Long-wavelength radiation along a straight-section axis in an electron storage ring

The long-wavelength radiation emitted along a straight-section axis of an electron storage ring is considered. A bending magnet at the beginning or end of a straight section produces cylindrically-symmetric ''edge'' radiation with radial polarization, collimated in a cone with opening angle of similar to 1/gamma, where gamma is the relativistic mass factor. A small deflection from a steering magnet or misaligned quadrupole results in ''kicker'' radiation, also collimated with an opening angle of similar to 1/gamma, for which the photon flux is proportional to the square of the deflection angle. Intermediate deflection angles of similar to 1/gamma produce a photon flux comparable to edge radiation. Downstream of a typical straight section which includes entrance and exit bending magnet edges, wiggler or undulator, and miscellaneous steering kicks comparable to 1/gamma, the long-wavelength radiation is a superposition from numerous sources, each producing a comparable photon flux with opening angle of similar to 1/gamma.