Ultra-cold Plasmas

Abstract

Traditionally, the concept of plasma, is associated with a very hot gas. It is sometimes considered that the basic four states of matter, solid, liquid, gas and plasma, are the modern counterpart of the ancient elements: Earth, Water, Air and Fire. So, the plasma state corresponds to the possible highest internal energy of the medium, the star material being the most striking example. We can identify a plasma with a medium containing a large fraction of free charged particles, which interact between themselves by long range electromagnetic forces [1, 2, 3]. The Universe is dominated by plasma. The solar corona is a very hot plasma with temperatures around one million degrees Kelvin, from where a plasma flow called the solar wind is emitted and propagates to very large distances, interacting with the Earth magnetosphere. The Earth can be seen as a cold drop in the middle of a hot plasma environment. In the last 50 years, plasma physics has been mainly driven by the quest for a nuclear fusion reactor. It is known that fusion of light elements provides the source of energy of the stars, and is the basis for the Hydrogen bomb, but its use in a controlled and sustained way, for peaceful applications in electrical power plants is still in the far horizon for mankind.