Design considerations for a fast modulator in a 'crossed undulator'

The modulator, a short electromagnetic wiggler, can be used to generate a phase shift between the synchrotron radiation of the two undulators in a crossed undulator. The switching frequency between two polarization states can be as high as 10 Hz. A discussion is presented of some physical requirements for the modulator and a conceptual design of the magnet for a crossed undulator at the Aladdin storage rings (Synchrotron Radiation Center, University of Wisconsin, Madison) as a prototype development for the Advanced Light Source (ALS) and the Advanced Photon Source (APS).<<ETX>>