Which dosimeter is recognized as the primary standard for exposure/air kerma for KV x-ray beams?

The free air ionization chamber is recognized as the primary standard for measuring exposure and air kerma for kilovolt (KV) x-ray beams because it operates by measuring the charge produced by ionization occurring in a volume of air directly exposed to the radiation beam. This type of dosimeter is highly effective in providing an accurate and reproducible measurement of x-ray exposure due to its design, which allows for precise control and calibration based on known radiation standards.

The free air ionization chamber can measure high-energy x-ray radiation with minimal energy dependence, making it particularly suitable for clinical and calibration settings where standardized measurements are essential. It uses a thin entrance window allowing the x-rays to enter the chamber while reducing any additional interactions that could skew results. The ability of this dosimeter to provide direct measurements of air kerma and exposure at various beam qualities establishes it as the reference for calibration of other dosimeters, ensuring consistent accuracy in radiation measurement across different devices and applications.

In contrast, other dosimeters, such as cylindrical ionization chambers, film dosimeters, and thermoluminescent dosimeters, serve important roles in various aspects of radiation measurement but are either secondary standards or have limitations that prevent them from being used as the primary standard for KV x-ray