ionikammioita

Ionikammioita, literally "ion chambers," are a class of radiation detectors that measure ionizing radiation by collecting charge generated in a gas-filled cavity. The basic design consists of a sealed volume of gas (often air, argon, or a mixture) between two electrodes connected to an electrometer. When radiation—such as alpha, beta, gamma, or X‑ray photons—passes through the gas, it ionizes gas molecules, producing positive ions and free electrons. An applied electric field drives these charges to the electrodes, creating a measurable current proportional to the radiation dose rate.

The simplest form, the conventional ion chamber, is widely used in medical radiography, nuclear power plants, and environmental monitoring to provide accurate dose measurements. A parallel‑plate ion chamber provides a uniform electric field, enhancing response linearity, while a cylindrical geometry is common in high‑energy physics experiments for its mechanical robustness. Miniaturized versions, such as solid‑state ionization chambers, allow integration into mobile radiation monitors.

Calibration against traceable standards (e.g., Co‑60 or Cs‑137 gamma sources) ensures accurate dose equivalent readings, typically within a few percent. Ion chambers are valued for their energy independence in the photon energy range of a few hundred keV to several MeV, low sensitivity to temperature and pressure, and ability to operate in high‑dose environments where semiconductor detectors would saturate.

Limitations include relatively large physical size for the required gas volume and the need for periodic buildup‑time calibration. Despite these drawbacks, ion chambers remain the reference standard for radiation dosimetry in many scientific and industrial fields.