Dear Linear Collider Colleagues,
  Those of you arriving at the Michigan Linear Collider Workshop early on 
Thursday are invited to attend a seminar given by Bob Wilson of
Colorado State on the BaBar Cerenkov Imaging system. The seminar
will be held at 4:00 Thursday March 25 in 335 West Hall (same building
the workshop will be held in). An abstract is appended below. Please let
me know if you have any questions.

						Keith Riles

                       The DIRC Particle ID System at BaBar
                                 Robert J. Wilson
                             Colorado State University

The BaBar experiment at the SLAC PEP-II B-factory will begin taking data in
May 1999. A unique feature of the experiment is the use of a DIRC (Detection
of Internally Reflected Cerenkov light)  for particle identification. This is
the first implementation of this novel Cerenkov ring-imaging  technique in a
full-scale experiment.

I will describe first the physics motivation for a DIRC and the basic
principles of the device. Next, I will show the implementation for the BaBar
experiment including results from a recent cosmic ray run just prior to
installation. Finally, I will present some ideas for future DIRCs  involving
the use of UV-sensitive Avalanche Photodiode pixel arrays to form a  compact,
magnetic field insensitive readout.