CWO

From Detec-Rad.com

Cadmium Tungstate CdWO4 (CWO) is a popular scintillation material due to its low intrinsic background and afterglow together with reasonably high light yield. Although not as famous as NaI(Tl), it is one of the most promising materials for spectrometry and computed tomography applications.

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Discussion

  • CWO is an excellent scintillator for gamma-rays with energy > 1 MeV, and good for most applications over 650 keV. This property enables to limit the unwanted background activity that is usually measured on NaI.
  • Energy resolution of Re = 9.9% is slightly higher than that of NaI (8.7%) but can be adequate in most applications.
  • Volumic price is roughly twice that of NaI, but being three times more efficient at full absorption peak, dimensions can be reduced in consequence, depending on the application.
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Comparison with other scintillators

Compared with other scintillators, CWO has unparalleled advantages:
  • With a bigger average atomic number than NaI, it is better fitted to absorb gamma-rays
  • Very good stability from negative temperatures up to around 80°C
  • Not hygroscopic, meaning that it is better fitted for harsh environment
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Applications

Exemples of applications where CWO is used

  • Detection of 16N (6 MeV) for controling steam generators
  • Spectrometry
  • Computed tomography
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Technical Data

Material CdWO4
DescriptionCadmium Tungstate
Density (g/cm3)7.9
Melting point (°C)1325
Crystal structureMonoclinic
Cleavage plane<010>
Hygroscopic no
Wavelength of emission maximum (nm) 540
Refractive index at emission maximum2.25
Light output (for gamma rays) (in % of NaI(Tl))40
Resolution (%) 9.9
Decay constant (µs) 5
Maximum dimensions 35mm dia. x 35mm
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