CaF2(Eu)
Calcium Fluoride
Scintillation Material
CaF2(Eu) is a transparent material used for detecting γ-rays up to several hundred keV and for detecting charged particles. Because of its low atomic number, the material’s photofraction is relatively small which limits its use in γ-ray spectrometry at higher energies. However, the low atomic number makes CaF2(Eu) an ideal material for the detection of β-particles because of the small amount of backscattering.
CaF2(Eu) is not hygroscopic and is relatively inert. It has a sufficiently high resistance to thermal and mechanical shock, and it is easily fabricated into a variety of detector geometries.
CaF2(Eu) has a very low vapor pressure, allowing it to be used in a wide variety of vacuum applications. It is insoluble in water and most organic solvents, permitting radioactive samples in solution to be placed in direct contact with the crystal.
Due to its refractive index of 1.47, which is close to that of most PMT windows and optical coupling compounds, a high light collection efficiency can be obtained. Furthermore, the emission maximum at 435nm is well matched to bialkali photocathode photomultiplier tubes.
CaF2(Eu) transmits visible light well, but it has a sharp absorption band at 400nm which partly overlaps with the scintillation emission band. This causes some self-absorption of the scintillation light. Figure 1 shows the scintillation emission spectrum. In applications where optimum energy resolution is required, crystal lengths of less than one inch are recommended due to the self-absorption of CaF2(Eu).
CaF2(Eu)
Calcium Fluoride
Scintillation Material
Figure 2 shows a pulse height spectrum of 40 keV X-rays emitted by 129I measured with a CaF2(Eu) scintillator. When a 241Am α-source is used, the 5.5 MeV alpha peak appears at an equivalent γ-ray energy of about 1 MeV, indicating approximately 20% light yield per MeV for α-particles relative to γ-rays.
The decay time of CaF2(Eu) for γ-ray excitation is 940ns. The scintillation intensity changes with temperature as shown in Figure 3. At 25℃, the slope of the curve is approximately -0.3%C-1.
Thin layers of 0.004” thick CaF2(Eu) have been used with 2x2” NaI(Tl) to make phoswiches. These are capable of separating α, β and γ. Typical use is in health physics applications.
NOTICE: We can customize various sizes of crystals according to the demand of the customers.
More:
