D retention in Be exposed to fusion relevant mixed species D2−He plasma. (August 2017) - Baldwin, M.J.
Highlights: D retention in Be is explored in ITER relevant D2 and mixed species D 2 − α He plasma exposure with up to 10% ( α = 0.1) He ions in the incident plasma flux. With α = 0.1, A threefold reduction in D retention is found for target exposure temperature ∼300 K. The reduction diminishes toward ∼473 K, and is not apparent above 473 K. The reduction is associated with an ability of He to hinder the accumula- tion of D in low-release temperature, supersaturated binding states in the Be target surface. The reduction mechanism is not understood, but the implications toward T inventory assessment/control are encouraging for reactors utilizing Be, particularlyIter . Abstract: He admixture to D2 plasma incident on Be targets is used to study the influence of a fusion-ash relevant He concentration on D retention. A variation of exposure parameters such as He ion fraction: 0.02 ≤ α ≤ 0.1, exposure temperature: 330 ≤ T exp ≤ 650 K, ion-fluence: 5 × 10 24 ≤ Φ ≤ 1 × 10 27 m − 2 and energy: 40 ≤ E i ≤ 90 eV, are explored. Results are compared to D retention values in Be observed in D2 plasma ( α = 0 ). With α = 0.1, a factor ∼3 reduction in D retention is noted for exposure at ∼300 K, but is less as T exp approaches ∼473 K, and not apparent above 473 K. The reduction is caused by the ability of He to hinder D saturation in low-release-temperature supersaturated binding states.