Question: What is a cosmic ray detector?

Kate Husband answered on 16 Jun 2013:

Cosmic rays are detected by using a large piece of plastic, called a scintillator, which flashes or emits light when a cosmic ray hits it. Then this light is recorded by something called a photomultiplier tube. We only want to record the light from the plastic so it is wrapped up in tin foil and black plastic to stop any stray light (i.e. from the Sun!) being recorded.
The pieces of plastic are about 1m by 2m by 5cm in size and look slightly cloudy.