WIDE-BANDPASS "MULTILAYER" MONOCHROMATOR FOR SMALL ANGLE X-RAY SCATTERING AND FIBER DIFFRACTION STUDIES ON BIOLOGICAL SYSTEMS. H. Tsuruta, T.C. Irving^#, H.W. Tompkins, Z.U. Rek, S. Brennan, K.O. Hodgson. SSRL/SLAC, Stanford University; BioCAT, Illinois Institute of Technology^#.

We have utilized a "multilayer" monochromator (a pair of layered synthetic microstructures) in small-angle x-ray scattering and diffraction studies of biological materials. Many biological applications of the small angle scattering technique, in particular time-resolved studies, are often limited by the flux incident on the sample. The wider energy bandpass of the multilayer monochromator can provide a higher beam flux by up to two orders of magnitude as compared with that of the typical Si(111) double-crystal monochromators used at synchrotron beam lines. On Beam Line 4-2 at the Stanford Synchrotron Radiation Laboratory, we have implemented two types of multilayers Mo/C and Mo/B₄C in the standard SSRL monochromator tank for the studies of x-ray fiber diffraction and solution scattering. In the fiber diffraction experiments, a pair of the latter type of multilayers provided ~10¹² photons/s in the beam size 0.6 mm x 1.5 mm (FWHM) at photon beam energy 9 keV, an increase of a factor of ~10 over Si(111) in the same configuration. We observed no significant smearing or effects of increased beam divergence due to the wide energy bandpass in fiber diffraction patterns and low-angle resolution in solution scattering was likewise unaffected. These results demonstrate significant advantages of the multilayer monochromators over Si crystal monochromators for non-crystalline biological x-ray diffraction applications.