The Effect Of Strontium Ion Irradiation On The Surface Morphology Of Pure Tungsten And Its Change In Properties

Tungsten materials have been chosen as the plasma-facing materials(PFMs)in nuclear fusion devices as its high melting point,thermal conductivity,low hydrogen retention,low sputtering rate,long service life and other excellent performance.As the deuterium triton nuclear fusion reaction products,helium ions inevitably interact with tungsten,especially in the diverter target plate.High-density helium ions bombarding the surface of the metal tungsten,will lead to the evolution of the microstructure of metal materials,resulting in the use of performance changes,which will affect the stable operation of the fusion reactor.Therefore,the study of helium plasma irradiation on tungsten has very important scientific significance and engineering application value.In this paper,low-energy and high-flux helium irradiation experiment of pure W was carried out by using hollow cathode method.The surface morphology change of irradiated tungsten was studied by changing the helium implantation doses.It was found that changes in surface morphology of pure tungsten were closely related to the irradiation doses,the original smooth surface morphology changed into three different morphologies,namely wavy,triangular pyramid and nano-fuzz layer.With the increase of helium injection,the smooth state,the wavy state and the triangular pyramidal state are gradually transformed into the surface of the nano-fuzz layer.The nano-fuzz is preferentially formed on the surface of the triangular pyramid,and when the helium injection is large enough,the three topologies will eventually be replaced by nano-fuzz layer.These morphology changes of tungsten surface after helium irradiation are closely related to the grain orientation of the tungsten surface.We found that:near(101)crystal direction of tungsten surface will keep smooth after irradiation,near(001)grain direction will turn to wavy layer,and near(111)grain direction will take on the triangular pyramid layer and nano-fuzz layer.In this paper,the surface composition and electronic state of the irradiated surface were studied.XRD and XPS results showed that the tungsten content and the electronic state were all pure tungsten before and after irradiation,and the surface did not oxidize.In addition,the change of surface morphology of pure tungsten under irradiation voltage was studied by changing the incident voltage of helium irradiation.It was found that there was no significant difference in the surface morphology of pure tungsten in the 330V-530V voltage range.The mechanical properties of tungsten and nano-fuzz after helium irradiation were studied by means of nanometer indentation instrument and micro-hardness tester.The results show that the nanometer surface has the lowest nano-hardness,and the hardness of the triangular pyramid,wavy and smooth surface as increase.And nano-fuzz showed a good ductility.In this paper,The nano-layer 's absorption of light was test by measuring the surface scatter rate of different helium injection samples in the wavelength range of 350nm to 600nm,the results show that the nano-fuzz surface formed after helium irradiation has higher absorption rate of UV-visible light band.At the end of this paper,the sputtering of the pure tungsten surface during helium irradiation was studied by collecting the spectrum of the helium irradiation under the non-hollow cathode at 330V and the weight loss percentage of the sample after tungsten helium irradiation at different voltages.,With the increase in voltage,the weight loss percentage of the sample first increase and then change is not obvious.In this experiment,the surface sputtering of tungsten during Ar stable discharge is more obvious than that of tungsten during the stable discharge process.In this project,the interaction between helium ion and refractory metal tungsten at high temperature is studied by observing the characteristics of tungsten surface morphology and the change of performance of high density helium ion,which enriches the high density helium ion irradiation The experimental evidence of damage has deepened the understanding of the influence of irradiation damage on the tungsten performance,which provides reference for the application of tungsten as the application to the plasma material and the safe operation of the reactor.