Electron redistribution and coherent radiation of laser-sliced beam bunches in storage ring

Coherent radiation in the millimeter and sub millimeter wavelength regions can be generated using short electron beam bunches and laser-sliced beam bunches in a storage ring. Longitudinal dipped profiles produced by the laser slicing are rapidly smeared by the synchrotron motion and by the electron diffusion due to a random photon emission. In the present work, the characteristics of the diffusion are studied in detail but simply for practical applications. Diffusion effects are expressed as a point transfer probability function, with which the smearing of dipped profiles can be calculated straightforwardly. The emittance of diffusion gradually increases and finally reaches the natural emittance of the beam. Smeared profiles by the diffusion can be observed as a pulsed coherent radiation at the time of half multiples of synchrotron oscillation period, when there is almost no smearing by the synchrotron motion. Expected coherent radiation spectra due to the dipped profiles are given for the New SUBARU storage ring. (author)