Design of a planar probe diagnostic system for plasmatron VISIONI and its application for the study of deuterium retention in W–Ta alloys

Abstract

One of the issues still to be clarified with respect to the possible use of tungsten and tungsten alloys as first wall material in fusion reactors is the retention of hydrogen isotopes under fusion-relevant conditions, such as the presence of helium ash, neutron irradiation, thermal shock. The low flux, high temperature plasma simulator VISIONI, being currently constructed at the Belgian nuclear research center SCK·CEN, will have the unique ability to handle radioactive materials – neutron irradiated samples and tritium plasma. Currently it is being tested with non-irradiated samples and deuterium plasma. To monitor the plasma parameters near the investigated specimen, a planar probe system has been developed. It was demonstrated that the plasmatron is able to provide conditions relevant for the ITER first wall. Investigations of deuterium retention in W–Ta alloys have been performed, using thermodesorption spectroscopy. A hypothesis of the existence of three kinds of trapping sites for deuterium in W–Ta alloys, based on deuterium release studies, is suggested.