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 ∼1γ, where γ 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 ∼1γ, for which the photon flux is proportional to the square of the deflection angle. Intermediate deflection angles of ∼1γ 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 1γ, the long-wavelength radiation is a superposition from numerous sources, each producing a comparable photon flux with opening angle of ∼1γ.