Current status of the End-of-Substructure (EoS) card project for the ATLAS Strip Tracker Upgrade using final ASICs

The silicon tracker of the ATLAS experiment will be upgraded for the upcoming High-Luminosity Upgrade of the LHC (HL-LHC). The main building blocks of the new strip tracker are modules that consist of silicon sensors and hybrid PCBs hosting the read-out ASICs. The modules are mounted on rigid carbon-fibre substructures, that provide common services to all the modules. At the end of each substructure, a so-called End-of-Substructure (EoS) card facilitates the transfer of data, power, high voltage and control signals between the modules and the off-detector systems. The module front-end electronics transfer data to the EoS card on 640Mbit/s differential lines. The EoS connects up to 28 data lines to one or two lpGBT chips that provide data serialisation and uses a 10GBit/s versatile optical link (VTRx+) to transmit signals to the off-detector systems. The lpGBT also recovers the LHC clock on the down-link and generates clock and control signals for the modules. To meet the tight integration requirements in the detector, several different EoS card designs are needed. Production-ready EoS card’s electronic design integrating final lpGBTv1 and VTRx+ ASICs from CERN are described, as well as results from recent quality assurance tests including detailed characterisation of the opto-electronics system by its bit error rate, jitter, and eye diagram representation. Since each EoS sits at a single-point-of-failure for an entire side of a substructure, a dedicated quality control (QC) procedure for the production has been developed.