What does a PIC measure?

A precise ion chamber (PIC) is designed to measure the ions that are generated from alpha radiation. This type of detector operates by utilizing the principle of ionization; when alpha particles interact with the air or the chamber material, they produce ions. The PIC can then measure the resulting electric current produced by these ions, allowing for quantification of the alpha radiation present in a given area.

The other options do not accurately describe the function of a PIC. While gamma particles and beta particles also contribute to the overall radiation spectrum, they are measured using different types of detectors tailored for their specific characteristics. Therefore, the primary role of a PIC is to focus exclusively on alpha particles and the ions they create, making the first choice the most accurate representation of what a PIC measures.