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The Duoplasmatron is an
The duoplasmatron was first developed in 1956 by
Duoplasmatron-Animation
Ion source Plasma physics
The Duoplasmatron is an ion source
An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
Electron ionization
Electron ...
in which a cathode
A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in wh ...
filament emits electrons into a vacuum chamber
A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump. This results in a low-pressure environment within the chamber, commonly referred to as a vacuum. A vacuum environment allows researchers to con ...
. A gas such as argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...
is introduced in very small quantities into the chamber, where it becomes charged or ionized
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
through interactions with the free electrons from the cathode, forming a plasma. The plasma is then accelerated through a series of at least two highly charged grids, and becomes an ion beam, moving at a fairly high speed from the aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
An ...
of the device.
History
The duoplasmatron was first developed in 1956 by Manfred von Ardenne
Manfred von Ardenne (20 January 1907 – 26 May 1997) was a German researcher and applied physicist and inventor. He took out approximately 600 patents in fields including electron microscopy, medical technology, nuclear technology, plasma physics ...
to provide a powerful source of gas ions. Other contributors such as Demirkanov, Frohlich and Kistemaker continued development between 1959 and 1965. Throughout the 1960s, many continued to investigate, discovering negative ion extraction and multiply charged ion production. There are two types of plasmatrons, the uniplasmatron and the duoplasmatron. The prefix refers to the constriction of discharge.
Operation
The standard duoplasmatron consists of three main components that are responsible for its operation. These include the hot cathode, the intermediate electrode, and the anode. The intermediate electrode's main job is to produce discharge. This discharge is confined to a small portion near the anode and a short magnetic field between the intermediate electrode and the anode. The duoplasmatron has two different types of plasma: the cathode plasma which is close to the cathode and the anode plasma which is close to the anode. The cathode works by injecting a beam of electrons with a suitable amount of energy. This injection ionizes the gas molecules, typically Argon gas, in the anode and increases the potential near the anode. The ions that are repulsed, however, combine with the ions that contain enough energy to pass the deceleration region and this combination of ions fills the expansion cup with directed ions and electrons. The best operational mode for the duoplasmatron is considered to be when the cathode is adjusted to an emission where the intermediate electrode and the cathode potential are approximately equal.Applications
The duoplasmatron is a type ofion source
An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines.
Electron ionization
Electron ...
. Ion sources are necessary to form ions for mass spectrometers and other types of instruments. In comparison to Penning ionization sources, the duoplasmatron features advantages such as less expenditure, easier handling, and a longer lifetime. However, the duoplasmatron does have lower beam intensity, which can be a large disadvantage.
References
Further reading
* Brown, I.G., "The Physics and Technology of Ion Sources", Wiley-VCH (2004), p. 110 * Dass, Chhabil (24 August 2006). Fundamentals of Contemporary Mass Spectrometry. John Wiley & Sons, Inc. {{ISBN, 9780471682295.External links
Duoplasmatron-Animation
Ion source Plasma physics