Charge-sharing observations with a CdTe pixel detector irradiated with a57Co source

Charge sharing is a limiting factor of detector spatial resolution and contrast in photon counting imaging devices because multiple counts can be induced in adjacent pixels as a result of the spread of the charge cloud generated from a single X-ray photon of high energy in the detector bulk. Although this topic has been debated for a long time, the full impact of charge sharing has not been completely assessed. In this work, we look at the importance of charge sharing in CdTe pixel detectors by exposing such a device to a low-activity (37 kBq)57Co source, whose main emission line is at 122 keV.The detectors used are 1 mm thick with a pixel pitch of 55 μm. These detectors are bump-bonded to Medipix2 photon-counting chips. This study gives an insight of the impact on the design and operation of pixel detectors coupled to photon-counting devices for imaging applications.