The HCAL optics radiation damage study

The radiation damage of the optical components of the LHCb Hadron Calorimeter have been studied. The scintillating tiles and fibers were irradiated in the vicinity of the internal target station of the Serpukhov 70 GeV proton accelerator. The irradiation has been done with a wide energy range and a natural mixture of the charged particles with gammas and neutrons. Several set-ups have been assembled for this study. The X-Y coordinate beta-source scanner operated by a PC computer have been developed for precise tile response measurements. Moving along the fiber a blue LED has been used for attenuation length studies. The modified SF-46 spectra- photometer was used to measure fiber emission spectra. A typical degradation of 20% in light yield have been seen in scintillating tile up to dose of N0.5 Mrad. This increases to 50% for 1.5 Mrad. The tile response non-uniformity has been measured. The fibers of type Yll(S200) and Pot. Hi.Téch.(S250) have almost the same behaviour but BCF-92 show stronger degradation in attenuation length after irradiation. The measurement of the emitting light spectra for BCF-92 fibers shows that most of transparency losses are concentrated below 550 nm of the wave length range.