Ionization chamber, radiation detector used to determine the intensity of a radiation beam or to count individual charged particles. An ionization chamber (or ion chamber) is usually portable. An ion camera is used to measure the rate of radiation exposure (the amount of radiation exposure received in a specific period of time). The ability of the ion chamber to measure the exposure rate of a radionuclide is based on the ability of the emission to reach the active part of the meter and the energy of the emission.
Ion cameras are used when there is measurable exposure or the possibility of measurable exposure to x-rays and gamma rays. When the atoms or gas molecules between the electrodes are ionized by the incident ionizing radiation, ion pairs are created and the resulting positive ions are created and the dissociated electrons move to the electrodes of the opposite polarity under the influence of the electric field. All types of these devices have a filter in the opening of the chamber to prevent the passage of particulate radioactive materials, such as radon decay products, into the chamber. There are two basic configurations; the integral unit with the camera and electronics in the same housing, and the two-piece instrument that has a separate ion chamber probe attached to the electronics module by a flexible cable.
Ionization chambers are widely used in the nuclear industry, as they provide an output that is proportional to the radiation dose. They find wide use in situations where a constant high dose rate is measured, as they have a longer useful life than standard Geiger-Müller tubes, which suffer from gas, decompose and are generally limited to a life of approximately 10-11 counting events. A positively charged electret is used together with an ionization chamber made of an electrically conductive plastic. In other words, all the energy of the primary electrons produced in the sensitive volume of the chamber must dissipate in the chamber.
The ionization chamber is the only gas-filled detector that allows direct determination of the absorbed dose. Ionization chambers are widely used to assess the activity of artificial radionuclides during processing. With reference to the attached ion pair collection graph, it can be seen that in the operating region of the ion chamber the charge of a collected ion pair is effectively constant over an applied voltage range, since due to its relatively low electric field strength, the ion chamber has no effect of multiplication. A more recent application of primitive total ionization chambers (such as the electroscopes used, for example, by Rutherford in the early 20th century), is based on the use of an electret, which maintains a charge for an extended period and is discharged by exposure to radiation.
Multi-cavity ionization chambers can measure the intensity of the radiation beam in several different regions, providing information on the symmetry and flatness of the beam. A simple ionization chamber consists of a metal cylinder with a thin axial wire enclosed in a glass envelope in which some inert gas is filled with some inert gas. An ionization chamber consists of a gas-filled cavity surrounded by two electrodes of opposite polarity and an electrometer. Open-air ionization chambers are the defining instrument of the Roentgen unit and, as such, are fundamentally linked to the absorbed dose.
Devices that are designed for short-term measurements use a short-term electret and a short-term camera that incorporates a spring-loaded mechanism to expose the electret to the entire volume of the chamber at the time of placement. When the gas between the electrodes is ionized by the incident ionizing radiation, positive ions and electrons are created under the influence of the electric field. .