Amptek manufactures X-ray detectors using both Si-PIN and CdTe sensors, each of which has advantages in certain applications. The plots below show detailed comparisons of the efficiency and resolution performance of Amptek Si-PIN and CdTe X-ray detectors.
The key points are:
Figure 1 (linear). Shows the intrinsic full energy detection efficiency for Si-PIN detectors. This efficiency corresponds to the probability that an X-ray will enter the front of the detector and deposit all of its energy inside the detector via the photoelectric effect.
Figure 2 (log). Shows the probability of a photon undergoing any interaction, along with the probability of a photoelectric interaction which results in total energy deposition. As shown, the photoelectric effect is dominant at low energies but at higher energies above about 40 keV the photons undergo Compton scattering, depositing less than the full energy in the detector.
Both figures above combine the effects of transmission through the Beryllium window (including the protective coating), and interaction in the silicon detector. The low energy portion of the curves is dominated by the thickness of the Beryllium window, while the high energy portion is dominated by the thickness of the active depth of the Si detector. Depending on the window chosen, 90% of the incident photons reach the detector at energies ranging from 2 to 3 keV. Depending on the detector chosen, 90% of the photons are detected at energies up to 9 to 12 keV.
For 1 mm thick CdTe (Be window dominates low energy response).
Figure 3. Log-log plot of interaction probability between 1 keV and 1 MeV.
For more information on the efficiency of the CdTe detector see the ANCZT-1 application note. This note includes the numeric table of efficiencies that created the figures above .
Pb Resolution (eV FWHM)
|Pb La1 (10.55 keV)||237||418|
|Pb Ka1 (74.96 keV)||532||793|
241Am Resolution (eV FWHM)
|5.9 keV Resolution (eV FWHM)||160||220|
|Peak to Background (P/B) Ratio||6000:1||100:1|
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Figure 11. Mini-X X-Ray Tube (Ag) Output Spectrum taken with a 500 µm thick Si-PIN and a 1 mm thick CdTe.