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WHAT IS COLD PLASMA?
In our thought experiment above, plasma is produced by the provision of heat to a gas. Hence, we might think that plasma is always hot in nature. However, not every plasma is hot. Before proceeding further, let us try to refresh our knowledge of temperature and heat. It is a common misconception that higher temperature should always mean a lot of heat. When defining the hotness or coldness of a given substance, one must not only consider its actual temperature but also its heat capacity. For example: the temperature of the electrons inside the fluorescent lamp in your room is *0,**0 K, although the lamp does not feel hot when you touch it. This is because the number of high-temperature electrons inside your lamp is very low compared to the air at room temperature. Thus total heat transfer to the wall of the lamp by these electrons striking the wall is not sufficiently high. Hence, the heat capacity of the plasma in the fluorescent lamp is low, keeping the wall of the lamp at room temperature. Let us take another example: You might have experienced accidentally dropping the ash of a cigarette on your hand. Even though the temperature of the ash is very high, you were probably not immediately burned. This is because the total amount of heat involved is very low.
Cold plasma (or non-equilibrium plasma) is the plasma where the temperature of the individual constituents are different from each other. Electrons are at higher temperature (more than *0,**0K) and neutral atoms are at room temperature. However, the density of the electrons in the plasma is very low compared to the density of the neutral atoms. In the laboratory, cold plasmas are generally produced by the provision of electrical energy to different inert gases. This can be done at room temperature and at atmospheric pressure. This means that we avoid all the hassles of big costly instruments, making cold plasma technology affordable.
There are two very fascinating things about cold plasma. First, cold plasma is a source of high-tempera