## 3 Results
### Spatial Distribution of the Plasma Parameters  
The average values of \(\overline{n}_{e}\), \(\overline{T}_{e}\) and \(\overline{T}_{h}\) are presented in Figure 2 for different axial distances \(d\) from the nozzle outlet. Thereby, the values estimated for the discharge pulsed at a frequency of 60 kHz are presented on the left-hand side of Figure 2, whereas the values determined for 43 kHz are shown on the right-hand side. Additionally, the spectroscopic results for both frequencies are also presented in Figure 2. In both cases, the experimental setups are triggered at the peak current (see Figure 3) with the current amplitude set to \(\sim\)1 A (i.e., a power setting of 100%). According to the results, a higher electron density of \(2.0\times 10^{21}\) m\({}^{-3}\) is obtained for the lower operating frequency of 43 kHz at a distance of 1 mm. At the same distance, a slightly lower mean density of \(1.7\times 10^{21}\) m\({}^{-3}\) is reached for the higher frequency of 60 kHz. The difference is, however, present only in the immediate vicinity of the nozzle exit. The electron densities estimated for 2 mm and 3 mm are only marginally higher for the slower pulsed process and, similar to the data points further downstream, can be assumed to be constant at about \(1.5\times 10^{21}\) m\({}^{-3}\) when the standard deviation is taken into account. In contrast, the spectroscopically estimated electron number densities increase insignificantly in the axial direction up to about 3 mm downstream from nozzle exit when operating at 60 kHz. However, after consideration of the measurement error, the density can be assumed to be constant at \(0.52\times 10^{21}\) m\({}^{-3}\) for distances \(d<3\) mm. Thereafter, the values decrease for larger distances from nozzle outlet. The axial distribution of \(n_{e}\) determined for the lower working frequency of 43 kHz, presented on the right-hand side in Figure 2, displays a similar character as for 60 kHz with maximal values measured at a distance of 2 mm. After consideration of the measurement error, an almost twice as high mean electron density of \(0.95\times 10^{21}\) m\({}^{-3}\) is obtained in the analyzed distance range for the lower pulse repetition rate. The progression of the axial distribution of the electron temperature in the downstream direction is somewhat different. The values decrease for both frequencies at a rate of approx. 10%/mm up to a distance of 3 mm. Throughout this distance range, the electron temperatures estimated for the lower operating frequency are about 15% higher than for 60 kHz. Thereafter, \(\overline{T}_{e}\) reaches about 43,000 K in both cases and can be assumed to be constant up to 7 mm for the higher frequency. The temperature of heavy particles, on the contrary, is higher for the higher working frequency over the entire range of distance studied. It should be also noted that the \(\overline{T}_{h}\) values vary only insignificantly around 5900 K up to 5 mm for the higher and around 5200 K up to 3 mm for the lower frequency. The values start to decrease slowly from there on in both analyzed cases. As can be seen in the last row of Figure 2, the temperatures of heavy particles obtained by synthetic spectra fitting are almost identical to those estimated by laser scattering for the higher frequency. In the other case studied, the spectroscopically estimated temperatures are higher than the scattering estimates, but the absolute values are lower than the values determined for 60 kHz. To assess the temperature of heavy particles at larger downstream distances, further measurements are undertaken for the discharge pulsed at 60 kHz.