Application Brief: nVent/Schroff Develops 3U MicroTCA.4 Chassis for High-Energy Physics Experimentation

nVent / Schroff developed a unique MicroTCA.4 solution based on special requirements from the European Spallation Source (ESS) in Sweden.  ESS saw the standard 12 slot MicroTCA chassis platforms on the market that were defined for experiments at DESY and CERN but wanted a smaller package for a lower number of AMC and MicroRTM cards.  Other existing MicroTCA chassis that supported lower slot counts arranged the modules horizontally and used a side-to-side airflow path for cooling.  While efficient, this airflow path requires special cabinet arrangements to support management of the cold and hot air.  ESS wanted the advantages of the smaller chassis arrangement but with a front-to-back airflow pattern that would be compatible with their equipment cabinets.

Schroff engineering conceptualized a 3U MicroTCA.4 chassis with 6 AMC slots and 4 MicroRTM sots arranged horizontally that also accommodated the front-to-rear airflow need.  The concept was realized using an air plenum in the extra U of height where air intake is at the front.  An air baffle forces cold air to the side of the chassis where it moves across the modules and is ejected out the back of the chassis.  The advantages of this design saved cost and space while allowing standard equipment racks to be deployed.  This arrangement also allows for the 3U chassis to be deployed in the same equipment racks as the 12 slot solutions defined by DESY and CERN.

The specific application at ESS is for data acquisition at above 100 kHz as part of the beam instrumentation.  Currently the chassis is not used in low-level RF (LLRF) applications as it does not have an associated RF backplane.  The chassis is deployed in areas where only 6 AMC modules are needed.  400 deployments are expected between 2017 and 2019.

The Schroff solution accommodated front-to-rear airflow with cooling for up to 80W per slot.  The current solution uses a fan tray with two fans and one cooling unit manager (CU EMMC).  Expansion to three fans is available by also adding an additional CU EMC as the power requirements of the additional fan exceed the limit of one cooling unit.  Slots are available for 4 Double Mid-Size AMCs with associated MicroRTMs and one additional Double Mid-Size and one Double Full-Size AMC.  There are two Double Full-Size Power Module slots on the rear of the chassis.  The backplane supports 2x x16 links to AMC 1 and 2, optional x8 links to all six slots and there is an option for an integrated JSM module.

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