DETECTOR VOLTAGE
Radiation Detectors
Summary
The alpha curve is higher than the beta curve from Region I to part of Region IV due to the
larger number of ion pairs produced by the initial reaction of the incident radiation. Detector
voltage principles are summarized below.
Gas Amplification Region Summary
Recombination Region
The voltage is such a low value that recombination takes place before most of the
negative ions are collected by the electrode.
Ionization Region
The voltage is sufficient to ensure all ion pairs produced by the incident radiation are
collected.
No gas amplification takes place.
Proportional Region
The voltage is sufficient to ensure all ion pairs produced by the incident radiation are
collected.
Amount of gas amplification is proportional to the applied voltage.
Limited Proportional Region
As voltage increases, additional processes occur leading to increased ionizations.
Since positive ions remain near their point of origin, further avalanches are impossible.
Geiger-Müller Region
The ion pair production is independent of the radiation, causing the initial ionization.
The field strength is so great that the discharge continues to spread until amplification
cannot occur, due to a dense positive ion sheath surrounding the central wire.
Continuous Discharge Region
The applied voltage is so high that, once ionization takes place, there is a continuous
discharge of electricity.
IC-06
Page 18
Rev. 0
