Negative Momentum Compaction at KEKB

KEKB is a high luminosity e+e- collider for studying B mesons and has achieved the design luminosity of 1034cm-2s-1 in 2003. In order to get higher luminosity, we tested negative momentum compaction optics in the summer of 2003. We measured the bunch length using three methods at 0.7mA to 1.17mA bunch current and confirmed the length was shortened with the negative momentum compaction optics.