St. Elmo's fire is one of these substances, which are usually found at very high temperatures.
Pressure on a cylindrical column containing these substances can cause the sausage instability. The experiment ALICE at CERN is studying one of these substances composed of free quarks and gluons. The electron temperature of these substances can be determined using a Langmuir probe. These substances circulate in a torus-shaped chamber and are confined by a magnetic field in a tokamak. St. Elmo's fire is one of these substances, which are usually found at very high temperatures. For 10 points, name these ionized gases that are called the fourth state of matter. 
Pressure on a cylindrical column containing these substances can cause the sausage instability.
plasmas