Discharge Current Density And Evolution Laws Of Dielectric Barrier Single-multi Column Discharge In Atmospheric Pressure Helium

Dielectric barrier discharge is widely applied as a low-temperature plasma source in industry.Columnar discharge is an important form of dielectric barrier discharge.However,its discharge theory has not been clear yet.In this thesis,dielectric barrier discharges in helium at atmospheric pressure were carried out at the background air pressure of 40 Pa,3mm gas gap,frequency of 11.41 k Hz and 14 k Hz below the initial discharge voltage.Different evolution processes of columnar discharge were realized.The spatio-temporal evolution of columnar discharge was discussed.The evolution mechanism of the single-multi column discharge form was analyzed.The influence factors of the confinement potential in the Turing pattern dynamics of the dielectric barrier discharge pattern are discussed.The bottom discharge image of single-multi column discharge was taken by ICCD,and the spatio-temporal evolution characteristics of single-multi column discharge were studied.The momentary discharge of a small change in the applied voltage presents a dynamic evolution process of single column-1+7 two-layer multi-column and a discharge form of 1+8two-layer elliptical multi-column discharge was found.The column diameter and column spacing are measured.It was found that the column diameter gradually increased from the center to the outer layer,and the column diameter of the center column increased with the decrease of the applied voltage.Based on discharge characteristics of the columnar discharge,the discharge current,the total discharge current density and the discharge current density of the center column under different discharge forms were calculated.The influence of the discharge current density on the transformation of the columnar discharge form was studied.The results showed that compared with the applied voltage amplitude and frequency,the number of discharge columns(discharge area)played an important role in the amplitude of the discharge current.The discharge current density of the center column under the same discharge mode is similar regardless of different frequencies and applied voltages.It was considered that the discharge current density of the center column had a limit range.With the applied voltage decreased,the discharge current increased.If the original discharge mode were maintained,the discharge current density of the center column would exceed its threshold.New discharge columns were split so the discharge current density of the center discharge column decreases under the new discharge mode.The factors affecting the confinement potential in the evolution dynamics of columnar discharge single-multi-columns were studied.The Coulomb force and the magnetic field force exerted by the discharge column by all other columns were calculated.It was found that the Coulomb force under different voltages and positions was different.Based on the balance of the Coulomb force and the confinement potential in columnar discharge,it is suggest that the strength of the latter may also follow the same law.