ss than for a continuous
beam, such as that obtained from a conventional cyclotron (see Table I).
This is part of the price paid for higher energies.

_Internal Targets and Beam Extractor_

The simplest target is one placed inside the vacuum tank where the
circulating beam will strike it. The target may be any substance that
the physicist or chemist wants to irradiate. The target material is
attached to a movable probe. If the experimenter wants to use the
full-energy beam, he places the target at the maximum usable radius of
the circulating beam (82 inches). However, if he desires to use ions
having less than the maximum energy, he inserts the target further into
the cyclotron so that it is intercepted sooner.

TABLE I

=============================================================
Comparison of external-beam energy and current for a
synchrocyclotron and a conventional cyclotron
-------------------------------------------------------------

184-Inch Synchrocyclotron
-------------------------

Protons Deuterons Alpha particles
------- --------- ---------------
Beam energy --
maximum (Mev) 730 460 910

Beam intensity --
peak current ([mu]a)[6] 120 120 40

Beam intensity --
average current ([mu]a) 0.75 0.75 0.25

60-Inch Cyclotron
-----------------
Beam energy --
maximum (Mev) 12 24 48

Beam intensity --
peak current ([mu]a) 100 150 100

Beam intensity --
average current ([mu]a) 70 80 60
-------------------------------------------------------------
[6] [mu]a = microampere
=============================================================

[Illustration: Fig. 7. Plan view of the cyclotron, showing the method
for obtaining an external beam of protons, deuterons, or alpha
particles.]

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