Both scintillators and semiconductors are effective radiation detectors suited for a variety of applications in Civil Nuclear radiation detection. Common scintillators include sodium iodide (NaI), Lanthium bromide (LaBr3) and caesium iodide (CsI). Meanwhile, silicon (Si), germanium (Ge), cadmium telluride (CdTe) and cadmium zinc telluride (CZT) are the more common semiconductor materials.
The key difference
One key difference which influences their performance is direct conversion. Scintillators convert radiation energy into light (indirect conversion) whilst semiconductors convert radiation energy directly into electricity (direct conversion). Scintillator-based detectors require photodetectors for a second step: converting the light produced into electricity.
The benefits of direct conversion
As a result of operating via direct conversion, semiconductors have a higher energy resolution than scintillators. This means they are optimal for taking precise energy measurements, important for applications such as quality control in radiopharmaceutical manufacturing and nuclear event monitoring. In the spectra produced, more distinct spectral peaks are plotted for more accurate isotope identification and analysis.
Semiconductor-based detectors also have no need for photodetectors. Therefore, semiconductor-based detectors can often be built with a compact, lightweight design and a small form factor. This is ideal for integration into custom devices, constructing linear arrays and for mounting these detectors onto UAVs or UGVs for large area radiation monitoring.
Kromek’s GR1 and CZT probe for the RayMon contains the semiconductor cadmium zinc telluride (CZT), giving it a resolution of >2.5% @ 662 keV.
CZT also has a unique feature amongst semiconductors of no cooling being required for it to operate at room temperature, making it a cost-effective solution for radiation detection with low power requirements.
If direct conversion is so good, when would you need a scintillator?
Scintillators are typically less expensive and come into their own in applications requiring larger detector volumes and when energy resolution is less critical, such as in wide-area environmental surveys. Their higher sensitivity, due to their larger size and higher density of the material, allows them to detect lower levels of radiation more effectively.
Kromek’s caesium iodide scintillators the SIGMA 25 and SIGMA 50 have bigger crystals than the GR1.
The SIGMA 25 has a 25.4×25.4×25.4mm crystal size whereas SIGMA 50 has a 25.4×25.4×51mm.
The NaI Probe for our Next Generation RayMon is also a high sensitivity detector but unlike the SIGMA 25 and 50, it uses a sodium iodide scintillator.
Teamwork makes the dream work
Sometimes, it can be beneficial to use a scintillator and semiconductor in conjunction with one another. For example, when both are mounted to a UAV, the scintillator with its higher sensitivity beneficial for identifying hotspots, whilst the semiconductor with its high resolution can then be used to provide a precise spectral analysis of the radioisotopes present at the hotspot.
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