Study of a PANDA Barrel DIRC design based on radiator plates

Abstract

A Cherenkov detector based on the DIRC (Detection of Internally Reflected Cherenkov light) principle [1] will be used in the target spectrometer of the PANDA experiment to distinguish between charged pions and kaons for momenta between 0.5 and 3.5 GeV/c. It is centered around the target point, in the shape of a barrel to cover polar track angles between 22 and 140◦. The design of the PANDA Barrel DIRC is based on the BABAR DIRC [2] (the first successful DIRC counter) with some important improvements, such as fast photon timing, focusing optics, and a compact expansion volume [3]. In the PANDA Barrel DIRC baseline design the barrel of 47.6 cm radius comprises 16 sections with 5 fused silica radiator bars (1.7 cm×3.2 cm×240 cm) each. Cherenkov photons, produced along the charged particle track in the bar, are guided inside the radiator via total internal reflection. A mirror is attached to the forward end of the bar to reflect photons towards the read out end, where they are focused with a lens and projected onto a flat photo detector plane behind the 30 cm-deep oil-filled expansion volume. An array of Micro-Channel Plate Photomultiplier Tubes (MCP-PMTs) is used to detect the photons and measure their arrival time with a precision of about 100 ps.