The Medipix2 ASIC is a high spatial, high contrast resolving CMOS pixel read-out chip working in single photon counting mode. It can be combined with different semiconductor sensors which convert the X-rays directly into detectable electric signals. This represents a new solution for various X-ray and gamma-ray imaging applications.

The core concept of the Medipix2 chip was originally invented for pattern recognition in tracing of particles in the LHC. Since then the technological platform has evolved and is being developed in different application specific directions.

Advantages & Applications


  • Life Sciences
  • Digital Autoradiography
  • Astrophysics
  • Various X-ray and gamma-ray imaging applications
  • Neutron imaging
  • Diffraction analysis


  • Count of photons within a given energy region
  • High maximum count rates, allowing for high intensity illumination up to the order of 0.4 GHz/mm2
  • High sensitivity, large dynamic range and low contrast detectability, exceeding present charge integrating techniques; dose reduction is a consequence of these features
  • Noise-free
  • No sensitivity¬†to dark currents, allowing for long exposure times under very low intensity illumination
  • High-speed imaging and readout - 20 frames per second.



  • Pixel size: 55 micrometers
  • Chip size: 256x256 pixels
  • Active area: 1.4x1.4cm
  • Couting rate: 1MHz
  • Energy range: from 3keV upwards
  • Imaging rate: 20 frames per second

The chip is limited to 256x256 pixels (1.4x1.4m). However, the chip is 3-side buttable so an array of 2xn chips is feasible. For instance, a detector comprising of four Medipix2 chips gives an acgive area of 2.8x2.8cm.

Innovative Features

  • The chip is designed to accept either positive or negative charge input
  • A window of energy can be selected through the pixelwise adjustment of upper and lower threshold
  • Pixel size reduced to 55 microns
Medipix Collaborations
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