Effects Of Metal(Tungsten,Niobium,Copper) Ion Irradiation On Deuterium Permeability And Retention Behavior In Tungsten

With the continuous development of society,the energy problem is increasingly prominent.Due to a series of advantages such as clean and abundant reaction resources,nuclear fusion is regarded as one of the major energy sources in today’s society.In 2003,China participated in the international thermal nuclear fusion experimental reactor(ITER)project,and subsequently launched the China fusion engineering experimental reactor(CFETR)project in China.Tungsten is the main candidate material for the first wall of tokamak device.The mechanism for hydrogen isotope transportation in tungsten is still unclear,which is closely related to the assessment of fusion fuel used and the safety towards environment.During the operation of fusion reactors,the face plasma materials will be subjected to high thermal loads and various kinds of etching of energetic ions,atoms and neutrons.This will cause defects(such as vacancy,dislocation,etc.)in the material,thus reducing its performance,which will lead to the stable operation of the fusion device and even lead to the safety hazard of the device.In order to explore the retention and permeation of hydrogen isotopes in the materials of fusion reaction devices,the tungsten samples were treated by annealing and ion implantation in order to simulate the influence of fusion environment on the materials.The samples were analyzed by means of gas-driven permeation,thermal desorption,X-ray Diffraction(XRD),Scanning Electron Microscope(SEM),X-ray Photoelectron Spectroscopy(XPS)and other experimental methods to study the influence of surface microstructure and chemical composition on hydrogen isotope transport.In the first part of the experiment,the microstructure of tungsten was regulated by annealing and self-ion implantation,and the samples were characterized by X-ray Diffraction(XRD)and Scanning Electron Microscope(SEM).Through thermal desorption and permeation experiments,it was found that annealing treatment at a temperature below 1073 K had little effect on grain size,but reduced the number of defects such as vacancy and dislocation in the material.It is also found that the bulk and surface microstructure have significant effects on the retention and permeation of deuterium.Combined with the above results,the permeation mechanism related to the microstructure of samples is discussed.In the second part of the experiment,the tungsten samples were treated by niobium and copper ion implantation respectively,and the sample element composition was characterized by X-ray photoelectron spectroscopy(XPS).The XPS results showed that the oxygen elements on the sample surface were removed by denudation in the process of niobium and copper ion implantation.Through the thermal desorption and permeation experiments,it is found that the deuterium retention of tungsten samples after the same annealing treatment ofniobium ion implantation and copper ion implantation is significantly reduced,and the resulting defects have the same deuterium capture energy.Compared with the initial tungsten sample,it was found that the injection of niobium ion reduced the permeability activation energy,possibly because the surface defects of the material are increased due to ion implantaion,and the barrier of deuterium particles entering into the sub-surface is reduced.