  A prototype detector is being developed which combines the functions of a
Time Projection Chamber for charged particle tracking and a Cherenkov detector
for particle identification. The TPC consists of a 10x10x10 cm3 drift volume
where the charge is drifted to a 10x10 cm2 triple GEM detector. The charge is
measured on a readout plane consisting of 2x10 mm2 chevron pads which provide a
spatial resolution ~ 100 microns per point in the chevron direction along with
dE/dx information. The Cherenkov portion of the detector consists of a second
10x10 cm2 triple GEM with a photosensitive CsI photocathode on the top layer.
This detector measures Cherenkov light produced in the drift gas of the TPC by
high velocity particles which are above threshold. CF4 or CF4 mixtures will be
used as the drift gas which are highly transparent to UV light and can provide
excellent efficiency for detecting Cherenkov photons. The drift gas is also
used as the operating gas for both GEM detectors. The prototype detector has
been constructed and is currently being tested in the lab with sources and
cosmic rays, and additional tests are planned in the future to study the
detector in a test beam.
