Plasma is the fourth fundamental state of matter. It is a gas with so much energy the electrons orbiting the atoms have too much energy to remain in orbit, giving us ions and free electrons. Plasma can be artificially generated by heating (a lightning bolt is made of plasma), electromagnetic fields (see fluorescent light bulbs) or radiation.
Plasma at ALPHA
At ALPHA, we manipulate the ingredients to make antihydrogen as plasmas. We use several so-called non-neutral plasmas made up of either positrons, electrons or antiprotons (or mixtures of these). Each of these particle plasmas are prepared separately: the positrons and electrons have no ions to orbit, and the antiprotons have not (yet) got positrons orbiting them.
As charged plasmas, they are easy to manipulate in the vacuum of the experiment. We can confine them with magnetic and electric fields (see Penning Trap). Their charged nature also helps with diagnostic measurements (see Faraday Cup and MCP).