How does a cyclotron work?
First you have to understand two basic points about electric and magnetic fields and their effects on charged particles. • When a charged particle is in a electric field it feels a force that accelerates it in the direction of the field (or in the direction opposite to that direction if it is a negatively charged particle). If this force is in the direction that the particle is already traveling then clearly this acceleration speeds up its motion and thus adds energy (and this is what we want our accelerator to do). • When a charged particle is moving through a magnetic field region it feels a force that is perpendicular to its direction of motion (and also perpendicular to the magnetic field). Such a force makes the particle change direction but does not change its speed. This means that in a large enough region of magnetic field the particle will travel in a circle. The size of the circle depends on the speed of the particle and the strength of the magnetic field. Now how can we use
The term “cyclotron” was originally laboratory slang for “magnetic resonance accelerator.” A cyclotron is composed of two semicircular electrodes called “dees” because they are shaped like the letter “D.” These dees are encased inside a vacuum chamber that is exposed to a powerful external magnetic field. The application of a voltage to the two dees creates an electric field in the gap between them. When ions (charged particles) are introduced into the center of the vacuum chamber, the magnetic field causes them to begin to move in a circular path. As the ions cross the gap between the dees and they are given an energy kick that causes them to accelerate. The ions cross this accelerating gap twice during each orbit. Because the strength of magnetic field never changes, the orbit of the ions widens each time they gain energy. The accelerating ions continue to spiral from the cyclotron chamber’s center until they reach their peak energy at the chamber’s outer edge. At that point, the ene
There are two evacuated beam paths in the shape of the letter “D”. Each of these is placed between the poles of a large electromagnet, which is used to confine the beam to the circular path, and to help it “accelerate” as the beam passes between the gap between the two D’s. In this case, relatively small potential differences, applied with each pass of the ion beam, result in beam energies that can be quite high. The best example of a cyclotron is the one located at the Fermilab in Batavia, Illinois. This circular accelerator has a circumference of many miles. In it, both protons and anti-protons are accelerated in the same ring, but traveling in opposite directions. They are then brought together in a head-on collision, producing a number of useful effects. What kinds of ionizing radiation are associated with accelerators? Actually, there are two types. These are “prompt” radiations and “induced radiations”. What are prompt radiations? These are the radiations present only when the ac
