Plasma

Q: What is plasma?

A plasma is a gas that is so hot that the constituent atoms or molecules are ionized. Because the gas is now composed of charges, it reacts very strongly and quickly to both electric and magnetic fields. Plasmas comprise 99% of the visible matter in the universe. The sun, for example, is a big ball of plasma. Typical plasmas have equal numbers of positive and negative charges, so as a whole have no net charge.

Because an ionized gas typically has a large number of particles (of order 10²³), considering the electromagnetic interactions between each of the particles can become enormously complicated. The plasma approximation simplifies this by considering the collective effects of a very large number of electromagnetic interactions. The plasma approximation is valid when nλ_D³ >> 1 where n is number density of the particles and λ_D is Debye Length, the range of influence of the electromagnetic field for a particular particle.

Q: How is it generated?

Any process that ionizes molecules while maintaining the validity of the plasma approximation mentioned above will generate a plasma, for example heat or electric current.

Q: What can it be used for?

Fluorescent lights use plasma trapped in long glass cylinders to create light. Plasmas are used to etch silicon wafers in the production of integrated circuits and can even be used as a plasma scalpel during surgery. The ultimate use of plasmas would be to create an almost unlimited source of power through controlled nuclear fusion. The goal would be to heat and compress a hydrogen plasma so that hydrogen nuclei fuse into helium nuclei.

-Jeff Tessein and Mike Shay