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CdWO4 Cadmium Tungstate
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.
Uses/Applications
- Medical - Computed Tomography (CT)
- Security - Luggage, container and cargo scanning
Features/Benefits
- Low afterglow
- Withstands high energy radiation damage
- High density, high Z scintillator
- Suitable for low activity counting applications
- Relatively high light yield
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.
| Properties | Value |
|---|---|
| Density [g/cm3] | 7.9 |
| Melting point [K] | 1598 |
| Thermal expansion coefficient [C-1] | 10.2 x 10-6 |
| Cleavage plane | <010> |
| Hardness (Mho) | 4-4.5 |
| Hygroscopic | No |
| 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 |