  A combination Time Projection Chamber-Cherenkov prototype detector has been
developed as part of the Detector R&D Program for a future Electron Ion
Collider. The prototype was tested at the Fermilab test beam facility to
provide a proof of principle to demonstrate that the detector is able to
measure particle tracks and provide particle identification information within
a common detector volume. The TPC portion consists of a 10x10x10cm3 field cage,
which delivers charge from tracks to a 10x10cm2 quadruple GEM readout. Tracks
are reconstructed by interpolating the hit position of clusters on an array of
2x10mm2 zigzag pads The Cherenkov component consists of a 10x10cm2 readout
plane segmented into 3x3 square pads, also coupled to a quadruple GEM. As
tracks pass though the drift volume of the TPC, the generated Cherenkov light
is able to escape through sparsely arranged wires making up one side of the
field cage, facing the CsI photocathode of the Cherenkov detector. The
Cherenkov detector is thus operated in a windowless, proximity focused
configuration for high efficiency. Pure CF4 is used as the working gas for both
detector components, mainly due to its transparency into the deep UV, as well
as its high N0. Results from the beam test, as well as results on its particle
id capabilities will be discussed.
