Ionization chambers are a popular choice for high radiation dose rates due to their lack of “downtime”, which can affect the accuracy of a Geiger-Mueller tube. This is because the ionization current is large enough to be measured with a “microammeter”. The transmission ionization chamber is typically composed of layers of PMMA coated with a conductive material. Additionally, ionization chambers with transparent X-ray plates made from aluminized plastic or thin metal mesh are used to detect fluorescent radiation. Ionization chambers larger than 2 or 3 cubic centimeters in volume are not suitable for use in a ghost or for determining the intensity of radiation on the patient's skin.
This is because they require large and heavy dry cells or a “B” battery eliminator to supply the charged plate(s) with large currents at high voltages, making them not very portable. Proportional counters work by successive ionization through collisions between ions and gas molecules, and can amplify the primary ions by 103-104 times in order to obtain enough energy near the thin central electrode to cause more ionization in the detector. Two types of amplifiers are used to make the pulse height proportional to the amount of ionization produced by the particle in the chamber. An ionization chamber consists of a gas-filled cavity surrounded by two electrodes of opposite polarity and an electrometer. When ionization chambers are not suitable for side profile measurements, an alternative is to use 2D detectors such as scintillation detectors and Gafchromic films. Ionization chambers are considered radiation indicators, while calorimetry measures the heat released into water and ionization chambers record the number of ion pairs produced in air.
Small ventilated air ionization chambers with a volume of 0.01 to 0.3 cm3 are suitable for measuring field parameters up to 2 cm × 2 cm. Pressurized well type cylindrical ionization chambers are often used for determining radioactive sample activity, and the gas amplification curve describes the behavior of an ionization chamber as a function of the applied voltage.
