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The BABAR experiment at the Stanford Linear Accelerator
Center is designed to perform a search for CP violation by ana-lyzing
the decays of a very large sample of B and B(Bar) mesons
produced at the high luminosity PEP-II accelerator. The
data acquisition system must cope with a sustained high event
rate, while supporting real time feature extraction and data
compression with minimal dead time.
The BABAR data acquisition system is based around a common
VME interface to the electronics read-out of the separate detec-tor
subsystems. Data from the front end electronics is read into
commercial VME processors via a custom "Personality Card"
and PCI interface. The commercial CPUs run the Tornado
operating system to provide a platform for detector subsystem
code to perform the necessary data processing. The data is read
out via a non-blocking network switch to a farm of commercial
UNIX processors.
The current implementation of the BABAR data acquisition sys-tem
has been shown to sustain a Level 1 trigger rate of 1.3 kHz
at an event size of 25 kbytes and with negligible deadtime.
Upgrades currently in development will permit the system to
support the design Level 1 rate of 2 kHz with negligible dead-time.
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