This paper investigates the transition from α to α–γ-mode of a dual frequency (5 MHz/50 kHz) dielectric barrier discharge (DBD) at atmospheric pressure. The study is based on both experiments and modeling of a plane/plane DBD in a Penning mixture (Ar–NH₃). The discharge is in the α-RF mode with three different voltage amplitudes (250, 300 and 350V) and biased by a low-frequency (LF) voltage with an amplitude varying from 0 to 1300V. At a given threshold of LF voltage amplitude (of about 400V for a 2mm gap and 133 ppm of NH₃), a transition from α to α–γ-mode occurs. It is characterized by a drastic increase of both the argon and NH emissions. Increasing the NH₃ concentration leads to a decrease of the LF voltage amplitude required to reach the α–γ-mode (experiment). The transition from α to α–γ-mode is initiated when the ionization in the sheath increases and the α–γ-mode is established when this ionization becomes higher than the self-sustainment criterion (1/γ). The transition from α to α–γ-mode results in an increase of the particle densities and a stabilization of the gas voltage independently of the LF voltage amplitude. Without secondary electron emission there is no transition. In the model, increasing the secondary emission coefficient from 0.05 to 0.15 leads to a decrease of the LF voltage amplitude required to switch from α to α–γ-mode from 700 to 550V.

本文研究了大气压下双频（5 MHz / 50 kHz）介质阻挡放电（DBD）从α到α – γ模式的转变。该研究基于Penning混合物（Ar–NH ₃）中的平面/平面DBD的实验和建模。放电处于α- RF模式，具有三个不同的电压幅度（250、300和350V），并被幅度为0至1300V的低频（LF）电压偏置。在给定的LF电压幅度阈值下（对于2mm的间隙和133 ppm的NH ₃约为400V ），从α过渡到α – γ-模式发生。其特点是氩气和氨气排放量都急剧增加。NH ₃浓度的增加会导致达到α – γ模式（实验）所需的LF电压幅度减小。当鞘中的电离增加时，从α过渡到α - γ-模式；当电离高于自我维持标准（1 / γ）时，则建立α - γ-模式。从α到α – γ的过渡-模式导致与LF电压幅度无关的颗粒密度的增加和气体电压的稳定。没有二次电子发射，就没有过渡。在该模型中，将二次发射系数从0.05增加到0.15会导致从α模式切换到α – γ模式从700V到550V所需的LF电压幅度减小。