CALCULATED AND MEASURED PERFORMANCE OF AN X-RAY WIGGLER BEAMLINE AT DORIS-III

The new BW1 beamline at the DORIS III storage ring at HASYLAB in Hamburg was characterized using ray tracing and finite element analysis programs. The angular distribution of the beam, power densities at different locations and spectral distributions were calculated. The main aspect for the calculations was the thermal deformation of the optical elements, especially the distortion of the first monochromator crystal resulting from the high power emitted by the wiggler. In the present setup a 4 m long X-ray wiggler is used as the source, imposing a heat load of up to 2.5 kW on a directly cooled Si(111) crystal. The bending of this crystal was analyzed by means of X-ray diffractometry. The experimental results were in good agreement with theoretical calculations and reveal the basic characteristics of the directly cooled crystal. The present limitations of the design indicate ways for optimization which are clearly needed for the available high powers.