Plasma source
Encyclopedia
Plasma sources generate plasmas
.
Excitation of a plasma requires partial ionization
of neutral atom
s and/or molecule
s of a medium.
There are several ways to cause ionization
:
collisions of energetic particles, strong electric fields acting on bond
electron
s, or ionizing radiation. The kinetic energy
for ionizing collisions may come from the heat
of chemical or nuclear reactions of the medium, as in flame
s, for instance. Alternatively, already released charged particles may be accelerated by electric field
s, generated electromagnetically or by radiation fields.
If at least as many charge carrier
s are created per time unit as
recombine, the plasma can be sustained.
Plasma excitation by electromagnetic field
s can be classified according to:
Plasma sources have numerous technical applications, for instance in light generation and plasma processing
of materials.
They can be used for extracting an ion beam, in which case they are also called ion sources. An innovative and emerging field is the application of non-thermal atmospheric pressure plasma sources in plasma medicine
.
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
.
Excitation of a plasma requires partial ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
of neutral atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s and/or molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s of a medium.
There are several ways to cause ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
:
collisions of energetic particles, strong electric fields acting on bond
electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s, or ionizing radiation. The kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
for ionizing collisions may come from the heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
of chemical or nuclear reactions of the medium, as in flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...
s, for instance. Alternatively, already released charged particles may be accelerated by electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
s, generated electromagnetically or by radiation fields.
If at least as many charge carrier
Charge carrier
In physics, a charge carrier is a free particle carrying an electric charge, especially the particles that carry electric currents in electrical conductors. Examples are electrons and ions...
s are created per time unit as
recombine, the plasma can be sustained.
Plasma excitation by electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
s can be classified according to:
- Frequency classification of plasmasFrequency classification of plasmasElectrical discharges applied in a plasma source for the generation of plasmas can be classified by the frequency of the exciting field. A rough classification is:*Direct current discharge *Pulsed DC discharge...
- Energy coupling mode
- Inductively coupled plasmaInductively coupled plasmaAn inductively coupled plasma is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields.-Operation:...
- Solenoid coil
- Planar coil
- Helical resonatorHelical resonatorA helical resonator is a passive electrical component that can be used as a filter. Physically, a helical resonator is a wire helix surrounded by a square or cylindrical conductive shield. Like cavity resonators, helical resonators can achieve Q factors in the 1000s...
- Capacitively coupled plasmaCapacitively coupled plasmaA capacitively coupled plasma is one of the most common types of industrial plasma sources. It essentially consists of two metal electrodes separated by a small distance, placed in a reactor. The gas pressure in the reactor can be lower than atmosphere or it can be atmospheric.A typical CCP system...
- Single-frequency capacitively coupled plasma
- Dual-frequency capacitively coupled plasma
- Wave-heated plasma
- Electron cyclotron resonanceElectron cyclotron resonanceElectron cyclotron resonance is a phenomenon observed both in plasma physics and condensed matter physics. An electron in a static and uniform magnetic field will move in a circle due to the Lorentz force...
- Helicon discharge
- Surface-wave-sustained modeSurface-wave-sustained modePlasmas that are excited by propagation of electromagnetic surface waves are called surface-wave-sustained. Surface wave plasma sources can be divided into two groups depending upon whether the plasma generates part of its own waveguide by ionisation or not. The former is called a self-guided plasma...
- Resonator modeResonator modeIn the resonator mode, the plasma density does not exceed thecritical density.A standing electromagnetic wave, which is confined by aresonator cavity, penetrates the plasma and sustains it in the regions of highest field...
- Electron cyclotron resonance
- Electrodeless plasma excitation
- Inductively coupled plasma
- Pressure range classification
- Low pressure dischargeLow pressure dischargeLow-pressure discharges are discharges made under gas pressures from a few millitorr to a little less than atmospheric. They have the benefit of less power requirement of sustenance of the discharge as volume-recombination rates are lower....
- Atmospheric pressure dischargeAtmospheric pressure dischargeAn atmospheric pressure discharge is an electrical discharge in air at atmospheric pressure.An electrical discharge is a plasma, which is an ionized gas. Plasmas are sustained if there is a continuous source of energy to maintain the required degree of ionization and overcome the recombination...
- Low pressure discharge
- MAGPIEMAGPIEMAGPIE stands for Mega Ampere Generator for Plasma Implosion Experiments and is a pulsed power generator based at Imperial College London, United Kingdom. The generator was originally designed to produce a current pulse with a maximum of 1.8 million Amperes in 240 nanoseconds...
,aka, Mega Ampere Generator for Plasma Implosion Experiments
Plasma sources have numerous technical applications, for instance in light generation and plasma processing
Plasma processing
Plasma processing is a plasma-based material processing technology that aims at modifying the chemical and physical properties of a surface.Plasma processing techniques include:*Plasma activation*Plasma etching*Plasma modification*Plasma functionalization...
of materials.
They can be used for extracting an ion beam, in which case they are also called ion sources. An innovative and emerging field is the application of non-thermal atmospheric pressure plasma sources in plasma medicine
Plasma medicine
Plasma medicine is an innovative and emerging field combining plasma physics, life sciences and clinical medicine to use physical plasma for therapeutic applications. Initial experiments confirm that plasma can be effective in in vivo antiseptics without affecting surrounding tissue and, moreover,...
.
External links
- Plasma Source as Atom Source, Ion Source and Atom/Ion Hybrid Source