Cadmium Telluride Sensors for Hard X-ray Radiation
The PILATUS3 X CdTe detector series uses cadmium telluride (CdTe) crystals as the sensor material for direct conversion of the hard X-ray radiation. This high-Z semiconductor material (Cd with Z=48, Te with Z=52) provides excellent stopping power, resulting in high detection efficiency even at high X-ray energies.
DECTRIS employs CdTe material from the leading manufacturer in almost the largest size available today. Each PILATUS3 CdTe detector module is built from two large CdTe sensors of dimension 42 mm × 34 mm, leaving a horizontal gap of only 3 pixels in between the two crystals. The CdTe thickness of 1000 µm provides high quantum efficiency for hard X-ray energies up to 100 keV.
Figure 2 and Table 2 show the quantum efficiency (QE) for the 1000 µm cadmium telluride sensors as a function of energy. The QE values were simulated for the PILATUS3 pixel size and geometry and measured in the PTB laboratory at BESSY II from 20 to 60 keV. The measurements confirm the values predicted by simulation.
Figure 2: Quantum efficiency of PILATUS3 X CdTe module measured in cooperation with PTB at the BAM beamline at BESSY II. The dip in the QE from above 26 keV is caused by fluorescence losses occurring for photon energies above the Cd and Te K-edges. The QE is measured for energy threshold set to 50% of the photon energy.
|Photon energy||CdTe 1000 µm|
|20.0 keV||>90 %|
|40.0 keV||81 %|
|60.0 keV||90 %|
|80.0 keV||77 %|
|100.0 keV||56 %|
Table 2: Quantum efficiency of PILATUS3 CdTe sensors.