what is a cyclotron. what is its principle , working ,construction,theory ,limitation. [5 marks]
Cyclotron is a device to accelerate charged particles to very high speed. It employs an electric and magnetic field for the same purpose.
The working of a cyclotron is based on the fact that the frequency of revolution of charged particle is not dependent on the energy.
- Particle moves inside the two semi-circular disc-like metal containers D 1 and D 2 called Dees.
- When the particle moves from one Dee to another, it is acted upon by electric field.
- Electric field changes sign alternately. Therefore, the particle is accelerated by the electric field, which increases the energy of the particle.
- The increase in energy increases the radius of the circular path.
Hence, the path is a spiral one.
- Time period of revolution is his frequency is called the cyclotron frequency.
The working principle of a cyclotron involves the use of an electric field to accelerate charge particles across the gap between two D shaped magnetic field regions. The magnetic field is perpendicular to the paths of the charged particles makes them follow circular paths within two Dees. An alternating voltage accelerates the charged particles each time they cross the Dees. The radius of each particle�s path increases with its speed, so the accelerated particles spiral toward the outer wall of the cyclotron.
Limitations
- Light particles like electrons(e-) and positron(e+) cannot be accelerated by cyclotron as frequency will no more be constant. So resonance condition cannot always be satisfied.
- As cyclotrons are very big, it is difficult to maintain constant magnetic field over a large area.