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Medipix is a family of photon counting pixel detector developed by an international collaboration, hosted by CERN.

Detectors in the Medipix family include:

  • Medipix 1
  • Medipix 2
  • Medipix MXR
  • Timepix
  • Medipix 3 (currently at the prototype development phase)


The detectors are hybrid detectors. This means that a sensor material, typically silicon, is bonded on to an electronics layer. The sensor layer is a semiconductor in which the incident radiation makes and electron/hole pair. The charge is then collected, via bump bonds, and processed by a CMOS electronics layer. The electronics count the number of events in each pixel. Discriminators are used so that the electronics only count events within a selected energy range.

Medipix-2, Timepix, and Medipix-3 are all 256x256 pixels, each 0.055mm square.

Timepix allows for recording time information regarding when events occur relative to when the shutter opens. In addition Time over Threshold (ToT) mode allows for recording the duration an event is above a threshold.

Medipix-3 has better energy resolution through real time correction of charge sharing. It also has multiple counters per pixel that can be used in several different modes. This allows for continuous readout and up to eight energy thresholds.



  • Medipix-1: Early 90s.
  • Medipix-2: Late 90s.
  • Medipix-3: Collaboration formed 2006.

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