A scintillation counter detects radiation by converting energy into light that is detected by what component?

• A. A PMT directly absorbing radiation
• B. A photodiode array
• C. A photomultiplier tube in a scintillation cocktail
• D. A spectrophotometer diode

Answer: (C)

In a scintillation counter, the radiation’s energy is first converted into light by the scintillation medium (the scintillation cocktail). That light is then detected by a photomultiplier tube, which is a highly sensitive light detector. The PMT changes each photon into an electron, and cascades of dynodes multiply those electrons to produce a measurable electrical pulse that can be counted. This high gain is essential because the light from scintillation can be very faint, something a photodiode array or a simple diode wouldn’t amplify sufficiently. The PMT doesn’t absorb radiation directly; it detects the light emitted by the scintillator.