Английская Википедия:Cadmium tungstate

Материал из Онлайн справочника
Перейти к навигацииПерейти к поиску

Шаблон:Chembox

Cadmium tungstate (CdWO4 or CWO), the cadmium salt of tungstic acid, is a dense, chemically inert solid which is used as a scintillation crystal to detect gamma rays. It has density of 7.9 g/cm3 and melting point of 1325 °C. It is toxic if inhaled or swallowed. Its crystals are transparent, colorless, with slight yellow tint. It is odorless. Its CAS number is Шаблон:CASREF. It is not hygroscopic.

The crystal is transparent and emits light when it is hit by gamma rays and x-rays, making it useful as a detector of ionizing radiation. Its peak scintillation wavelength is 480 nm (with emission range between 380 and 660 nm),[1] and efficiency of 13000 photons/MeV. It has a relatively high light yield, its light output is about 40% of NaI(Tl), but the time of scintillation is quite long (12−15 μs).[1] It is often used in computed tomography. Combining the scintillator crystal with externally applied piece of boron carbide allowsШаблон:Citation needed construction of compact detectors of gamma rays and neutron radiation.

Cadmium tungstate was used as a replacement of calcium tungstate in some fluoroscopes since the 1940s.[2][3] Very high radiopurity allows use of this scintillator as a detector of rare nuclear processes (double beta decay, other rare alpha and beta decays) in low-background applications.[4] For example, the first indication of the natural alpha activity of tungsten (alpha decay of 180W) was found in 2003 with CWO detectors.[5] Due to different time of light emission for different types of ionizing particles, the alpha-beta discrimination technique has been developed for CWO scintillators.[6]

Cadmium tungstate films can be deposited by sol-gel technology. Cadmium tungstate nanorods can be synthesized by a hydrothermal process.[7]

Similar materials are calcium tungstate (scheelite) and zinc tungstate.

It is toxic, as are all cadmium compounds.

References

External links

Шаблон:Cadmium compounds