The “Notch”
•The Booster uses multi-turn injection, resulting in a continuous beam around the ring. •If beam is passing through the extraction septum while it is ramping, some of it will be steered into beam elements. •This is the single largest source of radiation resulting from the booster. •Solution:  Early in the cycle, the old extraction kicker is pulsed, blowing a “notch” in the beam.  Extraction is timed to coincide with the notch. •Problem:  although it’s a factor of 20 better to lose the beam early in the cycle, it’s still not negligible (more in a minute)