TA-POS-2017-010

The PANDA experiment at the Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD.
A fast focusing DIRC (Detection of Internally Reflected Cherenkov light) counter will provide hadronic particle identification (PID) in the barrel region of the PANDA detector.
To meet the PID requirements, the Barrel DIRC has to provide precise measurements of the Cherenkov angle, which is conserved for Cherenkov photons propagating through the radiator by total internal reflection.
The radiators, rectangular quartz bars, have to fulfill strict optical and mechanical requirements.
This includes the squareness and parallelism of the sides of the bars, sharp corners, and a very smooth surface polish, ensuring that the Cherenkov photons reach the optical sensors without angular distortions.
Two possible radiator shapes are being considered for the final detector design: either a conservative design with narrow bars or a cost-saving option using a wide plate
An optical setup, consisting of a computer-controlled positioning and multi-wavelength laser system, is used to evaluate the radiators to obtain critical values like transmittance and reflectivity.
The Setup, measuring procedure and results from radiator bar- and plate measurements will be presented on this poster.
Work supported by HGS-HIRe.