In beam performances of the MIMOSIS-2.1 CMOS Monolithic Active Pixel Sensor

MIMOSIS is a CMOS Monolithic Active Pixel Sensor developed to equip the Micro Vertex Detector of the Compressed Baryonic Matter (CBM) experiment at FAIR/GSI. The sensor will combine an excellent spatial precision of $5\mu m$ with a time resolution of $5\mu s$ and provide a peak hit rate capability of $\sim 80\mathrm{M}\mathrm{H}\mathrm{z}\mathrm{/}\mathrm{c}{\mathrm{m}}^2$. To fulfill its task, MIMOSIS will have to withstand ionising radiation doses of $\sim 5\mathrm{M}\mathrm{R}\mathrm{a}\mathrm{d}$ and fluences of $\sim 7\times {10}^{13}{\mathrm{n}}_{\mathrm{e}\mathrm{q}}\mathrm{/}\mathrm{c}{\mathrm{m}}^2$ per year of operation. This paper introduces the reticle size full feature sensor prototype MIMOSIS-2.1, which was improved with respect to earlier prototypes by adding on-chip grouping circuts and by improving the analog power grid. Moreover, it features for a first time a $50\mu m$ epitaxial layer, which is found to improve the performances of the non-irradiated device significantly. We discuss the in beam sensor performances as measured during beam tests at the CERN-SPS.