Ionization chamber

Last revised by Raymond Chieng on 21 Mar 2023

Citation, DOI, disclosures and article data

Citation:

Wong M, Chieng R, Bell D, et al. Ionization chamber. Reference article, Radiopaedia.org (Accessed on 18 Apr 2024) https://doi.org/10.53347/rID-71248

DOI:

https://doi.org/10.53347/rID-71248

Permalink:

https://radiopaedia.org/articles/71248

rID:

71248

Article created:

25 Sep 2019, Monica Wong ◈

Disclosures:

At the time the article was created Monica Wong had no recorded disclosures.

View Monica Wong's current disclosures

Last revised:

21 Mar 2023, Raymond Chieng ◉

Disclosures:

At the time the article was last revised Raymond Chieng had no financial relationships to ineligible companies to disclose.

View Raymond Chieng's current disclosures

Revisions:

6 times, by 6 contributors - see full revision history and disclosures

Sections:

Imaging Technology

Tags:

physics

Synonyms:

Ionization chambers
Ionisation chambers
Pocket ionisation chambers
Geiger counters

Ionization chambers measure exposure by detecting liberated electron charge when x-ray photons ionize the gas within the chamber. The chambers need a high positive voltage applied at the collecting anode to attract the liberated electrons. The electron charge is collected and used to determine the radiographic exposure expressed in coulombs per kilogram (C/kg), the preferred SI unit, or the legacy unit, roentgens (R).

There are different types of ionization chambers:

ionization chambers are dosimetry devices used to measure the output of x-ray tubes. They function as photo timers in automatic exposure controls and in nuclear medicine, as dose calibrators.
pocket ionization chambers are a portable form of dosimetry devices in the shape of large pens. They provide immediate readings, are easily recharged and reused but are not very accurate due to their mechanical fragility.
Geiger counters have a high voltage across the chamber. Due to the high voltage and positive potential, liberated electrons are accelerated and gain energy, resulting in more liberated electrons from the chamber and amplification of liberated charge (electron avalanche). Therefore, they are highly sensitive and are used to detect radioactive contamination (low level of radiation).