The Influence Of Dust Particles And Magnetic Fields On The Properties Of Gas Discharge Plasma

There are a large number of plasma state materials in the universe,and plasma plays very important roles in the development of modern science and technology: the main regions of the Earth’s ionosphere and magnetosphere of human space exploration activities are plasma environments;the plasma technologies are widely applied in the material processing process,such as etching,but in these plasma environments or related applications the plasma may contain a large number of dust particles or be affected by exrernal magnetic fields.The existance of these two agents can significantly change the properties of the plasma: the presence of dust particles leads to changes in the composition of the plasma,altering the physical properties of the plasma and even leads to new phenomena;the presence of a magnetic field changes the motion of charged particles in the plasma and also changes the relevant properties of the plasma.Therefore,studying the effects of dust and magnetic fields on the parameters and related properties of plasma is of great significance to solve many practicalplasma issues occuring in national defense science and technology,aerospace field,material processing and so on.Motivated by this,this dissertation takes the gas discharge plasma in the laboratory as my research object,and studies the influences of dust particles and magnetic field on the basic properties of gas discharge plasma through experiments as well as numerical simulation.Firstly,the effects of different types of radial distributions of dust particles and different densities on the radial distribution of charged particle density,flux and ambipolar electric field in argon direct current glow discharge were studied by theoretical simulation methods,and then the effects of dust particles on electron energy distribution function of direct current glow discharge plasma under local and nonlocal approximations were investigated.While studying the effects of dust on plasma,the effects of magnetic fields on direct current glow discharge plasmas and nonlocal largescale gas discharge plasmas were explored by experimental research and theoretical simulation methods.The main research content are organized as follows:Based on the existing direct current glow discharge dust plasma fluid equations,onedimensional argon dc glow discharge dust plasma fluid model is established,and to solve the model,the finite element method is used and the radial distributions are obtained in the radial domain 0-R,0-0.75 R,0-0.5R and 0-0.25 R,respectively,and the influences of dust particle density on the electron density,dust particle charge distribution,correlation flux and ambipolar electric field in the argon direct current glow discharge plasma plasma are obtained.The non-monotonic distribution of electron density in the presence of dust particles and the conditions for the occurrence of ambipolar electric field reversal phenomena are discussed,and the possibile theoreticalreasons behind the above phenomena are analyzed.Based on the local and non-local kinetic theories of dust plasma,particularly on the existing local approximation Boltzmann equation,the Holstein-Tsendin method is used to obtain the non-local space-averaged kinetic equations,and considering the effects of dust particles on the electron energy distribution function of direct current glow discharge plasma are solved for under local and non-local approximation,and then the effects of different radial distributions of dust plasma are examined on the basis of non-local approximation of electron energy distribution function.Effects of different dust particle densities on direct current glow discharge plasma electron energy distribution functions,and effects of dust particles on plasma electron energy distribution functions in the presence of non-monotonic distribution of electron density and ambipolar electric fields are also investigatived.Next,based on the plasma fluid model equations,the effect of the external magnetic field is introduced.The one-dimensional axisymmetric direct current glow discharge plasma fluid model in the presence of the external magnetic field is established,and the influence of magnetic field on the relevant parameters of the plasma in the positive column region of dc glow discharge plasma are simulated.According to our theoretical model,the direct current glow discharge device under the influence of the magnetic field is constructed,and the electron density of the direct current glow discharge plasma is diagnosed by the single Langmuir probe.The obtained experimental results were compared with the simulation results.Finally,the magnetic field was applied to a large-scale glow discharge plasma to see how the plasma parameters change under the influence of the non-uniform magnetic field.The plasma parameters were studied by the Langmuir probe diagnosis and microwave diagnostic methods.Based on the diagnostic data,the relevant microwave transmission experiment is conducted,and the influence of the magnetic field on the microwave transmission characteristics in the plasma is obtained.