In gamma-ray instrumentation, what is the primary use of an ionization chamber?

• A. To detect neutron flux.
• B. To measure exposure rate in air for surveys and instrument calibration.
• C. To monitor skin temperature.
• D. To measure surface alpha contamination.

Answer: (B)

An ionization chamber uses a gas-filled chamber where incident gamma rays ionize the gas; the resulting ions are collected by an electric field, producing a current proportional to the radiation intensity. In gamma-ray instrumentation, this makes it ideal for measuring the exposure rate in air, which is exactly what surveys and instrument calibration require. It provides a straightforward, accurate readout of how much gamma radiation is present per unit time, useful for field surveys and for setting reference responses on other instruments. It isn’t typically used for detecting neutron flux (that needs neutron-specific detectors), it isn’t a tool for monitoring skin temperature, and it isn’t the go-to device for assessing surface alpha contamination (that uses alpha detectors or swipe tests).