With laser output powers this large, I bet plasma has little to do with its cutting ability. Would not any substance hammered by enough photons eventually yield? Of course, the planet Mercury could be said to have been hammered by plenty of photons, and it still seems to stand. So maybe not.
An ionized substance is one where an electron is missing or added to give the molecule (or atom) a charge. Rusty water is brown because it contains ionized (aqueous, in this case) particles of iron. Not all ionized substances are plasma, but all substances in a state of plasma are all ionized and gaseous.
A bit of trivia: compared to the other states of matter, solid, liquid and gas, plasma is by far the most common state of matter in the universe. Our sun outweighs everything else in our solar system combined and is one bad ass ball of plasma.
Lasers that are strong enough to ionize the air (gas) are creating what is known as cold plasma. I think lightning is classified as cold plasma, too. Cold plasma is where only parts of the gas are ionized, meaning it’s localized. The plasma is very short lived. Like 0.00000000001 seconds. This kind of plasma isn’t famous for its cutting ability.
Plasma torches, on the other hand, completely ionize the gas passing through the system, and make what is known as hot (ass) plasma. If you’ve never used a plasma torch or seen one at work, you’ve really missed something remarkable. It cuts through metal like a hot knife cuts through butter. Working with one can make you feel like a deity.
Plasma torches form a tiny rocket engine at the tip. A gas is pumped through a small nozzle where an electrical charge is applied to the gas. The gas becomes ionized, expands rapidly and turns into plasma. Its temperature is like 30,000F and travels at 20,000 fps. The tip focuses the gas into a lovely little blue point about two inches long.
The gas used need not be anything special. Nitrogen, Oxygen and Argon are pretty common. I cannot say for sure, but I don’t think there isn’t any substance it can’t cut. These are not to be confused with Oxygen-Acetylene torches that burn the acetylene to reach temperatures of 6500F.
CO2 lasers (and many others in the IR range) can ionize gas and cause a popping sound, as that point of gas rapidly expands. I have even teased my children by suggesting that popping sound results from a teeny tiny supernova. But those lasers cut using the heat of the wavelength, not by their plasma making abilities.
Still, writing this post and thinking about lasers and plasma creates a pretty cool feeling in my head. This is a fun and thought provoking thread.
