Betatron

Betatron

A betatron is a cyclotron developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons. The betatron is essentially a transformer with a torus-shaped vacuum tube as its secondary coil. An alternating current in the primary coils accelerates electrons in the vacuum around a circular path.

How it works

In a betatron, the magnetic field spins the injected electrons and accelerates them at the center where there is a ring-shaped vacuum tube changing the magnetic field and producing an electric field in the vacuum ring.

The stable orbit for the electrons satisfies heta_0=2pi r_0^2 H_0 where heta_0 is the flux with the orbit at r_0 is the radius and H_0 is the magnetic field at r_0. In other words, the magnetic field at the orbit must be half the average magnetic field over its circular cross section.

Etymology

The name "betatron" (a reference to the beta particle, a fast electron) was chosen during a departmental contest. Other proposals were rheotron, inductron, and even "Ausserordentlichhochgeschwindigkeitelektronenentwickelndenschwerarbeitsbeigollitron", supposedly German for "extraordinarily high-speed electron producing hard work by golly-tron.".

Applications

Betatrons were historically employed in particle physics experiments to provide high energy beams of electrons—up to about 300 MeV. If the electron beam is directed at a metal plate, the betatron can be used as a source of energetic x-rays or gamma rays; these x-rays may be used in industrial and medical applications (historically in [http://en.wikibooks.org/wiki/Radiation_Oncology/Physics#Megavoltage_Units_.28.3E1_MeV.29 radiation oncology] ).

The Radiation Center, the first private medical center to treat cancer patients with a betatron was opened by Dr. O. Arthur Stiennon, in a suburb of Madison, Wisconsin in the late 1950s [ [http://digicoll.library.wisc.edu/cgi-bin/UW/UW-idx?type=turn&entity=UW002406780037&isize=text "Wisconsin alumnus", Volume 58, Number 15 (July 25, 1957)] ] .

Limitations

Because the mass of the electron increases at relativistic speeds, the cyclotron becomes less efficient at higher energies, placing an upper limit on its beam energy. These relativistic effects are accommodated in the next generation of accelerators, the Synchrotrons.

In Popular Culture

* In the Frank Black song "Los Angeles", the betatron is referenced in the line "I met a man; he was a good man, sailing and shoring; he got a betatron, man."

References

External links

* [http://link.aps.org/abstract/PR/v60/p53 Kerst, D. W. "Electronic Orbits in the Induction Accelerator." Phys. Rev. 60, 53–58 (1941).]
* [http://link.aps.org/abstract/PR/v60/p47 Kerst, D. W. "The Acceleration of Electrons by Magnetic Induction." Phys. Rev. 60, 47-53 (1941).]
* [http://link.aps.org/abstract/PR/v58/p841 Kerst, D. W. "The Acceleration of Electrons by Magnetic Induction." Phys. Rev. 58, 841 (1940).]
* [http://www.physics.uiuc.edu/history/Betatron.asp The Betatron at UIUC ]


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  • betatron — BETATRÓN, betatroane, s.n. (fiz.) Aparat de accelerare a electronilor. – Din fr. bêtatron. Trimis de paula, 02.06.2002. Sursa: DEX 98  betatrón s. n. (sil. tron), pl. betatroáne Trimis de siveco, 10.08.2004. Sursa: Dicţionar ortografic … …   Dicționar Român

  • Betatrón — Saltar a navegación, búsqueda Un betatrón es un acelerador de partículas desarrollado por Donald Kerst en la Universidad de Illinois en 1940 para acelerar electrones. El betatrón es esencialmente un transformador con un gran tubo vacío como su… …   Wikipedia Español

  • bêtatron — [ bɛtatrɔ̃ ] n. m. • v. 1936; de 1. bêta et (cyclo)tron ♦ Sc. Cyclotron à électrons. ⇒ accélérateur (II, 4o). ● bêtatron nom masculin (de rayons bêta et électron) Synchrotron dans lequel l accélération des électrons produit des rayons X utilisés… …   Encyclopédie Universelle

  • betatrón — betatron betatron m. instrum. Acelerador de electrones mediante un campo magnético circular que permite obtener haces de electrones de alta energía u otro tipo de radiaciones (rayos X o gamma). Se utiliza en medicina para combatir procesos… …   Diccionario médico

  • betatron — e ta*tron n. a type of particle accelerator which accelerates a continuous beam of electrons to high speeds by means of the electric field produced by changing magnetic flux. Syn: induction accelerator. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • bétatron — s. m. [Física] Aparelho acelerador de partículas que serve para produzir elétrons animados de uma grande energia. • [Brasil] Plural: betátrones ou bétatrons.   ♦ Grafia em Portugal: betatrão …   Dicionário da Língua Portuguesa

  • betatron — bȅtatrōn m DEFINICIJA fiz. kružni akcelerator za proizvodnju visoko energetskih elektrona (do 340 MeV), uključujući proizvodnju visoko energetskih X zraka, elektroni se ubrzavaju pomoću magnetske indukcije ETIMOLOGIJA v. beta + v. ciklotron …   Hrvatski jezični portal

  • betatrón — m. Fís. Máquina aceleradora de electrones, con aplicaciones en radioterapia …   Diccionario de la lengua española

  • betatron — ☆ betatron [bāt′ə trän΄ ] n. [< BETA RAY + (ELEC)TRON] an electron accelerator which uses a rapidly changing magnetic field to accelerate the particles and maintain them in a focused circular path …   English World dictionary

  • Betatron — Historisches Betatron (6MeV, Konstruktionsbeginn 1942) Das Betatron (auch anschaulich „Elektronenschleuder“ genannt) ist ein für leichte geladene Teilchen (wie Elektronen oder Positronen) geeigneter Kreisbeschleuniger. Das Betatron ähnelt dem… …   Deutsch Wikipedia

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