Magnetic Bottle

From TFC Galactopedia

A "magnetic bottle" (also a "tokamak" or "magnetic mirror") is a type of device that uses magnetic fields to contain dangerous or corrosive materials, such as plasma or antimatter. Charged particles react in predictable ways when subjected to certain magnetic field stresses, and if these stresses are carefully balanced, they can be used to "bottle" dangerous materials without them ever coming into contact with the container wall.