Discharge Transitions Of Dielectric Barrier In Atmospheric Pressure Helium Under Lower Applied Voltages

Dielectric barrier discharges can easily generate a large volume of non-equilibrium cold plasmas with moderate energy and density of active particles,which leads to numerous potential industrial applications.However,the dielectric barrier discharge could operate in filamentary discharges,columnar discharges,and diffuse discharges under different conditions.Besides,transitions among them could occur.In this thesis,discharge transitions of parallel dielectric barrier in atmospheric pressure helium were investigated by changing the amplitude of applied voltage and the background air presure.In the case of the background air pressure of 20 Pa,40 Pa,in the 3-mm,2-mm gas gap,the dielectric barrier discharges were carried out.The partial diffuse discharges,columnar discharges and filamentary discharges were obtained under applied voltages below the discharge inception voltages.Transitions among filamentary discharges,columnar discharges,partial diffuse discharges,or diffuse discharges covering the whole electrodes,and methods to distinguish filamentary discharges from columnar discharges were investigated based on the simultaneous measurements of loop currents and light emissions.Forming conditions of dielectric barrier columnar discharges were also investigated based on the method of orthogonal experimental design.The orthogonal tests were established with the gas gap,the voltage frequency,and the applied electric field as factors in the case of a background air pressure of 30 Pa,in a 3-mm gas gap.The variance analysis shows that all the 3 factors has the great influence on the formation of columnar discharges.And the influential degree of applied electric field rank the first,while the gas gap,voltage frequency the second.The range analysis shows that a shorter gas gap(2 mm,3 mm),a lower voltage frequecy(10~16 kHz),a lower electric field(0.212~0.282 kV/mm)are beneficial to the formation of the columnar discharge.