How does a PMT measure Alpha particles?

A photomultiplier tube (PMT) measures alpha particles by counting light pulses generated when the alpha particles interact with a scintillating material, typically a coating on the tube. When an alpha particle strikes the material, it excites the atoms, resulting in the emission of photons (light). These light pulses are then collected and amplified by the PMT, allowing for the detection and counting of the alpha particles that have been emitted, for instance, from radon gas and its decay products.

This method is highly effective because the intensity of light produced is proportional to the energy of the alpha particles, providing detailed information about the level of radioactivity in the sample being measured. Because the measurement relies on light detection rather than direct particle counting, this method is particularly sensitive and suitable for detecting low levels of alpha radiation.