Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

HEALTH PHYSICS
INSTRUMENTATION
RADIATION DETECTORS
9
Humans do not possess any sense organs that can detect ionizing radiation. As a consequence,
they must rely entirely on instruments for the detection and measurement
of radiation. Instruments used in the practice of health physics serve a wide variety
of purposes. It is logical, therefore, to find a wide variety of instrument types. We
have, for example, instruments such as the Geiger-Müller counter and scintillation
counter, which measure particles; film badges, pocket dosimeters, and thermoluminescent
dosimeters, which measure accumulated doses; and ionization-chambertype
instruments, which measure dose and dose rate. In each of these categories,
one finds instruments designed specifically for the measurement of a certain type
of radiation, such as low-energy X-rays, high-energy gamma rays, fast neutrons, and
so on.
Although there are many different instrument types, the operating principles
for most radiation-measuring instruments are relatively few. The basic requirement
of any such instrument is that its detector interacts with the radiation in such a
manner that the magnitude of the instrument’s response is proportional to the
radiation effect or radiation property being measured. Some of the physical and
chemical radiation effects that apply to radiation detection and measurement for
health physics purposes are listed in Table 9-1.
During the last few decades, there has been relatively little change in the basic
detectors that interact with radiation to produce an output signal. During this same
period, there have been enormous advances in the electronic processing of the output
signals from these detectors and in the subsequent treatment of the information
contained in them. These advances are the result of the invention of the transistor
and the integrated circuit. Since integrated circuits were introduced, the number of
transistors that could be placed on a silicon chip has doubled approximately every
1.5 years. As a consequence, microprocessor technology advanced at a very rapid rate.
Integrated circuits continue to become smaller and also to require ever-decreasing
amounts of power. In health physics instrumentation, these advances have resulted
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