Two-beam interference of long wavelength synchrotron radiation

The synchrotron radiation emitted from the NSLS VUV ring is found to contain significant spectral structure at long wavelengths (/spl lambda/ > 0.5mm), suggesting multiple beam interference effects. A predominant pattern occurs as a result of direct radiation interfering with radiation reflected from the curved outer wall of the electron beam dipole chambers. This structure appears for both normal incoherent synchrotron radiation emission and coherent emission, the latter resulting from an instability-driven density modulation within the electron bunch.