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BGO scintillators
Scintillation is the flash of light made by ionizing radiation upon striking a phosphor or a crystal detector.
In most of scintillation applications, ionization is made by a gamma or an X-ray radiation having energy from one thousand to several million electron volt (keV to MeV).
The flash of light emitted by the scintillation material is collected by a photodiode or a photomultiplier. These light sensitive detectors produce for each light pulse a current pulse which is analysed in a processing electronic. Light pulses emitted by a scintillator are proportional to the energy of the incident beam. This is why scintillation detectors are used for radiation detection and spectroscopy. It exists various scintillation materials
A suitable material has a good stopping power, a high optical transparency to its own light and good detection efficiency with a high light output. The shape of light pulses is also important. It is defined by the rise time (usually very fast, 100 ps to 1ns) and the decay time.
The decay time is important for fast counting and timing applications.
Sodium Iodide Thallium doped (NaI (Tl)) offers good compromise for all these specifications but is hygroscopic and has a low stopping power. It is the most widely used scintillator. BGO gives less light output but has a very high stopping power. It is the best choice for nuclear physics spectrometers and positron emission tomography.
Plastics are non hygroscophic, they can be made in very large dimensions up to some meters and are the only alternative when a big detection area is necessary.
Characteristics of usual scintillation materials :
Material |
Density |
Decay time |
Hygroscopic |
NaI(Tl) |
3.67 |
230 ns |
yes |
Ba F2 |
4.88 |
0.8 and 630 ns |
no |
BGO |
7.13 |
300 ns |
no |
CsI(Tl) |
4.51 |
1 µs |
slightly |
YAP |
5.5 |
30ns |
no |
LaCl3 |
3.79 |
28 ns |
yes |
Plastic |
1 |
1 to 3 ns |
no |
Cyberstar makes a regular use of all scintillators available on the market. Any kind of detectors in any shape to be used in any environment can be studied.
We can also propose pulse processing electronics and all surrounding pieces of equipment as frame and positioning mechanism.
Cyberstar is accustomed to collaborate in large international programs such as those involved in nuclear physics (Eurogam - Euroball).
For a tutorial reading on radiation detection, we recommend the following books :
G.F. Knoll - Radiation measurement and processes - J.Wiley and Sons.
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