Convergent beam neutron crystallography

摘要

Applications of neutron diffraction for small samples (<1mm~3) or small fiducial areas are limited by the available neutron flux density. Recent demonstrations of convergent beam electron and x-ray diffraction and focusing of cold (λ>1 A) neutrons suggest the possibility to use convergent beam neutron diffraction for small sample crystallography. We have carried out a systematic study of diffraction of both monoenergetic and broad bandwidth neutrons at the NIST Research Reactor and at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. Combining convergent beams with time-of-flight Laue diffraction is particularly attractive for high efficiency small sample diffraction studies. We have studied single crystal and powder diffraction of neutrons with convergence angles as large as 15°and have observed diffracted peak intensity gains greater than 20. The convergent beam method (CBM) shows promise for crystallography on small samples of small to medium size molecules (potentially even for proteins), ultra-high pressure samples, and for mapping of strain and texture distributions in larger samples.