The GBT based readout concept for the Silicon Tracking System of the CBM experiment

The Silicon Tracking System (STS) of the CBM experiment at FAIR is designed to handle interaction rates up to 10 MHz with hundreds of tracks in fixed target heavy ion collisions of up to 35 AGeV.
STS data will be read out from 14000 STS-XYTER ASICs on 1800 frontend boards (FEBs) with a total of 1.8 million channels operating at rates from below 15 up to 1000 kHz and located in the STS detector box inside the CBM magnet with challenging conditions in terms of available space, radiation, magnetic field and temperature.
Up to 40 ASICs mounted on FEBs which are operated at varying sensor potential will be connected via AC-coupled 320 MHz SLVS uplinks to a readout board (ROB) employing radiation hard GBTX and Versatile Link components developed at CERN for data aggregation and optical readout.
The approximately 1000 ROBs will be located inside the STS detector box, 4000 optical links will be routed from there to the subsequent FPGA based CBM data processing board (DPB).
The concept of the GBT based STS readout including the FEB-ROB connection scheme for data readout and control as well as planned prototype systems using a common CBM prototype ROB will be presented.