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[[Image:Westinghouse Van de Graaff atom smasher - cutaway.png|thumb|upright=1.5|The [[Westinghouse Atom Smasher]], an early [[Van de Graaff accelerator]] built 1937 at the Westinghouse Research Center in Forest Hills, Pennsylvania. The cutaway shows the fabric belts that carry charge up to the mushroom-shaped high voltage electrode. To improve insulation the machine was enclosed in a 65 ft. pressure vessel which was pressurized to 120 psi during operation. The high pressure air increased the voltage on the machine from 1 MV to 5 MV.]]
An '''electrostatic particle accelerator''' is one of the two main types of [[particle accelerator]]s, in which [[charged particle]]s are accelerated to a high energy by passing through a static [[high voltage]] potential. This contrasts with the other category of particle accelerator, [[Particle accelerator#Oscillating field particle accelerators|oscillating field particle accelerators]], in which the particles are accelerated by passing successively through multiple voltage drops created by oscillating voltages on electrodes. Owing to their simpler design, historically electrostatic types were the first particle accelerators. The two main 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 Walton]] in 1932. The maximum particle energy produced by electrostatic accelerators is limited by the accelerating voltage on the machine, which is limited by [[electrical breakdown|insulation breakdown]]. Oscillating accelerators do not have this limitation, so they can achieve higher particle energies than electrostatic machines.
However these machines have advantages such as lower cost, and the ability to produce continuous beams and higher beam currents, so they are by far the most widely used particle accelerators. They are used in industrial irradiating 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. More powerful accelerators usually incorporate an electrostatic machine as their first stage, to accelerate particles to a high enough velocity to inject into the main accelerator.
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