What type of dosimeter serves as the primary standard for exposure/air kerma at 60Co energy?

The graphite cavity ionization chamber serves as the primary standard for exposure and air kerma measurements at 60Co energy due to its design and the physical properties of graphite. The structure of the ionization chamber allows for accurate measurements of ionization in air, a key factor in determining radiation exposure levels.

Graphite has an atomic composition that is primarily composed of carbon, which has similar radiation interaction properties to human tissue, making it suitable for calibration in terms of therapeutic radiology. When measuring radiation exposure in the context of a cobalt-60 source, which emits gamma rays, the ionization chamber effectively responds to the high-energy photons, facilitating precise calibration against known standards.

This type of chamber can also be designed with a volume small enough to reduce uncertainties related to the collimation of radiation and other geometric factors. The use of ionization chambers is well-established in dosimetry due to their stability, reproducibility, and the ability to provide direct measurements in absolute terms, which is crucial for establishing primary standards in radiological practices.

Other dosimeters listed, while useful in different contexts, do not serve as the primary references for exposure/air kerma at cobalt-60 energy and have differing applications and limitations related to their materials and methods of