By Sunil Bhardwaj

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Accelerators are the devices or machines with the help of which we can increase the velocity of projectiles or we can increase the energy of projectiles. As,$$ E = \frac12 mV^2 $$ Where m is mass of projectile and V is its velocity.

Cyclotron.Lawrence and Livingston, developed a method that avoids the limitations of linac. The instrument used is known as Magnetic Resonance Accelerator or Cyclotron.

Principle: When a charged particle (projectile) is placed under a magnetic field it start revolving in a circular path, the velocity of particle can be increased by the application High frequency oscillator in the direction of particle motion.

Construction: The cyclotron is consist of two flat semicircular shaped metal boxes called dees. These hollow boxes are slightly separated from each other as shown in figure. A source of projectile is placed at the mid-point of the gap between two dees. The two dees are connected to two terminals of high frequency oscillator. So that alternating high potential can be applied between two dees which acts as the electrodes. The dees are enclosed in a large insulated metal box. Whole metal box is placed between two poles of strong magnets which provide magnetic field perpendicular to the plane of the dees.

Working: Suppose the positive ions projectiles are emitted by the source. Let Da is connected to the positive terminal and D, to the negative terminals of high frequency oscillator so that projectile is accelerated to Dg inside D, it will be moving with uniform accelerated velocity. As soon as projectile come out from D, and remain in the gap between D, and Dr. The polarity is changed so the projectile is again accelerated. Like this in every gap, projectile is acc. After passing through number of orbits, the projectile is highly acc. The two dee shaped boxes are arranged in an evacuated metal box: