Reflection and implantation of low energy helium with tungsten surfaces

Reflection and implantation of low energy helium (He) ions by tungsten (W) substrate are studied using molecular dynamics (MD) simulations. Motivated by the ITER divertor design, our study considers a range of W substrate temperatures (300 K, 1000 K, 1500 K), a range of He atom incidence energies ($\le$100 eV) and a range of angles of incidence ($0^{\circ}$-$75^{\circ}$) with respect to substrate normal. The MD simulations quantify the reflection and implantation function, the integrated moments such as the particle/energy reflection coefficients and average implantation depths. Distributions of implantation depths, reflected energy, polar and azimuthal angles of reflection are obtained, as functions of simulation parameters, such as W substrate temperature, polar angle of incidence, the energy of incident He, and the type of W substrate surface. Comparison between the MD simulation results, the results obtained using SRIM simulation package, and the existing experimental and theoretical results is provided.