Some experiments require an external beam of protons, deuterons, or alpha particles. A beam of this type can be brought out of the machine by means of a LeCouteur regenerator (Fig. 7). The construction of the regenerator is very simple. It is made of a number of steel laminations of various sizes. What the regenerator does is perturb the magnetic field of the cyclotron at one radial position. Each time the beam passes through the regenerator it receives a kick. With each kick the beam builds up its radial amplitude, until finally it enters a magnetic channel. This channel focuses the beam and steers it outside the main magnetic field. Once outside, the beam travels through an evacuated tube, which is integral with the main vacuum tank. By means of a steering magnet, the beam can be sent into either the physics cave or the medical cave. (These experimental areas are called "caves" because they are rooms inside the massive concrete shielding wall.)
Other experiments may require an external beam of mesons.[6] A meson beam is obtained in the following way (Fig. 8): A movable target such as a block of carbon is placed inside the cyclotron near the end of the outward-spiraling proton beam. When the proton beam hits this target, a shower of mesons is produced. These mesons are bent in various directions by the main magnetic field. Some of them pass through a thin metal window in the vacuum-tank wall and are focused by a magnetic lens into a beam. This meson beam then travels through a hole in the concrete shielding wall into the meson cave. The maximum intensity of this extracted meson beam depends on both the charge and energy desired. Beams of more than 100,000 mesons per second have been obtained through an aperture 4 × 4 in. in the shielding wall.
CYCLOTRON EXPERIMENTS
Nuclear Physics
About 86% of the operating time of the 184-inch synchrocyclotron is devoted to experiments in nuclear physics. Most of the experiments study the production and interaction of π mesons. These particles are considered to be essential factors in the intense but short-range forces that bind the nucleus together. The three types of π mesons are designated according to their electric charge as π+, π0, and π-.[7] These mesons materialize only in high-energy nuclear collisions.
