ASCOT input for SPARC for scaling testing

This is an ASCOT input for SPARC alpha-slowing-down simulation. This test case represents a modeled reference scenario similar to that design point (see Creely et al. J. Plasma Phys. (2020)), with an assumed 140 MW of fusion power. The magnetic field model includes realistic perturbations arising from the finite number of toroidal field coils, while the plasma profiles are obtained from transport simulations. The wall is represented by a simplified geometric model of the actual structure.This test case is intended for exploring how ASCOT simulations scale on GPU/CPU clusters, and the markers and the simulation options are chosen to reflect that. To ensure it finishes in reasonable time, the simulation does not cover the full alpha population over the entire slowing-down time (~0.5 s). Instead, it focuses on alphas born near the plasma edge, which are most prone to prompt losses, and the simulation time is limited to cover only the prompt losses.