What is an ionization chamber?

• A. measures ionization with amplification
• B. measures ionization without amplification
• C. detects only beta particles
• D. measures magnetic field changes

Answer: (B)

An ionization chamber works by filling a chamber with inert gas and applying an electric field across electrodes. When ionizing radiation enters, it creates ion pairs in the gas. The electric field collects these ions and electrons, producing a small current. The size of that current is proportional to the ionization rate, i.e., the amount of radiation, but there is no internal amplification of the signal. So it measures ionization without amplification.

This is different from detectors that rely on amplification, such as a Geiger-Müller tube, which uses a Townsend avalanche to boost a single ionization event into a large pulse. Because there’s no amplification, the ionization chamber gives a more linear response over a wide range of dose rates and is widely used for accurate exposure or dose measurements.

It doesn’t restrict detection to beta particles, and it isn’t designed to detect magnetic field changes.