Supercooling of bunched beams by coherent synchrotron radiation

Longitudinal and transverse dimensions of bunched beams may be cooled by coherent synchrotron radiation in storage rings. The cooling starts if the bunches are short enough. Coherent synchrotron radiation with wavelengths of the order of the length of the bunch will propagate in the vacuum chamber of the bending magnet. Achievement of such condition, linked to the bunch dimensions, is generally not possible if only the main RF system is used. Therefore it is necessary to add a tunable idle or powered extra RF cavity, whose frequency depends on the transverse dimensions of the vacuum chamber of the bending magnet and on the radius of the orbit curvature. By this mean, a self-consistent effect can be achieved. The energy transfer among particles of the same bunch leads to a dynamic reduction of all bunch dimensions. For these reasons the whole radiated spectrum becomes coherent. This should be true for all storage rings with particles which emit synchrotron radiation. Our experimental results observed on a e⁺/e^- storage ring are described