Effect of tungsten/graphene/tungsten interface on helium diffusion kinetics and mechanical properties and defects of tungsten as first wall material - first principle calculation

Abstract

In Tokamak device, helium atoms caused by the fusion reaction will generate helium bubbles and point defects after entering the first wall material composed of tungsten metal, which will seriously affect the stability of the first wall material. Therefore, we designed the tungsten/graphene/tungsten interface material as a new first wall material. It was found from first-principles calculations that the interface can trap helium atoms to reduce the diffusion of helium atoms from the interface to the tungsten phase again. The interface also traps vacancies and accelerates the recombination of vacancies and self-interstitial atoms. Using the quasi-harmonic Debye model, we found that the presence of the graphene layer can also improve the ductility, at a cost of reducing the mechanical modulus of the tungsten metal.