Cyclotron

Earnest Lawrence, of the University of California, Berkeley, is credited with the development of the cyclotron in 1929. A cyclotron is a type of particle accelerator. Cyclotrons accelerate charged particles using a high-frequency, alternating voltage (potential difference). A perpendicular magnetic field causes the particles to spiral almost in a circle so that they re-encounter the accelerating voltage many times.

• Working of Cyclotron
  

A cyclotron consists of two D-shaped regions known as dees. In each dee there is a magnetic field perpendicular to the plane of the page. There is a uniform electric field pointing from one dee to the other in the gap separating the dees. The electric field accelerates the charge released from rest in the gap and carried into one of the dees. The magnetic field in the dee causes the charge to follow a half-circle that carries it back to the gap.While the charge is in the dee the electric field in the gap is reversed, so the charge is once again accelerated across the gap. The cycle continues with the magnetic field in the dees continually bringing the charge back to the gap. Every time the charge crosses the gap it picks up speed. This causes the half-circles in the dees to increase in radius, and eventually the charge emerges from the cyclotron at high speed.

• Problems solved by the cyclotron

The cyclotron is an improvement of the linear accelerator . A linear accelerator accelerates particles in a straight line, through evacuated tubes. A series of cylindrical electrodes in the tubes switch from positive to negative voltage. To accommodate the low frequency, or more stages were required to compensate for the low power at each stage.

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Faster particles required longer accelerators than scientists could afford. Later linear accelerators could use high power klystrons and other devices imparting much more power at higher frequencies, but before these devices existed, the cyclotron was cheaper.

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Cyclotrons accelerate particles in a circular path. Therefore, a compact accelerator can contain much more distance than a linear accelerator, with more opportunities to accelerate the particles.

Advantages of the cyclotron

1. Cyclotrons have a single electrical driver, which saves both money and power, since more expense may be allocated to increasing efficiency.

2. Cyclotrons produce a continuous stream of particles at the target, so the average power is relatively high.

3. The compactness of the device reduces other costs, such as its foundations, radiation shielding, and the enclosing building.