Development of lightweight carbon-fiber mirrors for the RICH 1 detector of LHCb

The design, manufacture and characterization of lightweight carbon-fiber spherical converging mirrors for the RICH 1 Cherenkov detector of the LHCb experiment at CERN are described. The mirrors need to be lightweight to minimize the material for traversing particles and fluorocarbon-compatible to avoid degradation in the C4F10 gas radiator of RICH 1. Four large-sized carbon-fiber mirrors covering a total surface area of ∼ 2 m 2 were installed in RICH 1 in July 2007. The mirrors have a radius of curvature of ∼ 2700 mm , a high reflectivity of ∼ 90 % in the 200–600 nm wavelength band, a low areal density of ∼ 5 kg / m 2 equivalent to ∼ 1.2 % of a radiation length. Results of the radiation and fluorocarbon testing of the mirror prototypes are also reported.