Developments towards the Technical Design and Prototype Evaluation of the PANDA Endcap Disc DIRC
Monday, 24 April, 2017
The envisaged physics program of the PANDA (antiProton ANnihilation at Darmstadt) experiment at the future Facility for Antiproton and Ion Research (FAIR) requires excellent particle identification over the full solid angle. The Endcap Disc DIRC (EDD) will cover forward polar angles between 5 and 22◦ and is one of three dedicated subdetectors for the identification of charged hadrons and the separation of pions and kaons in particular. DIRC stands for Detection of Internally Reflected Cherenkov light and implies that the emitted Cherenkov photons are trapped inside the radiator by total internal reflection. The central part of each DIRC detector is its optical system which is responsible for a lowloss and angle-preserving transport of the Cherenkov photons. The work at hand experimentally addresses several objectives in connection with the optical components and the system as a whole. Radiator prototypes were evaluated with high precision and adapted specifications were identified based on the results. The imaging performance of the Focusing Elements (FELs) was verified and different options regarding the coupling of the individual components were evaluated. In addition a radiation hardness study of a new fused silica material provided an insight into the long term behavior of induced defects and confirmed the material to be suitable for high energy physics experiments. A conceptual design for the mechanical integration was developed featuring a rigid optical system which is mounted into a cross-like structure. In this context the spatial constrains for the holding structure and the FELs were identified and an assembly procedure was developed. The existing prototype was revised and newly developed concepts were integrated and tested. Furthermore a data analysis of an earlier prototype test at a mixed hadron beam at CERN was carried out. It was the first evaluation of an EDD prototype which consisted of optical components made of fused silica only and had highly segmented MCP-PMTs (Micro-Channel Plate PhotoMultiplier Tubes) for the photon detection. A single photon resolution down to 5.68 mrad could be achieved and a good agreement with Monte-Carlo predictions was reached. At 3 GeV/c a 5σ separation of pions and protons was accomplished using a single MCP-PMT column.