CHAPTER 18
THE DETECTION OF PARTICLES*
18—1.
Introduction.—The ionization currents measured in the
preceding chapter represent statistical averages of a comparatively large number of individual processes. However, small
.
variations around the mean value can be observed if the detecting
apparatus is suiciently sensitive and rapid in response. Further,
when the ionizing source is very weak and the apparatus very
-
sensitive, impulses or discontinuities will be observed. For
example, the ionization due»to a single alpha particle can be
detected With certain instruments.
It is the purpose
of this
chapter to discuss theionization and expansion chambers, counter
tubes, etc., used to detect and measure the impulses due to single
(or, at least, only a small number of) elementary processes.
SHALLOW/ IONIZATION CHAMBERS
,
-
18—2.
The Principle of Shallow ChambersJ—In gure 18—1,
a heavy particle such as an alpha particle, proton or a nucleus
projected during a disintegration proceSs, ionizes the gas between
-
ms CHAMBER
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