Betatron is a machine for accelerating electrons to high speeds. It consists of a circular tube called a doughnut placed between the poles of an electromagnet. A device known as an electron gun shoots the electrons into the doughnut.
The electromagnet creates a changing magnetic field, a magnetic influence in the region around itself. The changes in the magnetic field, in turn, produce an electric field. The electric field transfers energy to the electrons, causing them to be pushed along at a steadily increasing speed. They whirl around the inside of the doughnut, held in a circular path by the magnetic field. When the electrons reach their highest energy, they are made to collide with the nuclei of the atoms of a small target made of tungsten or a similar heavy metal. These collisions produce X rays and gamma rays.
The first betatron was built at the University of Illinois in the United States in 1940. Betatrons that achieve energies of about 20 million electronvolts (20 MeV) have uses in industry and medicine. One electronvolt is the amount of energy needed to move an electron through a potential difference of 1 volt. Nuclear physicists formerly used betatrons in certain experiments. Today, devices known as linear accelerators and electron synchrotrons are used instead.
See also Particle accelerator with its list of Related articles; Gamma rays; X rays.
