When a gas is subjected to high voltage and transformed into plasma, it gains a significant amount of energy. This energy excites the atoms or molecules in the gas, causing them to ionize and break apart into charged particles (ions and electrons).
The cooling down of plasma and its reversion to a gas state upon switching off the high voltage occurs relatively quickly due to a few key factors:
Energy Dissipation: Plasma contains highly energetic particles, including ions and electrons, which are continuously colliding with each other and the surrounding gas molecules. When the high voltage is turned off, the energy source that sustains the plasma is removed. As a result, the highly energetic particles begin to lose their excess energy through collisions and interactions with the surrounding particles.
Recombination: As the plasma cools down, the ions and electrons lose energy and eventually recombine to form neutral atoms or molecules. Recombination is a process where ions capture electrons to form neutral species. This recombination occurs more rapidly at lower temperatures because the likelihood of ions and electrons colliding and recombining increases.
Energy Transfer: The energy in the plasma is quickly transferred to the surrounding gas through collisions and radiation. As the high-energy particles in the plasma collide with the surrounding gas molecules, they transfer their energy to these molecules. This energy transfer helps cool down the plasma and restore the surrounding gas to its original state.
It's important to note that the specific timescale for plasma to cool down and transition back to a gas state can vary depending on various factors, such as the gas composition, pressure, temperature, and the initial energy input. In some cases, additional mechanisms like radiative cooling or particle loss processes can also influence the cooling rate of plasma.