A comparison of an elliptical multipole wiggler and crystal optics for the production of circularly polarized x rays

We have compared the circularly polarized x‐ray flux obtained from an elliptical multipole wiggler to that obtained from a planar undulator combined with phase retarding crystal optics. This comparison is carried out for low (3.5–13 keV) and high (50–100 keV) x‐ray energies. For both these energy regimes, we demonstrate that phase retarding crystal optics are not only a viable alternative to specialized insertion devices but in some cases provide a superior source of circularly polarized x rays.