Plasmaspoor

Plasmaspoor is a term used in some Dutch-language plasma literature to describe a regime in which the plasma portion of a gas is scarce. It denotes a state with a low degree of ionization and a relatively small density of free charged particles (electrons and ions) compared with the neutral component. The term is not a universally standardized designation in all plasma physics literature, but it is helpful for describing environments where ionization remains minimal.

In plasmaspoor conditions, ionization is insufficient to sustain strong collective plasma effects. The Debye length tends to be relatively long, screening is weak, and quasi-neutrality may break down on small scales. Interactions are dominated by collisions between neutrals and the few charged particles present, rather than by long-range electromagnetic fields, leading to a plasma behavior that is closer to that of a neutral gas with occasional ionization events.

Ionization mechanisms in plasmaspoor environments are typically modest, arising from electron impact at low temperatures, photoionization, or rarefied cosmic-ray interactions. Recombination quickly reduces the ionization fraction, so sustaining a significant population of free charges is challenging. Temperatures and pressures vary with the specific setup, but the common feature is a predominantly neutral gas with only a small fraction of ionized species.

Diagnostics in plasmaspoor regimes reveal low electron densities and weak emission, with currents that are small under applied electric fields. Such conditions are relevant for certain plasma processing applications and for modeling astrophysical and atmospheric plasmas, where ionization fractions can be very low. Related concepts include weakly or partially ionized plasmas, which describe similar situations in broader contexts.