College Park, Maryland      June 6 - 10 , 2004

T2-C2 (1:45 PM): Convergent Beam Neutron Crystallography

W. M. Gibson, R. Youngman (X-Ray Optical Systems, Inc., 15 Tech Valley Drive, East Greenbush, NY 12061), A. J. Schultz, J. W. Richardson, J. M. Carpenter, M. E. Miller, E. R. Maxey (Intense Pulsed Neutron Source, Argonne National Lab), D. F. R. Mildner, H. H. Chen-Mayer (National Institute of Standards and Technology)

Two monolithic polycapillary optics of different focal length and beam convergence are used to investigate the use of focusing lenses for the neutron convergent beam method for time-of-flight crystallography with a broad wavelength band. The lens of short focal length (15.5 mm) with a beam convergence of 16.8 1.0 degrees has a focal width of about 120 microns. For a single crystal sample of this diameter on a pulsed neutron source, this lens gives an integrated intensity gain of ~ 50 for a (020) Bragg peak in MnF2 with 3.2 neutrons and a measured peak width (FWHM) of 4.5 degrees. Further measurements on a powder diffractometer show that the expected diffracted beam intensities have gains as much as 500 for powder samples of this diameter. The degradation of resolution is minimized in the back scattering geometry. The intensity gains for the powder diffraction peaks increase with wavelength and closely follow the expected transmission of the optic as a function of wavelength.

Work at XOS was supported by the US DOE, BES-MS, contract nos. OF-01385 and DE-FG02-02-ER83575. Work at Argonne National Laboratory was supported by the US DOE, BES-MS, under contract no. W-31-109-ENG-38. We also thank the NIST Center for Neutron Research.

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