Which detector uses current proportional to dose rate?

• A. Geiger-Müller counter
• B. Ionization chamber
• C. Scintillation detector
• D. Semiconductor detector

Answer: (B)

The charged-current signal that directly tracks how much radiation energy is deposited comes from an ionization chamber. In this device, radiation creates ion pairs in a gas, and the electric field collects those charges, producing a continuous current. The rate of ion-pair production—and thus the collected current—scales with the dose rate for a given radiation type and spectrum. That linear, current-mode response across a wide range makes ionization chambers ideal for measuring dose rate.

Geiger-Müller counters output pulses of fixed size for each event, not a current proportional to dose rate, and their response becomes non-linear at higher rates. Scintillation detectors produce light proportional to energy deposited, but the final signal depends on how the light is converted to an electrical signal and often is used in pulse counting or requires different electronics; the direct, proportional current readout is most characteristic of an ionization chamber. Semiconductor detectors can provide current or pulse signals too, but in the context of straightforward dose-rate measurement, the ionization chamber is the standard choice.