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YAG Single Crystal Scintillator Discs
YAG (Yttrium Aluminum Garnet activated by Ce3+) has a very fast response time of 50-60ns and they do withstand well to the bombardment by electrons or ions far better than plastic or phosphor scintillators. Light emission peaks at about 560nm which means that S20 photocathodes are most suitable for detecting the emission. YAG is suited for high current operations. The response is better then for the P47 discs below 5kV and again at higher accelerating voltages. where the performance of powder scintillators fall off while the response of the YAG continues to increase linearly.
The crystal should be coated with 50nm of aluminum prior to use. If the layer becomes damaged it can be removed with sodium hydroxide. The crystals are mounted with the matt surface in contact with the light pipe as this has shown to increase the efficiency.
YAP Single Crystal Scintillator Discs
YAP (Yttrium Aluminum Perovskite activated by Ce3+) shares the same advantages as YAG but is more efficient in terms of light output than YAG crystals. As well. the emission spectrum peaks at about 378nm. and this corresponds closely to the maximum sensitivity of the S11 photocathode which in general is used in most scanning electron microscopes. (There would be more improvement in signal by using a YAP crystal rather than YAG in these microscopes). The decay time of YAP (40ns) is faster than YAG (80ns) so its overall performance is superior to YAG. YAP crystals should be coated with 50nm of aluminum prior to use.
Converting from P-47? Use YAP and no need to change the PMT!
The best of both worlds: Emission characteristics of a P47 - using the same photomultiplier - plus the durability of the YAG! Made of yttrium aluminum perovskite. the YAP single crystal is a breakthrough in the light output efficiency. Its emitted spectrum peaks at 378nm (close to the S-11's maximum sensitivity). meaning your SEM does not have to be refitted with a more sensitive photomultiplier. And because the decay time of the YAP crystal is faster than the YAG crystal (40ns vs. 80ns). overall performance is significantly improved. All YAP scintillators should be aluminum coated prior to use in an SEM application and therefore. the SPI YAP scintillators come 50 nm aluminum coated as "standard". freeing the customer from the burden of having to apply aluminum and not knowing for sure just how much to apply. If a YAP is desired without the aluminum coating. be sure to state that you want the scintillator uncoated.
But for many users. the real advantage of the single crystal scintillator is that when compared to P-47. the useful life time is essentially forever, and that is because of its high resistance to radiation damage. While we can not guarantee it, far more often than not, the scintillator far outlives the useful lifetime of the SEM.
Other important features
Excellent signal-to-noise ratio.
Just select the scintillator and SPI # that is right for your microscope and that is all there is to it!
Scintillators for Scanning Electron Microscopes
Semiconductor single crystals of CdxZn1-xTe (CdZnTe, CZT, Cadmium Zinc
Telluride) are important materials for the development of far-infrared,
visible light, X-ray detectors, and gamma-ray detectors as medical imaging
devices. CdZnTe (CZT, Cadmium Zinc Telluride) radiation detectors have
the advantages of a large absorption coefficient, compact size and room
temperature operation. Currently used high purity Ge and Si detectors
in industry and medical imaging can only work efficiently at the liquid-nitrogen
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