Studies On Impedance Matching And Energy Transfer Efficiency In Radio Frequency Atmospheric Pressure Discharges

Radio frequency atmospheric pressure discharges?RF APDs?have advantages such as low breakdown voltage,high density,and uniform spatial distribution,but the high gas temperature limits its application fields.Pulse-modulated radio frequency atmospheric pressure discharges?PM RF APDs?solve the problem of high gas temperature in continuous wave RF APD,but at the same time,undesired localized pattern discharge occurs.When the pulse modulation discharge is performed under the existing impedance matching conditions of the research group,it is found that changing the carrier frequency in a small range affects the space-time stability of the discharge pattern.Preliminary analysis suggests that the instability of the discharge pattern is not only related to the carrier frequency,but also related to impedance matching?matching mode,matching component resistance?.It has been found in continuous wave RF discharge that as the excitation frequency increases,the?mode discharge range increases,and the influence of the pulse modulation download wave frequency on the?-?mode conversion needs further study.The discharge impedance at different frequencies is also related to other specific discharge conditions.Not only different impedance matching networks are required,but the optimal impedance network parameters also need to be studied.In addition,as the frequency increases,the influence of the spurious parameters on the RF circuit increases,and the impedance matching is more complicated.In order to study the influence of carrier frequency on PM RF APD pattern and?-?mode conversion in the future,in this paper we study the impedance matching network of RF discharge under different excitation frequencies,and analyzes the different matching networks and excitation frequency versus signal bandwidth.The effect of energy transfer efficiency is proposed and an optimized impedance matching method is proposed.The specific research content and conclusions obtained are as follows:?.The impedance matching of radio frequency circuits under different excitation frequencies is studied.An impedance matching network with a frequency range of 3 MHz-40MHz is designed.The experiment found that at the same excitation frequency,the smaller the inductance in the matching network,the larger the bandwidth of the matching network,and the more stable the discharge system.?.Comparing the digital display power P_AR of the power meter head,the power P_zscan measured by the Z-Scan,and the calculated power ???_pa of the plasma absorbed power in the continuous wave and the pulse discharge:in the continuous wave mode,the power values obtained by the three measurement methods are linear as a whole and P_AR>P_zscan>???_pa;The power meter P_AR of the power meter head deviates linearly.The Z-Scan measurement power P_zscan and the calculated power ???_pa are linear,but the Z-Scan itself is not suitable for measuring the pulse power,and the measured average power can only be used for experimental observation.?.The effects of matching network and excitation frequency on signal bandwidth and energy transmission efficiency are studied.The following conclusions are obtained:?a?Under the same impedance matching network,the lower the excitation frequency,the wider the frequency band.?b?The inductance in the matching network is small at the same excitation frequency,and the corresponding ohmic loss is low,and the energy transmission efficiency of the matching network is high.?c?In the normal glow discharge region,the energy transfer efficiency increases rapidly as the plasma absorption power increases.When the discharge enters the abnormal glow region from the normal glow discharge region,the energy transfer efficiency achieves a local maximum,which is abnormal.In the glow region,as the absorbed power of the plasma increases,the energy transfer efficiency remains basically unchanged.When the discharge enters the?mode,at the?-?mode transition point,the energy transfer efficiency has a small increase and then tends to be gentle.?d?In the frequency range of3 MHz-40 MHz,the energy transmission efficiency increases as the excitation frequency increases.As the excitation frequency increases,on the one hand,the skin effect causes the effective overcurrent area of the inductance in the matching network to decrease,but the inductance?length?required for impedance matching decreases,the actual effective resistance of the inductance decreases,and the corresponding ohmic loss decreases.On the other hand,as the excitation frequency increases,the electron trapping effect is enhanced and the plasma absorption resistance is increased.