National Synchrotron Light Source Seminar

The longitudinal beam dynamics of high intensity beams is not well understood despite its importance to the success of such applications as free electron lasers and light sources, heavy ion inertial fusion, and high energy colliders. To address this issue, a series of experiments is carried out at University of Maryland for the space-charge dominated electron beams. Longitudinal modulations in particle densities are deliberately generated at the source, and their evolutions are tracked downstream using a number of diagnostics. With the aid of a high resolution energy analyzer, energy modulations converted from the initially generated density modulations are observed. The results show very good agreement with both one dimensional theory and simulations with a PIC code, Warp. Furthermore, using a high resolution gated ICCD camera coupled with very fast emitters such as prompt optical transition radiation (OTR) or fast Phosphor screens with 3-ns time resolution, time resolved images are achieved on the longitudinal modulations. These results, for the first time, reveal the effect of longitudinal modulations on the transverse beam modulations. These experiments represent significant progress towards understanding the longitudinal physics of intense beams.