It is a device used to accelerate charged particles like protons, deutrons,αα-particles, etc, to very high energies.

PRINCIPLE :A charged particle can be accelerated to very high energies by making it pass through a moderate electric field a number of times. This can be done with the help of aperpendicularmagnetic field which throws the charged particle into a circular motion, the frequency of which does not depend on the speed of the particle and the radius of the circular orbit.

CONSTRUCTION :As shown in figure, a cyclotron consists of the following main parts:

1. It consists of two small, hollow, metallic half-cylindersD1D1andD2D2calleddeesdeesas they are in the shape ofDD.2. They are mounted inside avacuum chamberbetween the poles of a powerful electromagnet.3. The dees are connected to the source of high frequency alternating voltage of few hundred kilovolts.4. The beam of charged particles to be accelerated is injected into the dees near their centre, in a plane perpendicular to the magnetic field.5. The charged particles are pulled out of the dees by a deflecting plate (which is negatively charged) through a windowWW.6. The whole device is in high vacuum (pressure∼10−6∼10−6mm of Hg) so that the air molecules may not collide with the charged particles.