Isochronism Studies at IUCF

A non-intercepting, charge sensitive, sampling beam phase probe, similar to the design developed for the 15 MeV injector cyclotron, was recently installed on the moveable south valley probe of the Indiana 200 MeV main stage cyclotron. The probe permits continuous measurement of beam phase from inflection to extraction radius at beam intensities as low as 200 nanoamperes. The measured phase histories obtained show that small deviations from the predictions of our field mapping data are required for isochronous acceleration. The characteristics of the phase probe and the results of the beam phase measurements are discussed.