What gas is primarily used in gas ionization chambers for radiation measurement?

The correct answer is Xenon. This gas is commonly used in gas ionization chambers for a few reasons related to its physical and ionization properties. Xenon has high atomic number and mass, which makes it effective in interacting with ionizing radiation, thus producing a measurable ionization event. The ionization efficiency is elevated due to its density, allowing it to capture more radiation events per volume compared to lighter gases.

In addition, Xenon is a noble gas with a low tendency to react with other substances, contributing to the stability and reliability of the ionization chamber, making it an excellent choice for precise radiation measurements. Its relatively high ionization energy and ability to create a significant number of ion pairs when radiation interacts with it further enhance its effectiveness in this application.

Argon, while also used in some radiation detection applications, does not have the same level of performance as Xenon in terms of ionization efficiency for certain types of radiation. Krypton and Helium, although they can be used in specific scenarios, are not as commonly utilized as Xenon in gas ionization chambers for accurate and sensitive radiation measurement.