Phase resolved spectroscopy synchronized to low-frequency self-organized mode of an atmospheric pressure plasma jet

Summary form only given. Simultaneous monitoring of the phase resolved discharge development in a miniaturized plasma jet operating at 27.12 MHz with respect to its specific low-frequency discharge regime is reported for the first time. Phase resolved optical emission spectroscopy (PROES) was applied [1]. The plasma jet, used for surface modification e.g. thin film deposition is composed of a quartz capillary surrounded by two ring electrodes that are capacitively coupled to an RF generator. The outer capillary is fed with pure argon and as a first step no precursor was used for this study. By adjusting the applied RF power and gas flow rate the plasma jet can be operated in two different discharge regimes (stochastic or self-organized modes). Deposition experiments were carried out in the self-organized regime. Here, two modes are distinguished: the stationary mode features spatio-temporally stable filaments between the electrodes. Under specific discharge conditions, the locked mode occurs [2]. This exclusively stable mode is characterized by equidistantly rotating filaments with a constant frequency (few 10 to 100 Hz) in azimuthal direction along the inner wall of the outer capillary. The optical setup - a fast gating ICCD camera with a mounted macro objective - delivers a spatial resolution of about 30 μm. With gating times down to 300 ps the camera was triggered synchronously to the excitation frequency of the plasma jet. Additionally, this carrier signal from the plasma jet is modulated by the periodic optical signal from the rotating filaments via an analogous signal mixer. This constitutes a special challenge for the signal processing due to small jitter tolerances at 27.12 MHz combined with a factor of 10⁶ between the time scales. This approach enables the simultaneous iSimultaneous monitoring of the phase resolved discharge development in a miniaturized plasma jet operating at 27.12 MHz with respect to its specific low-frequency discharge regime is reported for the first time. Phase resolved optical emission spectroscopy (PROES) was applied [1]. The plasma jet, used for surface modification e.g. thin film deposition is composed of a quartz capillary surrounded by two ring electrodes that are capacitively coupled to an RF generator. The outer capillary is fed with pure argon and as a first step no precursor was used for this study. By adjusting the applied RF power and gas flow rate the plasma jet can be operated in two different discharge regimes (stochastic or self-organized modes). Deposition experiments were carried out in the self-organized regime. Here, two modes are distinguished: the stationary mode features spatio-temporally stable filaments between the electrodes. Under specific discharge conditions, the locked mode occurs [2]. This exclusively stable mode is characterized by equidistantly rotating filaments with a constant frequency (few 10 to 100 Hz) in azimuthal direction along the inner wall of the outer capillary. The optical setup - a fast gating ICCD camera with a mounted macro objective - delivers a spatial resolution of about 30 μm. With gating times down to 300 ps the camera was triggered synchronously to the excitation frequency of the plasma jet. Additionally, this carrier signal from the plasma jet is modulated by the periodic optical signal from the rotating filaments via an analogous signal mixer. This constitutes a special challenge for the signal processing due to small jitter tolerances at 27.12 MHz combined with a factor of 10⁶ between the time scales. This approach enables the simultaneous investigation of the spatiotemporal behavior of the plasma jet in the scale of ns as well as ms. The results of the emission profiles for different emission lines (ArI @ 750 nm, ArI @ 707 nm) and with respect to the discharge mode will be presented.nvestigation of the spatiotemporal behavior of the plasma jet in the scale of ns as well as ms. The results of the emissi