Cadmium tungstate (CdWO4) is a high density, high atomic number scintillator with relatively high light yield. The emission maximum is at 475nm and the total light output is 12 to 15 photons/keV. The light yield relative to NaI(Tl) on a bialkali PMT is 30 to 50%. The high density and stopping power of CdWO4 make it an efficient absorber, particularly for high energy X-ray. It takes only 3mm to stop up to 150keV photons.
CdWO4 is non-hygroscopic and does not require a hermetic package. Crystals are typically provided in block or arrray form and is a good match to photodiodes.
Arrays with pixels as small as 0.3mm x 1mm have been provided. In other forms, round crystals range from 50mm diameter x .5mm minimum; for rectangular sizes, (depending on geometry), crystals can typically range in cross-sections as large as 130mm x 50mm or as thin as 10 microns (size dependant). Contact Saint-Gobain for specific applications and alternate sizes.
|Melting point [K]||1598|
|Thermal expansion coefficient [C-1]||10.2 x 10-6|
|Wavelength of emission max. [nm]||475|
|Lower wavelength cutoff [nm]||330|
|Refractive index @ emission max||2.2-2.3|
|Primary decay time [ns]||14000|
|Light yield [photons/keVγ]||12-15|
|Photoelectron yield [% of NaI(Tl)] (for γ-rays)||30-50|