The variation in the power radiated by electrons in a circular orbit through an aperture was investigated numerically as a function of the distance along a tangent to the orbital ring. For electron energies above 0.1 GeV, the power radiated into a rectangular aperture, placed at a distance greater than the radius of curvature of the orbit, does not differ by more than 4 parts in 10<sup>6</sup> from the power radiated into a similarly sized rectangular aperture (subtending the same solid angle) placed at a large distance from the orbital ring. Our conclusion is that, within the limits considered, synchrotron radiation can be calculated accurately for practical radiometric calibrations.
© 1982 Optical Society of America
J. S. Risley, W. B. Westerveld, and J. R. Peace, "Synchrotron radiation at close distances to the orbital ring," J. Opt. Soc. Am. 72, 943-946 (1982)