# Temporal Stability of Modified Surfaces of Insulating HV Devices Using Atmospheric Pressure Plasma
## 4 Interpretation of Modeled and Measured Data
**(a1,b1)** The RF generator output power \(P_{\text{out}}=500\) W, Ar flow rate \(w=4\) m\({}^{3}\)/h and N\({}_{2}\) flow rate \(w=1.5\) L/min; **(a2,b2)** the RF generator output power \(P_{\text{out}}=600\) W, Ar flow rate \(w=6\) m\({}^{3}\)/h and N\({}_{2}\) flow rate \(w=3.5\) L/min. Figure 15:3 Comparison of the influence of gas admixture in Ar, the influence of Ar flow rate and the influence of output RF power supplied from the source on the dynamic behavior of plasma channels at a plasma nozzle slit width of 150 mm (**a**—front view, **b**—side view with a high-speed camera) for a plasma nozzle mouth height of 10 mm above the dielectric substrate (\(\varepsilon_{r}=10\)) and a stationary state (without sample substrate movement). **(a1,b1)** The RF generator output power \(P_{\text{out}}=500\) W, Ar flow rate \(w=4\) m\({}^{3}\)/h and O\({}_{2}\) flow rate \(w=1\) L/min; **(a2,b2)** the RF generator output power \(P_{\text{out}}=600\) W, Ar flow rate \(w=4\) m\({}^{3}\)/h and O\({}_{2}\) flow rate \(w=1\) L/min;  
The received frequency spectra were obtained during scanning not only during the movement of the plasma over the surface of the samples, but also when passing over their rising and falling edges of the material. It should be noted that the plasma also dynamically interacts with the edges of the samples (front, back, side) during the movement of the samples, since the width of the plasma generated by the nozzle is larger than the width of the samples. The height of the edges of the samples is approx. 5 mm. In the spectral lines, those caused by the intrinsic dynamical effects of the interaction of the plasma and the surface of the material may appear. One of the causes is, for example, the morphology of the affected material sample, or its 3D geometry and macrostructure. This effect occurs as a response coupling in the EMG field of the plasma and the sample surface depending on the chemical composition and micro-/macro-morphology of the sample material. Therefore, to eliminate these possible instantaneous changes, an accumulation of \(s_{\mathrm{k}}=64\) is used when scanning the spectrum, and the averaged spectrum is further recorded. It is evident from the experiments that the spectrum sensed in this way is stable and does not change either the frequency or the amplitude of the evaluated power. To clarify the measured and recorded frequency spectra, the arrangement of the plasma chamber and the modified surface of the dielectric sample is shown schematically in Figure 15:4 To clarify the measured and recorded frequency spectra, the arrangement of the plasma chamber and the modified surface of the dielectric sample is shown schematically in Figure 21a. Figure 23 shows a comparison of the power \(P_{\mathrm{s}}\) in the laboratory without an ignited plasma discharge, without switching on the RF power generator and with the RF generator switched on. It can be found that the differences in the frequency and amplitude of the sensed spectrum are in the range of 5 dBm. One can observe the spectral line of the excitation generator at the frequency \(f_{\mathrm{g}}=13.56\) MHz. Figure 15:5 Substitute numerical model of plasma discharge in the chamber: (**a**) electrical diagram of the substitute model; (**b**) spectrum of the generated electric current (hereinafter referred to as electromagnetic signal sources). For a quantitative assessment of the quality of the sensed spectrum of signals, it is convenient to convert the power quantity \(P_{slog}\) from dBm units to mW units. Figure 15:6  
Then, for example, \(P_{sdBm}\)= 5 dBm is the power \(P_{smW}\) = 3.162 mW; \(P_{sdBm}\)= \(-\)120 dBm is adequate power at \(P_{smW}\) = 1.00 pW; \(P_{sdBm}\) = \(-\)125 dBm represents the power \(P_{\rm{smW}}\) = 0.3162 pW. Therefore, for example, the difference in the background power spectrum of the laboratory (\(P_{sdBm}\) = \(-\)120 dBm and \(P_{sdBm}\) = \(-\)125 dBm) is \(\Delta P_{smW}\) = 0.6837 pW. The above combined or hybrid modeling approach explains the underlying causes of the measured spectra.