The CBM Micro-Vertex Detector: Toward production readiness with MIMOSIS MAPS

Le résumé fourni par la source

The Compressed Baryonic Matter (CBM) Experiment at FAIR aims to investigate strongly interacting matter in a regime of high net-baryon density and moderate temperature using a fixed-target setup. Its Micro Vertex Detector (MVD) employs CMOS Monolithic Active Pixel Sensor (MAPS), called MIMOSIS, to achieve high-precision tracking and vertex reconstruction close to the interaction point. MAPS offer high spatial resolution, a minimal material budget, and tolerance against radiation, which makes them well-suited candidates for vertexing and tracking in the harsh CBM environment. MIMOSIS features 1024 × 504 pixels with a frame time of 5 μ s and a spatial precision of about 5–6 μ m. The sensors are required to withstand a total ionizing dose (TID) of about 5 MRad and Non-Ionizing Energy Loss (NIEL) equivalent fluences of approximately 7 × 1 0 13 n eq /cm 2 per year of CBM operation. Various prototypes have been developed through a joint R&D effort by IPHC Strasbourg, Goethe University Frankfurt and GSI Darmstadt. This contribution presents the MVD detector concept and results from radiation-tolerance measurements performed on MIMOSIS sensors. We demonstrate that AC-coupled p-stop pixel variant sustains efficiency above 99% and spatial precision of 5–6 μ m up to the combined target dose of CBM (10 14 n eq /cm 2 + 5 MRad), with the 50 μ m-thick epitaxial variant offering a wider operational threshold margin. As the 50- μ m epitaxial is not a production-standard wafer option, the 25 μ m-thick epitaxial p-stop variant is being considered for the pre-production of the MVD, which equally meets the CBM requirement.

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