Characterization of CharTPix-180A, a strip-shaped monolithic sensor for the STCF inner tracker

The Super Tau-Charm Facility (STCF) is a future high-luminosity electron-positron collider operating in the center-of-mass energy range of 2 to 7 GeV. The monolithic active pixel sensor (MAPS) is one of the options being considered for the STCF inner tracking detector. This application requires a MAPS capable of providing simultaneous position, time, and charge measurements under a constrained power budget of approximately 50 $\mathrm{m}\mathrm{W}\mathrm{/}\mathrm{c}{\mathrm{m}}^2$. To address these requirements, a baseline sensor concept featuring a strip-shaped pixel geometry has been proposed to balance power consumption and detection performance. The first prototypes of this concept, referred to as CharTPix-180A, have been developed to evaluate the proposed design. Two prototypes with different design focuses were characterized in this study. An analog readout prototype, CharTPix-180A-c4, was used to evaluate the intrinsic sensor behavior, while a fully functional digital readout prototype, CharTPix-180A-c3, was used to investigate the overall sensor functionality on a small scale. Electrical, radioactive-source, and beam tests were performed to characterize the prototypes. The measured detection efficiency exceeded 99%, the fake-hit rate was below ${10}^{-3}$ /pixel/s, and the spatial resolution was better than 10 $\mu \mathrm{m}$. A best time resolution of 37 ns was achieved, and the power consumption was about 50 $\mathrm{m}\mathrm{W}\mathrm{/}\mathrm{c}{\mathrm{m}}^2$. These results support the feasibility of the strip-shaped MAPS concept for the STCF inner tracker and provide guidance for further design optimization.