Oxidation of beryllium and exposure of beryllium oxide to deuterium plasmas in PISCES B

Abstract The oxidation behaviour of Be in air was studied as a function of temperature. Below 660 °C oxidation is limited by diffusion of Be through the growing BeO layer and closed oxide layers up to 100 nm thickness are formed. Above 660 °C a rapid increase in the oxidation rate sets in. Secondary electron micrographs show that this fast oxidation goes along with massive structural changes of the surfaces. Oxidised samples were exposed on the witness-manipulator of PISCES B to deuterium atoms reflected from a plasma-exposed W target. The energy of the reflected D was varied by changing the bias voltage on the W target (floating, −50 V and −100 V). The BeO temperature during exposure was varied between 20 and 250 °C. The erosion of the exposed surfaces and the uptake of D were investigated by ion beam analysis. The retained amount of D increases with increasing bias voltage and decreasing exposure temperature. At room temperature saturation of the D concentration at about 12 at.% in a surface layer correlated to the maximum particle range is observed. At temperatures above 100 °C the concentration level decreases strongly, but retention spreads over the total oxide thickness.