Characterization of cutting-edge CMOS active pixel sensors within the CYGNO experiment

Abstract Time Projection Chambers equipped with Gas Electron Multipliers and optical readout by scientific CMOS cameras are a promising technology for low-energy particle detection, as demonstrated by the CYGNO experiment. To help identify an optimal detector configuration, we performed a characterization of two state-of-the-art CMOS sensors focusing on dark signal behavior across different exposure times and on detection sensitivity, assessed using the X-ray emissions from a 55Fe radioactive source, reproducing the low-light conditions expected in the experiment. CYGNO currently employs a low-noise ORCA-Fusion sensor produced by Hamamatsu for validation of its detection system. However, Hamamatsu has introduced two new sensors that could be of interest for future upgrades. The first is an upgraded model of the current sensor, the ORCA-Fusion-BT, featuring a back-illuminated design that reaches a quantum efficiency of up to 95% at 550 nm. The second is a next-generation sensor referred to as the ORCA-Quest. While its peak quantum efficiency is not as high as that of the ORCA-Fusion-BT, it offers high sensitivity across a broader spectral range, extending into the ultraviolet region, and delivers ultra-low readout noise of 0.27 electrons, about 2.6 times lower than that of the Fusion family. These sensors therefore represent an opportunity to enhance the performance of experiments, including those conducted by the CYGNO collaboration. This document presents a characterization of these sensors to evaluate their relevance in photon-limited environments and their suitability for integration into the CYGNO detector system.