Improvement of the time structure and reproducibility of the Bevalac spill

The time structure of the Bevalac beam spill has been measured for spills with and without feedback. A new filter across the magnet has reduced spill ripple near 170 Hz. Low frequency (∼ a few Hz) spill structure has been improved by removing the scintillator used for feedback from the vacuum chamber, detecting instead radiation generated by collisions of beam particles with a wire chamber. Pulse-to-pulse variation of the circulating beam intensity has been reduced, and continuous tunability of the intensity introduced, by using a new feedback system. This system reduces the rf bucket height to spill beam until the proper intensity is reached