Investigation of hydrogen isotope retention mechanisms in beryllium: High resolution TPD measurements

Abstract

The retention of ion-implanted deuterium in beryllium poly- and single crystals at room temperature is studied using high precision temperature programmed desorption spectroscopy (TPD). Slow temperature ramps of 0.01 K/s in combination with well-defined experimental conditions are used to resolve the low temperature desorption regime for the first time revealing three sharp desorption peaks. The comparison to results of a coupled reaction diffusion system (CRDS) model shows, that the corresponding release mechanisms cannot be described by thermally activated rate processes. SEM images of a polycrystalline beryllium sample after implantation of deuterium with 2 keV per D atom show the formation of blisters of roughly 1 µm in diameter. Additionally, cracks on top of the blisters are found as well as spots, on which blisters are peeled off. Both processes are discussed to play a role in the low temperature release regime of the retained deuterium. Investigation of TPD spectra performed on single crystalline beryllium shows a jagged pattern in the low temperature release regime, which can be connected to blisters bursting up, releasing big amounts of deuterium in short time scales. Keywords: Hydrogen retention, Beryllium, Temperature programmed desorption spectrum, Deuterium implantation, Blisters, Low temperature desorption