Other advantages of hybrid pixel imaging detectors are that they can achieve high frame rates with zero dead time because of the digital processing and parallel readout of the ASIC. The layout of the ASICs and readout boards allows a modular approach such that larger detector areas can be achieved.
From the effort of the Medipix collaboration ASI provides detectors based on three types of ASICs.
When the Medipix 3 chip was developed, it stood out by making dead time free operation and colour imaging possible by improving the energy resolution. The Medipix3RX ASIC operates in counting mode and has an increased frame rate, up to 1800 frames/s, and can operate in zero dead time (continuous read/write mode).
Besides speed, the Medipix3RX ASIC has improved spectral performance with respect to other imaging ASICs. Selection on the pulse threshold and spectral resolution can suffer from the charge spread problem. Depending on impact position, energy of the incoming particle and choice of the sensor material, the generated charge can arrive on multiple neighbouring pixels of the ASIC. When the threshold is on a fixed level events which have high charge spread can be lost. The Medipix3RX ASIC has a special inter pixel circuit that assigns the sum of the charge to the pixel with the highest charge. This is called the charge summing mode. The Medipix3RX also has an enhanced spectral configuration when bump bonding is done with 110 µm pitch instead of 55 µm. In this configuration and with charge summing mode activated, particles can be counted with four user settable thresholds. This allows simultaneous detection in multiple spectral ranges.
Medipix3RX is currently available for X-ray in our LynX 1800 detector systems.
The Timepix3 ASIC is the latest design of the Medipix collaboration and successor of Timepix. Compared to the latter, Timepix3 has a higher time resolution and reduced timewalk and has a timing accuracy of 1.6 ns. Besides frame read-out, it offers data driven or list mode read-out of pixels above the threshold. The most important improvement with respect to the original Timepix is the possibility of collecting Time-over-threshhold (ToA) and Time-of-Arrival (ToT) information simultaneously. This makes Timepix3 an excellent chip for tracking application.