The nuclear-resonance-scattering station at the PETRA II undulator beamline

PETRA II, a 12 GeV accelerator at DESY, Hamburg, is used to produce synchro tron radiation (SR) for experiments in the hard X-ray regime when it is not running as injector for HERA. The beam from an undulator is split by a dia mond crystal in Laue geometry to feed two experimental stations, one of whi ch is now dedicated for nuclear resonance experiments. The X-ray energy may be chosen in the range from 5 to 55 keV covering all isotopes already obse rved with SR and many interesting candidates for new resonances. Tuning may be performed by optimising the magnetic gap and the storage ring energy. I n particular, the opportunities for timing experiments are unique due to a very flexible filling mode of the storage ring. The flux at the sample posi tion is comparable to undulator beams at ESRF. The second beamline covers h igher energies up to some 300 keV and may also be used for nuclear resonanc e experiments.