Alpha losses and wall loads in ARC

The ARC tokamak, currently under design by Commonwealth Fusion Systems, is expected to produce over 1 GW of fusion power in a deeply burning plasma regime with Q > 50. Fusion-produced alphas will carry over 200 MW of power and act as the dominant source of heating in ARC, and if poorly confined, can cause melting or sputtering of the first wall. This work will use Monte Carlo orbit-following code ASCOT5 to predict prompt and ripple-induced alpha losses in ARC, including an analysis of the impact of radial and toroidal misalignments on confinement as previously performed for SPARC [Scott JPP 2020]. Borrowing an approach from stellarator theory, a strong correlation between magnitude of non-axisymmetric Fourier components of the magnetic field strength and ripple-induced losses is found. Wall loads are calculated for an axisymmetric first wall, as well as to edges of simple midplane ports. Finally, as the vacuum vessel for ARC is intended to be produced in two halves which are welded together and replaced regularly, misalignments of the two vacuum vessel halves are considered and heat loads to leading edges predicted.