Which layer converts light into electrons in a scintillation detector?

The correct answer is the photocathode layer because this component is specifically designed to convert photons, which are particles of light, into electrons through the photoelectric effect. When the scintillation crystal absorbs radiation, it emits light (scintillation photons) as a result of the energy deposited by the incoming radiation. The photocathode layer then interacts with these scintillation photons; when a photon hits the photocathode, it can free an electron from the material, leading to the generation of an electron cascade.

In a scintillation detector, this process is crucial because it allows the conversion of the light signal into an electrical signal that can be subsequently amplified and processed to quantify the incident radiation. The effectiveness of the conversion depends on the materials used and their properties, but fundamentally, the role of the photocathode is to initiate the first step in the detection process by generating electrons based on the detected light signals.