Mirroring of fibre ends for the LHCb SciFi project

The relatively low light yields for tracks close to the midplane (y=0) of the SciFi tracker, in particular after radiation damage due to ionizing radiation, suggests to mirror the fibre ends. This note describes a set of tests and measurements in order to establish a viable mirror technology which combines high reflectivity with simplicity and low cost. The following technologies were evaluated: Aluminized Mylar film glued to the fibre ends, 3M Enhanced Specular Reflectance film glued to the fibre ends, Thin Film Aluminium vacuum coated on the fibre ends. The tests show that Aluminized Mylar film is a viable solution fulfilling all SciFi requirements. ESR film leads potentially to a higher reflectivity but its usability when glued to fibre ends could not (yet) be demonstrated. The Thin Film Aluminium coating disqualifies for reasons of cost and complexity without any performance gain. This report is meant as backup document for the LHCb SciFi TDR document to be submitted in February 2014.