Theoretical Evaluation Of Electron Swarm Parameters In Ar/CF₄,Ar/CF₄/CF₃I,and Ar/humid-air Mixtures By Monte Carlo Method

In the past few years,atmospheric pressure low temperature plasma has been widely used in biomedicine,material surface treatment,environmental protection,and other fields.Therefore,atmospheric pressure low temperature plasma as well as its applications in the related fields has become research hotspot.The numerical simulation is an effective solution to study of the discharge plasmas.Due to its advantages of convenience and higher accuracy in use,the liquid model has been extensively utilized for the numerical simulation of the discharge plasmas.The electron swarm parameters are basic input data for the liquid model,including electron mean energy,electron drift velocity,electron longitudinal diffusion coefficient,and effective ionization reaction rate coefficient.The usage of reliable electron swarm parameters is a primary requirement in order to strictly and exactly simulate the discharge plasmas.Experimentally,it is difficult to determine the electron swarm parameter.Because of this,the theoretical valuation becomes an important method to obtain the electron swarm parameter.In the applications of the discharge plasma,the mixed gases,as a working gas,are more used.Ar is an important working gas and is widely used in atmospheric pressure low temperature dielectric barrier discharges and in the atmospheric pressure plasma jets.Especially,the mixtures of Ar and other gases,such as Ar/CF4,Ar/CF4/CF33I,and Ar/humid-air,are of great interest due to their beneficial characteristics and significant applications in many fields.Accordingly,to obtain the electron swarm parameters in these mixed gases is of great significance.In this thesis,a systematical calculation on the electron swarm parameters in three mixtures,Ar/CF4,Ar/CF4/CF3I and Ar/humid-air,has been carried out with the use of Monte Carlo method,providing a more accurate data for the numerical investigation on the gas discharge in these three mixtures.In addition,the effects of the concentration ratio on the electron swarm parameters are also analyzed.This thesis includes the following contents and results:1.After performing the analyses on the cross sections of Ar,including elastic,excitation and ionization scattering cross sections from the three databases,a set of cross section data of Ar is suggested.Using the cross section data suggested,the electron drift velocity and electron longitudinal diffusion coefficient in pure Ar have been calculated.The calculated results are in better agreement with the experiments than those calculated using the other cross section data.2.With the use of Monte Carlo method,the electron swarm parameters in three mixtures,Ar/CF4,Ar/CF4/CF3I and Ar/humid-air,have been calculated.The effect of concentration ratio on the electron swarm parameter are also analyzed.For Ar/CF4 mixture,the effects of CF4 concentration on the electron swarm parameters mainly occur at low reduced electric fields.For Ar/CF4/CF3I mixture,the electron swarm parameters decrease with the increase in CF3I concentration and this dependence become evident at high reduced electric fields.For Ar/humid-air mixture,the electron drift velocity and electron longitudinal diffusion coefficient decrease with the increase in humid-air concentration.In addition,the effects of humid-air concentration on the effective ionization reaction rate coefficient are evident only at reduced electric fields.