Diffractometer for high energy X-rays at the APS

The Basic Energy Sciences Synchrotron Radiation Center (BESSRC) has designed and built a diffractometer specialized for high energy synchrotron radiation (E>60 keV) at the Advanced Photon Source (APS). The diffractometer, which is installed at the elliptical multipole wiggler, uses linearly polarized light (U. Rütt et al., Proc. SPIE 3348 (1998) 132.). The instrument is a triple-axis diffractometer allowing high resolution measurement in two dimensions of the reciprocal space. As opposed to the other diffractometers for high photon energies at HASYLAB (Germany) and ESRF (France) (R. Bouchard et al., 5 (1998) 90; K.-D. Liss et al., J. Synchrotron Rad. 5 (1998) 82), this diffractometer utilizes the vertical scattering plane to take full advantage of the small vertical divergence of the beam and to allow horizontal focusing of the broad beam from the wiggler without disturbing the resolution of the instrument. The instrument is designed to carry heavy sample equipment up to a weight of 200 kg, while maintaining high resolution and low background. First tests have been done to check the overall performance, stability, background and resolution of the diffractometer.