Editing Fusor (section)

==History==
{{See also|Inertial electrostatic confinement#History}}
[[Image:US3386883 - fusor.png|thumb|upright=1.0|{{US patent|3,386,883}} – fusor&nbsp;– Image from Farnsworth's patent, on 4 June 1968. This device has an inner cage to make the field, and four ion guns on the outside.]]
The fusor was originally conceived by [[Philo T. Farnsworth]], better known for his pioneering work in television. In the early 1930s, he investigated a number of [[vacuum tube]] designs for use in television, and found one that led to an interesting effect. In this design, which he called the "multipactor", [[electron]]s moving from one [[electrode]] to another were stopped in mid-flight with the proper application of a [[high-frequency]] [[magnetic field]]. The charge would then accumulate in the center of the tube, leading to high amplification. Unfortunately it also led to high erosion on the [[electrode]]s when the electrons eventually hit them, and today the [[multipactor effect]] is generally considered a problem to be avoided.

What particularly interested Farnsworth about the device was its ability to focus electrons at a particular point. One of the biggest problems in [[fusion power|fusion research]] is to keep the hot fuel from hitting the walls of the container. If this is allowed to happen, the fuel cannot be kept hot enough for the [[Nuclear fusion|fusion reaction]] to occur. Farnsworth reasoned that he could build an [[electrostatic]] [[plasma equilibria and stability|plasma confinement]] system in which the "wall" fields of the reactor were electrons or ions being held in place by the ''multipactor''. Fuel could then be injected through the wall, and once inside it would be unable to escape. He called this concept a virtual electrode, and the system as a whole the ''fusor''.

===Design===
Farnsworth's original fusor designs were based on cylindrical arrangements of electrodes, like the original multipactors. Fuel was ionized and then fired from small accelerators through holes in the outer (physical) electrodes. Once through the hole they were accelerated towards the inner reaction area at high velocity. Electrostatic pressure from the positively charged electrodes would keep the fuel as a whole off the walls of the chamber, and impacts from new ions would keep the hottest plasma in the center. He referred to this as [[inertial electrostatic confinement]], a term that continues to be used to this day. The voltage between the electrodes needs to be at least 25 kV for fusion to occur.

===Work at Farnsworth Television labs===
All of this work had taken place at the [[Philo Farnsworth|Farnsworth Television labs]], which had been purchased in 1949 by [[ITT Corporation]], as part of its plan to become the next [[RCA]]. However, a fusion research project was not regarded as immediately profitable. In 1965, the board of directors started asking  [[Harold Geneen]] to sell off the Farnsworth division, but he had his 1966 budget approved with funding until the middle of 1967. Further funding was refused, and that ended ITT's experiments with fusion.{{Citation needed|date=October 2009}}

Things changed dramatically with the arrival of [[Robert L. Hirsch|Robert Hirsch]], and the introduction of the modified Hirsch–Meeks fusor patent.<ref>{{Cite journal |last=Jaff |first=Geby |date=2023-09-05 |title=High-frequency light conversion to solar power in Farnsworth Fusor: Challenges and Procedures |url=https://www.techrxiv.org/articles/preprint/High-frequency_light_conversion_to_solar_power_in_Farnsworth_Fusor_Challenges_and_Procedures/24082515/1/files/42258648.pdf |access-date=2023-10-04 |doi=10.36227/techrxiv.24082515 }}</ref> New fusors based on Hirsch's design were first constructed between 1964 and 1967.<ref name= "Hirsch" />  Hirsch published his design in a paper in 1967.  His design included [[ion beam]]s to shoot ions into the vacuum chamber.<ref name= "Hirsch" />

The team then turned to the [[United States Atomic Energy Commission|AEC]], then in charge of fusion research funding, and provided them with a demonstration device mounted on a serving cart that produced more fusion than any existing "classical" device. The observers were startled, but the timing was bad; Hirsch himself had recently revealed the great progress being made by the Soviets using the [[tokamak]]. In response to this surprising development, the AEC decided to concentrate funding on large tokamak projects, and reduce backing for alternative concepts.{{Citation needed|date=October 2009}}

===Recent developments===
[[George H. Miley]] at the [[University of Illinois at Urbana–Champaign|University of Illinois]] reexamined the fusor and re-introduced it into the field. A low but steady interest in the fusor has persisted since. An important development was the successful commercial introduction of a fusor-based [[neutron generator]]. From 2006 until his death in 2007, [[Robert W. Bussard]] gave talks on a reactor similar in design to the fusor, now called the [[polywell]], that he stated would be capable of useful power generation.<ref>{{cite conference |url=http://www.askmar.com/ConferenceNotes/2006-9%20IAC%20Paper.pdf |author=Robert W. Bussard |title=The Advent of Clean Nuclear Fusion: Super-performance Space Power and Propulsion |archive-url=https://web.archive.org/web/20110929075949/http://www.askmar.com/ConferenceNotes/2006-9%20IAC%20Paper.pdf |archive-date=2011-09-29 |conference=57th International Astronautical Congress, October 2–6, 2006}}</ref> Most recently, the fusor has gained popularity among amateurs, who choose them as home projects due to their relatively low space, money, and power requirements. An online community of "fusioneers", The Open Source Fusor Research Consortium, or Fusor.net, is dedicated to reporting developments in the world of fusors and aiding other amateurs in their projects. The site includes forums, articles and papers done on the fusor, including Farnsworth's original patent, as well as Hirsch's patent of his version of the invention.<ref>{{cite web|url=http://fusor.net|title=Home|website=Fusor.net}}</ref>