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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 3.0 (currently in use)


The detectors are hybrid detectors. This means that a semi-conductor sensor layer is bonded on to an electronics layer. The sensor layer is a semiconductor, such as silicon, GaAs, or CdTe in which the incident radiation makes an electron/hole cloud. 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, thus enabling full spectroscopic x-ray imaging.

Medipix-2, Timepix, and Medipix-3 are all 256×256 pixels, each 0.055mm (55μm) square, forming a total area 14.08mm × 14.08mm.

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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