PLASMA: THE FOURTH STATE OF MATTER

  The different states of matter generally found on earth are solid, liquid, and gas. Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma, in 1879. Plasma is by far the most common form of matter. Plasma in the stars and in the tenuous space between them makes up over 99 per cent of the visible universe and perhaps most of that which is not visible.On earth we live upon an island of "ordinary" matter.

    Plasma temperatures and densities range from relatively cool and tenuous (like aurora) to very hot and dense (like the central core of a star). Ordinary solids, liquids, and gases are both electrically neutral and too cool or dense to be in a plasma state. The word PLASMA was first applied to ionized gas by Dr. Irving Langmuir, an American chemist and physicist, in 1929.Plasma consists of a collection of free-moving electrons and ions - atoms that have lost electrons. Energy is needed to strip electrons from atoms to make plasma. The energy can be of various origins: thermal, electrical, or light (ultraviolet light or intense visible light from a laser). With insufficient sustaining power, plasmas recombine into neutral gas.

    Plasma can be accelerated and steered by electric and magnetic fields which allows it to be controlled and applied. Plasma research is yielding a greater understanding of the universe. It also provides many practical uses: new manufacturing techniques, consumer products, and the prospect of abundant energy. Because plasmas are conductive and respond to electric and magnetic fields and can be efficient sources of radiation, they are usable in numerous applications where such control is needed or when special sources of energy or radiation are required.

    Many people believe the space in between the the Sun and its planets is empty, a vacuum devoid of energy or matter. But space is not empty. Our Sun constantly emits plasma, a superheated state of matter, which moves out in all directions at very high speeds to fill the entire solar system and beyond.By studying processes that occur in the earth’s magnetosphere (where earth’s magnetic field has a greater influence than the Sun’s interplanetary field), in interplanetary space, and around other planets, one can better appreciate the important role of plasmas throughout our plasma universe.

    The vast power radiated by our sun is generated by the fusion process wherein light atoms combine with an accompanying release of energy. In nature, proper conditions for fusion occur only in the interior of stars. Researchers are attempting to produce the conditions that will permit fusion to take place on earth. In order to meet future needs, long-term sustainable energy sources are required. Ideally future energy sources will comprise a mix of energy technologies - solar, renewables, advanced nuclear fission and fusion.

    Plasma-based sources can emit intense beams of UV and X-ray radiation or electron beams for a variety of environmental applications. For water sterilization, intense UV emission disables the DNA of microorganisms in the water which then cannot replicate. There is no effect on taste or smell of the water and the technique only takes about 12 seconds. This plasma-based UV method is effective against all water-born bacteria and viruses. Intense UV water purification systems are especially relevant to the needs of developing countries because they can be made simple to use and have low maintenance, high throughput and low cost. Plasma-based UV water treatment systems use about 20,000 times less energy than boiling water!

    A plasma device being developed produces hydrogen-rich gas from diesel fuel, gasoline, methane and other hydrogen-rich fuels; provides cleaner burning fuels for conventional engines; works with fuel cells for higher efficiency and reduced pollution; and dramatically reduces environmentally toxic substances in the products of combustion.

    Home applications of plasma include high efficiency lighting; manufacturing of semiconductors for home computers, TVs and electronics; flat-panel displays; and surface treatment of synthetic cloth for dye adhesion. In the field of business application , plasma ranges from surface cleaning; processing of plastics; gas treatment; spraying of materials; chemical analysis; high-efficiency lighting and semiconductor production for computers, TVs and electronics to sterilization of medical tools. In transportation, plasma spraying of surface coatings for temperature and wear resistance, treatment of engine exhaust compounds, and ion thrusters for space flight is done.

    Plasmas for national security span an enormous range in temperature and density. For example, high energy density plasma research helps assure the safety and reliability of nuclear weapons stockpiles under the Comprehensive Test Ban Treaty(CTBT). Plasma-related experiments are excellent vehicles for illustrating and understanding complex physical concepts and for exploring cutting-edge topics in physics, materials sciences, computer sciences, and mathematics. In India, plasma research is being carried out in the Facilitation Centre for Industrial Plasma Technologies, Gandhinagar, Centre for Advanced Technologies, Indore ;Institute for Plasma Research, Bhat,Physical Research Laboratory, Ahmedabad and the Plasma Physics Division at Saha Institute of Nuclear Physics, Kolkata.