Multibunch Phase Detection in DESY III

To detect individual bunch phase oscillations a standard toroidal intensity monitor with about 30 MHz bandwidth is used. The bunch selection is done with track & hold devices. At DESY III the revolution frequency changes by a factor of 3 due to the momentum change. To manage t,his variation, the beam signals are converted up to a fixed intermediate frequency of 60 MHz. Crystal filters for noise suppression are used to optimize resolution for longitudinal dipole oscillations. Quadrature detectors in conjunction with low pass filtering deliver analog phase signals from each of t,he 11 bunches.