Vermes
Advanced Member level 4
It is a design of scintillation detector based on photomultiplier combined with scintillator – sodium iodide crystal activated by thallium.
This diagram presents the principle of operation. From the top: scintillator, which is a substance which activated by quantum of ionizing radiation emits flash of light. That flash is very weak, but still possible to strengthen and process into an electrical signal by the photomultiplier.
Photomultiplier is a vacuum tube, which has so called dinodes between the cathode and anode. On those dinodes, electrons ejected by the light from the photocathode are multiplied and even if at the beginning a single photon ejected only one electron, a huge amount of them can reach the anode, generating quite a big electrical impulse. Photomultiplier requires quite a high power voltage, so for the experiment you have to build an adjustable negative voltage power supply in the range of 400-2000V.
Photomultiplier together with the scintillator were placed in a metal housing, to cut off all the possible sources of light and interferences.
Impulses produced on the anode are passed to the ground through a resistor, on which the voltage drop is derived by a capacitor separating from BNC socket which is connected to the oscilloscope.
Detector differs from G-M counters – impulses are proportional to the energy of the ionizing radiation particle. It can be used for building a spectrometer for the analysis of sources of radiation.
Link to original thread - Scyntylacyjny detektor promieniowania jonizującego