The Foundations of Chemistry

gap between the dees. The dees are connected to a source of high-frequency alternating

current that keeps them oppositely charged. The positively charged particles are attracted

toward the negative dee. The magnetic field causes the path of the charged particles to

curve 180° to return to the space between the dees. Then the charges are reversed on the

dees, so the particles are repelled by the first dee (now positive) and attracted to the second.

This repeated process is synchronized with the motion of the particles. They accelerate

along a spiral path and eventually emerge through an exit hole oriented so that the beam

hits the target atoms (Figure 26-8).

1022 CHAPTER 26: Nuclear Chemistry

Strong

magnetic field Oscillating

circuit

Small negative

electrode

Hollow D-shaped

electrode

(–)

High-energy beam

Figure 26-7 Schematic representation of a cyclotron.

The path of the particle is initially
circular because of the interaction
of the particle’s charge with the
electromagnet’s field. As the particle
gains energy, the radius of the path
increases, and the particle spirals
outward.

Figure 26-8 A beam of protons (bright blue stream) from a cyclotron at the Argonne

National Laboratory. Nuclear reactions take place when protons and other atomic particles

strike the nuclei of atoms.