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Description
Monolithic Active Pixel Sensors (MAPS) have demonstrated excellent performance in the field of high-energy physics, especially with improved timing performance with respect to standard CMOS imaging sensor. Their application to low-energy spectroscopy seems promising, however, requires dedicated sensor optimization in order to minimize the inactive entrance layer and enhance charge collection efficiency. This work presents the characterization of a Monolithic Imager sensor developed in a modified TowerJazz 0.18 µm CMOS imaging process and optimized for low-energy particle and photon detection.
The back side of the sensor was post-processed with ion implantation and laser annealing by IBS [1]. This treatment enables the formation of an ultra-thin entrance window, significantly improving sensitivity to low-energy particles.
Sensor characterization was performed using a low-noise readout system to study the noise and energy resolution. Measurements with the 55Fe source show a clear separation between characteristic lines and demonstrate the suitability of the sensor for spectroscopic applications. Additional measurements results obtained with a tritium source prove that the sensor can detect very low-energy beta particles.
The results confirm the effectiveness of the backside processing approach and highlight the potential of MAPS technology for applications requiring direct detection of low-energy radiation, including environmental monitoring, radioprotection, and scientific instrumentation.
[1] Laser activation of Ultra Shallow Junctions (USJ) doped by Plasma Immersion Ion Implantation (PIII), Applied Surface Science 255 (2009) 5647–5650