The BW1 x-ray undulator beamline at HASYLAB offers high intensity for a wide variety of diffraction and absorption experiments. The x-ray undulator is a 4-m-long device with 127 periods. At 4.5 GeV energy of the positron storage ring DORIS III it can be tuned in its 3rd harmonic to photon energies from 9 to 15 keV. The basis for such a beamline is a high precision monochromator which has to be able to cope with high heat loads from the insertion device. There are four operating modes: (i) focused white beam using two mirrors with a cutoff energy of approximately 11 keV, (ii) focused monochromatic beam using both mirrors with a cutoff energy of ≈12 keV and a double-crystal monochromator, (iii) unfocused monochromatic beam using the monochromator without mirrors, and (iv) focused monochromatic beam using the monochromator without mirrors but with a sagittally focusing second crystal. Currently, a horizontal diffractometer for the investigation of liquid surfaces, an ultrahigh vacuum chamber for standing wave measurements and a versatile x-ray multicircle diffractometer are installed in the experiment hutch. Typical scientific investigations performed at this beamline will be discussed to demonstrate the capabilities of the whole setup. © 1995 American Institute of Physics.
