Betatron
A betatron is a type of cyclic particle accelerator for electrons. It consists of a torus-shaped
vacuum chamber with an electron source. Circling the torus is an iron transformer core with a
wire winding around it. The device functions similarly to a transformer, with the electrons in
the torus-shaped vacuum chamber as its secondary coil. An alternating current in the primary
coils accelerates electrons in the vacuum around a circular path. The betatron was the first
machine capable of producing electron beams at energies higher than could be achieved with a
simple electron gun, and the first circular accelerator in which particles orbited at a constant
radius.[1]
One of the first betatrons built by
Donald Kerst (visible right) at
University of Illinois, 1940. Its 4-ton
magnet could accelerate electrons to
24 MeV.
A German 6 MeV betatron (1942)
, A 35 MeV betatron used for photonuclear
physics at the University of Melbourne.
The concept of the betatron had been proposed as early as 1922 by Joseph Slepian.[2] Through the
1920s and 30s a number of theoretical problems related to the device were considered by
scientists including Rolf Wideroe,[3][4] Ernest Walton, and Max Steenbeck.[5] The first working
betatron was constructed by Donald Kerst at the University of Illinois Urbana-Champaign in
1940.[6][7][8]
History
After the discovery in the 1800s of Faraday's law of induction, which showed that an
electromotive force could be generated by a changing magnetic field, several scientists
speculated that this effect could be used to accelerate charged particles to high energies.[2]
Joseph Slepian proposed a device in 1922 that would use permanent magnets to steer the beam
while it was accelerated by a changing magnetic field.[9] However, he did not pursue the idea past
the theoretical stage.
In the late 1920s, Gregory Breit and Merle Tuve at the Bureau of Terrestrial Magnetism
constructed a working device that used varying magnetic fields to accelerate electrons. Their
device placed two solenoidal magnets next to one another and fired electrons from a gun at the
outer edge of the magnetic field. As the field was increased, the electrons accelerated in to
strike a target at the center of the field, producing X-rays. This device took a step towards the
betatron concept by shaping the magnetic field to keep the particles focused in the plane of
acceleration.[2]
A betatron is a type of cyclic particle accelerator for electrons. It consists of a torus-shaped
vacuum chamber with an electron source. Circling the torus is an iron transformer core with a
wire winding around it. The device functions similarly to a transformer, with the electrons in
the torus-shaped vacuum chamber as its secondary coil. An alternating current in the primary
coils accelerates electrons in the vacuum around a circular path. The betatron was the first
machine capable of producing electron beams at energies higher than could be achieved with a
simple electron gun, and the first circular accelerator in which particles orbited at a constant
radius.[1]
One of the first betatrons built by
Donald Kerst (visible right) at
University of Illinois, 1940. Its 4-ton
magnet could accelerate electrons to
24 MeV.
A German 6 MeV betatron (1942)
, A 35 MeV betatron used for photonuclear
physics at the University of Melbourne.
The concept of the betatron had been proposed as early as 1922 by Joseph Slepian.[2] Through the
1920s and 30s a number of theoretical problems related to the device were considered by
scientists including Rolf Wideroe,[3][4] Ernest Walton, and Max Steenbeck.[5] The first working
betatron was constructed by Donald Kerst at the University of Illinois Urbana-Champaign in
1940.[6][7][8]
History
After the discovery in the 1800s of Faraday's law of induction, which showed that an
electromotive force could be generated by a changing magnetic field, several scientists
speculated that this effect could be used to accelerate charged particles to high energies.[2]
Joseph Slepian proposed a device in 1922 that would use permanent magnets to steer the beam
while it was accelerated by a changing magnetic field.[9] However, he did not pursue the idea past
the theoretical stage.
In the late 1920s, Gregory Breit and Merle Tuve at the Bureau of Terrestrial Magnetism
constructed a working device that used varying magnetic fields to accelerate electrons. Their
device placed two solenoidal magnets next to one another and fired electrons from a gun at the
outer edge of the magnetic field. As the field was increased, the electrons accelerated in to
strike a target at the center of the field, producing X-rays. This device took a step towards the
betatron concept by shaping the magnetic field to keep the particles focused in the plane of
acceleration.[2]
