Electron emission from tungsten induced by slow, fusion-relevant ions

Tungsten has recently been introduced as a new wall material for fusion, because it exhibits favourably low sputtering yields and a very low tritium retention as compared to the commonly used graphite wall and divertor tiles. We measure total electron emission yields due to impact of slow singly and multiply charged ions (deuterium, helium and carbon) on sputter-cleaned polycrystalline tungsten surfaces by using a current method in combination with a retarding grid. Results are presented in the eV to keV impact energy region as typical for fusion edge plasma conditions and discussed in terms of potential and kinetic electron emission.