Circular accelerators

In particle accelerators, the speed of charged particles is artificially increased with the help of strong magnetic and electric fields. Circular accelerators, as the name suggests, have a path twisted into a circle.

History
Ernest Rutherford (early 20th century) was the first to discover the nucleus of an atom (Nobel Prize for Chemistry). After the First World War, he achieved the transmutation of the elements. He was looking for a way to break the nucleus of an atom, and this is where the idea of ​​accelerating particles first appears.

Rolf Widerøe (first half of the 20th century) built a fully functional linear accelerator after initial failures.

Ernest Orlando Lawrence (first half of the 20th century) built the first circular accelerator, for which he won the Nobel Prize. Accelerators kept getting bigger and better.

CERN (second half of the 20th century) as an international scientific laboratory for nuclear research began as an attempt to improve the state of science in post-war Europe.

Division of Accelerators
Circular Accelerators'

The particle is accelerated by the electric field. Their orbit is arranged cyclically, allowing for a dipole magnetic field that keeps them in a circular orbit. The advantage of cyclic accelerators is the ability to slowly and repeatedly increase the speed of particles. The disadvantage is the more complicated tuning of the electron beam and the loss of energy during the flight due to bremsstrahlung.

Linear Accelerators

They accelerate the particles during their movement along a linear straight path. Their advantage is that there is no need for a dipole magnetic field and simpler focusing. The disadvantage is that the particle can pass through the accelerator only once. So the runway must be very long.

Betatron
The Betatron is a cyclic particle accelerator, basically a transformer with a TORUS-SHAPED tube as a secondary coil. The alternating current in the primary coils accelerates the electron in a vacuum along a circular path. The betatron was the first important device for producing high-energy electrons.

History
The first to come up with the idea was the Norwegian physicist Rolf Wideroe, whose invention of the induction accelerator failed due to a lack of transverse focusing. In the 40s of the 20th century, there were efforts to construct it on the territory of Germany, thanks to Max Steenbeck. The betatron itself was perfected to accelerate electrons in 1940 by Donald Kerst at the University of Illinois.

Usage
Betatrons were previously used in particle physics experiments to provide high-energy electron beams, up to 300 MeV. When directing an electron beam to a metal plate, we can use the betatron as a source of X-ray or gamma irradiation. This X-ray radiation is used in industry and healthcare (previously, for example, in radiation oncology).

Scaled-down versions of betatrons have also been used to provide electrons converted to hard X-rays, in the development of experimental nuclear weapons.

The first private medical radiation center to treat cancer patients with betatrons was opened by Dr. O. Arthur Stiennon in Madison, Wisconsin, in the late 1950s.

Restrictions
The maximum energy a betatron can deliver is limited by the strength of the magnetic field due to iron saturation and the practical side of the magnetic core. The next generation of accelerators, synchrotrons, overcame these shortcomings.

Cyclotron
The cyclotron is a basic type of circular accelerator designed by E. Lawrence as the first ever circular accelerator. Its magnetic field is constant and a high-frequency electric field (duants) occurs between the electrodes.

Construction of a cyclotron
The cyclotron consists of two semi-circular metal half-cylinders (duants: D1, D2 see figure) located in an air-free space that serves as an acceleration gap. The space is bounded by two poles of an electromagnet, which are connected to a high-frequency generator of alternating voltage. So that the vacuum space is not too large, accelerators with a fixed circular path are used.

Principle
The moving particles inside the two duants are placed between the poles of a huge magnet. The duants are connected to a high-frequency voltage generator. The strong magnetic field bends the path of the particle that is emitted from the source and in duant describes a normally semicircular path. Both duants alternately attract the particle whenever it occurs with the oppositely charged duant, causing the particle to accelerate. Accelerated particles are deflected by the negatively charged plate from the spiral path into the exit window. In more detail, for example, here see cyclotron.

Special types of cyclotrons
TheSynchrotronn is used to accelerate particles to very high energy (on the order of 100GeV to several TeV). Due to its too large size and financial demands, the synchrotron has no practical use. It is used only in multinational research laboratories of nuclear physics.

A microtron is a special type of cyclotron used in accelerating electrons. A vacuum chamber with a high vacuum is placed between the pole extensions of the strong electromagnet. Instead of ducts, an electric acceleration system, a cavity resonator, is used here. Microtrons are used to accelerate electrons to speeds of the order of MeV. Their advantage is the achievement of high intensities of the flow of accelerated electrons in the beam.

The Isochronic Cyclotron' has a magnet divided into sectors where there is an alternating strong and weak magnetic field. This makes it possible to create a much larger stream of beams than a synchrocyclotron.

Usage
Cyclotrons are used to accelerate heavy charged particles (protons, deuterons, alpha particles, and ions) along a spiral path. Radionuclides are produced using a cyclotron, which is then used in medicine and other fields.

Resources

 * HUŠÁK, Václav. ZDROJE IONIZUJÍCÍHO ZÁŘENÍ [online]. [cit. 2015-01-05]. < http://eamos.pf.jcu.cz/amos/kra/externi/kra_7169/ch01.htm >.
 * NAVRÁTIL, Leoš. RADIOBIOLOGIE [online]. [cit. 2015-01-05]. < http://fbmi.sirdik.org/4-kapitola/43/431.html#cyklotron >.
 * ULLMANN, Vojtěch. Jaderná a radiační fyzika. 1.5. Elementární částice [online]. [cit. 2015-01-05]. < http://astronuklfyzika.cz/JadRadFyzika5.htm#Cyklotron >.
 * NAVRÁTIL, Vladislav. Urychlovače elementárních částic [online]. [cit. 2015-01-05]. < https://is.muni.cz/th/cbysw/bc.txt?so=nx >.
 * ULLMANN, Vojtěch. Jaderná a radiační fyzika. 1.5. Elementární částice [online]. [cit. 2015-01-05]. < http://astronuklfyzika.cz/JadRadFyzika5.htm#KruhUrychlovace >.
 * WIKIPEDIA CONTRIBUTORS, Betatron [online]. [cit. 2015-01-05]. < https://en.wikipedia.org/wiki/Betatron >.
 * WIKIPEDIA CONTRIBUTORS,. Rolf Widerøe [online]. [cit. 2015-01-05]. < https://en.wikipedia.org/wiki/Rolf_Wider%C3%B8e >.