The ionization chamber is a type of gas-filled radiation detector that is widely used for the detection and measurement of certain types of ionizing radiation, such as x-rays, gamma rays, and beta particles. It is also known as an ion chamber. The detector voltage is adjusted so that the conditions correspond to the ionization region, and the voltage is insufficient to cause gas amplification (secondary ionization).Detectors in the ionization region operate at a low electric field strength, so gas multiplication does not occur. The collected load (output signal) is independent of the applied voltage.
Individual minimum ionization particles tend to be quite small and generally require special low-noise amplifiers for efficient operating performance.“Ionization chambers are preferred for high radiation dose rates because they have no “dead time”, a phenomenon that affects the accuracy of the Geiger-Mueller tube at high dose rates.” This is because there is no inherent signal amplification in the operating medium; therefore, these meters do not require much time to recover from large currents. In addition, because there is no amplification, they provide excellent energy resolution, which is mainly limited by electronic noise. An ionization chamber consists of a gas-filled cavity surrounded by two electrodes of opposite polarity and an electrometer. The electric field established between the electrodes accelerates the ions produced by the radiation to be collected by the electrodes. This charge is read by the electrometer and can be converted into absorbed dose. An ion chamber is an extremely simple device that uses this principle to detect ionizing radiation.
The basic chamber is simply a conductive can, usually made of metal, with a wire electrode in the center, well insulated from the walls of the chamber. The chamber is most commonly filled with ordinary dry air, but other gases such as carbon dioxide or pressurized air can give greater sensitivity. A DC voltage is applied between the outer can and the center electrode to create an electric field that sweeps ions toward the oppositely charged electrodes. Typically, the outer can has most of the potential relative to ground, so that the circuitry is close to the ground potential. The center wire is kept close to zero volts and the resulting current in the center wire is measured. The alpha particle causes ionization inside the chamber, and the ejected electrons cause additional secondary ionizations.
They respond to any ionizing radiation that may enter the chamber from 100 nm ultraviolet light through X-rays and gamma rays. Ionization chambers have a uniform response to radiation over a wide range of energies and are the preferred means for measuring high levels of gamma radiation. For example, high-pressure xenon ionization (HPXe) chambers are ideal for use in uncontrolled environments, as their response has been proven to be consistent over wide temperature ranges (20 to 170 °C). The response of an ionization chamber depends to a large extent on the voltage applied between the outer electrode and the center electrode. This little trick allows you to unload the camera without any additional components that could pose leakage problems; note that the only element of the circuit connected to the camera cable is the JFET gate. The gas amplification curve describes the behavior of an ionization chamber as a function of the applied voltage. Matsusada Precision offers a large number of high-voltage power supplies that can be used for ionization chambers with low ripple, compact body and 0 to 1 kV ratings.
The smoke detector has two ionization chambers, one open to the air and a reference chamber that does not allow particles to enter. An ionization chamber measures charge from the number of ion pairs created within a gas caused by incident radiation. 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. Parallel plane, sometimes called parallel plate, ionization chambers are commonly used in low energy (. This makes open-air ionization chambers an ideal reference dosimeter for Accredited Dosimetry Calibration Laboratories (ADCL), but their large size makes them unsuitable for clinical applications.
