Cyclotron
Definition and meaning of Cyclotron in chemistry.
A cyclotron is a type of particle accelerator that uses a fixed magnetic field combined with a rapidly alternating electric field to accelerate charged particles outward along a spiral path.
In more detail
Invented by Ernest O. Lawrence in 1932, the cyclotron confines charged particles, such as protons or deuterons, between two hollow D-shaped electrodes ("dees") inside an evacuated chamber placed between the poles of a large magnet. The magnetic field bends the particles into a circular path, while a fixed-frequency alternating voltage across the gap between the dees gives them a boost of energy each time they cross it, so the particle spirals outward with increasing speed and radius. Because the time for each half-loop stays constant as speed and radius grow together, the accelerating voltage can stay at one fixed frequency, at least until the particles approach relativistic speeds. Cyclotrons are essential tools in nuclear chemistry for manufacturing radioisotopes used in medical imaging and cancer therapy, as well as in nuclear and particle physics research.
Key facts
| Inventor | Ernest O. Lawrence (1932) |
|---|---|
| Field | Physical Chemistry |
| Key components | Two D-shaped electrodes ("dees"), a static magnetic field, and an alternating voltage |
| Common application | Production of medical radioisotopes (e.g., fluorine-18, carbon-11) |
A medical cyclotron accelerates protons and directs them at an oxygen-18-enriched water target, producing fluorine-18, the radioisotope used to make the PET imaging agent FDG.
Frequently asked questions
How is a cyclotron different from a linear accelerator?
A cyclotron uses a magnetic field to bend particles into a spiral so they repeatedly cross the same accelerating gap, while a linear accelerator (linac) speeds particles up in a single straight-line pass through many separate stages.
Why can't a standard cyclotron reach very high particle energies?
As particles approach the speed of light their relativistic mass increases, throwing them out of sync with the fixed-frequency accelerating voltage; synchrocyclotrons and synchrotrons, which adjust frequency or field strength over time, are used to reach higher energies.