This proposal aims at validating a novel readout concept for the front-end of 2D pixelated detectors that is under development by the ESRF and the University of Heidelberg under the name of digital integration. This new concept combines features of both photon-counting and charge-integrating techniques. It is particularly suitable for X-ray detectors that need to operate with very high photon fluxes, under strong pileup conditions, and have to provide high sensitivity with noise-free effective operation. A very important additional feature of the digital integrating approach is the possibility of implementing signal processing operations at the detector front-end.
The digital integration concept consists in dividing the total exposure interval for an image acquisition into very short, sub-microsecond, time slices for which the integrated signals are digitised by fast in-pixel ADCs of moderate resolution. The sub-samples thus obtained are then further accumulated, manipulated and stored in the digital domain directly in the very front-end of the detector. This scheme allows the extension of the dynamic range, the rejection of noise and leakage current contributions and the implementation of advanced functionalities at the detector front-end, making these devices much more versatile than conventional charge-integrating detectors. The detectors built based on this new concept should also be able to operate efficiently with both pulsed beams and under continuous illumination conditions with 100% duty cycle.
Although the main targets of this project are synchrotron radiation applications at diffraction-limited X-ray sources, such as the new generation of high energy storage rings, the same signal processing scheme can be applied to other domains that present requirements similar to those mentioned above. The proposed concept has already been partially validated by preliminary computer simulations and work is ongoing to prove experimentally the full concept and find suitable technical solutions for practical implementation in a real detector. Given the level of advancement, it is expected within the DINPAD project to produce and characterise a small-scale detector prototype that can serve as a full demonstrator of the concept and a step towards a fullscale detector system.