Shielding of infrared edge and synchrotron radiation

Long-wavelength edge and synchrotron radiation from an electron storage ring may be suppressed by nearby vacuum chamber walls. The suppression, known as shielding, occurs at wavelengths where the walls upstream of an observer reflect a large portion of the radiation within the near-field region. For a beamline whose vertical entrance aperture equals the vacuum chamber height, shielding is not expected at wavelengths where the radiation opening angle is smaller than that subtended by the entrance aperture.