Formation of W+ ions in collisions of low-energy H+, D+, T+ ions with tungsten atoms in the ITER near-wall plasma

Formation of tungsten ions W+ via ionization and charge exchange in slow collisions of W atoms with hydrogen-isotope ions H+, D+, and T+ in the ITER near-wall plasma is considered. The cross sections for both processes are calculated within the framework of the adiabatic theory of transitions in slow collisions [E.A. Solov'ev, Sov. Phys. Uspekhi, 32, 228, 1989] at ion energies E≈ 0.01–3 keV/u, taking into account the isotope effect. Calculations are performed for two pre-collision scenarios: (1) the W atom remains in the ground 5d46s25D0 state and (2) all 5d46s22S+1LJ states of the W atom are populated in the near-wall plasma. It is assumed that the population of the states is determined by the Boltzmann distribution, and plasma temperatures are in the range Te≈ 1–50 eV. It is shown that the cross sections for the formation of W+ ions are determined mainly by the charge exchange process, and the inclusion of all 5d46s22S+1LJ states in the calculations significantly increases the cross sections at collision energies below 0.1 keV/u.