Ion chambers are a popular choice for measuring high levels of gamma radiation, and are used in a variety of industries, from nuclear power to radiography and radiobiology. They have a uniform response to radiation over a wide range of energies, and can be used to measure the intensity of radiation beams in multiple regions. In medical physics and radiation therapy, they are used to ensure that the dose delivered is as intended. A gas ionization chamber measures charge from the number of ion pairs created within a gas caused by incident radiation.
It consists of two charged electrodes that collect ions formed within their respective electric fields. An applied voltage is large enough to collect all ion pairs produced in the gas by a radioactive source, but not large enough to cause any amplification of the gas. Ionization chambers are widely used in the nuclear industry, as they provide an output proportional to the radiation dose. They have a longer useful life than standard Geiger-Müller tubes, which suffer from gas breakage, and are generally limited to a life of approximately 1011 counting events.
A positively charged electret is used together with an ionization chamber made of an electrically conductive plastic. The energy resolution of an ionization chamber is the ability to distinguish between different energies of radiation. This is important for outdoor cameras, as the camera size for higher photon energies is extremely large. The energy resolution of an ionization chamber is determined by the size and shape of the chamber, as well as the type and pressure of gas used. The higher the pressure, the better the energy resolution.
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