Medipix

Medipix3 is a CMOS pixel detector readout chip designed to be connected to a segmented semiconductor sensor. It acts as a camera taking images based on the number of particles which hit the pixels when the electronic shutter is open. However, Medipix3 also permits colour imaging and dead time free operation. A novel charge summing and allocation scheme is implemented at the pixel level permitting proper binning of the energy of incoming photons overcoming the effects of fluorescence and charge diffusion. As there are 2 counters in each 55μm pixel the chip can be programmed such that one counter is being read out while the other is counting. It is also possible to connect the chip to a sensor matrix with a pitch of 110μm. In this way, up to 8 counters are available per pixel.

Medipix3 has applications in:

• 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

The Medipix4 ASIC is a CMOS pixel detector read-out chip working in single counting mode. It is designed to be combined with different semiconductor sensors depending on the applications, to convert X-rays into detectable electric signals. Medipix4 permits colour imaging and dead-time-free operation, and can be used in a range of X-ray, gamma and visible light imaging applications. Unlike the previous iterations of Medipix, the Medipix4 ASIC is 4-side buttable, permitting large area seamless tiling on all 4 sides by utilising Through-Silicon-Via (TSV) technology.

Medipix4 has applications in:

• X-ray and neutron imaging
• Particle track reconstruction
• Electron detectors
• Material analysis
• Synchrotrons

Specifications

	Medipix3RX (2011)	Medipix4 (2022)
Technology	130 nm + 8 metals	130 nm + 9 metals
Pixel pitch (µm)	Fine pitch mode: 55 mm Spectroscopic Mode: 110 mm	Fine pitch mode: 75 mm Spectroscopic Mode: 150 mm
Number of pixels	Fine pitch mode: 256x256Spectroscopic Mode: 128×128	Fine pitch mode: 320x320Spectroscopic Mode: 160×160
Matrix arrangement	3-side buttable (test vehicle for TSVs)	4-side buttable
Sensitive area (cm2)	1.98	5.76
Sensitive area / Total active area (%)	Without TSV: 88.7%With TSVs: 94.6%	Without TSV: 93.5%With TSVs: 99.4%
Acquisition mode	Single Pixel Mode (SPM) / Charge Summing Mode (CSM)	Single Pixel Mode (SPM) / Charge Summing Mode (CSM)
Energy Resolution (measurement, preliminary)	SPM: 1.4 keV FWHM (Cu Ka)CSM: 2.0 keV FWHM (Cu Ka)	SPM: 2.0 keV FWHM (Cu Ka)CSM: 2.6 keV FWHM (Cu Ka)
Dynamic Range (keV, CdTe)	110	150
Count Rate (10% dead time loss) (Mphotons/mm2s)  Spectroscopic Mode with CSM	4.3	19
Number of thresholds in SM-CSM	4 SPMa + 4 CSM	1 SPMa + 7 CSM
Pixel counters in SRW, Fine Pitch Mode (bit depth)	2x [1, 2, 6, 12] or 1x [24]	2x [1, 2, 6, 12]
Pixel counters in SRW, Spectroscopic Mode (bit depth)	8x [1, 2, 6, 12] or 4x [24]	8x [1, 2, 6, 12]
Pixel counters in CRW, Fine Pitch Mode (bit depth)	1x [1, 2, 6, 12]	2x [1, 12]
Pixel counters in CRW, Spectroscopic Mode (bit depth)	4x [1, 2, 6, 12]	8x [1, 12]