Last update:
Apr 1, 2000
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Richard Claus1,
Rowan Hamilton2,
Michael Huffer1,
Steffen Luitz1,
Christopher O'Grady1,
James Russell1,
Iain Scott3
- Stanford Linear Accelerator Center
- University of Iowa
- Royal Holloway and Bedford New College
Presented by:
Claus Richard
At the time of this conference, the BaBar CP violation experiment, located
in an interaction region of the PEP-II Collider at the Stanford Linear
Accelerator Center, will have commissioned a new portion of its two-tiered
hierarchical event builder. The event builder used in production running
thus far has used the TCP/IP network stack included with Wind River System's
VxWorks and Sun's Solaris for both tiers in its event building hierarchy.
Event fragments are transmitted from up to 32 fragment sources to up to 32
event processors using a datagram service based on IP and UDP. Backpressure
is asserted by means of acknowledgments transmitted using IP multicast
services to all fragment sources. This builder saturates at an L1 accept
rate of around 1.3 kHz with 35 kB event sizes. To accommodate an expected
2 kHz event rate at the design luminosity, the intra-crate layer of the
event builder makes use of custom code to exploit the VME abilities of the
Motorola MVME2306 single board computers used in the data acquisition system.
Preliminary results indicate that the new builder will comfortably achieve
the requirements. In this paper, the two methods of event building are
compared and contrasted. The architecture (based on OO methodology and
implemented in C++) and performance measurements are presented along with
traps and pitfalls encountered during the course of development.
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