Cyclotron: A device that is used to accelerate the charged particles like protons, using high frequency alternating voltage. It is also known as the particle accelerator. The frequency of the cyclotron is the frequency of the charged particle moving perpendicularly to the uniform magnetic field. This magnetic field causes the charged particles to move in a spiral path resulting in its circular motion.

In a cyclotron, two Dee's are kept close to each other with a gap between them to form a circular chamber. The entire assembly is kept between the two magnetic poles to provide a uniform magnetic field. The two dee's are connected to the two terminals of AC source. The frequency of the alternating source matches with the velocity of the charged particles.

In principle, when a charge moves perpendicular to a magnetic field, it would experience a magnetic Lorentz force due to which it moves in a circular path. When a charged particle is accelerates towards the “Dee” that has a negative polarity, at that instant, the perpendicular magnetic field produces the Lorentz force that acts on the moving charged particle as centripetal force to make it move on the circular path.

As the particle reaches the gap between the Dee, the polarity changes and the particle gets accelerated in the opposite direction by moving in the spiral path of increasing radius and velocity. The deflector plates are the ones which are used to take away these accelerated charged particle, as they reach the edge of the Dee.

Electrons can not be accelerated by cyclotrons because the mass of electron is very small and a small increase in energy of electron makes the electrons move with very high speed. As a result of it the electron go quickly out of step with oscillating electric field, Thus we have other accelerating machines such as synchrotron, betatron (for accelerating electrons) have been developed. Also note that the Cyclotron can not be used for accelerating the uncharged particle like neutrons. It can accelerate only charged particles.