The CLEO III Data Acquisition System

Paper: 153
Session: B (talk)
Speaker: Honscheid, Klaus, Ohio State University, Columbus
Keywords: CORBA, data acquisition systems, special architectures, event building

The CLEO III Data Acquisition System

K. Honscheid, C. Gwon, J. Lorenc, R. Wanke, A. Wolf
Ohio State University
174 W 18th Avenue
Columbus, Ohio 43210}

E. Lipeles, A. Shapiro, A. Weinstein, F. Würthwein
California Institute of Technology
A. Bean, D. Coppage, C. Darling, B. Forrest, T. Noor
University of Kansas

C. Strohman
Cornell University

V. Fadeyev, J. Staeck, I Volobouev
Southern Methodist University

CLEO Collaboration

CLEO Collaboration is involved in an ongoing study of the properties of
the heavy b and c quarks and of the tau lepton
using a precision detector situated in the CESR e+e- collider.
These studies are at the forefront of high energy physics and
provide stringent tests of the Standard Model
as well as the physics that lies beyond.
These precision measurements require
yet higher luminosity from CESR and an upgraded detector.
The approved upgrade project known as Phase III has a goal of
reaching luminosities >= 2 * 10^33 cm^-2s^-1
beyond 1998.
The increased luminosity and the new detector elements require a
state-of-the-art data acquisition system (DAQ)
designed to run at up to 1000 Hz with negligible deadtime,
and a system to configure and monitor the data taking components (slow

The design of the CLEO III data acquisition system is guided by the need
to reduce costs and complexity of both hardware and software, while
achieving the required performance.
This is accomplished by implementing
an integrated plan based as much as possible on commercially available
components and by making use of standards wherever possible.
We invested particular efforts to make the CLEO III data acquisition
system uniform and homogeneous: A standard VME-slave interface providing
the first implementation of the newly defined MCST and CBLT operations
(VME-P) will be used by all VME data-boards.
Using a CLEO designed Fastbus controller, we ensure that
Fastbus and VME based systems can use identical read-out and control
software, significantly cutting software development time.
A software layer based on the
CORBA standard and common to all processors -- VME, Fastbus,
Unix and NT workstations -- allows
the system to be designed and
to operate independent of the underlying hardware structure.
In close collaboration with Visigenic Corp. we achieved the first
implementation of the CORBA 2.0 standard under a real-time operating

Dataflow follows a traditional, hierarchical approach. Implemented using
state-of-the-art components this provides the most cost effective solution.
Front-end data are digitized in parallel and
buffered locally on each data-board for later asynchronous readout by the
data acquisition system. Data sparsification is performed directly on the
data-boards. A dedicated module in each front-end
crate, assures transfer times below 500 microseconds and provides a second
buffer level. Both Fastbus and VME are supported at this
level. Approximately 35 front-end crates are needed for the CLEO III
detector. Using optical or copper
data links running Fast Ethernet
the data will be transmitted from the
front-end crates to the Event-Builder unit where complete events are assembled.
The CLEO III Event-Builder is a modular design based on the PCI bus. It
is followed by a final trigger stage implemented
in software on a fast workstation.
The accepted triggers will then be transferred to mass storage.

We will present the status of the CLEO III data acquisition project and
provide details the unique and more interesting aspects of our design.