On the possibility of determination of the hydrogen binding energies with defects from thermal desorption measurements with different heating rates

Abstract

Hydrogen isotope retention in plasma-facing materials is a concern for fusion reactors. Thermal desorption spectroscopy is widely used for determination of detrapping energies of hydrogen isotopes from materials. This work is devoted to investigation of the possibility of determination of hydrogen detrapping energies from materials in a series of experiments on programmed thermal desorption (PTD) from identical samples performed with different heating rates. For that purpose, numerical simulations of hydrogen PTD with different heating rates were performed for tungsten. Influence of trap parameters (detrapping energy and trap concentration profile) as well as surface conditions (recombination rate at the surface) was investigated. It has been shown that for hydrogen in tungsten this technique is valid only in the case of the clean surface with a high hydrogen recombination rate. A criterion of validity of this method involving parameters characterizing hydrogen behaviour on the surface and in the bulk of the material has been proposed.