Ionization chamber

An ionization chamber is a gas-filled radiation detector that measures charge collected from ion pairs created by incident radiation. Its response is proportional to deposited energy over a wide operating range.

Gas ionization: The removal of electrons from gas atoms or molecules, producing positive ions and free electrons. Incident radiation produces the ion pairs that the chamber collects.
Radiation dosimetry: The measurement and calculation of absorbed dose from ionizing radiation. Ionization chambers are widely used to measure radiation dose.
Proportional counter: A gas-filled detector in which electron avalanches amplify the primary ionization signal proportionally. Unlike an ionization chamber, it deliberately multiplies charge in the gas.
Ionizing radiation: Radiation with enough energy to remove electrons from atoms or molecules. It supplies the energy that creates charge in the chamber’s gas.
Ion-pair collection: The movement of oppositely charged ions and electrons toward electrodes under an electric field. Collected charge is the chamber’s direct measurement signal.
Radiotherapy dosimetry: The measurement of absorbed dose delivered during radiation treatment. Chambers calibrate treatment beams and verify dose delivery.
Geiger–Müller tube: A gas-filled radiation detector that produces a large discharge pulse for each detected event. Its avalanche discharge yields event counts rather than an ionization-current dose measurement.
Electric field: A physical field that exerts forces on electric charges. The applied field drives ions and electrons toward the collecting electrodes.
Recombination: The process in which free electrons and positive ions reunite, neutralizing their charges. Recombination prevents some radiation-created charge from reaching the electrodes.
Farmer chamber: A cylindrical ionization chamber commonly used to measure absorbed dose in radiotherapy beams. This standard chamber design measures dose in water and tissue-equivalent phantoms.

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