In an ionization chamber, what quantity is measured to quantify radiation?

In an ionization chamber, what quantity is measured to quantify radiation?

• A. The energy deposited by the radiation in the gas
• B. The light output from the gas
• C. The electric charge collected from ion pairs produced in the gas
• D. The number of gamma photons arriving at the chamber

Answer: (C)

In an ionization chamber, radiation ionizes the gas and the resulting charge carriers are collected by an applied electric field. The signal you measure is the electric charge (or equivalently the current) collected from the ion pairs produced in the gas. This collected charge is proportional to the ionization rate, and thus to the radiation dose rate in the chamber. Energy deposited in the gas and light output are not what this detector directly measures, and counting gamma photons isn’t the readout for a gas-filled chamber.

In an ionization chamber, radiation ionizes the gas and the resulting charge carriers are collected by an applied electric field. The signal you measure is the electric charge (or equivalently the current) collected from the ion pairs produced in the gas. This collected charge is proportional to the ionization rate, and thus to the radiation dose rate in the chamber. Energy deposited in the gas and light output are not what this detector directly measures, and counting gamma photons isn’t the readout for a gas-filled chamber.