National Synchrotron Light Source Symposium

A unified analysis for Superradiant emission from bunched electron beams in various kinds of radiation scheme is presented. Radiation schemes that can be described by the formulation include Pre-bunched FEL (PB-FEL), Coherent Synchrotron Radiation (CSR), Smith-Purcell Radiation, Cerenkov-Radiation, Transition-Radiation and more. The theory is based on mode excitation formulation – either discrete or continuous. The discrete mode formulation permits simple evaluation of the spatially coherent power and spectral power of the source. These figures of merit of the radiation source are useful for characterizing and comparing the performance of different radiation schemes. When the bunched electron beam emits superradiantly, these parameters scale like the square of the number of electrons, orders of magnitude more than spontaneous emission. The formulation applies to emission from single electron bunches, periodically bunched beams, or emission from a finite number of bunches in a macro-pulse.
The formulation was employed to calculate a new kind of coherent radiation from electron beam: enhanced superradiant Electron Spin Resonance Emission from a polarized electron beam. Estimates of the characteristics and possible measurement of this effect will be presented. Analysis of the related problem of modulating the polarization state of a polarized spin beam by an electromagnetic wave will also be presented.