Longitudinal Behavior of the Beam in KEK Booster

The measurements of the longitudinal beam properties and high intensity effects of the KEK booster are presented. The capture efficiency has been improved by using two kinds of cure for beam loading instabilities appeared just after injection. Operation of the second RF station in cooperation with the existing one reduces the beam loss during acceleration. Severe longitudinal beam instabilities observed at the end of acceleration have been cured by incorporating a 2fs feedback loop.