uclei[5]
------- --------- --------------- ---------------
730 Mev 460 Mev 910 Mev 1140 Mev

In reaching an energy of 730 Mev a proton, for example, makes 75,000
revolutions in just 6 milliseconds (msec). It travels a distance of 450
miles and attains a velocity of 152,000 miles per second, or 82% of the
speed of light! During this brief journey its mass increases 75%, giving
very convincing evidence for the validity of Einstein's theory. Similar
data for other ions may be found in the appendix.

FOOTNOTES:

[4] A deuteron is the nucleus of an atom of heavy hydrogen and contains
one proton and one neutron; it carries a single positive electric
charge. An alpha particle is the nucleus of a helium atom and is made up
of two protons and two neutrons; it carries two positive charges.

[5] The machine is equipped for helium-3 operation, but to date it has
not been used for that purpose.

DESIGN AND CONSTRUCTION OF THE 184-INCH SYNCHROCYCLOTRON

_Magnet_

During the rebuilding of the cyclotron, the diameter of the magnet pole
pieces was increased from 184 to 188-3/4 inches. Also, the pole gap at
the center was reduced from 21 to 14 inches. These changes increased the
weight of steel in the magnet from 3700 to 4000 tons.

The main exciting coils, which contain 1300 turns of copper-bar
conductor each, were not altered. Two auxiliary coils containing 425
turns each were added. This brought the total weight of copper from 300
to 340 tons. The coils are layer-wound around the pole pieces close to
the pole gap. Other data about the coils are given in the appendix.

The effect of these modifications was to increase the field strength at
the center of the pole gap from 15,000 to 23,400 gauss. This increase
made it possible to obtain the higher-energy ions.

Power is supplied to the coils by two motor generator sets, which
produce the direct current required for a steady magnetic field. The
direct current from the motor generators is regulated so that the
magnetic-field fluctuation is less than one part in 10,000. This is
necessary if one wants an external beam of nearly uniform energy.

In order to prevent the beam from becoming unstable and striking the
dee, the magnetic field must be strongest at the center and decrease
radially (Fig. 4a). With flat pole faces the field does not decrease
uniformly. To give the desired rate of decrease, the pole faces are
shimmed with concentric steel