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Shaping the Future

Scientific Milestones During Israel’s First Half-Century
Shaping the Future

First published in 1997

Hot and Dense Plasmas

The fourth state

Plasma is the fourth, less well-known state of matter, a state in which gas particles are ionized and charged. There are different plasmas containing various substances, differing from each other in degrees of density, velocity, temperature or pressure. For example, a fluorescent light contains plasma. Plasmas are widely utilized in industrial applications.
In nature, the stars and the internal stellar space are composed of plasmas. It is possible to find plasmas arranged in layers resembling onion skins wherein each layer contains plasma at temperatures and density different from neighboring layers. Research into plasmas may greatly assist in understanding various processes in the stars and the universe. It should also be useful in a long list of industrial applications, including nuclear fusion (thought to be the energy source of the future). In order for nuclear fusion to take place in hydrogen gas, it must be in a plasma state.
Weizmann Institute scientists developed unique spectroscopic methods to measure various properties of plasma in contact with strong electric and magnetic fields. While developing new measurement techniques, the scientists took advantage of the various properties of the light that was emitted and absorbed by plasma, and also how plasmas react to strong illumination. (Light in the visible, ultraviolet and X-ray regions was utilized.) These techniques enable various reactions in plasma to be measured over very short time periods, down to a million-millionth of a second.
Researchers have already mapped out various physical occurrences in plasma, mainly changes in the time and space of the fields, and in the movement of particles during a hundred-millionth of a second. Further investigations delved into the processes occurring in plasma that is conducting a very strong electric current, which causes the formation of turbulent waves inside the plasma.