X-ray detection and tomography with Depleted Monolithic Active Pixel Sensors

X-ray detection for industrial and medical applications mostly focuses on the 10 keV (soft x-rays) to 300 keV (hard x-rays) energy range, where the spectrum of commercial x-ray tubes lies within. At these energies, high-Z materials are used as sensors, in combination with different detector technologies, to perform x-ray imaging and tomography. While employing high-Z materials is the standard when to maximize quantum efficiency, there are many applications where a lower sensor intrinsic efficiency may be compensated by other figures of merit (e.g. larger area, lower price, faster speed, higher spatial resolution, etc...) of the chosen detector.In particular, while Monolithic Active Pixel Sensor (MAPS) are rarely used for x-ray imaging, especially above 10 keV of energy, they offer critical performance advantages in therms of area, resolution, speed and cost when compared to the almost universally adopted high-Z hybrid detectors (sensor coupled to a separate readout chip).This contribution shows how Depleted MAPS (D-MAPS) of several hundreds micron thickness, where an electric field makes the whole silicon volume capable of collecting the photo-generated charge, are indeed suitable for x-ray detection in the full industrial/medical energy range. Furthermore, while a single sensor cannot match the performance of established high-Z technology, it is shown how a stack of D-MAPS may reach detection efficiencies comparable to the state-of-the-art, offering at the same time higher spatial resolution, higher speed, and significantly lower cost per unit of instrumented area.To demonstrate the potentiality of the idea, x-ray measures on working D-MAPS prototypes are illustrated and discussed, as well as quantitative simulations of the 3D reconstruction capabilities such an approach may led to, with detailed comparison of different tissues (bone, muscle, water, etc..) discerning capabilities in tomography applications.