大气压射频辉光放电电子数密度解析解及等离子体阻抗特性研究

为研究大气压射频辉光放电等离子体阻抗特性,基于射频放电的一维均匀假设模型,推导出了适用于α模式、高气压和小间隙条件下的电子数密度ne的解析解,从而可由实验测得的电压和电流幅值计算出ne;构建了描述整个放电区域的"电阻-电容混联"等效电路模型,模型参数可由ne计算得到。通过与他人数值模拟得到的ne对比,验证了该解析解的正确性。实验结果表明:放电电压和电子数密度随电流密度的增加而线性增加;鞘层厚度、准中性区的等效电容和鞘层的等效电容受电流密度变化影响不大;准中性区的等效电阻和放电间隙总等效阻抗随电流密度的增加而减小。实验结果还指出了前人工作中存在的一些问题:在小间隙时错误地忽略鞘层厚度,认为准中性区的长度就是电极间隙距离;不合理地将准中性区场强近似为0。未来工作希望进一步推导低气压或大间隙时电子数密度的解析解。

Research on the Analytical Solution of Electron Number Density and the Plasma Impedance of Radio-frequency Glow Discharge at Atmospheric Pressure

To study the characteristics of radio frequency atmospheric pressure glow discharge(RF APGD), based on one-dimensional uniform model, the analytical solution of electron number density ne is deduced, from which ne can be calculated using the measured amplitudes of the discharge voltage and current. This analytical solution is appliable in conditions of α mode, high pressure and small electrode gap. An equivalent circuit model of resistance-capacitance serial-parallel-connection is proposed to describe the whole discharge region. The parameters of the equivalent circuit model can be obtained using the calculated ne. The correctness of this analytical solution is verified by comparing our ne with other’s numerical simulation results. The experimental results show that the voltage and the electron number density increase almost linearly with the increasing of the discharge current density;the thickness of the sheath region, the equivalent capacitance of the quasi-neutral region and the equivalent capacitance of the sheath region negligibly change with the discharge current density;the equivalent resistance of the quasi-neutral region and the total impedance of the discharge region decrease with the increasing of the discharge current density. The results can also be used to point out some mistakes in others’ previous work: falsely ignoring the thickness of sheath region and regarding the electrode gap as the length of quasi-neutral region;unreasonably overlooking the electric field of quasi-neutral region and regarding it as zero. In our future work, we hope to apply the analytical solution of ne to more circumstances, such as low pressure or large electrode gap.