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We describe the construction and performance of a scintillating fiber detector used in the near detector for the K2K (KEK to Kamioka, KEK E362) long baseline neutrino oscillation experiment. The detector uses 3.7 m long and 0.692 mm diameter scintillating fiber coupled to image-intensifier tubes (IIT), and a CCD camera readout system. Fiber sheet production and detector construction began in 1997, and the detector was commissioned in March, 1999. Results from the first K2K runs confirm good initial performance : position resolution is estimated to be about 0.8 mm, and track finding efficiency is 98 ± 2 % for long tracks (i.e., those which intersect more than 5 fiber planes). The hit efficiency was estimated to be 92 ± 2 % using cosmic-ray muons, after noise reduction at the offline stage. The possibility of using the detector for particle identification is also discussed.

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We describe the results of a comparison of reference standards between three National Metrology Institutes: the National Institute of Standards and Technology (NIST, USA), the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology (NMIJ/AIST, Japan), and the Federal Office of Metrology (METAS, Switzerland). Open-beam- (free field) and optical-fiber-based measurements at wavelengths of 1302 and 1546 nm are reported. Three laboratories' reference standards are compared by means of two temperature-controlled, optical trap detectors. Measurement results show the largest differences of less than 4.2 parts in 10(3), which is within the expanded (k=2) uncertainty for the laboratories' reference standards.

The APMP.PR-S4 comparison of fiber optic power responsivity and nonlinearity at 1550 nm, from 1 mW to 250 mW, was carried out. In total three institutes participated: NMIJ (Japan), PTB (Germany) and NPL (United Kingdom). The measurements started in December 2008 and ended in December 2009.For fiber optic power responsivity, all participants reported their results and all results were used for the intercomparison: no measurement was subject to rejection. For nonlinearity two participants reported their results, therefore only a bilateral comparison was performed.The analysis method was carried out according to the Guidelines for CCPR Comparison Report Preparation and has been accepted by all participants. The reference value of fiber optic power responsivity was calculated using all participants' results. For fiber optic power from 10 mW to 250 mW all participants had unilateral DoE values consistent with their uncertainties at the k = 2 level. For fiber optic power of 1 mW all participants achieved consistency at the k = 3 level. For nonlinearity, the consistency of the measurements at both NMIJ and PTB was achieved with uncertainty at the k = 2 level.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).