It is widely known that when a solid body – which looks like a lattice built of atoms and molecules – is heated up to some given temperature, it turns to liquid. If heating continues, liquid evaporates resulting in gas. More heating turns vapour to ionized gas. This substance is called plasma, which appears to be the most unordered substance among mentioned above. Under certain conditions plasma can be “frozen” and turns to crystal.
This crystal is subject for said experiments. When physicists want to get such crystal, they introduce very small (microns in diameter) dust particles to plasma. Researchers take dust particles from ordinary smoke or sprayed metal. Each particle hosts about a million of electron charges. Charged particles start interacting and make ordered plasma, which consists of heavy particles, form crystals. Sometimes big – several cm in diameter – crystals, consisting of billions of particles, are formed. These objects can be observed with almost naked eye – a very important achievement. One can see them like through x-ray spectacles: observing their crystal structure, various properties, melting temperature, for example, etc. Various environments can produce dusty plasma – glow discharge or combustion products, for instance.
Eminent scientists from many countries unite their resources in order to develop plasma works, which include radioactive plasma as well. Experiments are carried out in the virtual laboratory, aimed at fundamental studies and finding practical aspects of dusty plasma. This substance can be used for catalysis and for nuclear induced batteries. Radioactive particles emit radiation, which, in its turn, is converted to electricity via complex transformations. Scientists also discovered a possibility to grow diamonds on these particles. Numerous future technologies are waiting for dusty plasma – nanotechnologies and microelectronics, as well.
Why were experimental works restricted for space? Space ultraviolet radiation brings positive charge to particles. Plasma particles are heavy and undergo strong impact of gravity. Earth’s gravity field flattens crystals, and space provides zero gravity, eliminating unwanted side effects. First experimental series was launched six or seven years ago on the “Mir” space station and was carried out by cosmonauts – creative people, who required some additional training. Airplanes’ parabolic paths generated short periods of zero gravity, which fitted training programmes perfectly. At the same time scientists developed and improved devices required for the experiment – a long and complicated process, resulting in 50 kg of various scientific units.
The experiment at the International space station was a success – cosmonauts worked hard and got a three-dimensional crystal of dusty plasma and great amount of data - enough for several years of intensive scientific experimentation. Many questions are still waiting for an answer: what is dusty plasma, what is its structure, what are its properties, how solar radiation and external fields influence its properties? Physicists are sure they will get all necessary answers and many more. Understanding mechanisms of various processes is essential in dealing with plasma – as well as with many other, not necessarily scientific, things. But it’s just the beginning.
Another important moment should be mentioned here. Dusty plasma experiment imitates processes taking place in space – the whole space system consists of charged dust particles. Dust concentrations affect radio-wave propagation, structure of comets and nebulae. What are the mechanisms involved? Described experiment helped us to make another step closer to the key to mysteries of our universe.