Batch Measurement of Attenuation Length of Wavelength-shifting Fibers for LHAASO Electromagnetic Detectors

Over 700 km of wavelength-shifting fibers are being used in 5242 electromagnetic detectors (EDs) of the LHAASO project. It is important to monitor the attenuation length of the fibers among spools for quality control as well as the performance uniformity among detectors. An apparatus was built-up in the laboratory of IHEP for the purpose. Eight fibers with length of 5.4 m could be measured in one round of testing within 15 minutes with the current configuration and will be upgraded to 16 after a further upgrade. The measurement has a systematic uncertainty of less than 3% and meets the requirement of the application.