Presented here are selections from two exhibits on Plasma Science and Technology sponsored by the Coalition for Plasma Science and shown in 1997 and 1998 in the House Office Buildings, Capitol Hill, Washington, District of Columbia
Congressmen, staff and the public saw a new face for plasmas - important basic science, multiscale phenomena from the lab to the universe, a large number of applications, and cutting edge technology for the 21st century.
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% of the visible universe and perhaps most of that which is not visible.
On earth we live upon an island of "ordinary" matter. The different states of matter generally found on earth are solid, liquid, and gas. We have learned to work, play, and rest using these familiar states of matter. Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma, in 1879.
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.
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.
The United Nations projects an increasing population and increasing energy demands. 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.
Fusion requires energetic collisions of very light elements, usually hydrogen isotopes, resulting in a nuclear reaction that leads to more stable helium nuclei and other byproducts. A net loss of mass results, yielding free energy as given by Einstein's famous equation.
There are three basic confinement mechanisms required for fusion reactions: gravitational, inertial, and magnetic. The Tokamak Fusion Test Reactor (TFTR) at Princeton (below) uses magnetic confinement.
Both inertial and magnetic confinement fusion research have focused on confinement and heating processes with dramatic results. The next stage of operating power reactors will produce about 1 GW of power and operate at
120 million degrees Kelvin. [from Contemporary Physics Education Project chart]
Plasma radiation within the Princeton Tokamak during operation.
Laser plasma interaction during inertial confinement fusion test at the University of Rochester.
Iron filings injected into a plasma release atoms that become excited and emit light which can be readily analyzed. An atomic metal emissions monitor can be positioned within a smokestack where it could detect hazardous emissions in real time.
Plasma-based sources can emit intense beams of UV & 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.
Pollution Monitoring: Exhaust gas flow from a furnace passes through a microwave plasma, becomes excited and emits light which is analyzed by a spectrometer to identify any hazardous elements.
Electron-beam generated plasma reactors can clean up hazardous chemical waste or enable soil remediation. Such systems are highly efficient and reasonably portable, can treat very low concentrations of toxic substances, and can treat a wide range of substances.
High-temperature plasmas in arc furnaces can convert, in principle, any combination of materials to a vitrified or glassy substance with separation of molten metal. Substantial recycling is made possible with such furnaces and the highly stable, nonleachable, vitrified material can be used in landfills with essentially no environmental impact.
• Computer chips and integrated circuits
• Computer hard drives
• Electronics
• Machine tools
• Medical implants and prosthetics
• Audio and video tapes
• Aircraft and automobile engine parts
• Printing on plastic food containers
• Energy-efficient window coatings
• High-efficiency window coatings
• Safe drinking water
• Voice and data communications components
• Anti-scratch and anti-glare coatings on eyeglasses and other optics
• Waste processing
• Coatings and films
• Electronics
• Computer chips and integrated circuits
• Advanced materials
(e.g., ceramics)
• High-efficiency lighting
Plasma Generation Devices
- Low pressure electrical discharge
- Penning plasma discharge
- Radio-frequency (RF) capacitive discharges
- RF inductively coupled plasmas
- Microwave generated plasma
Plasma Deposition of Films
- Polycrystalline SiO2 films for low cost solar cells
- Flat panel display transistors
- Diamond films for high heat conductivity and wear resistance
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, we are better able to appreciate the important role of plasmas throughout our plasma universe. This space plasma laboratory is truly our window to the stars.
The earth's magnetosphere is normally invisible because the dominant hydrogen and helium ions coming in the solar wind do not scatter light in visible wavelengths. However, comets emit heavier ions that are visible and which result in spectacular neutral and ion (plasma) tails. Images of earth's magnetosphere would show it to be a very large comet-like interaction region.
The Sun is a variable star, especially in its output of ultraviolet radiation, X-rays, particles and magnetic fields. Corresponding large variations occur throughout the region of the Sun's influence, which is called the heliosphere and which includes the solar wind and all solar system magnetospheres. Space weather is the study of how the space environment affects astronauts, satellite operations, communication systems and ground-based power grids. In the long term, space weather could contribute to global climate change primarily through slow changes in solar radiation.
As the solar wind flows past earth's magnetosphere, it interacts with the geomagnetic field and acts as a cosmic generator producing millions of amps of electric current. Some of this electric current flows into earth's upper atmosphere which lights up like a neon tube to create the beautiful aurora. The aurora are always present because the solar wind source is always present, and they form a ring of emissions within the ionosphere centered on both magnetic poles at high latitude. However, they are normally sub-visual except at nighttime and during geomagnetic storms. In midwinter, residents of Fairbanks, Alaska enjoy auroral display two out of every three nights!
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
In inertial-confinement fusion, laser beams or ion beams energize the inside of a small cylindrical target. X rays then rapidly heat the capsule (1) causing its surface to blow off (2). The resulting force compresses the plasma fuel (hydrogen isotopes), raising temperatures to 100,000,000 degrees C and densities to 20 times greater than lead. This ignites the plasma fuel (3) and produces fusion energy output (4) many times the laser energy input (thus yielding large energy gain).
The National Ignition Facility is a key element in our nation's Stockpile Stewardship and Management Program which aims to maintain confidence in the safety and reliability of the U.S. nuclear weapons stockpile under a Comprehensive Test Ban Treaty. Target data from this facility will be used to verify complex computer simulations of nuclear weapons physics.
The National Ignition Facility will be used for research in inertial fusion energy and applications and help build a basis for realistic development of inertial fusion energy systems.
Benefits at Home
High efficiency lighting; manufacturing of semiconductors for home computers, TVs and electronics; flat-panel displays; and surface treatment of synthetic cloth for dye adhesion.
Business Applications
Plasma enhanced chemistry; surface cleaning; processing of plastics; gas treatment; spraying of materials; chemical analysis; high-efficiency lighting; semiconductor production for computers, TVs and electronics; and sterilization of medical tools.
Plasmas in Transportation
Plasma spraying of surface coatings for temperature and wear resistance, treatment of engine exhaust compounds, and ion thrusters for space flight.
High-intensity sources are widely used in industrial and commercial settings as well as for outdoor and security lighting near homes and public areas. It is high-intensity arc lamps that give you the spectacular panoramic views of cities as you fly over them at night.
In high-intensity arc lamps the light we see is generally produced directly by the plasma. Color characteristics are controlled by the chemical elements put into the plasma rather than by a phosphor coating on the wall.
Inside every fluorescent lamp there lurks a plasma. It is the plasma that converts electrical power to a form that causes the lamp's phosphor coating to produce the light we see. The phosphor is the white coating on the lamp wall. A fluorescent lamp is shown here with part of the phosphor coating removed to reveal the blue plasma glow inside.
Plasma-based light sources are in fact observable from outer space. Indeed, it may be characteristics of the light from those lamps that tell an alien civilization of our presence.
Plasma scientists work with students
at all levels to develop the capabilities of America's future scientists, and to develop the science literacy and problem solving know how of all students.
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.
