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Photon Counting Principle
Gd
2
O
2
S
7.44 g/cm
3
CdTe
6.20 g/cm
3
-
+
+ +
+
+ +
+ +
-
-
-
-- ---
Scintillator-based detector:
• Detector divided up into small
blocks (pixelated)
• Conversion of the x-ray photon
into the visible light
• Isotropic emission of the light
collected by reflection at the septa
and then detected by the photodiode
Semiconductor-based detector:
• Continuous crystal with a
pixelated anode
• Conversion of the x-ray
photons into free charge carriers
• Drift of the charge cloud
towards the pixelated anode by a
bias voltage