Speaker
Description
Summary
The ATLAS Level-1 Calorimeter Trigger is a hardware-based pipelined
system designed to identify high-pT objects in the ATLAS
calorimeters within a fixed latency of 2.5us, including all
transmission delays. The real-time path in the trigger is subdivided
into three stages. The PreProcessor which conditions and digitizes
7200 pre-summed analogue signals from the calorimeters is followed by
two subsequent object-finding digital processor systems working in
parallel: the Jet/Energy-sum processor and the Cluster Processor. It
provides all the calorimeter based trigger information used by the
Central Trigger Processor to make the final Level-1 trigger decision.
The PreProcessor is a compact, highly modular system with the
majority of the processing performed on a dense Multi-Chip Module(MCM)
which handles four input channels and consists of nine unpackaged
dies: four FADCs, a time-adjustment ASIC with 1ns resolution,
a PreProcessor ASIC, and three LVDS serializers. The PreProcessor
ASIC is a complex pipelined digital processing element which converts
the digitized input signals into correctly time-aligned, calibrated
and noise-suppressed outputs and assigns the energy deposits to the
correct LHC bunch-crossing.
The basic MCM technology decisions have been taken a decade ago. At
that time it was not feasible to have standard, packaged and really
flexible components which would correspond to all requirements.
The pin-, size- and latency-compatible substitute for the MCM based
on today's components is being developed to profit from the exponential
growth of state-of-the-art electronics. Full compatibility with the
current module allows transparent replacement within the existing
concept of the PreProcessor mother- and daughter-cards as well as
mixed operation when old and new MCMs are used on the same board.
Two dual channel 105MHz FADCs AD9218 are used for compact, packaged,
fast, low noise, low power digitization. A Xilinx Spartan-6 FPGA serves
as a flexible, low-cost, configurable digital processing unit which
replaces not only the PreProcessor ASIC but the time-adjustment chip
and LVDS-serializers as well. A high degree of adaptability provided
by the FPGA could be used for an adaptation of the digital processing
algorithm if it will be required for a smooth operation after the LHC
upgrade for the high luminosity.
Standard components allow us to use commercially available evaluation
boards, together with the existing equipment for the current MCM
testing, for the FPGA configuration bitstream development and for
tests in parallel with the design of the PCB layout for the new module.
Results of the development and first tests are presented in this work.
