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[[File:KEK Cockcroft-Walton Accelerator (1).jpg|thumb|upright=1.5|750 keV [[Cockcroft-Walton accelerator]] initial stage of the [[KEK]] accelerator in Tsukuba, Japan. The high voltage generator is right, the ion source and beam tube is at left]]
An '''electrostatic particle accelerator''' is a [[particle accelerator]] in which [[charged particle]]s are accelerated to a high energy by a static [[high voltage]] potential. This contrasts with the other major category of particle accelerator, [[Particle accelerator#Electrodynamic (electromagnetic) particle accelerators|oscillating field particle accelerators]], in which the particles are accelerated by oscillating electric fields.
Owing to their simpler design, electrostatic types were the first particle accelerators. The two most common types are the [[Van de Graaf generator]] invented by [[Robert Van de Graaff]] in 1929, and the [[Cockcroft-Walton accelerator]] invented by [[John Cockcroft]] and [[Ernest
The advantages of electrostatic accelerators over oscillating field machines include lower cost, the ability to produce continuous beams, and higher beam currents that make them useful to industry. As such, they are by far the most widely used particle accelerators, with industrial applications such as plastic [[shrink wrap]] production, high power [[X-ray machine]]s, [[radiation therapy]] in medicine, [[radioisotope]] production, [[ion implanter]]s in semiconductor production, and sterilization. Many universities worldwide have electrostatic accelerators for research purposes. High energy oscillating field accelerators usually incorporate an electrostatic machine as their first stage, to accelerate particles to a high enough velocity to inject into the main accelerator.
Electrostatic accelerators are a subset of [[linear accelerator]]s (linacs). While all linacs accelerate particles in a straight line, electrostatic accelerators use a fixed accelerating field from a single high voltage source, while radiofrequency linacs use oscillating electric fields across a series of accelerating gaps.
== Applications ==
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Although these machines primarily accelerate [[atomic nuclei]], there are a number of compact machines used to accelerate [[electrons]] for industrial purposes including sterilization of medical instruments, x-ray production, and silicon wafer production.<ref name="hinterberger">{{cite web |last1=Hinterberger |first1=F |title=Electrostatic Accelerators |url=https://cds.cern.ch/record/1005042/files/p95.pdf |website=[[CERN]] |access-date=10 May 2022}}</ref>
A special application of electrostatic particle accelerator are dust accelerators in which nanometer to micrometer sized electrically charged dust particles are accelerated to speeds up to 100
== Single-ended machines ==
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It is not possible to make every element into an anion easily, so it is very rare for tandems to accelerate any [[noble gas]]es heavier than [[helium]], although KrF<sup>−</sup> and XeF<sup>−</sup> have been successfully produced and accelerated with a tandem.<ref>{{cite journal | journal=Nuclear Instruments and Methods in Physics Research Section B | volume=5 | issue=2 | pages=217 | year=1984 |author1=Minehara, Eisuke |author2=Abe, Shinichi |author3=Yoshida, Tadashi |author4=Sato, Yutaka |author5=Kanda, Mamoru |author6=Kobayashi, Chiaki |author7=Hanashima, Susumu | title= On the production of the KrF- and XeF- Ion beams for the tandem electrostatic accelerators | doi = 10.1016/0168-583X(84)90513-5 |bibcode = 1984NIMPB...5..217M }}</ref> It is not uncommon to make compounds in order to get anions, however, and [[titanium hydride|TiH<sub>2</sub>]] might be extracted as TiH<sup>−</sup> and used to produce a proton beam, because these simple, and often weakly bound chemicals, will be broken apart at the terminal stripper foil. Anion ion beam production was a major subject of study for tandem accelerator application, and one can find recipes and yields for most elements in the Negative Ion Cookbook.<ref>Middleton, R: ''A Negative Ion Cookbook'', University of Pennsylvania, unpublished, 1989 [http://www.pelletron.com/cookbook.pdf Online pdf]</ref> Tandems can also be operated in terminal mode, where they function like a single-ended electrostatic accelerator, which is a more common and practical way to make beams of noble gases.
The name 'tandem' originates from this dual-use of the same high voltage, although tandems may also be named in the same style of conventional electrostatic accelerators based on the method of charging the terminal.
The MP [[
<!-- want a long list of tandems before we promote a single laboratory An example of a tandem accelerator is [[ANTARES (accelerator)|ANTARES]] (Australian National Tandem Accelerator for Applied Research).-->
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In a single-ended electrostatic accelerator the charged particle is accelerated through a single potential difference between two electrodes, so the output particle energy <math>E</math> is equal to the charge on the particle <math>q</math> multiplied by the accelerating voltage <math>V</math>
:<math>E = qV</math>
In a tandem accelerator the particle is accelerated twice by the same voltage, so the output energy is <math>2qV</math>. If the charge <math>q</math> is in conventional units of [[coulomb]]s and the potential <math>V</math> is in [[volt]]s the particle energy will be given in [[joule]]s. However, because the charge on elementary particles is so small (the charge on the electron is 1.6x10<sup>−19</sup> coulombs), the energy in joules is a very small number.
Since all elementary particles have charges which are multiples of the [[elementary charge]] on the electron, <math>e = 1.6(10^{-19})</math> coulombs, particle physicists use a different unit to express particle energies, the ''[[electronvolt|electron volt]]'' (eV) which makes it easier to calculate. The electronvolt is equal to the energy a particle with a charge of 1''e'' gains passing through a potential difference of one volt. In the above equation, if <math>q</math> is measured in elementary charges ''e'' and <math>V</math> is in volts, the particle energy <math>E</math> is given in eV. For example, if an [[alpha particle]] which has a charge of 2''e'' is accelerated through a voltage difference of one million volts (1 MV), it will have an energy of two million electron volts, abbreviated 2 MeV. The accelerating voltage on electrostatic machines is in the range 0.1 to 25 MV and the charge on particles is a few elementary charges, so the particle energy is in the low MeV range. More powerful accelerators can produce energies in the giga electron volt (GeV) range.
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