A conical‐type X‐ray guide tube for diffraction experiments with small crystals

The divergence and intensity distribution of X‐rays transported through a conical‐type X‐ray guide tube (XGT) were measured. Diverging X‐rays from a point source were condensed by use of the conical‐type XGT. The parallelism of X‐rays through the XGT was better than that encountered for a cylindrical‐type XGT proposed previously [Nakazawa (1983). J. Appl. Cryst. 16 , 239–241]. The intensity of the X‐ray beam around the central axis of the conical‐type XGT was exceedingly high in comparison with that measured without the tube and almost uniform over a cross‐sectional area 60 μm in diameter. The high intensity provides the possibility of performing diffraction experiments with crystals as small as 20 μm in diameter with a conventional X‐ray diffraction system.