This work is a contribution to a better understanding of dual frequency discharge at atmospheric pressure. Based on experiments and numerical modeling, it is focused on radio frequency (5 MHz) – low frequency (50 kHz) plane/plane dielectric barrier discharge in a Penning mixture (Ar-NH3). The discharge is in the α-RF mode, biased by a LF voltage having an amplitude ranging from 0 to 1300 V. When the LF amplitude increases, there is a threshold (around 600 V for a 2 mm gap) from which the light intensity (experiment) and the ionization level (modelling) drastically increase. In this work the physics of the RF-LF DBD below and above this threshold is studied. Depending on the respective RF and LF polarity, the net voltage applied to the gas is alternatively enhanced or reduced which induces an increase or a decrease of the ionization level. In all cases the ion drift to the cathode due to the LF voltage results in an ion loss and a production of secondary electrons. For a LF voltage amplitude lower than 600 V, the ions loss to the cathode is higher than the ions creation related to the secondary electrons. The consequence is a decrease of the plasma density. This density oscillates at a frequency equal to 2LF: it is maximum each time the LF voltage amplitude is equal to 0 and minimum when the LF voltage amplitude is maximum. For a LF voltage amplitude higher than 600 V, when the LF and RF polarity are the same, the secondary electrons emission is high enough to counterbalance the ion loss, to enhance the bulk ionization and the discharge becomes a γ-RF. The gas voltage is controlled by the dielectric charge like a low frequency DBD. Around the gas voltage maximum, on each RF cycle, the discharge is alternatively an α-RF and a γ-RF discharge. When the discharge is in the γ mode, the ions flux at the cathode is increased by a factor 40.

中文翻译：

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大气压双 RF-LF 频率放电：LF 电压幅度对 RF 放电行为的影响

这项工作有助于更好地理解大气压下的双频放电。基于实验和数值建模，它专注于 Penning 混合物 (Ar-NH3) 中的射频 (5 MHz) – 低频 (50 kHz) 平面/平面电介质阻挡放电。放电是在 α-RF 模式下，由幅度范围为 0 到 1300 V 的 LF 电压偏置。当 LF 幅度增加时，存在一个阈值（对于 2 mm 间隙，大约为 600 V），光强度从该阈值开始（实验）和电离水平（建模）急剧增加。在这项工作中，研究了低于和高于此阈值的 RF-LF DBD 的物理特性。根据各自的 RF 和 LF 极性，施加到气体上的净电压交替增强或降低，这会引起电离水平的增加或减少。在所有情况下，由于 LF 电压导致的离子漂移到阴极导致离子损失和二次电子的产生。对于低于 600 V 的 LF 电压幅度，阴极的离子损失高于与二次电子相关的离子产生。结果是等离子体密度降低。该密度以等于 2LF 的频率振荡：每次 LF 电压幅度等于 0 时它最大，当 LF 电压幅度最大时它最小。对于高于 600 V 的 LF 电压幅值，当 LF 和 RF 极性相同时，二次电子发射足够高以抵消离子损失，以增强体电离并且放电变为γ-RF。气体电压由介电电荷控制，如低频 DBD。在气体电压最大值附近，在每个 RF 周期，放电交替地是α-RF和γ-RF放电。当放电处于 γ 模式时，阴极处的离子通量增加了 40 倍。