Overview of the PHENIX On-line Computing System

Paper: 464
Session: B (talk)
Speaker: Desmond, Edmond, Brookhaven National Laboratory, Upton
Keywords: C++, CASE, control systems, CORBA, data acquisition systems

Overview of the PHENIX On-line Computing System

Ed Desmond, John Haggerty
Hyon-Joo Kehayias, Martin L. Purschke, Chris Witzig

Physics Department, Brookhaven National Laboratory, Upton, NY, 11973

Thomas Kozlowski
Physics Division, Los Alamos National Laboratory, Los Alamos, NM 87545

PHENIX Collaboration

PHENIX is one of the two large experiments at the
Relativistic Heavy Ion Collider (RHIC) currently
under construction at Brookhaven National
Laboratory. The detector consists of 11 subdetectors,
that are further subdivided into 29 units ("granules'')
that can be operated independently, which includes
simultaneous data taking with independent data streams
and independent triggers.

The detector has 250,000 channels and is read out
by front end modules, where the data
is buffered in a pipeline while awaiting the level1
trigger decision. Zero suppression and calibration
is done after the level1 accept in custom built
data collection modules (DCMs) with DSPs before
the data is sent to an event builder (design
throughput of 2 Gb/sec) and higher level

The On-line Computing Systems Group (ONCS) has
two responsibilites. Firstly it is responsible
for receiving the data from the event builder,
routing it through a network of workstations to
consumer processes and archiving it at a
data rate of 20 MB/sec.
Secondly it is also responsible for the overall
configuration, control and operation of the detector and
data acquisition chain, which comprises the software
integration for several thousand custom built hardware
modules. The software must furthermore
support the independent operation of the above mentioned
granules, which includes the coordination of processes
that run in 60-100 VME processors and workstations.

ONCS has adapted the Shlaer-Mellor Object Oriented
Methodology for the design of the top layer software.
CORBA is used as communication layer
between the distributed objects, which are implemented as
asynchronous finite state machines.

We will give an overview of the PHENIX online system
with the main focus on the system architecture, software
components and integration tasks of the On-line Computing
group ONCS and report on the status of the current prototypes.