The WLS fiber time properties study

The pulse shape properties of different wave-length shifting fibers have been measured. This study intents to help in the right choice of fibers in terms of their further application in the LHCb Hadron Calorimeter as zero-level trigger detector. The measurements have been clone both at the X7 test beamline of the CERN SPS and using ultra-violet NZ laser as a short light pulse source. Fibers under study have been attached to the standard polystyrene based scintillating tile used in HCAL Prototype. The fast photo-multiplier FEU-115M and digital recording oscilloscope were used. It was found that the fiber BCF-91A is rather slow (rd > 10ns) to be accepted for calorimetry in LHCb. The Fibers Y-11 and Pol.Hi.Tech. are found to be faster (Td N 7 ns), and could be used provided their signals are considerably clipped. The fiber BCF-92 shows best results (rd N 3 ns).