A betatron is a particle accelerator developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons. The betatron is essentially a transformer with a doughnut shaped vacuum tube as its secondary coil. An alternating current in the primary coils accelerates electrons in the vacuum around a circular path. 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, German for "extraordinarily high-speed electron generator, hard work by golly-tron.". A 1960s single stage 2MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric and/or magnetic fields to propel electrically charged particles to high speeds. ... The University of Illinois is the set of three public universities in Illinois. ... Three-phase pole-mounted step-down transformer. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ...

The stable orbit for the electrons satisfies where θ₀ is the flux with the orbit at r₀ is the radius and H₀ is the magnetic field at r₀. In other words, the magnetic field at the orbit must be half the average magnetic field over its circular cross section.

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. Particles erupt from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... This article is about electromagnetic radiation. ...

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. Mass is a property of a physical object that quantifies the amount of matter it contains. ... The term mass in special relativity can be used in different ways, occasionally leading to confusion. ... For a non-technical introduction to the topic, please see Introduction to Special relativity. ... A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field (to turn the particles so they circulate) and the electric field (to accelerate the particles) are carefully synchronized with the travelling particle beam. ...

External links

• The First Betatron
• Kerst, D. W. "Electronic Orbits in the Induction Accelerator." Phys. Rev. 60, 53–58 (1941).
• Kerst, D. W. "The Acceleration of Electrons by Magnetic Induction." Phys. Rev. 60, 47-53 (1941).
• Kerst, D. W. "The Acceleration of Electrons by Magnetic Induction." Phys. Rev. 58, 841 (1940).