Sputtering of lithium and lithium compound films under deuterium and helium ion bombardment

Abstract

Conditioning of plasma facing components (PFCs) using lithium (Li) evaporation has shown to improve plasma performance in fusion devices by imposing low recycling boundary conditions. It is important to understand the retention and sputtering dynamics of deuterium (D) in Li and Li compound (LiO and LiCO) films to most efficiently make predictions on plasma performance. Energetic D2+ incident on thin Li films is shown to readily form LiD leading to a lower Li sputtering yield than the sputtering yield of pure Li. Measured sputtering yields for thin LiD films agree with previous simulations and bulk erosion measurements. The He+ sputtering yield of pure Li was 2–3 times higher than the sputtering yield of D2+ on LiD. Incident 1000–1200 eV/D2+ sputtered LiO films at a slower rate than D2+ on LiD and LiCO films. Keywords: Deuterium retention, Lithium carbonate, Lithium deuteride, Sputtering, Thin films