Accordingly, special instrumentation must be used for radiation detection and measurement. Since the degree of hazard from radiation to humans depends on the type of radiation, its energy spectrum, as well as the quantity to which a person has been exposed, radiation detectors used in the field must be capable of making qualitative as well as quantitative measurements. No single instrument at present has all the characteristics described. Accordingly, different types of instruments must be used depending upon the nature of the radiation hazard. The characteristics of some of the more commonly used detectors are summarized below.
Ionization chambers measure dose and dose rate from gamma and x-radiations.
A typical ionization chamber that measures total dose is the pocket dosimeter. It is the size of a large fountain pen. It has a chamber containing two electrodes, one of which is a quartz fiber loop free to move with respect to its mounting. Radiation entering the chamber causes ionization within the sensitive volume. The distance the fiber moves is proportional to the dose received in the chamber.