Speaker
Description
The Micro Vertex Detector (MVD) is the first downstream detector of the fixed-target CBM experiment at the future Facility for Antiproton and Ion Research (FAIR). It enables high-precision tracking of low-momentum particles in direct proximity of the target with the first station being placed only 8 cm downstream the interaction point. The four planar stations operate in the target vacuum and are equipped with∼ 300 MIMOSIS CMOS Monolithic Active Pixel Sensors (MAPS). Those are produced in TJ-180 nm process and feature a 1024 × 504 pixel matrix (26.88 × 30.24 µm2 pitch) with a global shutter (5 µs nominal frame time). The final MIMOSIS will be submitted by the end of the year after several successful prototype generations have been developed through a joint R&D effort by IPHC Strasbourg, Goethe University Frankfurt and GSI Darmstadt. A large variety of different designs have been tested, such as standard and modified pixel variants, two epitaxial options (25/50 µm), and AC/DC-coupled front-ends. The performance has been tested both in the laboratory and with minimum-ionizing particles during beam tests. Furthermore, comprehensive tests of radiation tolerance, robustness against heavy-ion impacts and response to inclined tracks have been performed. Beam tests show > 99% detection efficiency and a 5–6 µm spatial resolution, also after irradiation to 5 Mrad and 1 × 1014 neq/cm2 (TID+NIEL), fulfilling the requirements. For integration in the MVD, the sensors will be wire-bonded to thin flex cables and glued onto Thermal Pyrolytic Graphite (TPG; 380 µm) carriers, which provide stiff, low-X0 support with a high in-plane thermal conduction (∼1500 W/m.K) in the acceptance. Actively cooled Aluminum heat sinks outside the acceptance extract the heat. Sensors are integrated on both sides of carrier to achieve 100% fill factor. In this contribution, we present the detector concept, results from the prototype MIMOSIS sensors and its integration into the CBM Micro Vertex Detector. A focal point will be the challenges associated with the stringent material budget constraints (0.3–0.5% X0) and vacuum operation as we progress toward station assembly and readiness for first beam in 2028.
