A bypass for synchrotron radiation experiments at the storage ring PETRA II

The electron-positron collider PETRA, which is being reconstructed into a 1 4-GeV electron-proton booster for HERA (Hadron Electron Ring Accelerator), would be an excellent source for next-generation synchrotron radiation experiments. Insertion devices in such a high-energy storage ring would have unique properties in the photon energy range from 20 to 50 keV and open the possibility for experiments above 100 keV. However, all plants have to take into account that PETRA II has primarily to be used as a booster. A bypass at PETRA II seems to be the way to use the ring as a synchrotron radiation source without reducing the qualities of its booster functions. Results of first considerations, which lead to a bypass with two undulator beamlines, are presented.<>