标题： K2K的GPS时间同步系统 显示英文标题

标题： GPS Time Synchronization System for K2K

摘要： K2K（KEK E362）长基线中微子振荡实验需要在近探测器和远探测器地点（分别是KEK和超级神冈探测器）实现约100纳秒精度的时钟同步，这两个地点相距250公里。 全球定位系统（GPS）提供了一种以极低成本满足这一要求的方法。 除了低分辨率的时间数据（年份中的天数、小时、分钟、秒），商用GPS接收器还会输出一个每秒1脉冲（1PPS）信号，其上升沿与GPS秒的滚动同步，精度在所需范围内。 对于KEK的束流触发以及超级神冈探测器的事件触发，每个地点的50 MHz自由运行本地时间时钟（LTC）模块提供具有20纳秒刻度的分数秒数据。 在每个地点，两个GPS时钟并行运行，提供硬件备份以及数据质量检查。 显示英文摘要

摘要： The K2K (KEK E362) long-baseline neutrino oscillations experiment requires synchronization of clocks with ~100 nsec accuracy at the near and far detector sites (KEK and Super-Kamiokande, respectively), which are separated by 250 km. The Global Positioning System (GPS) provides a means for satisfying this requirement at very low cost. In addition to low-resolution time data (day of year, hour, minute, second), commercial GPS receivers output a 1 pulse per sec (1PPS) signal whose leading edge is synchronized with GPS seconds rollovers to well within the required accuracy. For each beam spill trigger at KEK, and each event trigger at Super-Kamiokande, 50 MHz free-running Local Time Clock (LTC) modules at each site provide fractional-second data with 20 nsec ticks. At each site, two GPS clocks run in parallel, providing hardware backup as well as data quality checks.