Prototype tests with the 3D Barrel DIRC of PANDA

The prototype tests of the Barrel DIRC counter, under development for the future PANDA experiment at FAIR, aim at the improvement of the original design, applied successfully by BABAR. Subjects of the R and D for this 3D Cherenkov counter include the focusing system and fast photon timing as well as the width of the radiators and the shape of the expansion volume. A modular prototype was built which allows an easy exchange of all key components under investigation. Prototype radiators from several optical companies, were tested in hadronic particle beams at CERN and at GSI. Data were recorded with narrow bars as well as with wide plates, coupled via an optional focusing lens system to a large solid fused silica prism, used as expansion volume. We present a study of the performance of the prototype in several configurations with a focus on the single photon Cherenkov angle resolution and photon yield.