Performance of new Kuraray wavelength-shifting fibers with short decay time

We measure the decay time and the attenuation length of newly developed wavelength-shifting fibers, YS series from Kuraray, which have fast response. Using a 405 nm laser, the decay times of the YS-2, 4, and 6 are measured to be $3.64 \pm 0.04$ ns, $2.15 \pm 0.03$ ns, and $1.47 \pm 0.02$ ns, respectively, for the light injection distance of 10 cm. The decay time of Y-11 is measured to be $7.10 \pm 0.09$ ns using the same system. All fibers are found to have similar attenuation lengths of more than 4 meters. When combined with the plastic scintillators EJ-200 and EJ-204, the YS series have better time resolution than Y-11, with light yields of 60-100% of Y-11.