads differ roughly by a factor of five.