Prototyping the WASA DIRC

The WASA-at-COSY experiment at the Forschungszentrum Jlich provides a nearly 4? detector including a forward spectrometer especially for studies on ? and ?' meson decays in proton-proton collisions. Simulations have shown that an additional detector of internally reflected Cherenkov light in front of the Forward Range Hodoscope improves the particle identification and energy resolution significantly. As a first prototype test has shown the feasibility, a large scale prototype is under construction. The concept and status of the enhanced prototype, optical performance studies and main characteristics of the used photomultiplier tubes and imaging properties of the PMMA optics are described.