Cyclotron particle

Particle spiraling inside a cyclotron, accelerated by alternating electric and magnetic fields to reach high energies.

About this subject

A cyclotron is a circular particle accelerator invented by Ernest Lawrence in 1929. Charged particles (such as protons or ions) are injected at the center and subjected to a static magnetic field that forces them into spiral paths. Simultaneously, an alternating electric field is applied between two D-shaped electrodes, called dees, so that each passage between them accelerates the particle. This increases the spiral radius until the particle reaches the desired energy and is extracted for use in nuclear physics experiments, radioisotope production, or cancer treatment (proton therapy). The cyclotron operates based on the cyclotron frequency, which depends only on the particle's mass, charge, and the magnetic field strength. A key limitation is that at very high energies, relativistic effects alter the mass, requiring frequency adjustments (as in synchrocyclotrons). Historically, the cyclotron was pivotal for particle physics discoveries and remains in use at hospitals and research centers worldwide.

Frequently Asked Questions

How does a cyclotron work?

A cyclotron uses a constant magnetic field to bend charged particles into spiral paths, while an alternating electric field accelerates them at each turn. The electric field frequency is tuned to the particle's cyclotron frequency, maintaining synchronous acceleration.

What are cyclotrons used for today?

Cyclotrons are widely used for producing radioisotopes for nuclear medicine, proton therapy for cancer, and research in nuclear physics and materials science. Hundreds of cyclotrons operate in hospitals and universities worldwide.

What is the difference between a cyclotron and a synchrotron?

In a cyclotron, the magnetic field is constant and the electric field frequency is fixed (or adjusted in synchrocyclotrons). In a synchrotron, both magnetic field and frequency vary to keep the particle in a fixed-radius orbit while accelerating, allowing much higher energies.