Regional Basic Professional Training Course in Korea

schematically in Fig. (2.7).
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2. Radiation Protection
As a charged particle passes through the gas it ionizes atoms and forms within the
chamber, ion pairs composed of the residual positively charged atoms and the negatively
charged electrons. The positive and negative charges thus produced have a force applied
to them by the voltage; positively charged particles tend to move toward the chamber
walls and negatively charged particles toward the central electrode, because, of course,
opposite charges attract. The central electrode is often referred to as the collector.
The main differences among the three types of gas‐filled detectors lie in the gas used, the
pressure at which that gas is maintained within the chamber, and the voltage level that is
maintained between the central electrode and walls of the chamber. Fig. (2.8) is a graph
of the voltage versus the amount of ionization that occurs.
Fig. (2.7) A Gas‐Filled Detector. The incoming ionizing A enters the detector B and causes
ionization. The residual positive ions move toward the chamber walls D, which are
negatively charged, and thus form the cathode. The electrons (negative ions) move
toward the central wire E, which is positively charged and thus forms the anode or
collector. The central wire and the chamber walls are electrically isolated from each
other by the insulating material F. The voltage level V is maintained by the power
source P. The resistor R capacitor C circuit integrates individual pulses from the
electrons.