These pulses are recorded on photomultiplier tubes, electronic sensors much more sensitive than the human eye.
The emitted light is filtered and detected by a photomultiplier tube.
These photons are then detected by the photomultiplier tube.
A photomultiplier tube noticed these drops in output and recorded them.
Many counters have two photomultiplier tubes connected in a coincidence circuit.
Phosphors in combination with photomultiplier tubes have also been used.
The article on the photomultiplier tube carries a detailed description of the tube's operation.
This is then amplified by photomultiplier tubes and converted into electrical impulses.
At opposing ends of the chamber were a pair of photomultiplier tubes.
One possible reason is that there is a problem with one of the photomultiplier tubes.