We describe the design and performance of a large-area scintillator hodoscope onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3 m^{2}sr. The hodoscope is configured such that 10 and 12 counters are respectively situated in upper and lower layers. Each counter is viewed from its ends by 2.5 inch fine-mesh photomultiplier tubes placed in a stray magnetic field of 0.2 Tesla. Various beam-test data are presented. Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for each layer, giving an overall time-of-flight resolution of 70 ps rms using a pure Gaussian resolution function. Comparison with previous measurements on a similar scintillator hodoscope indicates good agreement with the scaling law that timing resolution is proportional to 1/Npe, where Npe is the effective number of photoelectrons.
@article{arxiv.hep-ex/0002047,
title = {Large-Area Scintillator Hodoscope with 50 ps Timing Resolution Onboard BESS},
author = {Y. Shikaze and S. Orito and T. Mitsui and K. Yoshimura and H. Matsumoto and H. Matsunaga and M. Nozaki and T. Sonoda and I. Ueda and T. Yoshida},
journal= {arXiv preprint arXiv:hep-ex/0002047},
year = {2009}
}