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Presenter: Sergei Nagaitsev
Title: Noise in Intense Electron Bunches
Abstract: Noise and density fluctuations in relativistic electron beams are of critical importance to various Coherent Electron Cooling (CEC) concepts as well as to free-electron lasers (FELs). For CEC, the beam noise leads to diffusion processes that counteract cooling, and if this noise is not controlled at a minimal level, the noise-induced heating can overcome cooling. In conventional stochastic cooling in circular accelerators, the beam noise has been studied in great detail in the GHz range of frequencies. Recently proposed concepts of Coherent Electron Cooling, such as micro-bunched cooling (MBEC), plasma cascade (PCA) and optical stochastic cooling (OSC), shift the range of operational frequencies by several orders higher, to 10s of THz. Not much is known about the beam noise in this range of frequencies. The standard beam diagnostics do not respond to such small-scale density perturbations in the beam, so they remain invisible unless there is a dedicated diagnostic for microbunching in the beam line. UChicago, Fermilab, and SLAC will collaborate to carry out a systematic theoretical and experimental study of electron beam noise at micrometer wavelengths at the Fermilab FAST facility. This research could allow to characterize the noise properties of the beam for various experimental conditions and to give recommendations to the designers of coherent electron cooling systems for next generation hadron accelerators. Results of this study could also find application in a generation of low-noise beams for free electron lasers.