Scintillators and PMTs


A scintillator is a material that scintillates – emits light – when it is being hit by radiation. In that way a scintillator can be used to convert radiation from higher energies to light that in turn can be detected by a photo sensor – for example a PMT. The detector is covered in a reflective material so that as much light as possible reaches the sensor. In order to have as much light as possible to reach the sensor and as little light as possible to leak out, the detector is covered with a reflective followed by a light tightening material. One of the scintillators in the showcase has been peeled so that you can see how it looks like under the light tightening.

Scintillators can be different materials but both types that you can see here in the showcase are plastic scintillators.

Here you can see the difference between a piece of plexiglass (left) and a scintillator (right) when they are lit up by a UV lamp. The scintillator is radiating a lot of visible light – it scintillates. (Photo: M. Kiss)


A PMT – short for photomultiplier tube – is used to convert light to an electric signal. This is how it works:

Light hits the photocathode (red). The photoelectric effect leads to electrons being knocked out from the photocathode. The electrons are focused with an electrode (blue) towards the first dynode (black), where even more electrons are knocked out. This multiplication process continues until the electrons hit the anode (green). The number of electrons are now enough for an electric signal to be read out.


Page responsible:Jahangir Jazayeri
Belongs to: KTH Space Center
Last changed: Apr 19, 2018