Radiation Detectors
DETECTOR VOLTAGE
Continuous Discharge Region
In the continuous discharge region (Region VI), a steady discharge current flows. The
applied voltage is so high that, once ionization takes place in the gas, there is a
continuous discharge of electricity, so that the detector cannot be used for radiation
detection.
Radiation detectors are normally designed to respond to a certain type of radiation. Since the
detector response can be sensitive to both energy and intensity of the radiation, each type of
detector has defined operating limits based on the characteristics of the radiation to be measured.
A large variety of detectors are in use in DOE facilities to detect alpha and beta particles, gamma
rays, or neutrons. Some types of detectors are capable of distinguishing between the types of
radiation; others are not. Some detectors only count the number of particles that enter the
detector, while others are used to determine both the number and energy of the incident particles.
Most detectors used in DOE facilities have one thing in common: they respond only to electrons
produced in the detector. In order to detect the different types of incident particles, the particle’s
energy must be converted to electrons in the detector.
Gas-filled detectors are used, for the most part, to measure alpha and beta particles, neutrons, and
gamma rays. The detectors operate in the ionization, proportional, and G-M regions with an
arrangement most sensitive to the type of radiation being measured. Neutron detectors utilize
ionization chambers or proportional counters of appropriate design. Compensated ion chambers,
BF3 counters, fission counters, and proton recoil counters are examples of neutron detectors.
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