Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications.Plasma-surface interactions are complex and relatively poorly understood.Ex...Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications.Plasma-surface interactions are complex and relatively poorly understood.Experiments performed over the last decade by several groups prove that interactions of reactive species with relevant plasma-facing materials are characterized by distributions of adsorption energy and reactivity.In this paper,we develop a kinetic Monte Carlo(KMC)model that can effectively handle chemical kinetics on such heterogenous surfaces.Using this model,we analyse published adsorption-desorption kinetics of chlorine molecules and recombination of oxygen atoms on rotating substrates as a test case for the KMC model.展开更多
Tungsten,a leading candidate for plasma-facing materials(PFM) in future fusion devices,will be exposed to high-flux low-energy helium plasma under the anticipated fusion operation conditions.In the past two decades,ex...Tungsten,a leading candidate for plasma-facing materials(PFM) in future fusion devices,will be exposed to high-flux low-energy helium plasma under the anticipated fusion operation conditions.In the past two decades,experiments have revealed that exposure to helium plasma strongly modifies the surface morphology and hence the sputtering,thermal and other properties of tungsten,posing a serious danger to the performance and lifetime of tungsten and the steadystate operation of plasma.In this article,we provide a review of modeling and simulation efforts on the long-term evolution of helium bubbles,surface morphology,and property changes of tungsten exposed to low-energy helium plasma.The current gap and outstanding challenges to establish a predictive modeling capability for dynamic evolution of PFM are discussed.展开更多
One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a p...One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a possible weakness against the plasma heat flux on the plasma- facing component and also may destroy the reflectivity of optical mirrors. In this paper an inter- esting method for the recovery of such tungsten surfaces is shown. The recovery process depends on the grade and manufacturing process of tungsten materials.展开更多
A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanose...A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanosecond-pulsed spark discharges are ignited in liquid nitrogen.The hexagonal sheets are single crystals produced by gas phase condensation.Once nitrogen completely evaporates,the sheets change to PbO2by oxidation in air.The oxidation process induces stress that pleats the uppermost sheets or open cracks at the centre.The thickness of the individual objects typically varies from 4to 20nm.When the number of discharges is more than about 2000,in addition to sheets,two types of PbO2 sticks start to form:bundles composed of nanosticks (length 5p.m and diameter 50nm)and isolated sticks (length 20μm and diameter 500nm).These new nanostructures mainly form because of the way the discharge erodes the lead electrodes.Initially,anisotropic erosion driven by the orientation of the crystallographic planes of the lead crystals produces octahedra and nanosticks,and the nanosticks grow on the electrode surfaces as discharge proceeds.After about 2000discharges,the nanosticks are sufficiently long that they can be easily broken,probably by mechanical stress,and they fall onto the underlying substrate.展开更多
文摘Reactions of atoms and molecules on chamber walls in contact with low temperature plasmas are important in various technological applications.Plasma-surface interactions are complex and relatively poorly understood.Experiments performed over the last decade by several groups prove that interactions of reactive species with relevant plasma-facing materials are characterized by distributions of adsorption energy and reactivity.In this paper,we develop a kinetic Monte Carlo(KMC)model that can effectively handle chemical kinetics on such heterogenous surfaces.Using this model,we analyse published adsorption-desorption kinetics of chlorine molecules and recombination of oxygen atoms on rotating substrates as a test case for the KMC model.
基金supported by National Natural Science Foundation of China(No.11905071)the National MCF Energy R&D Program(No.2018YFE0308103)
文摘Tungsten,a leading candidate for plasma-facing materials(PFM) in future fusion devices,will be exposed to high-flux low-energy helium plasma under the anticipated fusion operation conditions.In the past two decades,experiments have revealed that exposure to helium plasma strongly modifies the surface morphology and hence the sputtering,thermal and other properties of tungsten,posing a serious danger to the performance and lifetime of tungsten and the steadystate operation of plasma.In this article,we provide a review of modeling and simulation efforts on the long-term evolution of helium bubbles,surface morphology,and property changes of tungsten exposed to low-energy helium plasma.The current gap and outstanding challenges to establish a predictive modeling capability for dynamic evolution of PFM are discussed.
基金supported by a Grant-in-aid for scientific Research (B) (20360414) from JSPS
文摘One of the serious concerns for tungsten materials in fusion devices is the radiation defects caused by helium plasma irradiation since helium is a fusion product. The fiber-formed nanostructure is thought to have a possible weakness against the plasma heat flux on the plasma- facing component and also may destroy the reflectivity of optical mirrors. In this paper an inter- esting method for the recovery of such tungsten surfaces is shown. The recovery process depends on the grade and manufacturing process of tungsten materials.
文摘A simple method to synthesise hexagonal lead sheets,which belong to the class of two-dimensional materials,is proposed.These objects are collected on a substrate located under two lead electrodes, between which nanosecond-pulsed spark discharges are ignited in liquid nitrogen.The hexagonal sheets are single crystals produced by gas phase condensation.Once nitrogen completely evaporates,the sheets change to PbO2by oxidation in air.The oxidation process induces stress that pleats the uppermost sheets or open cracks at the centre.The thickness of the individual objects typically varies from 4to 20nm.When the number of discharges is more than about 2000,in addition to sheets,two types of PbO2 sticks start to form:bundles composed of nanosticks (length 5p.m and diameter 50nm)and isolated sticks (length 20μm and diameter 500nm).These new nanostructures mainly form because of the way the discharge erodes the lead electrodes.Initially,anisotropic erosion driven by the orientation of the crystallographic planes of the lead crystals produces octahedra and nanosticks,and the nanosticks grow on the electrode surfaces as discharge proceeds.After about 2000discharges,the nanosticks are sufficiently long that they can be easily broken,probably by mechanical stress,and they fall onto the underlying substrate.
