An ionization chamber is a gas-filled radiation detector that measures ionizing radiation by collecting the electrical charge produced when incoming radiation ionizes the gas between two electrodes held at a fixed voltage, with the resulting current proportional to the intensity of the radiation present. Simpler in design than the related Geiger counter, which operates at higher voltage to produce an amplified avalanche signal for each individual particle, an ionization chamber instead measures the cumulative ionization current, making it well suited to measuring radiation dose rate rather than counting individual particle events. Ionization chambers have been used since the early twentieth century in radiation dosimetry and remain a standard instrument in radiation therapy calibration and environmental radiation monitoring, and a small radioactive source ionizing air inside a chamber is also the operating principle behind common household smoke detectors.
Facts
Measuresthe electrical charge produced by ion pairs created in a gas by incident ionizing radiation, used to determine radiation dose 1 Operating PrincipleA voltage applied between two electrodes in a gas-filled chamber collects the ion pairs produced by incident radiation, generating a continuous current proportional to the radiation dose, with no charge multiplication, unlike a Geiger-Muller tube or proportional counter. 1 Operating Rangethe resulting ionization current is typically in the range of femtoamperes to picoamperes 1 Classification
Instrument Class Connections
Precursor To
Early radioactivity researchers used simple gas-filled ionization chambers to detect and measure radiation; the Geiger-Muller tube (1908, refined 1928) added avalanche gas amplification to the same basic gas-ionization principle, producing an audible, countable pulse per particle.
Used In
The ionization chamber detects and measures ionizing radiation by collecting the charge freed in a gas volume, an early instrument of radioactivity and nuclear-physics measurement.
Sources
1. Ionization Chamber (Wikipedia)
WikipediaWikipedia, Ionization chamber article, Principle of operation section, first sentence
A gas ionization chamber measures the charge from ion pairs created within a gas caused by incident radiation.
Wikipedia, Ionization chamber article, Principle of operation section, describing current mode
This mode of operation is referred to as "current" mode, meaning that the output signal is a continuous current, and not a pulse output as in the cases of the Geiger-Müller tube or the proportional counter.
Wikipedia, Ionization chamber article, Principle of operation section, electrometer current figure
This generates an ionization current which is measured by an electrometer circuit in the region of femtoamperes to picoamperes, depending on the chamber design, and is proportional to the radiation dose.
Lede, instrument class
An ionization chamber is a gas-filled radiation detector that measures ionizing radiation by collecting the electrical charge produced when incoming radiation ionizes the gas between two electrodes held at a fixed voltage, with the resulting current proportional to the intensity of the radiation present.
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