Determination of the electron concentration and temperature, as well as the reduced electric field strength, in the plasma of a high-voltage nanosecond discharge initiated in atmospheric-pressure nitrogen by a runaway electron beam

We report on the results of spectroscopic measurements of electron concentration $N_e$ and temperature $T_e$, as well as the reduced electric field strength $E/N$ in the plasma of a high-voltage nanosecond discharge in the gap with a strongly nonuniform electric field distribution, which is filled with nitrogen under the atmospheric pressure. The possibility of using the method for determining $T_e$ and $E/N$, which is based on the determination of the ratio of the peak intensities of the ionic N$_2^+$ ($\lambda$ = 391.4 nm) and molecular N$_2$ ($\lambda$ = 394 nm) nitrogen bands, is proved. We detected the mean values of quantities $N_e$, T e , and $E/N$ amounting to $\sim$ 2 $\times$ 10$^{14}$ cm$^{-3}$, $\sim$ 2 eV, and $\sim$ 240 Td, respectively. In addition, the dynamics of these quantities is determined.