An EPOCH Extension for Energetic-Particle Transport and Recoil Dynamics in Plasma-Facing Materials

Understanding how particle composition and energy transfer govern recoil and heating is important for tokamak first-wall assessment. We extend EPOCH by coupling material collisions and recoil cascades to relativistic particle-in-cell transport and self-consistent electromagnetic fields for electron, $\alpha$-particle and deuteron bombardment of tungsten (W), beryllium (Be) and carbon (C). Transport is tested against experiments and independent calculations ; independent cascade calculations and Geant4 11.4.1 coupled to heat conduction examine recoil and thick-target heating. For 10 MeV electrons in W, four recoil-energy groups reduce discrepancies in secondary-recoil production against an independent solution of the same collision model from 21.1 % with a single mean energy to 0.79%. At equal incident ion counts, 3.5 MeV $\alpha$ particles produce 4.8 times as many secondary recoils as 1 MeV deuterons, but deuterons leave 21.8% more W atoms in motion at the same observation time, distinguishing recoil production from subsequent atomic motion. At equal surface energy fluence and pulse duration without external magnetic fields , grazing incidence reduces total W absorption but concentrates deposition near the surface, producing higher peak temperatures and smaller molten volumes per unit area. These findings provide a reference for selecting irradiation compositions, observation times and angles and jointly evaluating recoil and thermal responses.