High-voltage microdischarge as a source of extreme density plasma

Abstract

The generation of non-equilibrium (cold) plasmas with the densities ∼1019–1020 cm−3 in a fully ionized state has been reported in several recent experimental studies. In this work, we simulate a high-voltage high-pressure nanosecond xenon microdischarge that provides an easily accessible source of such a fully ionized cold plasma. In our studies, we use self-consistent one-dimensional Particle-in-Cell Monte Carlo collisions model. We observe that the generation of a fully ionized plasma can be driven by the secondary electron emission from the cathode. Initially, secondary electrons propagate through the collisional sheath and generate the plasma with a density ∼1018 cm−3. Such a dense plasma generated in the vicinity of the cathode sheath makes sheath collisionless, which allows the acceleration of secondary electrons to keV energies. These energetic electrons are responsible for the generation of fully ionized plasma. We also obtain that accounting for the electron field emission allows faster generation of fully ionized plasma, although the main physical mechanisms remain unchanged.