On basic processes sustaining constricted glow discharge in longitudinal N₂ flow at atmospheric pressure

Abstract

The results of numerical calculations on a steady-state constricted discharge in N2 flow at atmospheric pressure are presented. Basic elementary processes responsible for sustaining the constricted discharge at low and high currents are found. It is shown that the charged particle generation in both regimes is controlled predominantly by an associative ionization . However, metastable states are created in these regimes by different processes. In low-current discharge N2(A) and N2(a′) metastables are created due to mutual collisions of the vibrationally excited molecules, and their collision frequency is determined by the vibration energy distribution function. In high-current discharge these metastables are excited by energetic electrons, and inelastic collision frequency is determined by the electron energy distribution function. The charged particle dynamic balance in the high-current constricted discharge in atmospheric pressure N2 is non-local and sustained by ionization and ambipolar diffusion like that in a low-current diffusive discharge in a tube at low pressure. It was demonstrated that blowing of the discharge by longitudinal gas flow leads to a more pronounced constriction.

Time-resolved optical emission spectroscopy of nanosecond pulsed discharges in atmospheric-pressure N2 and N2/H2O mixtures

“…however, the time scale for these reactions are >0.5 µs if the ion and metastable densities are smaller than 10 22 m −3 [40,42]. Short (30 ns) after the start of the emission of the FPS the emission of atomic and ionic nitrogen lines starts and the emission of molecular nitrogen collapses.…”

“…Due to the high electron temperature, the excited states N 2 (C), N 2 (B) and N + 2 (B) are created by direct electron impact. Note that N 2 (C) can also be created via a pooling reaction if the metastable density is large [40]:…”

“…Assuming that the electron temperature in the afterglow is T e = 10000 K (see section 3.3), the rate constants for reactions R1, R2 and R3 are 3. [40]) and subsequent dissociative recombination (R4 and R5 in table 1) are too slow to compete with reaction R2 to cause the n e decay.…”

“…As mentioned above, the jitter is about 15 ns. This results in an error in the decay time of maximum a factor 10, so this cannot [40,44] R8 N(…”

“…This indicates that there is a significant production of electrons during the recombination phase. One hypothesis is that electrons are created by Penning and associative ionization reactions [40,41,44], see table 2. These ionization processes should take place on a time scale in the order of 100 ns.…”