Reappearance of Linac Bunch Structure on Booster Bunches during Capture and Acceleration

During adiabatic capture and initial 30 MHz beam bunching in the Fermilab Booster very high frequency structure is observed on the bunches. The structure has the appearance of a bunch shape oscillation instability which appears and disappears in a sporadic manner. A computer simulation of injection dynamics reveals the fact that the observed structure is related to re-appearance of the injected linac bunch structure after relocation within the booster phase space.