# Temporal Stability of Modified Surfaces of Insulating HV Devices Using Atmospheric Pressure Plasma
## 3 Experimental Conditions of Plasma Surface Treatment of Test Samples
Figure 9: The RF spectrum comparison \(P_{\rm{slog}}\) with generator at \(f_{\rm{g}}\) = 13.56 MHz and with plasma generation under an argon atmosphere for frequency range \(f\) = 10 MHz- 200 MHz and attenuation limit \(P_{\rm{slog}}=-90\) dBm, with no samples (blue line) and with samples from thermoset (red line). Figure 11: The RF spectrum comparison \(P_{\rm{slog}}\) with generator at \(f_{\rm{g}}\) = 13.56 MHz and with plasma generation under an argon + nitrogen atmosphere for frequency range \(f\) = 10 MHz–200 MHz and attenuation limit \(P_{\rm{slog}}=-90\) dBm, with no samples (blue line) and with thermoplastic samples (red line). Figure 5.0 The RF spectrum comparison \(P_{\rm{slog}}\) with generator at \(f_{\rm{g}}\) = 13.56 MHz and with plasma generation under an argon + oxygen atmosphere for frequency range \(f\) = 10 MHz–200 MHz and attenuation limit \(P_{\rm{slog}}=-90\) dBm, with no samples (blue line) and with samples from thermoset (red line). Figure 6 shows an overview of the spectral background in space with plasma application, where \(f\) = 10 MHz-1000 MHz. The working space is without additional EMG shielding and thus the signal sources are as evident as in a normal urban agglomeration. When applying plasma discharge to insulator samples, the effects of changes in the plasma itself (without impurities) and on the surface of the material are evident. A detailed elucidation of the reasons for the effect would require thorough, in-depth research. The important fact remains that this is a process character, where this phenomenon of changes in the RF spectrum in a specific frequency interval is given by a unique combination of plasma and the treated material. However, this combination is repeatable. The results of the modified spectrum for the individual comparisons in Figures 7-13 correspond to the quantitative evaluation of the surface resistivity presented in the following text. Figure 7 shows the spectral background before sample modification for the frequency band \(f\) = 10 MHz to 200 MHz. It is necessary to respect this background because its shielding for industrial application is quite technically and financially demanding. Therefore, the evaluation was performed by evaluating the spectrum without the sample and with the sample. There is then an evident difference when comparing both records in the effect on the distribution of the power spectrum \(P_{\text{slog}}\) due to the interaction of plasma with the sample. As a result, there will be a change in the reflected/absorbed power (amplitude magnitude) \(P_{\text{slog}}\), and another effect is a change in the composition of the spectrum--the appearance of new spectral lines for the reasons previously mentioned. Figure 8 shows that the difference is not significant for plasma with an argon atmosphere and interaction with the thermoplastic sample. Only new lines appeared in the 115 MHz, 165 MHz and 180 MHz region. However, for plasma with an argon atmosphere, significant lines or bands of lines appeared for application to a thermoset sample, as shown in Figure 5.1 This is a band increase in Pslog power in the 13.56 MHz, 27 MHz, 43 MHz, 85 MHz, 130 MHz, 180 MHz and 210 MHz region. Figure 10 shows a comparison and evaluation of the argon-nitrogen atmosphere plasma applied to a thermoset sample. It is evident that the spectrum is changed only in the 40 MHz, 140 MHz  
Figure 5.2 The RF spectrum comparison \(P_{\text{slog}}\) with generator at \(f_{\text{g}}\) = 13.56 MHz and with plasma generation under an argon + oxygen atmosphere for frequency range \(f\) = 10 MHz–200 MHz and attenuation limit \(P_{\text{slog}}=-90\) dBm, with no samples (blue line) and with thermoplastic samples (red line). and 150 MHz region, and the lines around 180 MHz frequency.