Pelletron
Encyclopedia
A pelletron is a type of electrostatic
particle accelerator
similar to a Van de Graaff generator
. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts (kV) and beam energies up to 1 megaelectronvolt
(MeV) of kinetic energy, to the largest system, which has reached a DC voltage of over 25 megavolts and produced ion beam
s with energies over 900 MeV. Generating electric charge is done by a mechanical transportation system made of a chain of pellets (short conductive tubes connected by links made of insulating material), that is used to build-up high voltages on the Pelletron terminal. The system is enclosed by a pressure vessel filled with insulating gas, such as SF6 (sulfur hexafluoride
), and an evacuated beamline
. The potential difference between the terminal and ground
is used to accelerate several kinds of particles, such as positron
s, electron
s and negative and positive ion
s.
Compared to the Van de Graaff generator, the pellet chain can operate at a higher velocity than a rubber
belt, and both the voltage and currents that can be attained are far higher. The chain is charged more uniformly than the belt of a Van de Graaff, so the stability of the terminal voltage and the particle energy is also higher.
Pelletron accelerators are used as analytical tools in many fields, including materials analysis, nuclear physics
, semiconductor
development and production, pharmaceutical research, and as ultra-sensitive mass spectrometers for carbon dating and the measurement of other rare isotope
s.
Electrostatic generator
An electrostatic generator, or electrostatic machine, is a mechanical device that produces static electricity, or electricity at high voltage and low continuous current...
particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
similar to a Van de Graaff generator
Van de Graaff generator
A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high voltages on a hollow metal globe on the top of the stand. It was invented in 1929 by American physicist Robert J. Van de Graaff. The potential differences achieved in modern Van de Graaff...
. Pelletrons have been built in many sizes, from small units producing voltages up to 500 kilovolts (kV) and beam energies up to 1 megaelectronvolt
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
(MeV) of kinetic energy, to the largest system, which has reached a DC voltage of over 25 megavolts and produced ion beam
Ion beam
An ion beam is a type of charged particle beam consisting of ions. Ion beams have many uses in electronics manufacturing and other industries. A variety of ion beam sources exist, some derived from the mercury vapor thrusters developed by NASA in the 1960s.-Ion beam etching or sputtering:One type...
s with energies over 900 MeV. Generating electric charge is done by a mechanical transportation system made of a chain of pellets (short conductive tubes connected by links made of insulating material), that is used to build-up high voltages on the Pelletron terminal. The system is enclosed by a pressure vessel filled with insulating gas, such as SF6 (sulfur hexafluoride
Sulfur hexafluoride
Sulfur hexafluoride is an inorganic, colorless, odorless, and non-flammable greenhouse gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in...
), and an evacuated beamline
Beamline
In particle physics, a beamline is the line in a linear accelerator along which a beam of particles travels. It may also refer to the line of travel within a bending section such as a storage ring or cyclotron, or an external beam extracted from a cyclic accelerator.In materials science, physics,...
. The potential difference between the terminal and ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
is used to accelerate several kinds of particles, such as positron
Positron
The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...
s, 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 and negative and positive ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s.
Compared to the Van de Graaff generator, the pellet chain can operate at a higher velocity than a rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
belt, and both the voltage and currents that can be attained are far higher. The chain is charged more uniformly than the belt of a Van de Graaff, so the stability of the terminal voltage and the particle energy is also higher.
Pelletron accelerators are used as analytical tools in many fields, including materials analysis, nuclear physics
Nuclear physics
Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei. The most commonly known applications of nuclear physics are nuclear power generation and nuclear weapons technology, but the research has provided application in many fields, including those...
, semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
development and production, pharmaceutical research, and as ultra-sensitive mass spectrometers for carbon dating and the measurement of other rare isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s.
External links
- Pelletron operation animation at pelletron.com
- The Pelletron — Max Planck Institute for Metals ResearchMax Planck Institute for Metals ResearchThe Max Planck Institute for Metals Research is a research institute of the Max Planck Society located in Stuttgart. The institute was founded 1921 as Kaiser Wilhelm Institute for Metal Research in Berlin and closed 1932. 1934 it was reopened in Stuttgart and incorporated into the Max Planck...
, Stuttgart, Germany (archived link) - Pelletron.com — National Electrostatics Corporation