Medipix2 Collaboration
Learn about the Medipix2 Collaboration
The Medipix2 Collaboration was formed in 1999 with the aim of developing a single photon counting pixel detector readout chip using a 0.25 μm CMOS process. The work of the Collaboration was initially foreseen to take four years, it is still active now almost two decades later. A major reason for this is the number and variety of applications to which the technology has been applied. Moreover, the development and immediate success of the Timepix chip in 2006 has led to a second wave of applications.
There are two chips deriving from the Medipix2 Collaboration, the Medipix2 chip and the Timepix chip.
For questions related to the licensing.
The Timepix2 Chip
Timepix2 is a programmable, general purpose hybrid pixel detector readout ASIC. The Timepix2 ASIC consists of a matrix of256x256 pixels with pixel pitch of 55μm, and is applicable to a wide range of applications including X-ray imaging, particle tracking and material analysis.
The Timepix2 pixel can be programmed to operate in one of several modes depending on the application requirement, offering increased complexity compared to the predecessor Timepix ASIC. Readout is frame-based. The arrival time (Time-of-Arrival – ToA) and charge deposit information (Time-over-Threshold – ToT) can be recorded for each hit when used in sequential read/write mode. In continuous read/write mode one can chose between ToT, ToA or event counting. There are a total of 28 bits per pixel which can be allocated depending on the read/write mode chosen and the requirements of the application.
Key Facts
Collaboration Partners: View page
Intellectual Property Status:
Timepix2 is available for licensing.
Relevant documents:
Features:
- Pixel size 55μm x 55μm.
- 256 x 256 pixels.
- 28 bits/pixel.
- Simultaneous ToT and ToA.
- Separate ToT and ToA clock frequencies.
- Readout dead-time-free modes.
- Frame-based sequential or continuous read/write modes.
- Digital and analogue pixel masking available per pixel (turn off power consumption in unused pixels).
- Linear front-end gain, possibility to configure for ‘logarithmic’ gain mode only in positive polarity.
- 3-side buttable.
- Wire bonding pads can facilitate TSV processing.
Applications:
- X-ray imaging
- Material analysis
- Particle track reconstruction
- Non-destructive testing
| General | |
|---|---|
| CMOS technology | 0.13μm |
| Pixel size | 55μm x 55μm |
| Pixel matrix | 256 x 256 |
| Detector polarity |
Electron collection
Hole collection
|
| Leakage current |
Electron collection: Up to 12nA/pixel (non-uniform) Hole collection 2nA/pixel |
| Peaking time |
~100ns (Adaptive gain OFF) ~200ns (Adaptive gain ON) |
| Noise | 61e- rms |
| Threshold variation | ~40e rms after trimming 5-bit adjustment |
| Minimum operating threshold | ~600e- |
| Power consumption |
5µA/pixel @1.2V i.e., ~165mW/cm2 (low power mode) Digital 500mW Total 900mW |
| Analogue supply voltage | 1.2V |
| ToA bin size | 10ns |
The Medipix2 Chip
The Medipix2 ASIC, the successor of the Medipix1 chip, is a high spatial, high contrast resolving CMOS pixel read-out chip working in single photon counting mode. It benefits from the quick progress of CMOS technology which allows enhanced functionality of the pixel cell at the same time as providing a significant reduction in pixel size. The chip 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.
Key Facts
Intellectual Property Status:
It is no longer possible to get a licence on the Medipix2 or Timepix chip.
Relevant documents:
Features:
- Pixel size 55μm x 55μm
- 256 x 256 pixels
- 2 thresholds for window discrimination (adjustable per pixel with 3 bits each)
- Single particle counting
- Electron or hole collection -> compatible with various sensor materials
- Can be combined with Gas Gain Grid to readout electron deposition in a gas detector
- 3-side buttable
Applications:
- Adaptive optics and other visible or near visible light applications
- Astrophysics
- Digital Autoradiography
- Education
- Electron microscopy
- Life Sciences
- Neutron imaging
- Various X-ray and gamma-ray imaging applications
- X-ray polarimetry measurements
| General | |
|---|---|
| CMOS technology | 0.25μm |
| Pixel size | 55μm x 55μm |
| Pixel matrix | 256 x 256 |
| Design | CERN |
| Analog front end (pixel cell) | |
|---|---|
| Positive and negative signal polarity | |
| Leakage current | -10nA to +20nA |
| Time to peak | 100ns |
| Noise | 100 e- rms |
| Threshold variation (after tuning) | 35 e- rms |
| Minimum operating treshold | 700 e- |
| Digital part (pixel cell + periphery) | |
|---|---|
| 1 counter / shift register | 14 bits (stops at 11810 counts) |
| Periphery |
|
| Total analog power consumption (nominal conditions) | 440mW |
| Total digital power consumption (@100MHz) | 450mW |
The Timepix Chip
The Timepix chip evolved from the Medipix2 development. The pixels have identical size to those of Medipix2 but the functionality within each pixel has been changed. In Timepix each pixel can be programmed to count hits like Medipix2, or to record Time-Over-Threshold (providing rough analog information), or to measure arrival time of the first particle to impinge on the pixel. The Timepix development was driven by the requirements for TPC readout and supported by the EUDet project.
Features:
- Pixel size 55μm x 55μm
- 256 x 256 pixels
- Single energy threshold (adjustable per pixel with 4 bits)
- Three modes of operation: (1) single particle counting (2) Time over Threshold (TOT) and (3) Time of Arrival (TOA)
- Electron or hole collection -> compatible with various sensor materials
- Can be combined with Gas Gain Grid to readout electron deposition in a gas detector
- 3-side buttable
Applications:
- Adaptive optics and other visible or near visible light applications
- Astrophysics
- Background radiation monitoring
- Digital Autoradiography
- Dosimetry
- Education
- Electron microscopy
- Life Sciences
- Neutron imaging
- Various X-ray and gamma-ray imaging applications
- X-ray polarimetry measurements
| General | |
|---|---|
| CMOS technology | 0.25μm |
| Pixel size | 55μm x 55μm |
| Pixel matrix | 256 x 256 |
| Design | CERN |
| Analog front end (pixel cell) | |
|---|---|
| Positive and negative signal polarity | |
| Leakage current | -10nA to +20nA |
| Time to peak | 100ns |
| Noise | 100 e- rms |
| Threshold variation (after tuning) | 35 e- rms |
| Minimum operating treshold | 700 e- |
| Digital part (pixel cell + periphery) | |
|---|---|
| 1 counter / shift register | 14 bits (stops at 11810 counts) |
| Periphery |
13 8-bit DACs to set voltages in the chip Serial raedout 1-bit LVDS Parallel readout 32-bit CMOS Readout time in serial mode (100 MHz clock): 9μs Readout time in parallel mode (100 MHz clock): 266μs |
| Total analog power consumption (nominal conditions) | 440mW |
| Total digital power consumption (@100MHz) | 450mW |
Relevant Documents:
- Medipix2 and Timepix: Design and Characterization of 64K Pixels Chips Working in Single Photon Processing Mode, Thesis by Llopart Cudie, X(CERN; Mid Sweden Univ.) ;Frojdh, C (dir.) ;Campbell, M(dir.); https://cds.cern.ch/record/1056683?ln=p
- Timepix2: W.S. Wong, J. Alozy, R. Ballabriga, M. Campbell, I. Kremastiotis, X. Llopart, T. Poikela, V. Sriskaran, L. Tlustos, D. Turecek, Introducing Timepix2, a frame-based pixel detector readout ASIC measuring energy deposition and arrival time, Radiation Measurements, Volume 131, 2020, https://www.sciencedirect.com/science/article/pii/S1350448719305165