Home Current Projects Oxidation Processes PLASMA UWAP Present PROJECTS Pig Farms Source Point Services
| |
PICTURE OF SUN'S SOLAR WIND
Plasma - WHAT IS A PLASMA?:
The loosest definition of a plasma is that it is an electrically
conducting gas. At normal temperatures and pressures gases are usually
very good electrical insulators. This is because the electrons in the
gas are tightly bound inside gas atoms and are not free to move in
response to externally applied electric or magnetic fields.
Under certain conditions, however, some or all of the electrons can be
removed from their parent atoms, a process called ionization. The gas
then consists of a mixture of negatively charged electrons, positively
charged atoms, called ions, and un-ionized neutrally charged atoms. Now
the electrons and ions are free to move under the action of applied
electromagnetic fields and the gas can conduct electricity. Due to
their much smaller mass the electrons respond to the applied fields much
more readily than the ions and, consequently, carry most of the
current. Since electrons and ions are produced in pairs and have
opposite charges most of the plasma remains electrically neutral.
There are three principal methods for ionizing a gas. The first, called
field ionization, involves applying an extremely high electrical field
that acts on the electrons in a neutral atom and essentially disrupts
the atom. The second, called thermal ionization, involves raising the
temperature of the gas until collisions knock electrons out of the
atoms. Thus, a plasma does not have to be "hot", although some
are
extremely so. The third method involves bombarding the gas with
high energy radiation or other sub-atomic particles.
Because the properties of a plasma are so very different from those of a
neutral gas the plasma state is sometimes called " the fourth state of
matter ".
In practice the plasma state covers an extremely large range of
temperature and pressure, from the gas in the fluorescent lamps in your
house to the fusion
reactions in the center of the sun. Although you
may have to search for a plasma in your daily life, most of the visible
matter in the universe is in the plasma state.
Technological applications of plasmas include: fluorescent lights,
welding arcs, steelmaking furnaces, experimental fusion reactors,
semiconductor processing, flat panel displays,
photovoltaics, solar coatings, architectural coatings,
and
hazardous waste processing.
- J. McKelliget 1998

|