Results From a Prototype Combination TPC Cherenkov Detector With GEM Readout

A combined time projection chamber-Cherenkov (TPCC) prototype detector has been developed as part of the detector research and development program for a future electron-ion collider (EIC). The prototype was tested at the Fermilab test beam facility (FTBF) to provide a proof of the principle to demonstrate the ability to measure particle tracks and provide particle identification (PID) information within a common detector volume. The time projection chamber (TPC) portion consists of a 10 x 10 x 10 cm(3) field cage, which delivers charge from tracks to a quadruple gas electron multiplier (GEM) with zigzag-shaped charge collection anodes. The Cherenkov portion consists of a photosensitive quadruple GEM detector with a CsI photocathode. As tracks pass through 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. 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 N-0. Results from the beam test, including the position resolution as well as the particle id capabilities of the detector, are discussed in this paper.