Cyclotron

What is Cyclotron?

Cyclotron can be defined as a type of particle accelerator in which charged particles accelerate outwards from the centre along a spiral path. These particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying electric field.

Cyclotron Diagram

Working and Principle of Cyclotron

A cyclotron accelerates a charged particle beam using a high-frequency alternating voltage which is applied between two hollow “D”-shaped sheet metal electrodes called “dees” inside a vacuum chamber.

The dees are placed face to face with a narrow gap between them, creating a cylindrical space within them for the particles to move. Then, the particles are injected into the centre of this space. The magnetic field causes the path of the particles to bend in a circle due to the Lorentz force perpendicular to their direction of motion.

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Uses of Cyclotron

For several decades, these were the best sources of high-energy beams for nuclear physics experiments. However, these are still in use for this type of research.

Treatment of cancer:

Cyclotrons can be used in particle therapy to treat cancer, using the ion beams from cyclotrons can be used to penetrate the body and kill tumours by radiation damage.


What is Cyclotron Frequency?

The frequency is given by:

n=qB²πm

Where,

  • q is the charge of the particle,
  • B is the magnetic field used in the cyclotron,
  • M is the mass of the charged particle.

Consider a particle of charge q revolving in the path of radius r with a velocity v. Now for the circular motion we can write:

Centripetal force = Lorentz force due to magnetic field B

Therefore,

⇒ mv²r=qvB

Therefore,

⇒ Angular Velocity (ω) = vrω = qBm

⇒ Time Period (T) =2πω

⇒ T = 2πmqB

⇒ Cyclotron Frequency (n) =1T

⇒ n = ω²π

⇒ n = qB²πm

What are the Limitations of Cyclotron?

  • Cyclotron cannot accelerate electrons because electrons are of very small mass.
  • A cyclotron cannot be used to accelerate neutral particles.
  • It cannot accelerate positively charged particles with large mass due to the relativistic effect.

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