Nonlinear longitudinal dynamics studies at the ALS

We present an account of our efforts to understand unexpected observations in the course of performing measurements of the longitudinal beam transfer function. As the amplitude of excitation was increased, we observed a notch in the middle of the peak amplitude response of the transfer function. Our observations are explained by a bifurcation in the amplitude due to the nonlinearity of the oscillations, demonstrated by measurements of the longitudinal bunch profile using a streak camera.